Frequency-shift scanning based unknown high-power high-frequency microwave electric field measurement method and device

Abstract

The application discloses a kind of unknown high-power high-frequency microwave electric field measurement method and device based on frequency shift scanning, belong to optical sensing and microwave measurement field.The present application is to solve the problem of high cost, system equipment complex, unable to take into account field strength and frequency measurement when existing high-power high-frequency microwave electric field detection.The device of the present application includes data processing unit, control component, sweep component, detection component, signal acquisition unit.By using frequency shift scanning, by controlling the synchronous frequency shift of Stokes gain sideband and local oscillator sideband, the frequency and electric field intensity of unknown high-power high-frequency microwave signal can be obtained by monitoring only kHz-MHz order intermediate frequency signal, so that the frequency and field strength of high-frequency high-power microwave signal can be measured by using low-speed photoelectric detector and low-speed data acquisition card.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of optical sensing and microwave measurement, and particularly relates to a high-power high-frequency microwave electric field measurement method and device based on frequency shift scanning. BACKGROUND

[0002] In microwave technology research, the measurement of high-power high-frequency microwave radiation electric field is an important research content. Existing high-power high-frequency microwave electric field measurement methods include far-field electrical measurement methods, photonics-assisted measurement methods, and all-optical measurement methods.

[0003] The far-field electrical measurement method is to receive a microwave signal by a horn antenna in the far-field region of an antenna, measure the microwave power through coupling, attenuation and other links, and then obtain the to-be-measured microwave radiation electric field information according to the mathematical conversion between the microwave power and the electric field strength. This method is prone to breakdown, and different frequency band antennas need to be used to measure the same bandwidth microwave signal, resulting in complex structure and high cost of the detection equipment.

[0004] The photonics-assisted measurement method is to receive a microwave signal by an antenna, modulate the microwave signal to an optical carrier by a modulator, realize the conversion and transmission of the signal in an optical system, and then detect and analyze the signal by a high-frequency analysis instrument after electro-optical conversion. The signal reception of this method still depends on an antenna, so the measurement bandwidth and power are still limited.

[0005] The all-optical measurement method is to receive a microwave signal by a microwave photonics sensing probe designed purely by optics, which can measure higher frequency and higher power microwave signals. However, if the high-frequency signal detected by the probe is directly detected without any processing, a high-frequency analysis instrument needs to be used, which will increase the cost of the system. Moreover, the sensing signal of the electric field sensing probe based on electro-optical effect is weak, and optical amplification or electrical amplification equipment needs to be added to realize signal detection. The Chinese invention patent with publication number CN114720780A discloses a single sideband frequency conversion amplification high-power high-frequency microwave field strength sensing method and device based on the stimulated Brillouin scattering effect of an optical fiber. The method realizes low-noise amplification of the to-be-measured signal light by using the stimulated Brillouin scattering amplification method, and realizes the down-conversion of the to-be-measured signal by using the all-optical mixing method of the optical microwave signal. This method realizes the measurement of high-frequency high-power microwave signals by using a low-frequency detector and a low-speed data acquisition card, but the method requires the frequency of the to-be-measured microwave signal to be known, and can only be used for field strength detection of the microwave signal. SUMMARY

[0006] The present application provides a high-power high-frequency microwave electric field measurement method and device based on frequency shift scanning to solve the problems of high cost, complex system equipment, and the inability to measure the field strength and frequency simultaneously.

[0007] The specific technical solutions adopted by the present application are as follows:

[0008] In a first aspect, the present application provides a device for measuring unknown high-power high-frequency microwave electric field based on frequency shift scanning, comprising a data processing unit, a control component, a sweep component, a detection component and a signal acquisition unit.

[0009] The control component is used to control the signal acquisition of the signal acquisition unit and the scanning intensity and frequency of the sweep component, and to feed back control information to the data processing unit; the sweep component is used to send local oscillator sweep signals and pump sweep signals to modulate the detection component; the detection component is used to receive unknown microwave signals, and to output low-frequency mixed signals to the signal acquisition unit after Brillouin selective single sideband amplification and frequency conversion; the signal acquisition unit is used to acquire the low-frequency mixed signals output by the detection component and send them to the data processing unit; the data processing unit is used to receive the signals transmitted back by the signal acquisition unit and extract the intensity information of intermediate frequency signals in a specified frequency range, to receive the frequency and intensity information of the local oscillator signals and pump signals fed back by the control component, to process the data and determine whether the frequency of the unknown microwave signal is scanned, to send corresponding instructions to the control component according to the determination result, and to output the intensity and frequency information of the unknown microwave signal when the frequency of the unknown microwave signal is scanned.

