CN115250140A - Transmission device of wireless electromagnetic repeater while drilling - Google Patents
Transmission device of wireless electromagnetic repeater while drilling Download PDFInfo
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- H—ELECTRICITY
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- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/155—Ground-based stations
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
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Abstract
The invention provides a transmission device of a wireless electromagnetic repeater while drilling, which comprises a processing module and an active band-pass filter circuit, wherein the processing module is connected with the active band-pass filter circuit; the active band-pass filter circuit comprises a programmable amplifier and an analog band-pass filter module, wherein the output end of the programmable amplifier is connected with the input end of the analog band-pass filter module, the output end of the analog band-pass filter module is connected with a processing module, and the processing module is respectively connected with each programmable amplifier and the analog band-pass filter module; and the processing module adjusts the passband bandwidth of the analog bandpass filtering module according to the transmission rate of the active bandpass filtering circuit. Therefore, sinusoidal waveform distortion generated during high-speed transmission of electromagnetic wave signals can be effectively inhibited, the waveform accuracy of the electromagnetic wave signals during 2-cycle/bit high-speed transmission of the system is ensured, and the system has enough sensitivity for weak signal capture.
Description
Technical Field
The invention relates to the technical field of geological exploration measuring instruments, in particular to a transmission device of a wireless electromagnetic repeater while drilling.
Background
Under the conditions of discontinuous drilling fluid circulating medium environments such as underbalanced drilling and leak stoppage while drilling, the pulse measurement while drilling system cannot work normally, and an electromagnetic measurement while drilling (EM-MWD) system is required to be used for directional deflecting operation of horizontal wells and directional wells. However, the biggest problem of the EM-MWD is that the electromagnetic wave signal is attenuated during the formation transmission process, so that the EM-MWD transmission distance is short, and the signal interruption is easy to generate when the formation resistivity is too high or too low. Therefore, the wireless electromagnetic repeater while drilling is a key instrument for maintaining continuous transmission of electromagnetic signals in a complex formation environment. The wireless electromagnetic repeater while drilling (see patent 2012103850780) is installed between a downhole transmitter and a ground receiver of an electromagnetic measurement while drilling system, can receive electromagnetic signals sent by downhole EM-MWD in real time, re-encode and package the processed signals, and wirelessly transmit data to a ground receiving device of the EM-MWD in the form of electromagnetic signals, so that the signal strength of ground receiving is improved, the adaptability of the EM-MWD to different strata is enhanced, the measurement depth is improved, and the control precision of a well track is ensured. With the use of high-precision measurement modules such as gamma imaging and resistivity imaging, the data volume needing to be transmitted while drilling is larger and larger, and the requirement on the transmission rate of the repeater is higher and higher.
Like the EM-MWD system, the wireless electromagnetic repeater while drilling uses a very low frequency continuous sine wave for signal transmission, and two sets of sine waves with opposite phases are used to represent "0" and "1". Its transmission rate is determined by two parameters, carrier frequency f, which determines the number of sinusoidal waveforms that can be transmitted in 1 second, and "period/bit", which determines the representation of 1-bit data by several sinusoidal waveforms (see fig. 1). The relationship between them is shown in the following table.
TABLE 1 Carrier frequency, period/bit and Transmission Rate relationships
As can be seen from the above table, increasing the carrier frequency increases the transmission rate of the electromagnetic wave. However, due to the skin effect, the higher the carrier frequency of the electromagnetic wave during transmission, the more severe the attenuation in the formation, so that currently, no repeater or EM-MWD product on the market generally uses a signal of more than 20Hz to prevent the electromagnetic signal from attenuating too fast during transmission, which results in too short transmission distance. Then the only way to increase the transmission rate is to decrease the "period/bit". However, a large number of field applications prove that after the period/bit is reduced to 2, the waveform of the electromagnetic wave signal received on the ground is seriously distorted, so that the error rate is rapidly increased, and the normal work cannot be realized. Fig. 1 explains the cause of such distortion, and fig. 2 shows that the received waveform is distorted when 2 cycles/bit setting is used, which is actually measured in the field, and the waveform is severely distorted and cannot be decoded. Therefore, all repeaters and EM-MWD products sold in the market at present are transmitted by using the 3-cycle/bit setting, the highest transmission rate mentioned in a product manual is publicized according to the transmission rate in the ideal state of 1 cycle/bit, the transmission rate cannot be used in practice, the transmission rate of the actual field work is only about 6.67bps at most, and the requirements of high-capacity data transmission while drilling such as resistivity imaging and the like cannot be met. Therefore, it is desirable to provide a solution to this problem, which enables the electromagnetic measurement while drilling system to work normally in a low cycle/position state.
At present, in the prior art related to electromagnetic wave transmission while drilling, in order to make up for the disadvantage that the distance of electromagnetic wave signals while drilling is limited, a high-Q filter should be adopted to improve the capability of capturing weak signals of a repeater and an EM-MWD, that is, a passband of the used filter should be as narrow as possible and as close to a carrier frequency as possible, and the passband should be adjusted when the carrier frequency is changed. For example, patent ZL201510163071.8 sets the passband to the current signal carrier frequency f ± 1.5Hz, that is, when the current 10Hz carrier frequency is used, the filter passband is 8.5 to 11.5Hz, and both the digital filtering algorithm and the analog filtering circuit passband can be adjusted in real time.
Disclosure of Invention
In view of the above, there is a need to provide a wireless electromagnetic repeater transmission device while drilling.
A wireless-while-drilling electromagnetic repeater transmission device, comprising: the device comprises a processing module and at least one active band-pass filter circuit;
the active band-pass filter circuit comprises a programmable amplifier and an analog band-pass filter module, wherein the input end of the programmable amplifier is used for receiving electromagnetic signals, the output end of the programmable amplifier is connected with the input end of the analog band-pass filter module, the output end of the analog band-pass filter module is connected with the processing module, and the processing module is respectively connected with the control end of each programmable amplifier and the control end of the analog band-pass filter module;
the processing module is used for adjusting the passband bandwidth of the analog bandpass filtering module according to the transmission rate of the active bandpass filtering circuit.
In one embodiment, the algorithm used by the processing module to adjust the passband bandwidth of the analog bandpass filtering module according to the transmission rate is:
b is the pass band width of the analog band-pass filtering module; f is the center frequency of the active band-pass filter circuit; v is the transmission rate of the active band-pass filter circuit; γ is period/bit.
