CN105743491B - Microwave source system and its Microwave Diagnostics System based on filtering feedback locking phase - Google Patents

Abstract

The invention discloses a microwave source system based on filter feedback phase-locking, which includes a filter feedback loop for generating microwave signals, and the filter feedback loop includes a bandpass filter, a first microwave power amplifier and a directional coupler. The output end of the bandpass filter is connected with the input end of the first microwave power amplifier, the output end of the first microwave power amplifier is connected with the input end of the directional coupler, and the coupled output end of the directional coupler It is connected with the input end of the bandpass filter, and the output end of the directional coupler is used for microwave output. The invention also discloses a microwave measurement system and a plasma microwave diagnosis system including the microwave source system based on filter feedback phase-locked. The microwave source system based on filter feedback phase-locked in the present invention uses a band-pass filter as a positive feedback microwave loop, The system resonates on the bandwidth of the band-pass filter, so that the operating frequency of the microwave source system of the present invention is only controlled by the filter feedback loop, the frequency stability is high, and the system structure is simple, the cost is low, and the maintenance is easy.

Description

Microwave Source System and Its Microwave Diagnosis System Based on Filter Feedback Phase Locking

technical field

The invention relates to the field of microwave generation, in particular to a microwave source system based on filter feedback phase-locking, and also relates to a microwave diagnosis system including the microwave source system.

Background technique

Plasma microwave diagnosis can measure important parameters such as electron temperature and electron density distribution, turbulence and rotation speed inside high-temperature plasma. The measurement performance makes it one of the important measurement methods for the experimental research of magnetically confined controlled nuclear fusion plasma. In a microwave diagnostic system, the microwave source system is the most important component. At present, there are many types of microwave source systems, including return wave tube, gyrotron, klystron, EIO microwave tube, microwave solid source, microwave Synthetic sources, etc. Among them, microwave sources such as return wave tubes, EIO tubes, and klystrons require complex high-voltage systems and control systems. The life of the return wave tube is short, usually only more than 1,000 hours. Microwave sources such as return wave tubes, gyrotrons, klystrons, and EIO microwave tubes have poor frequency stability and are not suitable for direct use in plasma turbulence measurements. The output frequency of the microwave solid-state tube is fixed, and the adjustable range is small, but the output power is usually small; the microwave synthesis source generally uses a constant temperature crystal oscillator to lock the phase from the low frequency, and successively frequency multiplies to the microwave operating frequency, which requires complex filtering, frequency multiplication, and isolation. And the amplifier circuit, the system is more complicated. Most of these microwave systems mentioned above are expensive and difficult to maintain and maintain.

Contents of the invention

The technical problem solved by the present invention is that the existing microwave source system cannot meet the needs due to one or more of the following problems: complex structure, short life, poor frequency stability, high price, difficult maintenance and maintenance, and Provided is a microwave source system based on filter feedback phase-locking with simple structure, long service life, high frequency stability, low cost, easy maintenance and low phase noise.

In order to solve the problems of the technologies described above, the technical scheme adopted in the present invention is as follows:

A microwave source system based on filter feedback phase-locking, including a filter feedback loop for generating microwave signals, the filter feedback loop includes a band-pass filter, a first microwave power amplifier and a directional coupler, the output of the band-pass filter terminal is connected with the input terminal of the first microwave power amplifier, the output terminal of the first microwave power amplifier is connected with the input terminal of the directional coupler, and the coupled output terminal of the directional coupler is connected with the bandpass filter The input end of the directional coupler is connected, and the output end of the directional coupler is used for microwave output.

Preferably, the filtering feedback loop further includes a microwave resonant cavity, and the microwave resonant cavity is connected between the coupled output end of the directional coupler and the input end of the bandpass filter.

Preferably, the filtering feedback loop further includes an isolator for preventing parasitic reflection, and the isolator is arranged between the coupled output end of the directional coupler and the input end of the microwave resonant cavity.

Preferably, the filtering feedback loop further includes an adjustable phase shifter, and the adjustable phase shifter is connected between the output end of the bandpass filter and the input end of the first microwave power amplifier.