[0010] As a preferred embodiment, the detection component comprises a light source, an electro-optic intensity modulator for modulating the local oscillator signals, an electro-optic intensity modulator for modulating the pump signals, a reflective optical electric field sensing probe for receiving unknown microwave signals and modulating them onto an optical carrier, a fiber amplifier for amplifying the pump light, an optical fiber for generating stimulated Brillouin scattering, an isolator for isolating the forward pump light, and a low-speed photodetector for converting optical signals into electrical signals.

[0011] As a preferred embodiment, the detection component modulates the unknown microwave signals onto an optical carrier through the reflective optical electric field sensing probe to form unknown microwave signal sidebands, modulates the local oscillator sweep signals and pump sweep signals onto the optical carrier through two electro-optic intensity modulators to form local oscillator sidebands and pump sidebands that move in the frequency spectrum, and generates Stokes gain sidebands due to stimulated Brillouin effect; the unknown microwave signal sidebands will be amplified if they are within the Stokes gain sidebands, and the amplified (or unamplified) unknown microwave signal sidebands will be mixed with the local oscillator sidebands to generate mixed signals and output them to the signal acquisition unit.

[0012] Further, the optical fiber is a single-mode optical fiber or a high-nonlinear optical fiber with a length of more than 5 km.

[0013] Furthermore, the electro-optic intensity modulator used to modulate the pump signal operates in a carrier-suppressed double-sideband modulation mode; the electro-optic intensity modulator used to modulate the local oscillator signal and the reflective optical electric field sensing probe operate in one of the following modes: double-sideband modulation, single-sideband modulation, carrier-suppressed double-sideband modulation, or carrier-suppressed single-sideband modulation.

[0014] Furthermore, the electro-optic intensity modulator used to modulate the local oscillator signal and the reflective optical electric field sensing probe are connected in a cascaded or parallel manner.

[0015] Preferably, the frequency sweeping component includes a first microwave signal generator for generating a local oscillator signal and a second microwave signal generator for generating a pump signal; the local oscillator signal generated by the first microwave signal generator and the pump signal generated by the second microwave signal generator can achieve synchronous scanning, and the frequency difference between the two remains unchanged.

[0016] Secondly, the present invention provides a measurement method using any of the frequency-shift scanning-based unknown high-power high-frequency microwave electric field measurement devices described in the first aspect, as follows:

[0017] S1: Calibrate the measurement accuracy of the detection component using a standard electric field, generate calibration data, and determine the optimal value; set the intensity of the local oscillator signal and pump signal to the optimal value; use a spectrum analyzer to measure the Brillouin frequency shift f of the fiber used to generate stimulated Brillouin scattering in the detection component. B Let the frequency of the local oscillator signal be f. LO The unknown microwave signal frequency is f RF The intermediate frequency signal after mixing the two is f. IF =|f RF -f LO |, The pump signal frequency is f P The condition for the sideband of an unknown microwave signal on an optical carrier to be amplified with maximum gain is |f RF -f P |=f B Let the intermediate frequency signal frequency f be... IF It is a constant value within the range of kHz to MHz;

[0018] S2: Place the reflective optical electric field sensing probe in the detection assembly into the unknown microwave signal electric field, and start the measurement device; the frequency sweeping assembly emits a set of frequencies f LO(0) and f P(0) The local oscillator signal and pump signal are sent to the detection component; the signal acquisition unit receives the mixed signal output by the detection component and sends it to the data processing unit to initialize the measuring device;

[0019] S3: Monitoring frequency f via the data processing unit IF The intensity I of the intermediate frequency signalIF ;

[0020] S31: If the intermediate frequency signal strength I IF With noise intensity I noise Satisfy I IF >I noise This proves that an unknown microwave signal has been detected; then, based on the frequency relationship between the signals in S1 above, the frequency f of the unknown microwave signal is demodulated and output. RF and intensity I RF If the measurement of the unknown microwave signal has been completed, the measuring device will cease operation; if further measurement is required, monitoring will continue according to step S3. IF value;

[0021] S32: If the intermediate frequency signal strength I IF With noise intensity I noise Satisfy I IF ≤I noise If the unknown microwave signal is not detected, proceed to step S4.

[0022] S4: Measuring f IF Is there a difference frequency signal within the range of ±△f?

