Multi-channel microwave diagnosis system based on double microwave sources

Abstract

The invention discloses a multi-channel microwave diagnosis system based on double microwave sources, which comprises two independent microwave sources, a power divider, a frequency doubler, a band-pass filter, two directional couplers and a transmitting antenna, and is characterized in that microwave signals with different frequencies are generated through the two independent microwave sources, and each microwave source can generate a signal with a specific frequency; combining the generated microwave signals with different frequencies into a composite signal through a power divider (used as a beam combiner); a frequency doubler is used for carrying out frequency doubling on an input composite signal to form a series of spaced microwave signals; a band-pass filter is used to retain microwave signals of an effective frequency band; a microwave signal of an effective frequency band sequentially passes through the two directional couplers, and finally the microwave signal of the effective frequency band is transmitted into plasma through the transmitting antenna to be used as a detection microwave signal. The system can solve the problem of high microwave source cost caused by the need of a plurality of microwave sources in a multi-microwave source superposition scheme, and the problem of complex multi-channel signal power distribution adjustment.

Description

Technical Field

[0001] This invention relates to the field of microwave diagnostic technology, and in particular to a multichannel microwave diagnostic system based on dual microwave sources. Background Technology

[0002] The design of a single-channel Doppler backscattering (DBS) diagnostic system is relatively simple, mainly focusing on determining a suitable operating frequency and selecting a fixed-frequency or swept-frequency operating mode. However, a single-channel DBS can only measure the density and velocity fluctuations of plasma at a single radial location, and cannot measure the radial distribution of the radial electric field, lacking radial coverage capability. Multi-channel measurement schemes can be divided into two categories in principle: one is the multiple microwave source superposition scheme, which uses multiple independent signal sources or single-sideband modulators (SSBs) to generate microwave signals of different frequencies. Each signal source or modulator can generate a signal of a specific frequency, and then these signals are combined into a composite signal for transmission using a beam combiner. The advantage of this method is its simple system structure, ease of implementation, and the ability for each signal source to be independently adjusted, facilitating maintenance and replacement. However, mutual interference between signal sources and frequency and power distribution require careful management, and this scheme requires multiple signal sources, resulting in higher signal source costs.

[0003] The second category involves designing multi-frequency generation schemes, which generate signals of multiple frequencies from a single signal source. Common multi-frequency generation methods include: comb spectrum generator schemes, which have the advantage of producing clean signals and are relatively simple. However, this method suffers from unstable power distribution between frequency peaks, requiring periodic adjustments to maintain the uniformity of frequency peaks; VCO modulation schemes, which can achieve precise control of multiple frequencies, but require complex modulation and control circuits; and double-sideband modulator (DSBM) plus frequency multiplier schemes, which can generate signals with specific frequency shifts, but require optimization to reduce spurious signals and improve signal purity.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a multichannel microwave diagnostic system based on dual microwave sources to solve the aforementioned technical problems in the prior art. The system of this invention can solve the problem of high microwave source cost due to the need for multiple microwave sources in multi-source stacking schemes, as well as the problem of complex multichannel signal power distribution and adjustment.

[0006] The objective of this invention is achieved through the following technical solution: A multichannel microwave diagnostic system based on dual microwave sources includes two independent microwave sources, a power divider, a frequency doubler, a bandpass filter, two directional couplers, and a transmitting antenna, wherein: Microwave signals of different frequencies are generated by two independent microwave sources. Each microwave source can generate a signal of a specific frequency, which is expressed as follows: and ,in ; A power divider combines the generated microwave signals of different frequencies into a single composite signal, the frequency of which is expressed as... The frequency difference between the two microwave signals is ; A frequency doubler is used to multiply the input composite signal into a series of intervals. microwave signals; Use a bandpass filter to preserve microwave signals in the effective frequency band; The microwave signal in the effective frequency band passes through two directional couplers in sequence, and finally is transmitted into the plasma through the transmitting antenna to be used for microwave signal detection.

[0007] Compared with the prior art, the system provided by the present invention can solve the problem of high cost of microwave sources due to the need for multiple microwave sources in the multiple microwave source superposition scheme, as well as the problem of complex multi-channel signal power distribution and adjustment; it can simultaneously measure turbulence, plasma poloidal rotation velocity, etc. at multiple radial positions, and calculate the radial distribution of the radial electric field. Attached Figure Description

[0008] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0009] Figure 1 This is a schematic diagram of the structure of a multichannel microwave diagnostic system based on dual microwave sources provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the spectrum results of the dual microwave sources before the second harmonic in an example of the present invention; Figure 3 This is a schematic diagram of the multichannel spectrum results after dual microwave sources and frequency doubling in an example of the present invention. Detailed Implementation

[0010] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them, and do not constitute a limitation on the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0011] First, the following explanations are provided for the terms that may be used in this article: The term "and / or" means that either or both can be achieved simultaneously. For example, X and / or Y means that it includes both "X" or "Y" as well as the three cases of "X and Y".