Preferably, the microwave source system based on filter feedback phase-locking includes a band-pass filter array of different frequencies and a band-pass filter for selecting a different operating frequency from the band-pass filter array as the band-pass filter gear selector switch.

Preferably, the microwave source system based on filter feedback phase-locked also includes a power output system, the power output system includes an antenna and a second microwave power amplifier, the antenna is connected to the output end of the directional coupler, the A second microwave power amplifier is arranged between the antenna and the output end of the directional coupler.

Preferably, the power output system further includes a broadband microwave isolator, and the broadband microwave isolator is arranged between the antenna and the second microwave power amplifier.

Preferably, the power output system further includes a monitoring coupler and a microwave monitoring system, the monitoring coupler is arranged between the second microwave power amplifier and the broadband microwave isolator, and the coupling end of the monitoring coupler Coupling all the way to the microwave monitoring system.

The present invention also provides a plasma microwave diagnostic system including the microwave source system based on filter feedback phase-locking, the plasma microwave diagnostic system also includes a microwave receiving system, and the microwave receiving system receives the filter feedback-based phase-locked The corresponding microwave source system emits and passes the microwave of the medium to be tested to realize the microwave diagnosis function.

Preferably, a through hole much smaller than the size of the microwave resonant cavity is opened on the microwave resonant cavity.

The beneficial effects of the present invention are as follows:

The microwave source system based on filter feedback phase-locking in the present invention adopts a band-pass filter as a positive feedback microwave circuit, so that the system resonates on the bandwidth of the band-pass filter (in the scheme provided with a microwave resonant cavity, the system resonates in the microwave resonant cavity On the natural frequency), that is, through the phase-locking of the band-pass filter, so that the operating frequency of the microwave source system of the present invention is only controlled by the resonant circuit, the frequency stability is high, and it does not need to be multiplied multiple times like the crystal oscillator synthesis source , filtering and power amplification, and there is no need to set up high-voltage systems and complex control systems in microwave sources such as return wave tubes, and the system structure is simple. Since only the first microwave power amplifier is an active device in the system, the microwave source system of the present invention has longer service life, lower cost and simpler maintenance. Moreover, the output power of the microwave source system based on filter feedback phase-locking of the present invention is determined by the 1dB compression point power of the first microwave amplifier, and can satisfy high power output when a high-power microwave amplifier is used.

Description of drawings

Fig. 1 is the structural representation of the microwave source system based on filter feedback phase-locking of the present invention;

Fig. 2 is when band-pass filter is respectively 23GHz and 37GHz, the phase noise that microwave measurement system of the present invention measures;

Fig. 3 is a schematic structural view of a microwave resonator in an embodiment of the present invention;

Fig. 4 is a schematic structural diagram of a frequency-selectable microwave source system in an embodiment of the present invention;

In the picture:

1-microwave resonator, 2-bandpass filter, 3-adjustable phase shifter, 4-first microwave power amplifier, 5-directional coupler, 6-isolator, 7-second microwave power amplifier, 8- Monitoring coupler, 9-microwave monitoring system, 10-broadband microwave isolator, 11-antenna, 13-through hole, 14-medium to be tested, 15-input microwave coupling pole, 16-input port, 17-output microwave Coupling pole, 18-output port, 19-position selection switch.

Detailed ways

The technical solutions and beneficial effects of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

In the present invention, the so-called "first" and "second" do not represent any logical sequence, but are only used to distinguish two identical components included in the system.

As shown in Figure 1, the microwave source system based on filter feedback phase-locked of the present invention includes a filter feedback loop for generating microwave signals, and the filter feedback loop includes a bandpass filter 2, a first microwave power amplifier 4 and a directional coupler 5, the output end of the bandpass filter 2 is connected with the input end of the first microwave power amplifier 4, the output end of the first microwave power amplifier 4 is connected with the input end of the directional coupler 5, and the coupling output end of the directional coupler 5 is connected with the input end of the directional coupler 5 The input end of the bandpass filter 2 is connected, and the output end of the directional coupler 5 is used for microwave output.