In one embodiment, the processing module is further configured to detect a signal strength of an output of the analog band-pass filtering module, and adjust an amplification factor of the programmable amplifier according to a comparison result between the signal strength and a preset strength.
In one embodiment, the number of the active band-pass filter circuits is three, and the active band-pass filter circuits are sequentially connected in series.
In one embodiment, three of the active band-pass filter circuits include a first active band-pass filter circuit including a first programmable amplifier and a first analog band-pass filter module, a second active band-pass filter circuit including a second programmable amplifier and a first analog band-pass filter module, and a third active band-pass filter circuit including a third programmable amplifier and a first analog band-pass filter module,
the input of first programmable amplifier is used for receiving electromagnetic signal, first programmable amplifier's output with the input of first simulation band-pass filter module is connected, the output of first simulation band-pass filter module with the input of second programmable amplifier is connected, the output of second programmable amplifier with the input of second simulation band-pass filter module is connected, the output of second simulation band-pass filter module with the input of third programmable amplifier is connected, the output of third programmable amplifier with the input of third simulation band-pass filter module is connected, the output of third simulation band-pass filter module with processing module's signal input part is connected, processing module's control output respectively with the control end of first programmable amplifier the control end of second programmable amplifier the control end of third programmable amplifier the control end of first simulation band-pass filter module the control end of second simulation band-pass filter module and the control end of third simulation band-pass filter module is connected.
In one embodiment, the analog band-pass filter module is a second-order RC active band-pass filter.
In one embodiment, each analog band-pass filtering module includes a plurality of programmable varistors, and a control terminal of each programmable varistor is connected to a control output terminal of the processing module.
In one embodiment, each analog band-pass filtering module includes a first filtering submodule and a second filtering submodule, and the first filtering submodule is identical to the second filtering submodule.
In one embodiment, the first filtering submodule includes a first programmable rheostat, a second programmable rheostat, a third programmable rheostat, a fourth programmable rheostat, a first operational amplifier, a second operational amplifier and a third operational amplifier;
one end of the first programmable rheostat is used for receiving an electromagnetic signal, the other end of the first programmable rheostat is connected with a non-inverting input end of the first operational amplifier, a non-inverting input end of the first operational amplifier is used for grounding, an output end of the first operational amplifier is connected with one end of the third programmable rheostat, the other end of the third programmable rheostat is connected with a non-inverting input end of the second operational amplifier, a non-inverting input end of the second operational amplifier is used for grounding, an output end of the second operational amplifier is connected with a non-inverting input end of the third operational amplifier, a non-inverting input end of the third operational amplifier is used for grounding, an output end of the third operational amplifier is connected with a non-inverting input end of the first operational amplifier, one end of the second programmable rheostat is connected with an output end of the first operational amplifier, the other end of the second programmable rheostat is connected with a non-inverting input end of the second operational amplifier, and a control end of the second programmable rheostat, a control end of the third rheostat and a control end of the fourth rheostat are respectively connected with a control module of the programmable rheostat;
the processing module is used for controlling the resistance value change of the second programmable rheostat so as to adjust the passband width of the analog band-pass filter module and the center frequency of the active band-pass filter circuit;
the processing module is used for controlling the change of the resistance values of the third programmable rheostat and the fourth programmable rheostat so as to adjust the center frequency of the active band-pass filter circuit.
In one embodiment, the algorithm for the processing module to control the resistance value change of the second programmable rheostat to adjust the passband width of the analog bandpass filter module and the center frequency of the active bandpass filter circuit is as follows:
wherein R19 is the resistance of the second programmable varistor.
In one embodiment, the algorithm for controlling the variation of the resistances of the third programmable varistor and the fourth programmable varistor by the processing module to adjust the center frequency of the active band-pass filter circuit is:
wherein R20 is the resistance value of the third programmable varistor, and R21 is the resistance value of the fourth programmable varistor.
According to the transmission device of the wireless electromagnetic repeater while drilling, the active band-pass filter circuit is arranged, and the processing module adjusts the passband width, the center frequency and the amplification factor of a signal in real time according to the received electromagnetic signal, so that sinusoidal waveform distortion generated when the electromagnetic signal is transmitted at a high speed is inhibited, the waveform accuracy of the electromagnetic signal is ensured when the system is used for 2-cycle/bit high-speed transmission, sufficient sensitivity is provided for weak signal capture, and the normal work of the whole system can be ensured during high-speed transmission. The hardware circuit of the scheme has small size, low production cost and low algorithm complexity.
Drawings
FIG. 1 is a schematic diagram of the cause of waveform distortion after cycle/bit drop;
FIG. 2 is a waveform schematic diagram of a received waveform distortion caused when using a2 cycle/bit setting for field measurements;
FIG. 3 is a block diagram of a transmission device of a wireless electromagnetic repeater while drilling in one embodiment;
FIG. 4A is a circuit schematic of an active bandpass filter circuit in one embodiment;
figure 4B is a circuit schematic of a bandpass analog filter circuit in one embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
Example one
In this embodiment, as shown in fig. 3, a transmission device of a wireless electromagnetic repeater while drilling is provided, which includes: a processing module 300 and at least one active band-pass filter circuit 400; the active band-pass filter circuit 400 includes a programmable amplifier 410 and an analog band-pass filter module 420, an input end of the programmable amplifier is used for receiving electromagnetic signals, an output end of the programmable amplifier is connected with an input end of the analog band-pass filter module, an output end of the analog band-pass filter module is connected with the processing module, and the processing module is respectively connected with a control end of each programmable amplifier and a control end of the analog band-pass filter module; the processing module is used for adjusting the passband bandwidth of the analog bandpass filtering module according to the transmission rate of the active bandpass filtering circuit.
In one embodiment, the processing module is further configured to detect a signal strength of an output of the analog bandpass filtering module, and adjust the amplification factor of the programmable amplifier according to a comparison result between the signal strength and a preset strength.
It should be understood that, through testing, it can be seen that the main reason why the waveform is distorted after the period/bit is reduced to 2 is that the filter excessively pursues pass band narrowing, which results in the degradation of phase frequency characteristics, the occurrence of the distortion of the synchronization head, and the waveform distortion which results in the decoding failure. In order to avoid this problem, excessive widening of the passband may result in incomplete noise signal filtering, and when the useful signal is weak, the error rate is increased, resulting in a shortened transmission distance. Therefore, an optimal passband setting width needs to be found, the filtering performance is improved as much as possible on the premise of no waveform distortion, and the balance between the transmission rate and the transmission depth is achieved.