[0012] The terms "comprising," "including," "containing," "having," or other similar semantic descriptions should be interpreted as non-exclusive inclusion. For example, including a technical feature element (such as raw material, component, ingredient, carrier, dosage form, material, size, part, component, mechanism, device, step, process, method, reaction conditions, processing conditions, parameter, algorithm, signal, data, product or article of manufacture, etc.) should be interpreted as including not only the expressly listed technical feature element, but also other technical feature elements that are not expressly listed and are well-known in the art.

[0013] The term "composed of" excludes any technical features not expressly listed. When used in a claim, it closes the claim to exclude all technical features other than those expressly listed, except for associated conventional impurities. If the term appears only in a clause of a claim, it limits the claim to the elements expressly listed in that clause; elements recited in other clauses are not excluded from the overall claim.

[0014] The technical solution provided by this invention will be described in detail below. Contents not described in detail in the embodiments of this invention are prior art known to those skilled in the art. Where specific conditions are not specified in the embodiments of this invention, they shall be performed according to conventional conditions in the art or conditions recommended by the manufacturer. Reagents or instruments used in the embodiments of this invention whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0015] like Figure 1 The diagram shown is a structural schematic of a multichannel microwave diagnostic system based on dual microwave sources provided in an embodiment of the present invention. The system includes two independent microwave sources ( Figure 1 1 and 2 in the middle), power divider ( Figure 1 3) Frequency doubler ( Figure 1 6) Bandpass filter ( Figure 1 7) Two directional couplers ( Figure 1 (8 and 9 in the text) and the transmitting antenna ( Figure 1 10 of them), of which: Microwave signals of different frequencies are generated by two independent microwave sources. Each microwave source can generate a signal of a specific frequency, which is expressed as follows: and ,in ; A power divider (acting as a beam combiner) combines microwave signals of different frequencies into a single composite signal, the frequency of which is expressed as follows: The frequency difference between the two microwave signals is ; A frequency doubler is used to multiply the input composite signal into a series of intervals. microwave signals; A bandpass filter is used to preserve microwave signals within the effective frequency band. The specific process is as follows: the bandpass filter is composed of a cascaded high-pass filter and a low-pass filter. It utilizes the frequency characteristics of capacitors (passing high frequencies and blocking low frequencies) and resistors (passing low frequencies and blocking high frequencies) to preserve microwave signals within the effective frequency band, thereby ensuring the selected frequency band is retained. Signals within the frequency band are transmitted smoothly, while signals outside the frequency band are significantly attenuated. The microwave signal in the effective frequency band passes through two directional couplers in sequence. In specific implementation, the directional coupler used in this invention is a three-port passive microwave device, used to extract the forward or reverse portion of the signal in the main transmission path proportionally, without significantly affecting the main power transmission. The first directional coupler is used to retain one transmitted signal as a reference signal for the secondary I / Q mixing section, which is called the reference path in the secondary I / Q mixing section. The second directional coupler is used to receive the returned Doppler backscattered signal, which is called the receiving path in the secondary I / Q mixing section. Finally, the effective frequency band microwave signal is transmitted into the plasma through the transmitting antenna and used for microwave signal detection.

[0016] In practice, before using the frequency doubler, the composite signal is processed... bandpass filter ( Figure 1 4) and attenuator ( Figure 1 (5) Remove noise peaks and control the power to meet the input power requirements of the frequency doubler.

[0017] Alternatively, the frequency difference between the two microwave sources can be changed. Adjust the frequency interval between each microwave signal; Among them, the frequency difference between the two microwave sources This is equal to the frequency interval of each microwave signal, and the frequencies of the multiple microwave signals are based on... For tolerance, and also includes and A positive integer arithmetic sequence is represented as: ; and ; k represents the k-th microwave signal.

[0018] For example, when two microwave sources , The frequency difference is At that time, after the second harmonic, there should only be two frequencies. and However, the actual output is a series of frequencies spaced at intervals of... Multiple microwave signals, including and ; and when the microwave source frequency difference is changed to At that time, the frequency doubler still outputs multiple signals, and the frequency difference changes accordingly. In specific implementation, the frequency difference of the microwave source is used. Multiple experiments were conducted with the variable being changed, and the results all proved that changing the frequency difference between the two microwave sources... The frequency interval between each microwave signal can be adjusted. This phenomenon can be attributed to the nonlinear effect of the frequency doubler, which is the key to the multi-channel generation scheme of this invention.