Wherein, the first microwave power amplifier 4 is used to amplify the resonant frequency generated by the bandpass filter 2, and the gain of the first microwave power amplifier 4 is required to be greater than the loss of the entire filter feedback loop, usually requiring a gain greater than 20 dB. At the same time, the output power of the filtering feedback loop is determined by the power at the 1dB compression point of the first microwave power amplifier 4, and is usually about 1dB smaller than the 1dB compression point power considering the insertion loss of the system.

The directional coupler 5 is used to couple and feed back part of the power output by the first microwave power amplifier 4 to the bandpass filter 2, and generally requires a coupling degree of 10 to 20 dB and an isolation degree of greater than 20 dB.

The microwave source system based on filter feedback phase-locked of the present invention utilizes the filter feedback loop that band-pass filter, microwave amplifier etc. microwave power.

In the present invention, the filter feedback loop also includes a microwave resonant cavity 1, and the microwave resonant cavity 1 is connected between the coupled output end of the directional coupler 5 and the input end of the band-pass filter 2, when the bandwidth of the band-pass filter 2 is much larger than When the natural resonant frequency of the resonant cavity 1 is reached, the system works at the natural resonant frequency of the resonant cavity 1, so that the output frequency of the microwave source system can be adjusted by adjusting the parameters of the microwave resonant cavity 1, specifically, using the microwave resonant cavity 1 Resonance performance, change the size of the cavity to change the resonance frequency, so as to realize the adjustable output frequency of the system. In practice, a knob that can adjust the size of the cavity can be designed on the microwave resonator 1, so that the cavity can be easily changed. the size of. The microwave resonator 1 can adopt a rectangular waveguide cavity or a circular waveguide cavity with a high quality factor Q (average energy storage/average energy consumption, the size of which can be calculated based on common knowledge based on the shape and size of the waveguide) to improve system efficiency. The band-pass filter 2 can filter out non-dominant wave frequencies generated by the microwave resonator 1, such as higher harmonics and parasitic oscillations.

In the present invention, the filter feedback loop may further include an isolator 6 for preventing parasitic reflection, and the isolator 6 is arranged between the coupling output end of the directional coupler 5 and the input end of the microwave resonator 1 . In order to prevent parasitic reflections in the loop as much as possible, which will affect the operating frequency of the resonant cavity and cause a large drift in the operating frequency of the system, the isolator 6 should try to use a microwave isolator with high isolation (>20dB).

In the present invention, the filtering feedback loop may further include an adjustable phase shifter 3 connected between the output end of the bandpass filter 2 and the input end of the microwave power amplifier 4 . The adjustable phase shifter 3 is mainly used for fine-tuning the working frequency: the adjustable phase shifter 3 works near the natural frequency of the resonant cavity, and can generate a microwave phase shift of 0-360 degrees. By adjusting the adjustable phase shifter, it can be Change the microwave operating frequency within a certain range. Under certain circumstances, the adjustable phase shifter 3 can also assist the microwave source system of the present invention to start oscillation at the resonant frequency.

The microwave source system based on filter feedback phase-locking of the present invention can also include a power output system, the power output system includes an antenna 11, the antenna system 11 is mainly used to output microwaves, and the antenna 11 is connected to the output end of the directional coupler 5.

The power output system may further include a second microwave power amplifier 7 arranged between the antenna 11 and the output end of the directional coupler 5 . The microwave power amplifier 7 is mainly used to drive the output power of the filter feedback loop. The microwave output by the filter feedback loop through the directional coupler 5 is amplified by the second microwave power amplifier 7 and then output to the antenna 11 .

In the present invention, a broadband microwave isolator 10 may also be arranged in the power output system, and the broadband microwave isolator 10 is arranged between the antenna 11 and the second microwave power amplifier 7 . The broadband microwave isolator 10 is mainly used to prevent spurious reflections from the transmitting loop, which further affects the natural operating frequency of the filtering feedback loop.

