KR100691148B1 - Sensing signal process circuit of geomagnetic sensor - Google Patents

Abstract

The present invention is to provide a signal processing circuit of a geomagnetic sensor that can adjust the sensor signal of very small amplitude or very large amplitude to the set size by extending the variable amplification range, the configuration is a sensor of a constant frequency output from the geomagnetic sensor A mixer for mixing the signal with the reference frequency signal to convert the frequency; A first variable amplifier having an amplification degree inversely proportional to an amplitude of a sensor signal output from the geomagnetic sensor and amplifying a signal output from the mixer; A low pass filter configured to low pass filter the signal output from the first variable amplifier and output a voltage signal having a DC level; And a second variable amplifier in which the amplification degree is inversely proportional to the amplitude of the sensor signal output from the geomagnetic sensor and amplifies the voltage signal output from the low pass filter.

Geomagnetic sensor, electronic compass, variable amplifier, sensor signal, offset control, detection capability distribution,

Description

Sensing signal process circuit of geomagnetic sensor

1 is a circuit diagram showing a signal processing circuit of a conventional geomagnetic sensor.

2 is a signal waveform diagram showing a normal operating state when a conventional signal processing circuit is applied to an electronic compass.

3 is a signal waveform diagram showing an abnormal operating state when a conventional signal processing circuit is applied to an electronic compass.

4 is a signal detection capability distribution diagram of the geomagnetic sensor.

5 is a circuit diagram showing a signal processing circuit of the geomagnetic sensor according to the present invention.

Fig. 6 is a signal waveform diagram showing a signal processing state in the geomagnetic sensor signal processing circuit according to the present invention.

Explanation of symbols on the main parts of the drawings

51: mixer

52: first variable amplifier

53: low pass filter

54: second variable amplifier

55: control unit

56: offset control unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing circuit of a geomagnetism sensor used for sensing position, direction, and the like. In particular, the present invention relates to a geomagnetism sensor capable of converting a sensor signal having a wider range of magnitude to a set level by extending a variable amplification range. It relates to a signal processing circuit.

를 산출한다.The geomagnetic sensor outputs a sensor signal in response to the magnetic flux density of the surrounding geomagnetic field, and is mainly used for position and direction detection in navigation systems such as an electronic compass and an aircraft. The geomagnetic sensor outputs each magnetic flux in a sine and cosine waveform according to a rotating angle at which the sensor is placed. For example, an electronic compass uses an x-axis geomagnetic sensor and a y-axis geomagnetic sensor, and combines the x-axis sensor signal Vacx and the y-axis sensor signal Vacy to form an azimuth angle.

Calculate

However, the magnitude of the geomagnetic sensor may vary depending on the sensing ability or the strength or weakness of the surrounding magnetic field, and in order to calculate an accurate azimuth angle, it is necessary to adjust the x-axis sensor signal and the y-axis sensor signal to the same size.

In the related art, a signal processing circuit 12 as shown in FIG. 1 is formed to adjust the output of geomagnetic sensors to a predetermined level.

Referring to FIG. 1, the conventional signal processing circuit 12 converts a sensor signal of a predetermined frequency (for example, 1.6 MHz) output from the geomagnetic sensor 11 into a reference frequency signal (for example, 1.6 MHz). A mixer 121 for mixing, a first amplifier 122 for amplifying the frequency signal output from the mixer 121 with a fixed amplification, and a low pass for low pass filtering the output signal of the first amplifier 122. A filter 123 and a second amplifier 124 for amplifying the voltage signal output from the low pass filter 123 by varying the amplification degree according to external control.

The signal processing circuit 12 having the above-described configuration configures the second amplifier 124 as a variable amplifier, and changes the amplification factor according to the change in the magnitude of the sensor signal, thereby outputting a sensor signal of a constant level.