[0019] The power distribution among multiple microwave signals after the frequency multiplier is adjusted by changing the power distribution between the two microwave sources; specifically, this is achieved by increasing... Output power Increase frequency Less than the reference frequency A series of transmitted signal powers; conversely, by increasing Output power Increase frequency Greater than the reference frequency A series of transmitted signal powers.

[0020] For example, using two microwave sources , As a fundamental frequency source, the corresponding output powers are respectively and Using a reference frequency source Down-converting high-frequency signals facilitates data processing. Experiments showed that when adjusting... When the value is large, the frequency displayed on the spectrum analyzer is... Its transmitted signal power is also relatively strong, and the frequency is... The transmitted signal power is relatively weak; while when adjusted When the value is large, the spectrum analyzer results are exactly the opposite. Therefore, adjustments can be made by adding or removing attenuators, etc. and By changing the power distribution between the two microwave sources, the power distribution among the multiple microwave signals after the frequency multiplier can be adjusted, and the power of the three detection microwave channels used can be found to be roughly balanced. and Configuration.

[0021] For example, taking the Ka-band (26–40 GHz) multichannel Doppler backscattering meter as an example, a new multichannel generation method was developed using two microwave sources and a frequency doubler. This method simultaneously transmits a series of microwave signals (Ka-band) with a frequency spacing of 3 GHz into the plasma, and selects four of these signals to measure turbulence information at four different radial locations inside the magnetic confinement fusion experimental device. Figure 1 As shown: 1) In the microwave generation and transmission section, two microwave sources are used as the base frequency source, with frequencies of 13 GHz (number 1) and 16 GHz (number 2) respectively. A power divider (number 3) is used to combine the two signals into one.

[0022] After passing through a 12-18 GHz bandpass filter (number 4) and an attenuator (number 5), noise peaks are removed and the power is controlled to meet the input power requirements of the frequency doubler (number 6).

[0023] The input microwave signal is frequency-doubled using K and Ka band (18–44 GHz) frequency doublers (number 6) to generate a series of microwave signals with a frequency interval of 3 GHz from 17 GHz to 44 GHz (multi-channel microwaves are generated based on the nonlinear effect of the frequency doubler); such as Figure 2 The diagram shown is a schematic representation of the spectral results of the dual microwave sources before the second harmonic in an example of the present invention. Figure 3 The diagram shows the multichannel spectrum results after dual microwave sources and frequency doubling in an example of this invention. Due to the limitation of the spectrum analyzer's range of 9kHz-26.5GHz, only the microwave signal spectra at 17, 20, 23, and 26GHz are shown in the diagram. Figure 2 and Figure 3 The comparison clearly shows that the dual microwave source + frequency multiplier scheme is indeed effective in generating multiple channels.

[0024] Then, a 18-44 GHz bandpass filter (number 7) is used to preserve the microwave signal in the effective frequency band; Microwave signals at frequencies of 17, 20, 23, ..., 44 GHz were then sequentially transmitted through two 18–44 GHz directional couplers (numbered 8 and 9), and finally emitted from the antenna (numbered 10) into the plasma for subsequent turbulence measurements. In this example, ten fixed-frequency microwaves were emitted into the plasma, all of which could be used as probe microwave beams.

[0025] 2) In the secondary I / Q mixing section, a microwave source with a frequency of 15 GHz (No. 11) is used, and its frequency is doubled to 30 GHz as the local oscillator (LO) input of the receiving mixer (No. 12) and the reference mixer (No. 13).

[0026] Four intermediate frequency (IF) signals of the lower frequency range are selected for secondary mixing. First, two low-noise, high-gain amplifiers (numbered 14) of 0.3–6 GHz are used to amplify the IF signals of the reference path and the receiving path, respectively. Then, a four-channel power divider is used to split the signals into four almost identical paths. Based on the heterodyne measurement method, the first directional coupler (numbered 8) is used to retain one transmitted signal as the reference signal for the secondary I / Q mixing section, which is called the reference path in the secondary I / Q mixing section. The second directional coupler (numbered 9) is used to receive the returned Doppler backscattered signal, which is called the receiving path in the secondary I / Q mixing section. Then, narrowband pass filters (number 15) with different center frequencies (1, 2, 4, 5 GHz) were used to distinguish different detection frequencies; The intermediate frequency signals of the filtered reference path and the receiving path are used as the LO and RF inputs of the I / Q mixer (No. 16) for quadrature demodulation, respectively. In addition, according to the input power requirements of the I / Q mixer (No. 16), the 2GHz and 5GHz signals need to be additionally amplified by a low-noise amplifier (No. 17) to increase the power. The intermediate frequency signals of the reference path and the receiving path are demodulated into Acosφ and Asinφ (i.e., I signal and Q signal) in the I / Q mixer (No. 16), and the IQ signal is acquired by the high-speed data acquisition system (No. 18).