[0023] S41: If the frequency of occurrence is f IF The difference frequency signal of ', the data processing unit according to f IF '=|f RF -f LO The frequency f is calculated based on the frequency relationship between '| and S1 mentioned above. IF The target intermediate frequency signal requires the local oscillator frequency f LO(M) and pump signal frequency f P(M) , where f LO 'for f IF The local oscillator signal frequency is then measured; subsequently, the data processing unit sends corresponding instructions to the control component based on the processing results. The control component then controls the frequency sweep component to send the target frequency to the detection component based on the received instructions. At this time, the unknown microwave signal sideband is amplified and down-converted to a frequency of f. IF The intermediate frequency signal is used to output unknown microwave signal parameters; if the measurement of the unknown microwave signal is completed, the measuring device ends its operation; if further measurement is required, monitoring of I is continued according to step S3. IF value;

[0024] S41: If f IF If there is no difference frequency signal within the range of ±△f, proceed to step S5;

[0025] S5: Initiate frequency shift scanning to locate unknown microwave signals and measure f. IF Is there a difference frequency signal within the range of ±△f? Let the local oscillator sweep frequency signal and the pump sweep frequency signal be f respectively.LO(i) and f P(i) Where i = 1, 2, ..., n, and the two satisfy the relation |f LO(i) -f P(i) |=f B ±f IF ;

[0026] S51: If the frequency of occurrence is f IF The difference frequency signal of ', the data processing unit according to f IF '=|f RF -f LO The frequency f is calculated based on the frequency relationship between '| and S1 mentioned above. IF The target intermediate frequency signal requires the local oscillator frequency f LO(M) and pump signal frequency f P(M) The corresponding command is sent to the control component, which then controls the frequency sweep component to send the target frequency to the detection component based on the received command; at this time, the unknown microwave signal sideband is amplified and down-converted to a frequency of f. IF The intermediate frequency signal is used to output unknown microwave signal parameters; if the measurement of the unknown microwave signal is completed, the measuring device ends its operation; if further measurement is required, monitoring of I is continued according to step S3. IF value;

[0027] S52: If f IF If there is no difference frequency signal within the ±△f range, it indicates that the frequency (intensity) of the microwave signal under test is out of range or that the measuring device is faulty. The measurement needs to be terminated and the problem needs to be found and the system needs to be debugged.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1) This invention employs a combination of stimulated Brillouin scattering and optical mixing down-conversion to amplify the sideband of the high-power, high-frequency microwave electric field signal modulated by the optical electric field sensing probe in a single sideband and down-convert it to an intermediate frequency signal output in the kHz to MHz range, thereby reducing the bandwidth requirements of the detection instrument.

[0030] 2) This invention employs a frequency-shifting scanning method. By controlling the synchronous frequency shift of the Stokes gain sideband and the local oscillator sideband, the frequency and electric field intensity of an unknown high-power high-frequency microwave signal can be obtained by monitoring only the intermediate frequency signal in the range of kHz to MHz.

[0031] 3) This invention has an adaptive adjustment function. When the frequency of the electric field of an unknown microwave signal changes, it can automatically perform frequency shift scanning to find the signal and continue measurement through monitoring feedback, without the need for manual adjustment.

[0032] 4) The application realizes all-optical detection of high-power high-frequency microwave signals, and the upper limit of the detectable field strength reaches the air breakdown field strength, the measurement bandwidth is greater than 40 GHz, and the detection is suitable for ultra-wideband high-power high-frequency microwave electric field. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a schematic diagram of the unknown high-power high-frequency microwave electric field measuring device of the application.

[0034] Figure 2 is a schematic diagram of the detection assembly in embodiment 1 of the application.

[0035] Figure 3 is a frequency distribution graph when the to-be-detected microwave signal is not scanned in embodiment 1 of the application.

[0036] Figure 4 is a frequency distribution graph when the to-be-detected microwave signal is scanned in embodiment 1 of the application.

[0037] Figure 5 is a schematic diagram of the detection assembly in embodiment 2 of the application.

[0038] Figure 6 is a frequency distribution graph when the to-be-detected microwave signal is not scanned in embodiment 2 of the application.

[0039] Figure 7 is a frequency distribution graph when the to-be-detected microwave signal is scanned in embodiment 2 of the application.

[0040] Figure 8 is a step diagram of the unknown high-power high-frequency microwave electric field measuring method of the application.