For example, when the signal processing circuit 12 is applied to the x-axis geomagnetic sensor and the y-axis geomagnetic sensor of the electronic compass and the sensor signals output from the respective signal processing circuits 12 are called Vadcx and Vadcy, Depending on the sensing capability of the sensor, the levels of Vadcx and Vadcy may vary as shown in FIG. In this case, an error may occur in calculating the azimuth, and therefore, the levels of Vadcx and Vadcy should be adjusted equally.

 In the conventional signal processing circuit, the output level of the signal processing circuit 12 is set to a constant value, the set level is compared with the actual output level of the signal processing circuit 12, and accordingly, the second variable amplifier 124 is used. Increase or decrease the degree of amplification. Accordingly, in the case of (a) of FIG. 2, if the set level is 400 mV, the signal processing circuit connected to the x-axis geomagnetic sensor reduces the amplification factor of the second amplifier 124 to adjust the output level. At this time, if the variable range is within the variable range of the amplification of the second amplifier 124, the output level is normally adjusted so that the amplitudes of the x, y axis sensor signals Vadcx and Vadcy are the same as shown in FIG. As described above, the azimuth angle? Error when the amplitudes of the x and y axis output voltages coincide with each other becomes zero as shown in FIG.

Next, FIG. 3 shows a case where the magnitude of the sensor signal is out of a setting range.

That is, as shown in (a) of FIG. 3, the amplitudes of the sensor signals Vadcx and Vadcy may appear differently depending on the sensitivity capability difference between the x-axis geomagnetic sensor and the y-axis geomagnetic sensor. At this time, the second amplifier 124 of the signal processing circuit of the x-axis geomagnetic sensor is changed to the minimum amplification degree, but if the sensor signal Vadcx of the x-axis geomagnetic sensor is too large, as shown in FIG. 3 (b), the x-axis sensor signal Vadcx And the amplitude deviation of the y-axis sensor signal Vadcy are still not corrected. As such, when the amplitude of the x-axis sensor signal Vadcx and the y-axis sensor signal Vadcy is changed in the electronic compass, an azimuth error occurs in FIG. 3C, which reduces the reliability of the electronic compass.

Similarly, when the signal of the geomagnetic sensor is too small, it may occur that the sensing signal cannot be corrected to the set amplitude range even if the amplification factor of the second amplifier 124 is changed to the maximum amplification degree. Also in this case, an azimuth error occurs.

As shown in FIG. 4, the magnitude difference of the geomagnetic sensor signal is generated by the variation of the sensing capability of each sensor with respect to the same magnetic field or the variation of the surrounding magnetic field.

In FIG. 4, the bc section is a section in which output correction is possible through the conventional signal processing circuit 12. In the related art, correction is possible only when the amplitude of the sensor signal corresponds to the bc section. No correction is made for sensor signals with amplitudes that are either small or too large in the ab and cd sections.

Therefore, the geomagnetic sensor having a sensing capability of the a-b section and the c-d section cannot be used for the electronic compass, and there is a problem in that it is discarded.

For example, in the conventional signal processing circuit, the reference level of Vadc is set to 800 mV, the amplification degree Av1 of the first amplifier 122 is set to 20, and the amplification degree of the second amplifier 124 is variable range of Av2. When 4 to 20, the amplification degree adjustment value of the second amplifier 124 according to the amplitude A of the sensor signal is calculated as shown in Table 1 below.

Vadc [mV] Av1 A [mV] Av2 Controllability 800 20 5 12.6 Controllable 800 20 3 20.9 Out of control 800 20 20 3.1 Out of control

As shown in Table 1, when the sensor signal of the geomagnetic sensor 11 is smaller than 3mV or larger than 16mV, the required output signal of 800mV cannot be obtained, resulting in a decrease in reliability.

SUMMARY OF THE INVENTION The present invention has been proposed to solve the above-mentioned conventional problems, and an object thereof is to provide a signal processing circuit of a geomagnetic sensor that can adjust a sensor signal having a very small amplitude or a very large amplitude to a predetermined size by extending a variable amplification range. It is.