[0027] In practice, it can be seen from the spectrum of the primary mixing signal of the reference path and the receiving path that the dual microwave source + frequency multiplier scheme can generate multiple signals with less interference, thus meeting the usage requirements.

[0028] The aforementioned data acquisition system can operate throughout the discharge duration, with a maximum sampling rate of 80 MS / s.

[0029] It is worth noting that the contents not described in detail in the embodiments of the present invention belong to the prior art known to those skilled in the art.

[0030] In summary, the system described in the embodiments of the present invention has the following advantages: 1. The new dual-microwave source plus frequency multiplier solution only requires two microwave sources and one frequency multiplier, which significantly reduces costs compared to a single-channel microwave diagnostic system; 2. By changing the frequency difference between two microwave sources, the frequency interval between each channel can be flexibly adjusted. When the frequency interval between each channel is small, various fine structures can be measured, such as the balanced electric field and its shear; while when the frequency interval between each channel is large, it has a wider radial coverage capability. 3. This scheme uses only two microwave sources, which easily solves the problems of mutual interference and frequency allocation between microwave sources. Compared with the scheme of superimposing multiple microwave sources, the adjustment method is simpler and faster. 4. Compared with other multichannel generation schemes, it requires fewer microwave devices, has a simple structure, and is easy to maintain and replace.

[0031] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims. The information disclosed in the background section is intended only to enhance the understanding of the overall background technology of the present invention and should not be construed as an admission or implication in any way that such information constitutes prior art known to those skilled in the art.

Claims

1. A multichannel microwave diagnostic system based on dual microwave sources, characterized in that, The system includes two independent microwave sources, a power divider, a frequency doubler, a bandpass filter, two directional couplers, and a transmitting antenna, wherein: Microwave signals of different frequencies are generated by two independent microwave sources. Each microwave source can generate a signal of a specific frequency, which is expressed as follows: and ,in ; A power divider combines the generated microwave signals of different frequencies into a single composite signal, the frequency of which is expressed as... The frequency difference between the two microwave signals is ; A frequency doubler is used to multiply the input composite signal into a series of intervals. microwave signals; Use a bandpass filter to preserve microwave signals in the effective frequency band; The microwave signal in the effective frequency band passes through two directional couplers in sequence, and finally is transmitted into the plasma through the transmitting antenna to be used for microwave signal detection.

2. The multichannel microwave diagnostic system based on dual microwave sources according to claim 1, characterized in that, Before using a frequency doubler, the composite signal is passed through... Bandpass filters and attenuators remove noise peaks and control power to meet the input power requirements of the frequency doubler.

3. The multichannel microwave diagnostic system based on dual microwave sources according to claim 1, characterized in that, The specific process of using a bandpass filter to preserve the effective frequency band of the microwave signal is as follows: A bandpass filter is composed of a cascaded high-pass filter and a low-pass filter. It utilizes the frequency characteristics of capacitors (passing high frequencies and blocking low frequencies) and resistors (passing low frequencies and blocking high frequencies) to retain microwave signals within the effective frequency band, thereby ensuring the signal stays within the designated frequency range. Signals within the frequency band are transmitted smoothly, while signals outside the frequency band are significantly attenuated.

4. The multichannel microwave diagnostic system based on dual microwave sources according to claim 1, characterized in that, The directional coupler is a three-port passive microwave device used to extract a portion of the signal in the forward or reverse direction from the main transmission path proportionally. The first directional coupler is used to retain one transmit signal as a reference signal for the secondary I / Q mixing section, which is called the reference path in the secondary I / Q mixing section; The second directional coupler is used to receive the returned Doppler backscattered signal, and is referred to as the receiving path in the second I / Q mixing section.

5. The multichannel microwave diagnostic system based on dual microwave sources according to claim 1, characterized in that, By changing the frequency difference between the two microwave sources Adjust the frequency interval between each microwave signal; Among them, the frequency difference between the two microwave sources This is equal to the frequency interval of each microwave signal, and the frequencies of the multiple microwave signals are based on... For tolerance, and also includes and A positive integer arithmetic sequence is represented as: ； and ; k represents the k-th microwave signal.

6. The multichannel microwave diagnostic system based on dual microwave sources according to claim 1, characterized in that, By changing the power distribution between the two microwave sources, the power distribution among the multi-channel microwave signals after the frequency multiplier is adjusted. Specifically, by improving Output power Increase frequency Less than the reference frequency A series of transmitted signal powers; conversely, by increasing Output power Increase frequency Greater than the reference frequency A series of transmitted signal powers.

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