[0041] In the figure, the reference signs are: a data processing unit 101, a control assembly 102, a frequency sweeping assembly 103, a detection assembly 104, a signal acquisition unit 105; a first narrow-line-width laser 201, a 1x2 optical fiber coupler 202, a first electro-optic intensity modulator 203, a first optical fiber circulator 204, a first reflective optical electric field sensing probe 205, a first isolator 206, a first optical fiber 207, a second electro-optic intensity modulator 208, a first optical fiber amplifier 209, a second optical fiber circulator 210, a first low-speed photodetector 211; a second narrow-line-width laser 301, a 1x3 optical fiber coupler 302, a third optical fiber circulator 303, a second reflective optical electric field sensing probe 304, a second isolator 305, a second optical fiber 306, a third electro-optic intensity modulator 307, a second optical fiber amplifier 308, a fourth optical fiber circulator 309, a fourth electro-optic intensity modulator 310, a 2x1 optical fiber coupler 311, and a second low-speed photodetector 312. DETAILED DESCRIPTION

[0042] The present application will be further described and illustrated in conjunction with the accompanying drawings and specific embodiments. The technical features of each embodiment of the present application can be combined accordingly without conflict.

[0043] Firstly, the terms involved in the present application are explained: 1) fiber stimulated Brillouin scattering refers to a typical three-wave nonlinear interaction of coherent scattering of optical waves and acoustic phonons in an optical fiber; 2) Brillouin single sideband amplification refers to that when the pump light and the signal to be amplified are transmitted in the optical fiber, due to the stimulated Brillouin effect, the Stokes gain spectrum of the frequency downshift in the opposite direction (relative to the pump light) and the Anti-Stokes gain spectrum of the frequency upshift in the forward direction are generated, and since the Stokes gain bandwidth is narrow, the two sidebands of the signal to be amplified will not be in the Stokes gain spectrum at the same time, only the sideband of the signal to be amplified in the Stokes gain spectrum will be amplified, thereby realizing single sideband selective amplification; 3) frequency shift scanning refers to the movement of the pump sideband on the optical carrier caused by the frequency scanning of the pump signal, thereby causing the movement of the Stokes gain sideband, and the movement of the local oscillator sideband on the optical carrier caused by the frequency scanning of the local oscillator signal, thereby causing the change of the intermediate frequency signal.

[0044] As shown in Figure 1 The present application provides a high-power high-frequency microwave electric field measurement device based on frequency shift scanning, which mainly comprises a data processing unit 101, a control component 102, a frequency sweeping component 103, a detection component 104 and a signal acquisition unit 105. The components or units will be described in detail below.

[0045] The control component 102 is used for controlling the signal acquisition of the signal acquisition unit 105 and the scanning intensity and frequency of the frequency sweeping component 103, and feeding back the control information to the data processing unit 101. Specifically, the control component 102 is connected with the data processing unit 101, the signal acquisition unit 105 and the frequency sweeping component 103, and is used for controlling the signal acquisition of the signal acquisition unit 105 and the signal scanning intensity and frequency of the frequency sweeping component 103, and feeding back the control information to the data processing unit 101.

[0046] The frequency sweeping component 103 is used for emitting the local oscillator scanning signal and the pump scanning signal to modulate the detection component 104. Specifically, the frequency sweeping component 103 is connected with the detection component 104 and the control component 102, and is used for generating, controlling and feeding back the local oscillator signal and the pump signal. It is controlled by the control component 102 to emit the local oscillator scanning signal and the pump scanning signal (the frequency difference remains unchanged) to modulate the corresponding electro-optic intensity modulator in the detection component 104.

[0047] In practical application, the sweep component 103 preferably comprises a first microwave signal source for generating the local oscillator signal and a second microwave signal source for generating the pump signal. The local oscillator signal generated by the first microwave signal source and the pump signal generated by the second microwave signal source can realize synchronous scanning, and the frequency difference between them remains unchanged.

[0048] The signal acquisition unit 105 is connected with the detection component 104 and the data processing unit 101, and is used for acquiring the low-frequency mixed signal output by the detection component 104 and sending the low-frequency mixed signal to the data processing unit 101.

[0049] As a preferred mode of the present application, the signal acquisition unit 105 comprises a low-speed data acquisition card and necessary signal processing elements such as filters, low-noise amplifiers, etc.