In order to measure the frequency and the power output by the microwave source system of the present invention, a monitoring coupler 8 and a microwave monitoring system 9 are set in the power output system, and the monitoring coupler 8 is arranged between the second microwave power amplifier 7 and the broadband microwave isolator 10 , the coupling end of the monitoring coupler 8 is coupled to the microwave monitoring system 9 . The microwave source monitoring system can display the output frequency and power changes of the microwave source of the present invention, so as to use the adjustable phase shifter 3 to fine-tune the frequency.

In the present invention, in the embodiment that the filter feedback loop only has band-pass filter 2, first microwave power amplifier 4 and directional coupler 5, the system is more compact and economical, but at this time, band-pass filter 2 needs Only on the output frequency required by the work, the first microwave power amplifier 4 can be selected as a microwave power amplifier with higher gain and higher 1dB compression point power, and the directional coupler 5 needs to have higher isolation to prevent parasitic Reflection, specifically, the gain of the amplifier needs to be greater than the loss of the closed resonant circuit. The 1dB compression point power of the amplifier determines the output power of the system, which can be selected according to the power output requirements. For the selection of other specific devices, those skilled in the art can according to Common knowledge is complete.

On the basis of the microwave source system of the present invention, as shown in Figure 4, increase the band-pass filter 2 arrays of different frequencies, the gear selection switch 19, utilize the gear selection switch 19 to select the band-pass filter of different operating frequencies The device enables the microwave source system to achieve the required microwave frequency output.

The microwave source system of the present invention can be used as a local oscillator source of a microwave diagnosis system, and in some cases can replace a relatively expensive synthetic source or a solid-state oscillator. On the basis of the microwave source system of the present invention, the microwave receiving system needed in the microwave measurement system is added, such as a detection or frequency mixing system, and microwave interference can be realized by receiving the microwave emitted from the system and passing through the medium to be measured. Or microwave reflection measurement, so that the microwave source system of the present invention is used to emit microwaves to measure the reflection or interference signal of the medium to be measured.

The microwave source system of the present invention can also utilize the performance of the resonant cavity 1 to measure the velocity and quality of the moving medium. Specifically, the structure of the microwave resonant cavity 1 needs to be properly modified. As shown in Figure 3, on the microwave resonant cavity 1 Opening a through hole much smaller than the size of the microwave resonator 1 can take advantage of the resonance performance of the microwave resonator 1, and by measuring the frequency change caused by the moving medium passing through the microwave resonator 1, the moving medium passing through the microwave resonator 1 can be measured speed and quality, so that the microwave source system of the present invention can be applied to microwave diagnostic systems and to measure the speed and quality of high-speed moving media. During the measurement, the mass to be measured is quickly shot through the microwave resonator 1 through the through hole, and the change of the output frequency of the microwave frequency source is measured. The time of frequency change is the time for the medium to pass through the resonator, and the velocity and frequency of the medium can be obtained. The amount of change is related to the dielectric constant and volume of the medium. When the density of the medium is known, the mass of the medium can be obtained.

The working principle of a kind of microwave source system based on filter feedback phase-locking provided by the present invention is described in detail below in conjunction with accompanying drawing 1:

The microwave resonator 1, the bandpass filter 2, the adjustable phase shifter 3, the first microwave power amplifier 4, the directional coupler 5 and the isolator 6 form a filter feedback loop, which is essentially the positive feedback of the first microwave amplifier 4 The circuit, the band-pass filter and the isolator designed in the loop make the loop work at the resonant frequency of the microwave resonant cavity 1 . By adjusting the adjustable phase shifter 3, the resonant frequency of the loop can also be changed within a limited range, and at the same time, it can also facilitate the vibration of the filter feedback loop.

The feedback loop outputs microwaves through the directional coupler, amplifies the power through the second microwave power amplifier 7 and then outputs the microwaves to the microwave antenna system 11 . The frequency and power output by the system are measured by the microwave source monitoring system 10, and the frequency and power changes of the microwave source output are displayed in real time. In order to use the adjustable phase shifter 3 to adjust the working frequency of the system to the required frequency point.