As a construction means for achieving the above object, the present invention is a signal processing circuit of a geomagnetic sensor for outputting a sensor signal output from the geomagnetic sensor as a voltage signal of a predetermined level, the sensor signal of a constant frequency output from the geomagnetic sensor A mixer for mixing the frequency with the reference frequency signal; A first variable amplifier having an amplification degree inversely proportional to an amplitude of a sensor signal output from the geomagnetic sensor and amplifying a signal output from the mixer; A low pass filter configured to low pass filter the signal output from the first variable amplifier and output a voltage signal having a DC level; A second variable amplifier configured to amplify a voltage signal output from the low pass filter in inverse proportion to an amplification degree of the sensor signal output from the geomagnetic sensor and the first variable amplifier; And a control unit for comparing the level of the voltage signal Vacd output from the second variable amplifier with a reference level and adjusting the amplification degree of the first and second variable amplifiers so that the deviation becomes zero.

In addition, the signal processing circuit of the geomagnetic sensor according to the present invention may further comprise an offset control unit for adjusting the bias voltage of the first variable amplifier according to the control of the controller.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and the annexed drawings, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

5 is a circuit diagram showing a signal processing circuit of the geomagnetic sensor according to the present invention.

Referring to FIG. 5, the signal processing circuit of the geomagnetic sensor according to the present invention may convert the sensor signal of the geomagnetic sensor 1 of a set frequency (for example, 1.6 MHz) into a reference frequency signal (for example, 1.6 MHz). A mixer 51 for mixing and a first variable amplifier 52 for amplifying the amplification degree in inverse proportion to the amplitude of the sensor signal output from the geomagnetic sensor 1 to amplify the sensor signal output from the mixer 51; A low pass filter 53 for low pass filtering the sensor signal output from the first variable amplifier 52 and outputting a voltage signal having an average level thereof, and an inverse proportion to the amplitude of the sensor signal output from the geomagnetic sensor 1. The amplification degree is variable and consists of a second variable amplifier 54 for amplifying and outputting the voltage signal output from the low pass filter 53.

In the above description, the signal output from the second variable amplifier 54 is referred to as Vadc, which is a level corrected sensor signal of the geomagnetic sensor 1.

The signal processing circuit according to the present invention checks the signal Vadc level output from the second variable amplifier 54 in order to constantly control the level of the output signal Vadc of the second variable amplifier 54, thereby providing the Vadc. A control unit 55 for controlling the amplification degree of the first and second variable amplifiers 52 and 54 so that the level is set to the set level, and an offset voltage of the first variable amplifier 52 under the control of the control unit 55. Offset control unit 56 may be included.

The controller 55 adjusts the amplification degree of the first and second variable amplifiers 52 and 54 such that the output signal Vadc maintains a constant level.

The geomagnetic sensor signal processing circuit of the present invention described above includes two variable amplifiers 52 and 54, thereby extending the level adjustment range, thereby extending the signal amplitude range of the inputtable geomagnetic sensor 1.

In more detail, the first variable amplifier 52 may perform a first operation amplifier op1 for amplifying an input signal, an output of the mixer 51, and the first variable amplifier. Two resistors (R1) connecting the inverting (-) / non-inverting (+) input of the operational amplifier (op1) and the bias voltage (VREF + VC) is applied to the non-inverting input of the first operational amplifier (op1) And two variable resistors R2 connecting the non-inverting input and the output of the first operational amplifier op1.

The second variable amplifier 54 receives the output of the low pass filter 53 through the non-inverting input stage and amplifies the second operational amplifier op2 and bias voltage VREF of the second operational amplifier op2. A resistor R3 applied to the inverting input and a variable resistor R4 connecting the inverting input terminal and the output terminal of the second operational amplifier op2.

The control unit 55 converts the signal Vadc output from the second variable amplifier 54 into a digital signal, and adjusts the level of Vadc from the output data of the analog-digital converter 551. And a digital processor 552 for controlling the amplification degree of the first and second variable amplifiers 52 and 54 so as to be a set reference level. In addition, the digital processor 552 controls the operation of the offset control unit 56 according to the level of the Vadc. In other words, by adjusting the bias voltage VREF + VC through the offset controller 56, the characteristic of the first variable amplifier 52 is changed.