[0050] The data processing unit 101 is connected with the signal acquisition unit 105 and the control component 102, and is used for receiving the signal transmitted back by the signal acquisition unit 105 and extracting the intensity information of the intermediate frequency signal in a specified frequency range, receiving the frequency and intensity information of the local oscillator signal and the pump signal fed back by the control component 102, processing the data and judging whether the frequency of the unknown microwave signal is scanned, and issuing corresponding instructions to the control component 102 according to the judgment result, and outputting the intensity and frequency information of the unknown microwave signal when the frequency of the unknown microwave signal is scanned.

[0051] The detection component 104 is used for receiving the unknown microwave signal, and outputting the unknown microwave signal after Brillouin selective single sideband amplification and mixed conversion to the signal acquisition unit 105. Specifically, the detection component 104 is connected with the sweep component 103 and the signal acquisition unit 105, and is used for receiving the unknown microwave signal and outputting the unknown microwave signal after Brillouin selective single sideband amplification and mixed conversion. As a preferred mode, the detection component 104 comprises a light source, an electro-optic intensity modulator for modulating the local oscillator signal, an electro-optic intensity modulator for modulating the pump signal, a reflective optical electric field sensing probe for receiving the unknown microwave signal and modulating the unknown microwave signal onto an optical carrier, a fiber amplifier for amplifying the pump light, an optical fiber for generating stimulated Brillouin scattering, an isolator for isolating the forward pump light, a low-speed photodetector for converting the optical signal into an electrical signal, and various necessary optical fiber transmission elements. The detection component 104 can modulate the unknown microwave signal onto the optical carrier through the reflective optical electric field sensing probe to form an unknown signal sideband, modulate the local oscillator signal and the pump signal onto the optical carrier through the two electro-optic intensity modulators to form a local oscillator sideband and a pump sideband moving in the frequency spectrum, and generate a Stokes gain sideband due to the stimulated Brillouin effect. The unknown signal sideband will be amplified if it is in the Stokes gain sideband, and the amplified (or unamplified) unknown signal sideband will be mixed with the local oscillator sideband to generate a mixed signal and output the mixed signal to the signal acquisition unit 105.

[0052] In practical application, the optical fiber for generating stimulated Brillouin scattering is a single-mode optical fiber or a high nonlinear optical fiber with a length of more than 5 km, which is selected according to the required Brillouin frequency shift amount. The electro-optic intensity modulator for modulating the pump signal operates in a carrier-suppressed double-sideband modulation mode, and the electro-optic intensity modulator for modulating the local signal and the reflective optical electric field sensing probe can operate in a double-sideband modulation mode, a single-sideband modulation mode, a carrier-suppressed double-sideband modulation mode, a carrier-suppressed single-sideband modulation mode, etc. according to actual needs.

[0053] In practical application, the electro-optic intensity modulator for modulating the local signal and the reflective optical electric field sensing probe for receiving the unknown microwave signal and modulating the unknown microwave signal onto an optical carrier can be connected in series or in parallel. In the series connection, the single-sideband of the local signal and the single-sideband of the unknown microwave signal can be simultaneously selected; in the parallel connection, the mixed frequency signal obtained has fewer useless frequency sidebands, and the energy utilization rate of the mixed frequency down-conversion is higher.

[0054] The detection component 104 realizes Brillouin selection single-sideband amplification and mixed frequency down-conversion output of the unknown microwave signal based on the following conditions:

[0055]

[0056] In the formula, f RF , f P , f LO , f B , f IF respectively represent the frequency of the unknown microwave signal, the frequency of the pump signal, the frequency of the local signal, the Brillouin frequency shift amount of the optical fiber, and the frequency of the intermediate frequency signal generated by mixing. The Brillouin frequency shift amount f B is related to the material and temperature of the optical fiber, so the Brillouin frequency shift can be changed by using optical fibers made of different materials. In the case of constant optical fiber and constant temperature, the Brillouin frequency shift generated by the stimulated Brillouin in the system is a constant value.

[0057] When it is assumed that the measured intermediate frequency signal frequency f IF is a certain frequency in the order of kHz to MHz, the relationship between the local signal frequency f LO and the pump signal frequency f P can be expressed as:

[0058] |f LO -f P |=f B ±f IF =C (2) In the formula, C represents a constant. When f RF >f LO , formula (2) can be expressed as:

[0059]

[0060] When f RF LO When f

[0061]

[0062] When f LO P When f

[0063] |f LO(i) -f P(i) |=f B ±f IF =C(i=1,2,3,...,n) (5)

[0064] Where i represents the number of sweep. The unknown microwave signal frequency f LO and the pump signal frequency f P are swept synchronously (the frequency difference between them is kept at f B +f IF or f B -f IF ), and it is monitored whether the intermediate frequency signal with known frequency f IF is generated to realize the identification of the unknown microwave signal frequency f RF . When the intermediate frequency signal with known frequency f IF is generated, it means that one sideband of the unknown microwave signal on the optical carrier is amplified by the Brillouin selective single sideband, and it is assumed that the number of sweep at this time is i=M, then the following relationship formula is satisfied:

[0065]

[0066] The unknown microwave signal frequency can be calculated by using the relationship formula (6-1) or (6-2), and then the field strength and frequency of the unknown microwave signal are detected.