In this embodiment, the active band pass filter circuit may also be referred to as an active band pass filter. The active band-pass filter circuit is used for amplifying electromagnetic signals, filtering is input to the processing module, the processing module receives the signals amplified and filtered by the active band-pass filter circuit, whether the signals meet preset conditions or not is detected, if the signals do not meet the preset conditions, the passband width, the center frequency and the amplification factor of the active band-pass filter circuit are adjusted, so that the passband intermediate frequency gain is 1, in addition, the processing module is further used for carrying out secondary filtering on the received electromagnetic signals according to a preset filtering algorithm, therefore, sine waveform distortion generated when the electromagnetic wave signals are transmitted at a high speed is restrained, and the waveform accuracy of the electromagnetic wave signals when the system uses 2-cycle/bit high-speed transmission is ensured.
For example, the processing module is configured to adjust a passband bandwidth of the analog bandpass filtering module according to a transmission rate of the active bandpass filtering circuit. The algorithm that the processing module is used for adjusting the passband bandwidth of the analog bandpass filtering module according to the transmission rate is as follows:
b is the passband width of the analog bandpass filtering module; f is the center frequency of the active band-pass filter circuit; v is the transmission rate of the active band-pass filter circuit; γ is period/bit.
That is, when the repeater is at a carrier frequency of 10Hz at this time, and when a 2-cycle/bit setting is used, at this time 1-bit data is composed of 2 sinusoidal waveforms, the instrument transmission rate is 5bit/s, at this time the passband cutoff frequency is 5 and 15Hz, and the passband width is 15-5=10hz. And the rest frequencies are analogized, and the pass band width and the quality factor Q of the filter synchronously change along with the current transmission rate and the carrier frequency. The filtering processing method for automatically changing the passband maintains a good noise signal filtering effect, basically has no influence on the transmission depth, and can effectively eliminate the waveform distortion phenomenon when 2 cycles/bit setting is used, and when 24Hz carrier frequency is used for transmission, the maximum transmission rate of an instrument is increased from 8 bits/s of 3 cycles/bit to 12 bits/s, and is increased by 50%.
In this embodiment, when high-speed transmission is performed using 2 cycles/bit setting, the filter pass band width and center frequency corresponding to each carrier frequency are as follows:
when 2Hz signals are used for transmission, the transmission rate is 1bps, the central frequency of the filter is 2Hz, the passband is 1-3Hz, and the passband width is 2Hz.
When 3Hz signal transmission is used, the transmission rate is 1.5bps, the central frequency of the filter is 3Hz, the passband is 1.5-4.5Hz, and the passband width is 3Hz.
When 5Hz signal transmission is used, the transmission rate is 2.5bps, the central frequency of the filter is 5Hz, the passband is 2.5-7.5Hz, and the passband width is 5Hz.
When 10Hz signals are used for transmission, the transmission rate is 5bps, the central frequency of the filter is 10Hz, the passband is 5-15Hz, and the passband width is 10Hz.
When 15Hz signal transmission is used, the transmission rate is 7.5bps, the filter center frequency is 15Hz, the pass band is 7.5-22.5Hz, and the pass band width is 15Hz.
When 24Hz signal transmission is used, the transmission rate is 12bps, the center frequency of the filter is 24Hz, the pass band is 12-36Hz, and the pass band width is 24Hz.
Specifically, the active band-pass filter circuit is used for receiving electromagnetic signals, amplifying and filtering the electromagnetic signals, then sending the amplified and filtered electromagnetic signals to the processing module, the processing module receives the electromagnetic signals transmitted by the active band-pass filter circuit, the programmable amplifier and the analog band-pass filter module of the active band-pass filter circuit are adjusted according to the electromagnetic signals so as to adjust signals output to the processing module by the active band-pass filter circuit, the processing module performs secondary filtering on the electromagnetic signals according to a preset filtering algorithm, demodulates, decodes and re-encodes the secondarily filtered electromagnetic signals, and performs next signal transmission.
In this embodiment, by setting the active band-pass filter circuit, the processing module adjusts the passband width, the center frequency, and the amplification factor of the signal in real time according to the received electromagnetic signal, thereby suppressing sinusoidal waveform distortion generated during high-speed transmission of the electromagnetic signal, ensuring that the waveform of the electromagnetic signal is accurate when the system uses 2 cycles/bit high-speed transmission, having sufficient sensitivity for weak signal capture, and ensuring that the whole system can work normally during high-speed transmission. The hardware circuit of the scheme has small size, low production cost and low algorithm complexity.
In one embodiment, the processing module is further configured to compare the signal strength of the output of the analog band-pass filtering module with the first preset strength and the second preset strength, when the signal strength of the output of the analog band-pass filtering module is greater than the first preset strength, the amplification factor of the programmable amplifier is controlled to be reduced, and when the signal strength of the output of the analog band-pass filtering module is less than the second preset strength, the amplification factor of the programmable amplifier is controlled to be increased.
In this embodiment, the processing module adjusts the amplification factor of each programmable amplifier in real time. Specifically, the first preset intensity is greater than the second preset intensity, and the first preset intensity can be regarded as a greater intensity threshold, and when the signal intensity of the electromagnetic signal received by the processing module and output by the pseudo-band-pass filtering module is greater than the first preset intensity, which indicates that the signal intensity is too great, the programmable amplifier is controlled to reduce the amplification factor, so that the signal intensity of the electromagnetic signal received by the processing module and output by the pseudo-band-pass filtering module is reduced; when the signal intensity of the electromagnetic signals output by the pseudo-band-pass filtering module received by the processing module is smaller than the second preset intensity, the signal intensity is small, the programmable amplifier is controlled to increase the amplification factor, so that the signal intensity of the electromagnetic signals output by the pseudo-band-pass filtering module received by the processing module is increased, the control of the amplification factor of the programmable amplifier is realized, the adjusted signals can be maintained at stable intensity, and the accuracy of later-period signal decoding is improved.
In one embodiment, the number of the active band-pass filter circuits is three, and the active band-pass filter circuits are sequentially connected in series.