In this case, the digital processor 552 outputs the output signal using a point where the level of the voltage Vadc output from the second variable amplifier 54 is proportional to the amplification degree of the first and second variable amplifiers 52 and 54. The amplification degree is adjusted by adjusting the variable resistors R2 and R4 of the first and second variable amplifiers 52 and 54 according to the difference between Vadc and the set reference level.

FIG. 6 shows the output signals of the respective means shown in FIG. 5, and the operation of the signal processing circuit will be described below with reference to FIG.

First, a cosine wave or sine wave sensor signal having a predetermined frequency is output from the geomagnetic sensor 1. FIG. 6A illustrates a sensor signal output from the geomagnetic sensor 1, and the sensor signal has an amplitude A. FIG.

As shown in FIG. 6A, the sensor signal having amplitude A is input to the mixer 51 and mixed with the reference frequency. In this case, the output signal of the mixer 51 is the same as that of FIG. 6B.

의 진폭을 갖는다.The signal output from the mixer 51 is first amplified by the first variable amplifier 52, and its amplitude is increased. Here, when the amplification degree of the first variable amplifier 52 is Av1, the signal output from the first variable amplifier 52 is as shown in FIG.

Has the amplitude of.

가 된다.Subsequently, the signal output from the first variable amplifier 52 is input to the low pass filter 53, and the low pass filter 53 filters a frequency component to output a voltage signal having a nearly DC level. At this time, the level of the output signal of the low pass filter 53 is

Becomes

The output signal of the low pass filter 53 is input to the second variable amplifier 54 and amplified again. Here, when the amplification degree of the second variable amplifier 54 is Av2, the signal Vadc output from the second variable amplifier 54 is represented by Equation 1 below, and the signal form is shown in FIG. )

Referring to Equation 1, the signal Vadc outputted from the signal processing circuit of the present invention is equal to the sensor signal amplitude A of the geomagnetic sensor 1 and the amplification degrees Av1 and Av2 of the first and second variable amplifiers 52 and 54. Proportional.

Here, when the level of Vadc is fixed, the amplitude A of the sensor signal and the amplification degrees Av1 and Av2 are in inverse proportion. Accordingly, by adjusting the amplification degrees Av1 and Av2 in inverse proportion to the amplitude A of the sensor signal, Vadc of a constant level can be obtained.

At this time, the relationship between the amplitude A and the amplification degree Av1 and Av2 of the sensor signal is defined as in Equation 2 below.

Table 2 below shows examples of setting the amplification degrees Av1 and Av2 according to the sensor signal amplitude A of the geomagnetic sensor 1 when the output voltage Vadc of the signal processing circuit is set to 800 mV.

Vadc [mV] Av1 A [mV] Av2 Controllability 800 20 5 12.6 Controllable 800 30 3 14.1 Controllable 800 5 20 12.6 Controllable

As shown in Table 2, the amplification degree of the first and second variable amplifiers 52 and 54 is adjusted together with Av1 and Av2 according to the amplitude A of the sensor signal to further expand the size range of the controllable sensor signal. Can be. That is, the signals 3mV and 20mV, which were not controllable in the past, can also be controlled.

7 and 8 are graphs showing the amplitude range of the adjustable sensor signal according to the amplification degree Av1 and Av2 of the first and second variable amplifiers 52 and 54 in the geomagnetic sensor signal processing circuit according to the present invention. .

First, the graph of FIG. 7 shows the sensor signal input range according to the change in the amplification degree Av1 of the first variable amplifier 52. In FIG. 7, av1 (1)> av1 (2)> av1 (3)> av1 (4). That is, the size range of the sensor signal adjustable in proportion to the amplification degree of the first variable amplifier 52 is expanded. For example, when the amplification degree is av1 (2), the adjustable sensor signal size range is I1, but when the amplification degree is increased to av1 (4), it can be seen that the sensor signal size range is widened to I2.