[0067] Further, considering that the bandwidth of the electro-optic intensity modulator is limited, when the unknown microwave signal with frequency greater than f B is amplified, the pump signal with frequency lower than f RF is used as much as possible, therefore the electro-optic intensity modulator used to modulate the pump signal uses the carrier-suppressed double sideband modulation method to modulate the pump signal, and the pump sideband generated on the optical carrier is f C ±f P(i) (i=1,2,...,n). When the pump light power reaches the fiber stimulated Brillouin threshold, the stimulated Brillouin effect will occur in the optical fiber, and the pump light sideband f C ±f P(i) ​​(i = 1, 2,..., n) are respectively generated under the action of the fiber stimulated Brillouin scattering C ±f P(i) -f B (i = 1, 2,..., n) are respectively generated under the action of the fiber stimulated Brillouin scattering RF >f B When f C -f P(M) -f B amplifies the unknown microwave signal sideband f C -f RF ; when f RF <f B , the Stokes gain sideband f C +f P(M) -f B amplifies the unknown microwave signal sideband f C +f RF , so as to realize the Brillouin selective single sideband amplification of the unknown microwave signal in a wide frequency domain.

[0068] Further, if only the intensity of the intermediate frequency signal with the frequency f IF is measured to find the unknown microwave signal, the time consumed is longer, in order to improve the scanning speed, whether the difference frequency signal appears in the range of f IF ±△f (△f < f IF , which is determined according to actual requirements and conditions) can be found. If the difference frequency signal f IF ’ appears in the range of f IF ±△f, at this time the unknown microwave signal sideband has not been amplified with the maximum gain, but f IF ’ satisfies the following relationship formula:

[0069] f IF ′ = |f RF -f LO ′| (7)

[0070] Combining formula (6) and (7) can calculate the local oscillator frequency f LO(M) and the pump frequency f P(M) which can make the unknown microwave signal sideband obtain the maximum gain. Further, adjusting the local oscillator signal frequency and the pump signal frequency to f LO(M) and f P(M) can obtain the target intermediate frequency signal.

[0071] Embodiment 1

[0072] The embodiment provides a detection assembly which can realize a detection function, such as Figure 2As shown, the cascade type is adopted between the electro-optic intensity modulator for modulating the local oscillator signal and the reflective optical electric field sensing probe. The main part is composed of a first narrow linewidth laser 201, a 1x2 optical fiber coupler 202, a first electro-optic intensity modulator 203, a first optical fiber ring 204, a first reflective optical electric field sensing probe 205, a first isolator 206, a first optical fiber 207, a second electro-optic intensity modulator 208, a first optical fiber amplifier 209, a second optical fiber ring 210, and a first low-speed photodetector 211.

[0073] Specifically, the output end of the first narrow linewidth laser 201 is connected with the input end of the 1x2 optical fiber coupler 202. The 1x2 optical fiber coupler 202 divides the linearly polarized laser output by the first narrow linewidth laser 201 into two linearly polarized lights according to the coupling ratio thereof and outputs the two linearly polarized lights as a first branch and a second branch.