In the embodiment, the number of the active band-pass filter circuits is three, each active band-pass filter circuit comprises a programmable amplifier, so that the three programmable amplifiers are used for three-level amplification to carry out three-level amplification on signals, the final gain multiple of the source band-pass filter circuit is multiplied by the respective gain multiple of the programmable amplifiers with three levels, the amplification capacity is far higher than that of a single-stage amplifier, and the active band-pass filter circuit is more suitable for receiving weak electromagnetic wave signals which are seriously attenuated after long-distance transmission; in addition, the influence of the dynamic error of the gain amplifier on the intermediate frequency gain and the pass band width of the pass band of the filter circuit can be reduced by the three-stage amplifier structure, and meanwhile, the influence of the dynamic error of the gain amplifier on the center frequency of the filter is small, so that the phase error of a signal after passing through the filter circuit is greatly reduced.
To achieve a series connection of three stages of active bandpass filtering circuits, three stages of signal amplification and filtering are achieved, in one embodiment, the three active band-pass filter circuits comprise a first active band-pass filter circuit, a second active band-pass filter circuit and a third active band-pass filter circuit, the first active band-pass filter circuit comprises a first programmable amplifier and a first analog band-pass filter module, the second active band-pass filter circuit comprises a second programmable amplifier and a first analog band-pass filter module, the third active band-pass filter circuit comprises a third programmable amplifier and a first analog band-pass filter module, the input end of the first programmable amplifier is used for receiving electromagnetic signals, the output end of the first programmable amplifier is connected with the input end of the first analog band-pass filtering module, the output end of the first analog band-pass filter module is connected with the input end of the second programmable amplifier, the output end of the second programmable amplifier is connected with the input end of the second analog band-pass filtering module, the output end of the second analog band-pass filter module is connected with the input end of the third programmable amplifier, the output end of the third programmable amplifier is connected with the input end of the third analog band-pass filter module, the output end of the third analog band-pass filtering module is connected with the signal input end of the processing module, the control output end of the processing module is respectively connected with the control end of the first programmable amplifier, the control end of the second programmable amplifier, the control end of the third programmable amplifier, the control end of the first analog band-pass filtering module, the control end of the second analog band-pass filtering module and the control end of the third analog band-pass filtering module.
In this embodiment, as shown in fig. 4A, the third-level active band-pass filter circuit is a first active band-pass filter circuit, a second active band-pass filter circuit and a third active band-pass filter circuit, the first active band-pass filter circuit includes a first programmable amplifier 1 and a first analog band-pass filter module 2, the second active band-pass filter circuit includes a second programmable amplifier 3 and a first analog band-pass filter module 4, the third active band-pass filter circuit includes a third programmable amplifier 5 and a first analog band-pass filter module 6, the output end of the third analog band-pass filter module 6 is connected with the signal input end of the processing module 8, the processing module 8 is connected with the control end of the first programmable amplifier 1 through a bus 9, the control end of the second programmable amplifier 3 is connected with the control end of the third programmable amplifier 5, and the processing module 8 is connected with the control end of the first analog band-pass filter module 2, the control end of the second analog band-pass filter module 4 and the control end of the third analog band-pass filter module 6 through a bus 10 and a bus 11, respectively.
In this embodiment, the processing module is configured to adjust amplification factors of the first programmable amplifier, the second programmable amplifier, and the third programmable amplifier according to a received signal intensity of the electromagnetic signal output by the third analog band-pass filtering module and a comparison result between the signal intensity and a preset intensity, and the processing module is configured to adjust pass-band widths and center frequencies of the first analog band-pass filtering module, the second analog band-pass filtering module, and the third analog band-pass filtering module according to a current carrier frequency of the received electromagnetic signal.
Specifically, the processing module is configured to adjust the passband widths and the center frequencies of the first analog bandpass filtering module, the second analog bandpass filtering module, and the third analog bandpass filtering module according to a preset correspondence between the carrier frequency of the electromagnetic signal and the passband width and the center frequency, and according to the carrier frequency of the currently received electromagnetic signal.
In this embodiment, when high-speed transmission is performed using 2 cycles/bit setting, the filter pass band width and center frequency corresponding to each carrier frequency are as follows:
when 2Hz signals are used for transmission, the transmission rate is 1bps, the central frequency of the filter is 2Hz, the passband is 1-3Hz, and the passband width is 2Hz.
When 3Hz signal transmission is used, the transmission rate is 1.5bps, the central frequency of the filter is 3Hz, the passband is 1.5-4.5Hz, and the passband width is 3Hz.
When 5Hz signal transmission is used, the transmission rate is 2.5bps, the central frequency of the filter is 5Hz, the passband is 2.5-7.5Hz, and the passband width is 5Hz.
When 10Hz signals are used for transmission, the transmission rate is 5bps, the central frequency of the filter is 10Hz, the passband is 5-15Hz, and the passband width is 10Hz.
When a 15Hz signal is used for transmission, the transmission rate is 7.5bps, the center frequency of the filter is 15Hz, the passband is 7.5-22.5Hz, and the passband width is 15Hz.
When 24Hz signal transmission is used, the transmission rate is 12bps, the center frequency of the filter is 24Hz, the pass band is 12-36Hz, and the pass band width is 24Hz.
Like this, the processing module can compare the signal strength and the first intensity of predetermineeing and the second intensity of predetermineeing of the electromagnetic signal of received third simulation band-pass filter module output, works as the signal strength of the output of simulation band-pass filter module is greater than during first intensity of predetermineeing, control the magnification of first programmable amplifier, second programmable amplifier and third programmable amplifier and reduce, works as the signal strength of the output of third simulation band-pass filter module and is less than during the second intensity of predetermineeing, control the magnification increase of first programmable amplifier, second programmable amplifier and third programmable amplifier. In this embodiment, the selected amplifier is a programmable gain amplifier, and the respective amplification factors can be adjusted in real time by the CPU through the SPI1 bus, and when the received signal strength is high, a small amplification factor is selected, and when the received signal strength is low, a large amplification factor is selected, so that the conditioned signal is maintained at a stable strength, and the accuracy of decoding the signal in the later stage is improved.
In one embodiment, as shown in fig. 4A, the control output terminal of the processing module 8 is connected to the control terminal of the first programmable amplifier 1, the control terminal of the second programmable amplifier 3, and the control terminal of the third programmable amplifier 5 through an SPI1 bus 9, respectively.
In one embodiment, as shown in fig. 4A, the control output terminal of the processing module 8 is connected to the control terminal of the first analog band-pass filtering module 2, the control terminal of the second analog band-pass filtering module 4, and the control terminal of the third analog band-pass filtering module 6 through an SPI2 bus 10 and an SPI3 bus 11, respectively.