Because the system has adopted the microwave resonant cavity 1 of high quality factor Q as feedback control, the phase noise of the output frequency can be suppressed preferably, thereby the phase noise of the microwave source system of the present invention is low, and Fig. 2 is the band-pass filter respectively The phase noise measured by the system of the present invention is at 23GHz (the lower line in the figure) and 37GHz (the upper line in the figure). When the frequency deviation is 100kHz, the phase noise output by the loop system composed of 23GHz band-pass filter is 102dBc/Hz@100kHz, and the phase noise output by the loop system composed of 37GHz band-pass filter is 91dBc/Hz@100kHz, basically It has reached the noise level of the constant temperature crystal oscillator phase-locked microwave source.

The present invention has been described in detail above in conjunction with accompanying drawings and implementation, but the present invention is not limited to the above-mentioned examples of implementation, and within the scope of knowledge possessed by those of ordinary skill in the art, various Variety. The content that is not described in detail in the present invention can adopt the prior art.

Claims (9)

1. the microwave source system based on filtering feedback locking phase, it is characterised in that：It include the filtering feedback for generating microwave signal Circuit, the filtering feedback circuit include bandpass filter (2), the first microwave power amplifier (4) and directional coupler (5), The output end of the bandpass filter (2) is connect with the input terminal of first microwave power amplifier (4), first microwave The output end of power amplifier (4) is connect with the input terminal of the directional coupler (5), the coupling of the directional coupler (5) Output end is connect with the input terminal of the bandpass filter (2), and the output end of the directional coupler (5) is exported for microwave；

The filtering feedback circuit further includes microwave cavity (1), and the microwave cavity (1) is connected to the directional coupler (5) between coupled output and the input terminal of the bandpass filter (2).

2. the microwave source system based on filtering feedback locking phase as described in claim 1, it is characterised in that：The filtering feedback circuit Further include for preventing the isolator of parasitic reflection (6), coupling of isolator (6) setting in the directional coupler (5) Between output end and the input terminal of the microwave cavity (1).

3. the microwave source system based on filtering feedback locking phase as claimed in claim 2, it is characterised in that：The filtering feedback circuit Further include adjustable phase shifter (3), the adjustable phase shifter (3) is connected to the output end of the bandpass filter (2) and described the Between the input terminal of one microwave power amplifier (4).

4. the microwave source system based on filtering feedback locking phase as described in any one of claims 1 to 3, it is characterised in that：It is described Microwave source system based on filtering feedback locking phase includes the array of band-pass filters of different frequency and is used for from the bandpass filtering Select the bandpass filter of different operating frequency as the GSS Gear Select Switch (19) of the bandpass filter (2) in device array.

5. the microwave source system based on filtering feedback locking phase as claimed in claim 4, it is characterised in that：It is described to be based on filtering feedback The microwave source system of locking phase further includes power range system, and the power range system includes antenna (11) and the second microwave power Amplifier (7), the antenna (11) connect with the output end of the directional coupler (5), second microwave power amplifier (7) it is arranged between the antenna (11) and the output end of the directional coupler (5).

6. the microwave source system based on filtering feedback locking phase as claimed in claim 5, it is characterised in that：The power range system Further include wide-band microwave isolator (10), wide-band microwave isolator (10) setting is micro- in the antenna (11) and described second Between Power Amplifier (7).

7. the microwave source system based on filtering feedback locking phase as claimed in claim 6, it is characterised in that：The power range system Further include monitoring coupler (8) and microwave monitoring system (9), the monitoring coupler (8) is arranged in second microwave power Between amplifier (7) and the wide-band microwave isolator (10), the coupled end coupling of the monitoring coupler (8) is all the way to described Microwave monitoring system (9).

8. including the plasma microwave of the microwave source system based on filtering feedback locking phase described in any one of claim 1 to 7 Diagnostic system, it is characterised in that：The plasma microwave diagnostic system further includes microwave receiving system, the microwave receiving system System receives the microwave source system transmitting based on filtering feedback locking phase and by the microwave of testing medium, realizes microwave diagnostics work( Energy.

9. the plasma microwave diagnostic system of the microwave source system based on filtering feedback locking phase as claimed in claim 8, special Sign is：The through-hole (13) much smaller than the size of the microwave cavity (1) is provided in the microwave cavity (1).