[0074] Specifically, the first branch output by the 1x2 optical fiber coupler 202 is connected with the input end of the first electro-optic intensity modulator 203. The first electro-optic intensity modulator 203 performs double-sideband modulation on the input linearly polarized light under the modulation of the weak local oscillator sweep signal with the frequency f LO(i) ±f C ±f LO(i) (i=1, 2,..., n). Since the local oscillator signal is weak, the intensity of the generated local oscillator sideband is also weak. The 1 port of the first optical fiber ring 204 is connected with the output end of the first electro-optic intensity modulator 203, the 2 port is connected with the first reflective optical electric field sensing probe 205, and the 3 port is connected with the first isolator 206. The local oscillator light output by the first electro-optic intensity modulator 203 is input to the 1 port of the first optical fiber ring 204 and output from the 2 port to the first reflective optical electric field sensing probe 205. The first reflective optical electric field sensing probe 205 performs double-sideband modulation on the input linearly polarized light under the modulation of the unknown high-power high-frequency microwave electric field to generate a corresponding sideband on the optical carrier. Assuming that the frequency of the unknown high-power high-frequency microwave electric field is f RF ±f C ±f RFThe first electro-optic intensity modulator 203 and the first reflective optical electric field sensing probe 205 can also use other modulation methods, such as single sideband modulation, carrier-suppressed double sideband modulation, carrier-suppressed single sideband modulation, etc. The specific modulation method is determined according to actual needs. The optical signal with the local sideband and the unknown signal sideband output by the first reflective optical electric field sensing probe 205 is input to the 2-port of the first optical fiber circulator 204, and is output to the first isolator 206 through the 3-port. The output end of the first isolator 206 is connected with the first optical fiber 207 for generating stimulated Brillouin scattering. The optical signal output by the first isolator 206 is input to the first optical fiber 207 for generating stimulated Brillouin scattering as the signal light to be amplified.

[0075] Specifically, the second branch output by the 1x2 optical fiber coupler 202 is connected with the input end of the second electro-optic intensity modulator 208. The second electro-optic intensity modulator 208 performs carrier-suppressed double sideband modulation on the input linearly polarized light under the modulation of the pump sweeping signal with the frequency f P(i) ±f C ±f P(i) (i=1, 2,..., n). The output end of the second electro-optic intensity modulator 208 is connected with the input end of the first optical fiber amplifier 209. The output light of the second electro-optic intensity modulator 208 is input and amplified by the first optical fiber amplifier 209, and is output from the output end of the first optical fiber amplifier 209 as pump light after amplification. The 1-port of the second optical fiber circulator 210 is connected with the output end of the first optical fiber amplifier 209, the 2-port of the second optical fiber circulator 210 is connected with the first optical fiber 207 for generating stimulated Brillouin scattering, and the 3-port of the second optical fiber circulator 210 is connected with the input end of the first low-speed photodetector 211. The pump light is input to the 1-port of the second optical fiber circulator 210 and is input to the first optical fiber 207 for generating stimulated Brillouin scattering through the 2-port.

[0076] Specifically, the output light of the first branch and the pump light output by the second branch are transmitted in the first optical fiber 207 for generating stimulated Brillouin scattering in opposite directions. When the pump light power reaches the fiber stimulated Brillouin threshold, the stimulated Brillouin effect will occur in the fiber, and the pump light sideband f C ±f P(i) ±f C ±f P(i) -f B(i = 1, 2, …, n). Since the target intermediate frequency signal frequency is kHz ~ MHz order, one of the local oscillator sidebands on the optical carrier is also in the Stokes gain spectrum and is amplified. The output light of the first optical fiber 207 for generating stimulated Brillouin scattering contains the Stokes gain sideband and the local oscillator sideband (the single sideband is amplified by the Stokes gain sideband) and the unknown signal sideband which moves in the frequency domain with the frequency scanning, and the output light is input via the 2-port input of the second optical fiber circulator 210 and output from the 3-port to the first low-speed photodetector 211, and after the photoelectric conversion of the first low-speed photodetector 211 with square rate characteristics, the output mixed frequency signal.

[0077] As shown in Figure 3 , when f RF >f B , the measured microwave signal is not scanned, and the condition |f RF -f P | = f B is not met, the unknown microwave signal sideband has not been amplified, the difference frequency signal |f RF -f LO | ≠ f IF generated by the mixed frequency down-conversion, and therefore no target intermediate frequency signal with a frequency of f IF is generated in the mixed frequency signal output by the detection assembly 104.

[0078] As shown in Figure 4 , when f RF >f B , the measured microwave signal is scanned, and the condition |f RF -f P | = f B is met, the unknown microwave signal sideband is amplified, the difference frequency signal |f RF -f LO | = f IF generated by the mixed frequency down-conversion, and therefore the target intermediate frequency signal with a frequency of f IF is generated in the mixed frequency signal output by the detection assembly 104.

[0079] Example 2

[0080] This embodiment provides a detection assembly which can realize a detection function, as shown in Figure 5As shown, a parallel type is adopted between the electro-optical intensity modulator for modulating the local oscillator signal and the reflective optical electric field sensing probe. The second narrow linewidth laser 301, the 1x3 optical fiber coupler 302, the third optical fiber circulator 303, the second reflective optical electric field sensing probe 304, the second isolator 305, the second optical fiber 306, the third electro-optical intensity modulator 307, the second optical fiber amplifier 308, the fourth optical fiber circulator 309, the fourth electro-optical intensity modulator 310, the 2x1 optical fiber coupler 311, and the second low-speed photodetector 312 are mainly composed.