In one embodiment, the analog band-pass filter module is a second-order RC active band-pass filter. In this embodiment, first simulation band-pass filter module 2 second simulation band-pass filter module 4 and third simulation band-pass filter module 6 also can be called first simulation band-pass filter circuit second simulation band-pass filter circuit and third simulation band-pass filter circuit, first simulation band-pass filter module 2 second simulation band-pass filter module 4 and third simulation band-pass filter module 6 all adopt second order RC active band-pass filter, and three second order RC active band-pass filter establish ties together and has formed tertiary band-pass simulation filtering, and tertiary second order RC active band-pass filter has the same circuit structure and connected mode. Further description will be given in the following examples.
In one embodiment, each analog band-pass filtering module includes a plurality of programmable varistors, and a control terminal of each programmable varistor is connected to a control output terminal of the processing module. In this embodiment, the first analog band-pass filtering module 2, the second analog band-pass filtering module 4, and the third analog band-pass filtering module 6 respectively include a plurality of programmable varistors. The processing module realizes the adjustment of the passband width and the passband center frequency of the analog band-pass filtering module by controlling the adjustment of the resistance value of the programmable rheostat.
In one embodiment, each analog band-pass filtering module includes a first filtering submodule and a second filtering submodule, and the first filtering submodule is identical to the second filtering submodule. In this embodiment, each analog bandpass filtering module includes two filtering submodules with the same circuit structure, that is, the first analog bandpass filtering module 2, the second analog bandpass filtering module 4, and the third analog bandpass filtering module 6 include a first filtering submodule and a second filtering submodule, respectively. The filtering sub-modules can also be called as filtering sub-circuits, and each filtering sub-module is used for receiving one path of signal, wherein one path of filtering sub-module receives a Vin + signal, and the other path of filtering sub-module receives a Vin-signal. Each filtering submodule comprises four programmable rheostats, wherein one programmable rheostat is used for adjusting the width of the pass band, and two programmable rheostats are used for adjusting the center frequency of the pass band.
It should be understood that, because the received wireless electromagnetic signals are two paths of differential signals, the frequency, the signal intensity range and the modulation method are completely consistent, and only the phases are different, the filter circuit structures and the resistor-capacitor parameters through which the signals Vin + and Vin-pass are the same. In the following embodiment, the circuit structure of the filtering submodule is further explained by taking the filtering submodule through which Vin + passes as an example.
In one embodiment, as shown in fig. 4B, the first filtering sub-module includes a first programmable rheostat 18, a second programmable rheostat 19, a third programmable rheostat 20, a fourth programmable rheostat 21, a first operational amplifier 13, a second operational amplifier 14 and a third operational amplifier 12; one end of the first programmable rheostat is used for receiving an electromagnetic signal, the other end of the first programmable rheostat is connected with a non-inverting input end of the first operational amplifier, an inverting input end of the first operational amplifier is used for grounding, an output end of the first operational amplifier is connected with one end of the third programmable rheostat, the other end of the third programmable rheostat is connected with a non-inverting input end of the second operational amplifier, an inverting input end of the second operational amplifier is used for grounding, an output end of the second operational amplifier is connected with a non-inverting input end of the third operational amplifier, an inverting input end of the third operational amplifier is used for grounding, an output end of the third operational amplifier is connected with a non-inverting input end of the first operational amplifier, one end of the second programmable rheostat is connected with an output end of the first operational amplifier, the other end of the second programmable rheostat is connected with a non-inverting input end of the first operational amplifier, the other end of the fourth programmable rheostat is connected with a non-inverting input end of the second operational amplifier, and a control end of the second programmable rheostat, a control end of the third rheostat and a control end of the fourth rheostat are respectively connected with a control output end of the programmable rheostat processing module. The processing module is used for controlling the resistance value change of the second programmable rheostat so as to adjust the passband width of the analog band-pass filter module and the center frequency of the active band-pass filter circuit; the processing module is used for controlling the change of the resistance values of the third programmable rheostat and the fourth programmable rheostat so as to adjust the center frequency of the active band-pass filter circuit.
In this embodiment, the algorithm for controlling the resistance change of the second programmable rheostat to adjust the passband width of the analog bandpass filter module and the center frequency of the active bandpass filter circuit by the processing module is as follows:
wherein R19 is the resistance of the second programmable varistor.
In this embodiment, the processing module controls the variation of the resistances of the third programmable rheostat and the fourth programmable rheostat, and the algorithm for adjusting the center frequency of the active band-pass filter circuit includes:
wherein R20 is the resistance value of the third programmable varistor, and R21 is the resistance value of the fourth programmable varistor.
In this embodiment, compared with a conventional second-order RC active band-pass filter circuit, the circuit is optimized to some extent. Firstly, it keeps the advantages of the conventional second-order active band-pass filtering, and the pass-band width and the center frequency can be adjusted independently by adjusting the resistances of the first programmable varistor 18, the second programmable varistor 19, the third programmable varistor 20 and the fourth programmable varistor 21, wherein the second programmable varistor 19 determines the pass-band width B, and the value thereof is as follows
The third programmable rheostat 20 and the fourth programmable rheostat 21 are related to the center frequency of the passband, the center frequency of the passband is equal to the carrier frequency of the current transmission signal, and the value of the center frequency is
And R18= R19, R25= R26 to ensure a passband intermediate frequency gain of 1. The adjustment of these resistances is performed in real time by the processing module 8 via the SPI bus.
Secondly, the second-order RC active band-pass filter circuit in this embodiment has the advantages of deep dc negative feedback, difficulty in starting oscillation, and less deviation of the bandwidth and the center frequency in a high Q value state. When 2-cycle/bit high-speed transmission is adopted, the parameters of the digital rheostat corresponding to different carrier frequencies of the analog filter circuit are as follows:
according to the transmission device of the wireless electromagnetic repeater while drilling, the active band-pass filter circuit is arranged, and the processing module adjusts the passband width, the center frequency and the amplification factor of a signal in real time according to the received electromagnetic signal, so that sinusoidal waveform distortion generated when the electromagnetic signal is transmitted at a high speed is inhibited, the waveform accuracy of the electromagnetic signal is ensured when the system is used for 2-cycle/bit high-speed transmission, sufficient sensitivity is provided for weak signal capture, and the normal work of the whole system can be ensured during high-speed transmission. Through a large number of field application verifications, the invention has the advantages of good use effect, small hardware circuit size, low production cost and low algorithm complexity.