The amplification degree Av1 of the first variable amplifier 52 described above is R2 / R1, and the amplification degree Av2 of the second variable amplifier 54 is 1 + R4 / R3. Therefore, the output level of the output voltage Vadc can be adjusted by adjusting the resistance values of the variable resistors R2 and R4.

In addition, when the second variable amplifier 54 is configured such that the amplification degree Av2 is set as in Equation 3 below, and the variable n is controlled in Equation 3 below, an appropriate level may be applied to a higher range of sensor signals. Can be amplified by a value.

이며, 상기 n은 제2가변증폭기(54)의 기본 증폭도이고, s는 제2가변증폭기(54)의 단위 증폭도이고, GC는 제2가변증폭기(54)의 제어 레지스터 값이다.In Equation 3,

N is a basic amplification degree of the second variable amplifier 54, s is a unit amplification degree of the second variable amplifier 54, and GC is a control register value of the second variable amplifier 54.

In the above, the magnitude and amplification of the signal of the geomagnetic sensor 1 in the second variable amplifier 54 as the basic amplification degree n varies from n (1)> n (2)> n (3)> n (4) The relationship of FIG. Av2 is shown in the graph of FIG. 8.

As shown in FIG. 8, by adjusting n, the size range of the adjustable sensor signal can be extended from I3 to I4.

Meanwhile, in the above description, specific embodiments have been described, but the present invention is not limited to the above embodiments, and various modifications may be made without departing from the spirit of the present invention.

According to the above, the present invention is a signal processing circuit for adjusting and outputting the sensor signal of the geomagnetic sensor to a predetermined size, by configuring two variable amplifiers in multiple stages, according to the distribution of the sensor detection capability or changes in the surrounding magnetic field The sensing range of the geomagnetic sensor can be further extended with an adjustable signal size range. As a result, there is an excellent effect of adjusting the voltage signal at the required level even for a very small sensor signal or a very large sensor signal.

Claims (6)

delete In the signal processing circuit of the geomagnetic sensor for outputting the sensor signal output from the geomagnetic sensor as a voltage signal of a set level, A mixer for converting a frequency signal by mixing a sensor signal of a predetermined frequency output from the geomagnetic sensor with a reference frequency signal; A first variable amplifier having a variable amplification degree and amplifying a signal output from the mixer; A low pass filter configured to low pass filter the signal output from the first variable amplifier and output a voltage signal having a DC level; A second variable amplifier having a variable amplification degree and amplifying a voltage signal output from the low pass filter; And And a control unit for comparing the level of the voltage signal output from the second variable amplifier with a reference level, and adjusting the amplification degree of the first and second variable amplifiers so that the deviation becomes zero. Circuit. The method of claim 2, And an offset control unit for adjusting a bias voltage of the first variable amplifier according to the control of the controller. The method of claim 3, wherein the first variable amplifier A non-inverting / inverting input terminal having a non-inverting / inverting input terminal, the first operational amplifier op1 amplifying a signal applied to the non-inverting / inverting input terminal, and the output of the mixer and the first operational amplifier op1 Two resistors (R1) connecting the two, and a bias voltage is applied to the non-inverting input of the first operational amplifier (op1), two variable to connect the non-inverting input and output of the first operational amplifier (op1) A signal processing circuit of a geomagnetic sensor, characterized in that consisting of a resistor (R2). The method of claim 3, wherein the second variable amplifier A second operational amplifier op2 for receiving and amplifying the output of the low pass filter through a non-inverting input terminal, a resistor R3 for applying a bias voltage Vref to an inverting input terminal of the second operational amplifier op2; And a variable resistor (R4) connecting the inverting input terminal and the output terminal of the second operational amplifier (op2). The method of claim 4 or 5, wherein the control unit The analog digital converter 551 converts the voltage Vadc output from the second variable amplifier into a digital signal and the output data of the analog digital converter 551 are checked to check the level of the output voltage Vadc. And a digital processor (552) for controlling a resistance value of the variable resistors of the first and second variable amplifiers and a bias voltage output from the offset controller so as to be a set reference level.

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