Example two
The frequency and amplitude of electromagnetic interference of most well sites cannot be judged in advance, and the technical limit of a repeater CPU chip causes that a self-adaptive filtering technology for continuously adjusting a passband cannot be used, well site noise can be collected and analyzed only by means of large-scale field tests, several ultralow frequency bands which are most difficult to coincide with the electromagnetic interference frequency are selected from the ultralow frequency bands to serve as carrier frequencies of an electromagnetic measurement while drilling system and the repeater, and then the passband of a repeater receiving and filtering module is discretely adjusted according to the carrier frequency values. The method comprehensively analyzes the well site electromagnetic interference characteristics and the spectrum distribution diagram of each block under different conditions of composite drilling, top drive, electric drilling machine, mechanical drilling machine, different stratum structures, different blocks and the like, and finally determines that 2, 3, 5, 10, 15 and 24Hz are adopted as system carrier frequencies, and the carrier frequencies can effectively avoid on-site electromagnetic interference while ensuring the transmission performance.
In this case, if a band pass filter with a fixed bandwidth is used, as in patent ZL201510163071.8, the quality factor Q of the filter is only related to the center frequency, the resulting phase error will affect the intermediate frequency gain and the pass band width, and in order to increase the ability of the repeater to capture weak signals, the Q value of the filter used is very high, which causes such a deviation to be more serious, and when a 2-cycle/bit arrangement is used for high-speed transmission, as in fig. 1, the waveform phase is almost completely distorted, the synchronization head is deviated, and decoding cannot be successful. Therefore, in order to solve this problem, a design of a band pass filter capable of automatically adjusting the Q value to an optimum value according to the carrier frequency rather than seeking the highest one at a time should be adopted. In this embodiment, when the pass band width B of the band pass filter is adjusted to
Wherein B is the passband width; f the carrier frequency used for this, i.e. the center frequency of the filter; v is the transmission rate of the instrument at this time; γ is period/bit. That is, when the repeater is at a carrier frequency of 10Hz at this time, and when a 2-cycle/bit setting is used, at this time 1-bit data is composed of 2 sinusoidal waveforms, the instrument transmission rate is 5bit/s, at this time the passband cutoff frequency is 5 and 15Hz, and the passband width is 15-5=10hz. And the rest frequencies are analogized, and the pass band width and the quality factor Q of the filter synchronously change along with the current transmission rate and the carrier frequency. The filtering processing method for automatically changing the passband maintains a good noise signal filtering effect, basically has no influence on the transmission depth, and can effectively eliminate the waveform distortion phenomenon when 2 cycles/bit setting is used, and when 24Hz carrier frequency is used for transmission, the maximum transmission rate of an instrument is increased from 8 bits/s of 3 cycles/bit to 12 bits/s, and is increased by 50%. The specific design method is as follows
In order to obtain the best noise signal filtering effect, the filter adopts a mode of combining an analog active band-pass filter circuit and an eight-order digital filter algorithm. As shown in fig. 4A, the analog circuit portion of the filter and the automatic gain amplifier are integrated into three stages, each of which is composed of a programmable amplifier and an analog band-pass filter circuit. The gain multiple of each stage of amplifier can be adjusted by the CPU chip 8 through the SPI1 bus 9, and the pass band width and the center frequency of each stage of analog band-pass filter circuit are also adjusted by the CPU chip 8 according to the currently set signal carrier frequency through the SPI2 bus 10 and the SPI3 bus 11 respectively. Two paths of differential electromagnetic signals received by the repeater underground enter a CPU chip 8 after 3 times of amplification-filtering in sequence, the last filtering is carried out by a digital band-pass filtering algorithm 7 burnt in the chip, and then the extracted useful signals are delivered to the CPU chip 8 for subsequent demodulation, decoding, recoding and other processing.
The reason for adopting this structure is three: firstly, the final gain multiple of the filter is multiplied by the respective gain multiple of the three-stage amplifier, the amplification capacity is far higher than that of a single-stage amplifier, and the filter is more suitable for receiving weak electromagnetic wave signals which are seriously attenuated after long-distance transmission; secondly, the selected amplifiers are programmable gain amplifiers, the respective amplification factors can be adjusted in real time by the CPU through the SPI1 bus, a smaller amplification factor is selected when the received signal strength is large, and a larger amplification factor is selected when the received signal strength is small, so that the conditioned signal is maintained at a stable strength, and the later-stage signal decoding accuracy is improved; and thirdly, the influence of the dynamic error of the gain amplifier on the intermediate frequency gain and the pass band width of the pass band of the filter circuit can be reduced by the three-stage structure, and meanwhile, the influence of the dynamic error of the gain amplifier on the center frequency of the filter is small, so that the phase error of a signal after passing through the filter circuit is greatly reduced.
The band-pass analog filter circuits 2, 4, and 6 used in this embodiment are all the same second-order RC active band-pass filters, and are connected in series to form a third-order band-pass analog filter, and the third-order circuits have the same circuit structure and connection manner, so that the first-order band-pass analog filter circuit 2 is taken as an example, and the schematic circuit structure diagram thereof is shown in fig. 4. Because the received wireless electromagnetic signals are two paths of differential signals, the frequency, the signal intensity range and the modulation method are completely consistent, and only the phases are different, the filter circuit structure and the resistor-capacitor parameters through which the signals Vin + and Vin-pass are the same. Therefore, the path of the analog filter circuit through which Vin + passes is taken as an example.
Compared with a general second-order RC active band-pass filter circuit, the circuit is optimized to a certain extent in the application. Firstly, the advantages of the conventional second-order active band-pass filtering are maintained, the pass band width and the center frequency can be independently adjusted by adjusting the resistance values of the varistors R18, R19, R20 and R21 respectively, wherein R19 determines the pass band width B, and the value of the pass band width B is
R20 and R21 are related to the center frequency of the passband, the center frequency of the passband is equal to the carrier frequency of the current transmission signal, and the value of the center frequency is
And R18= R19, R25= R26 to ensure a passband intermediate frequency gain of 1. The resistance values are adjusted in real time by the CPU chip 8 through the SPI bus.
Secondly, it has the advantage of degree of depth direct current negative feedback, is difficult for the start of oscillation, and the bandwidth is few with the skew of central frequency under the high Q value state.
When 2-cycle/bit high-speed transmission is adopted, the parameters of the digital rheostat corresponding to different carrier frequencies of the analog filter circuit are as follows:
band-pass digital filtering:
the part is mainly realized by a software algorithm of a CPU chip 8 and is used for filtering electromagnetic interference in a received electromagnetic signal for the second time, and the utilization rates of the digital filtering algorithm are only related to carrier frequencies, so that the coefficients of a band-pass digital filtering module are unchanged when the carrier frequencies are changed, and the specific coefficients are as follows: the transfer function denominator coefficient is
a[4][3]＝{0.35782333306215364，-1.9684794934717509，0.97329550029861134}，
{0.35782333306215364,-1.9819283390517608,0.9837097107572661},
{0.08896294572929403,-1.979322768392979,0.98805114330040633},
{0.08896294572929403,-1.9949569489694319,0.9959525340035672}
Has a molecular coefficient of
b[4][3]＝{1,-1.8484637894808618,1},
{1,-1.9999442478447613,1},
{1,-1.9669024745808565,1},
{1,-1.9997368979908425,1}
In the embodiment, a processing method for realizing high-speed transmission of electromagnetic wave signals by optimizing the performance of a filter during operation of a wireless electromagnetic repeater while drilling is provided, and an electromagnetic measurement while drilling system and an optimization method for the passband of a filtering module of a signal transmission repeater in a well are provided. Through a large number of field application verifications, the invention has the advantages of good use effect, small hardware circuit size, low production cost and low algorithm complexity, and is very easy to realize under the state of the domestic prior art.
Fig. 4A to 4B are numbered: 1. the circuit comprises a first-stage programmable gain amplifier, a second-stage programmable gain amplifier, a third-stage programmable gain amplifier, a fourth-stage analog band-pass filter circuit, a digital band-pass filter algorithm, 8.CPU chips, 9.SPI1 buses, 10.SPI2 buses, 11.SPI3 buses, 12 operational amplifiers, 13 operational amplifiers, 14 operational amplifiers, 15 operational amplifiers, 16 operational amplifiers, 17 operational amplifiers, 18 programmable varistors, 19 programmable varistors, 20 programmable varistors, 21 programmable varistors, 22 resistors, 23 resistors, 24 capacitors, 25 resistors, 26 resistors, 27 resistors, 28 capacitors, 29 programmable varistors, 30 programmable varistors, 31 capacitors, 32 programmable varistors, 33 programmable varistors, 34 resistors, 35 resistors, 36 capacitors, 37 resistors, 38 resistors and 39 resistors.
EXAMPLE III
In the embodiment, the processing method for restraining the electromagnetic interference of the well site, accurately capturing the weak useful signals and ensuring the normal work of the underground signal transmission repeater is provided, and the underground signal transmission repeater is designed according to the principles of small size, low power consumption, less occupied resources and stable and reliable functional operation.
(1) Design method of band-pass filter with automatically adjusted Q value
In the embodiment, 2, 3, 5, 10, 15 and 24Hz are adopted as the system carrier frequency, when the formation resistivity is too low or too high to be suitable for electromagnetic wave signal transmission, electromagnetic waves with lower frequency can be used, when high-speed transmission is needed, electromagnetic waves with higher frequency can be used, and field engineering application verification of more than ten times of wells in a plurality of blocks proves that the carrier frequency can effectively avoid field electromagnetic interference while ensuring transmission performance, and a better effect is obtained.
When the design method of the band-pass filter provided by the invention is adopted and 2 cycles/bit setting is used for high-speed transmission, the pass band width and the center frequency of the filter corresponding to each carrier frequency are as follows:
when 2Hz signals are used for transmission, the transmission rate is 1bps, the central frequency of the filter is 2Hz, the passband is 1-3Hz, and the passband width is 2Hz.
When 3Hz signal transmission is used, the transmission rate is 1.5bps, the central frequency of the filter is 3Hz, the passband is 1.5-4.5Hz, and the passband width is 3Hz.
When 5Hz signal transmission is used, the transmission rate is 2.5bps, the filter center frequency is 5Hz, the pass band is 2.5-7.5Hz, and the pass band width is 5Hz.
When 10Hz signals are used for transmission, the transmission rate is 5bps, the central frequency of the filter is 10Hz, the passband is 5-15Hz, and the passband width is 10Hz.
When a 15Hz signal is used for transmission, the transmission rate is 7.5bps, the center frequency of the filter is 15Hz, the passband is 7.5-22.5Hz, and the passband width is 15Hz.
When 24Hz signal transmission is used, the transmission rate is 12bps, the filter center frequency is 24Hz, the pass band is 12-36Hz, and the pass band width is 24Hz.
(2) Band-pass analog filter circuit
In this application, can use embedded chips such as high temperature singlechip, FPGA, DSP as CPU chip 8, this embodiment is with high temperature FPGA: the Spartan6 chip from Xilinx corporation is exemplified. Spartan6 is a low-power-consumption FPGA, the maximum working temperature is 125 ℃, the data processing capacity and the working performance meet the application requirements, 5 paths of SPI interfaces are supported, the circuit requirements are met, the digital rheostat and the gain amplifier can be respectively communicated with,
the gain amplifiers 1, 3, 5 may be implemented as high temperature programmable gain chips supporting the SPI bus, as exemplified by the PGA203 from TI corporation. The PGA202 gain can be programmed to 1, 10, 100 and 1000, the establishment time, the working temperature, the power consumption and the common mode rejection ratio can meet the application requirements, and the maximum amplification factor can reach 10 when three stages are connected in series for use 9 And the amplification requirement of underground weak electromagnetic signals can be met.
The amplifiers 12, 13, 14, 15, 16 and 17 in the analog filter circuit can be selected from, but not exclusively use a precision operational amplifier OPA602 chip of TI company, the capacitors can be selected from commercial high-temperature patch ceramic capacitors, and the capacitance values of C24 and C31 can be selected from, but not exclusively use 680nF, and the capacitance values of C28 and C36 can be selected from, but not exclusively use 470nF. The resistances of the resistors R25, R26, R37, R38 should remain the same, and 10K Ω may be used optionally, but not exclusively. The programmable rheostat R18, R19, R20, R21, R29, R30, R32, R33 is an AD5231 of TI company, and is a 1024-step resolution digital controllable potentiometer with adjustable resistance value
Wherein R is 10k omega, 50k omega and 100k omega, the resistance value R of each rheostat corresponding to different carrier frequencies can be determined by comparing the parameters provided by the application w Thereby calculating the coefficient D, and the CPU chip 8 controls the coefficient D of the AD5231 through the SPI buses 10 and 11, thereby realizing the change in the resistance value.
(3) Band-pass digital filtering module
The digital filter is realized in SPARTAN6 by programming according to the algorithm formula provided by the invention, and the digital filtering effect meeting the application requirement can be obtained.
The performance and reliability of the method are verified through more than ten field applications, and the verification result shows that the method can effectively inhibit the waveform deformation condition during high-speed transmission and ensure the normal signal transmission of the repeater.
The invention provides a processing method for inhibiting sinusoidal waveform distortion generated during high-speed transmission of electromagnetic wave signals by optimizing the performance of a filter during operation of a wireless electromagnetic repeater while drilling, provides an electromagnetic measurement while drilling system and an optimization method for a passband of a filtering module of an underground signal transmission repeater, and provides key design parameters of a filtering algorithm, so that the waveform of the electromagnetic wave signals is accurate when the system uses 2-cycle/bit high-speed transmission, the weak signal capture has enough sensitivity, and the normal operation of the whole system can be ensured during high-speed transmission. Through a large number of field application verifications, the invention has the advantages of good use effect, small hardware circuit size, low production cost and low algorithm complexity, and is very easy to realize under the state of the domestic prior art.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by hardware instructions of a computer program, which can be stored in a non-volatile computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. Any reference to memory, storage, database, or other medium used in the embodiments provided herein may include non-volatile and/or volatile memory, among others. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically Programmable ROM (EPROM), electrically Erasable Programmable ROM (EEPROM), or flash memory. Volatile memory can include Random Access Memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms such as Static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double Data Rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous Link DRAM (SLDRAM), rambus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A wireless-while-drilling electromagnetic repeater transmission device, comprising: the device comprises a processing module and at least one active band-pass filter circuit;
the active band-pass filter circuit comprises a programmable amplifier and an analog band-pass filter module, wherein the input end of the programmable amplifier is used for receiving electromagnetic signals, the output end of the programmable amplifier is connected with the input end of the analog band-pass filter module, the output end of the analog band-pass filter module is connected with the processing module, and the processing module is respectively connected with the control end of each programmable amplifier and the control end of the analog band-pass filter module;
the processing module is used for adjusting the passband bandwidth of the analog bandpass filtering module according to the transmission rate of the active bandpass filtering circuit.
2. The apparatus according to claim 1, wherein the algorithm used by the processing module to adjust the passband bandwidth of the analog bandpass filtering module according to the transmission rate is:
b is the pass band width of the analog band-pass filtering module; f is the center frequency of the active band-pass filter circuit; v is the transmission rate of the active band-pass filter circuit; γ is period/bit.
3. The apparatus of claim 1, wherein the processing module is further configured to detect a signal strength of an output of the analog bandpass filtering module, and adjust the amplification factor of the programmable amplifier according to a comparison result between the signal strength and a preset strength.
4. The apparatus of claim 1, wherein the number of the active band-pass filter circuits is three, and each of the active band-pass filter circuits is connected in series in sequence.
5. The apparatus of claim 4, wherein three of the active bandpass filtering circuits comprise a first active bandpass filtering circuit comprising a first programmable amplifier and a first analog bandpass filtering module, a second active bandpass filtering circuit comprising a second programmable amplifier and a first analog bandpass filtering module, and a third active bandpass filtering circuit comprising a third programmable amplifier and a first analog bandpass filtering module,
the input of first programmable amplifier is used for receiving electromagnetic signal, first programmable amplifier's output with the input of first simulation band-pass filter module is connected, the output of first simulation band-pass filter module with the input of second programmable amplifier is connected, the output of second programmable amplifier with the input of second simulation band-pass filter module is connected, the output of second simulation band-pass filter module with the input of third programmable amplifier is connected, the output of third programmable amplifier with the input of third simulation band-pass filter module is connected, the output of third simulation band-pass filter module with processing module's signal input part is connected, processing module's control output respectively with the control end of first programmable amplifier the control end of second programmable amplifier the control end of third programmable amplifier the control end of first simulation band-pass filter module the control end of second simulation band-pass filter module and the control end of third simulation band-pass filter module is connected.
6. The device according to any one of claims 1-5, wherein each analog band pass filter module comprises a plurality of programmable varistors, and a control terminal of each programmable varistor is connected to a control output terminal of the processing module.
7. The apparatus of claim 6, wherein each of the analog bandpass filtering modules includes a first filtering sub-module and a second filtering sub-module, the first filtering sub-module being identical to the second filtering sub-module.
8. The apparatus of claim 7, wherein the first filtering sub-module comprises a first programmable varistor, a second programmable varistor, a third programmable varistor, a fourth programmable varistor, a first operational amplifier, a second operational amplifier, and a third operational amplifier;
one end of the first programmable rheostat is used for receiving electromagnetic signals, the other end of the first programmable rheostat is connected with the non-inverting input end of the first operational amplifier, the inverting input of the first operational amplifier is used for grounding, the output end of the first operational amplifier is connected with one end of the third programmable rheostat, the other end of the third programmable rheostat is connected with the non-inverting input end of the second operational amplifier, the inverting input of the second operational amplifier is used for grounding, the output end of the second operational amplifier is connected with the non-inverting input end of the third operational amplifier, the inverting input of the third operational amplifier is used for grounding, the output end of the third operational amplifier is connected with the non-inverting input end of the first operational amplifier, one end of the second programmable rheostat is connected with the output end of the first operational amplifier, the other end of the second programmable rheostat is connected with the non-inverting input end of the first operational amplifier, one end of the fourth programmable rheostat is connected with the output end of the second operational amplifier, and the control end of the second programmable rheostat, the control end of the third programmable rheostat and the control end of the fourth rheostat are respectively connected with the control end of the programmable rheostat;
the processing module is used for controlling the resistance value change of the second programmable rheostat so as to adjust the passband width of the analog band-pass filter module and the center frequency of the active band-pass filter circuit;
the processing module is used for controlling the change of the resistance values of the third programmable rheostat and the fourth programmable rheostat so as to adjust the center frequency of the active band-pass filter circuit.
9. The apparatus of claim 8, wherein the algorithm for the processing module to control the resistance change of the second programmable rheostat to adjust the passband width of the analog bandpass filter module and the center frequency of the active bandpass filter circuit is:
wherein R19 is the resistance of the second programmable varistor.
10. The apparatus of claim 8, wherein the processing module controls the variation of the resistances of the third programmable rheostat and the fourth programmable rheostat to adjust the center frequency of the active band-pass filter circuit according to an algorithm comprising:
wherein R20 is the resistance value of the third programmable varistor, and R21 is the resistance value of the fourth programmable varistor.
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