[0081] Specifically, the output end of the second narrow linewidth laser 301 is connected with the input end of the 1x3 optical fiber coupler 302. The 1x3 optical fiber coupler 302 divides the linearly polarized laser output by the second narrow linewidth laser 301 into three linearly polarized lights according to the coupling ratio of the 1x3 optical fiber coupler 302, and outputs the three linearly polarized lights as a first branch, a second branch, and a third branch.

[0082] Specifically, the first branch output by the 1x3 optical fiber coupler 302 is connected with the 1 port of the third optical fiber circulator 303. The 2 port of the third optical fiber circulator 303 is connected with the second reflective optical electric field sensing probe 304. The 3 port of the third optical fiber circulator 303 is connected with the second isolator 305. The linearly polarized light output by the 1x3 optical fiber coupler 302 is input into the 1 port of the third optical fiber circulator 303 and output from the 2 port to the second reflective optical electric field sensing probe 304. The second reflective optical electric field sensing probe 304 performs double sideband modulation on the input linearly polarized light under the modulation of the unknown high-power high-frequency microwave electric field to generate corresponding sidebands on the optical carrier. Assuming that the frequency of the unknown high-power high-frequency microwave electric field is f RF , the unknown microwave signal sideband generated on the optical carrier is f C ±f RF . The second reflective optical electric field sensing probe 304 can also use other modulation modes to modulate the unknown high-power high-frequency microwave electric field, such as single sideband modulation, carrier-suppressed double sideband modulation, carrier-suppressed single sideband modulation, etc. The specific modulation mode is determined according to the characteristics of the second reflective optical electric field sensing probe 304. The optical signal with the unknown signal sideband output by the second reflective optical electric field sensing probe 304 is input into the 2 port of the third optical fiber circulator 303 and output from the 3 port to the second isolator 305. The output end of the second isolator 305 is connected with the second optical fiber 306 for generating stimulated Brillouin scattering. The optical signal output by the second isolator 305 is input into the second optical fiber 306 for generating stimulated Brillouin scattering as the signal light to be amplified.

[0083] Specifically, the second branch output by the 1x3 optical fiber coupler 302 is connected with the input end of the third electro-optical intensity modulator 307. The third electro-optical intensity modulator 307 modulates the linearly polarized light at a frequency of f P(i)The input linearly polarized light is carrier-suppressed double sideband modulated under the modulation of the pump sweeping signals (i = 1, 2,..., n) to generate two pump sidebands f C ±f P(i) (i = 1, 2,..., n) at the output of the third electro-optic intensity modulator 307. The output light of the third electro-optic intensity modulator 307 is input into and amplified by the second fiber amplifier 308, and is output from the output end of the second fiber amplifier 308 as pump light. The 1 port of the fourth fiber circulator 309 is connected with the output end of the second fiber amplifier 308, the 2 port of the fourth fiber circulator 309 is connected with the second fiber 306 for generating stimulated Brillouin scattering, and the 3 port of the fourth fiber circulator 309 is connected with one of the input ends of the 2×1 fiber coupler 311. The pump light is input into the 1 port of the fourth fiber circulator 309 and input into the second fiber 306 for generating stimulated Brillouin scattering from the 2 port.

[0084] Specifically, the to-be-amplified signal light output by the first branch and the pump light output by the second branch are transmitted in the second fiber 306 for generating stimulated Brillouin scattering in opposite directions. When the pump light power reaches the fiber stimulated Brillouin threshold, the stimulated Brillouin effect occurs in the fiber, and the pump light sideband f C ±f P(i) (i = 1, 2,..., n) is generated under the action of the fiber stimulated Brillouin scattering, and the output light of the second fiber 306 for generating stimulated Brillouin scattering contains the Stokes gain sideband f C ±f P(i) -f B (i = 1, 2,..., n). The output light of the second fiber 306 for generating stimulated Brillouin scattering contains the Stokes gain sideband moving in the frequency domain with the frequency scanning, and the unknown signal sideband, and the output light is input via the 2 port of the fourth fiber circulator 309 and output from the 3 port to one of the input ends of the 2×1 fiber coupler 311.

[0085] Specifically, the third branch output by the 1×3 fiber coupler 302 is connected with the input end of the fourth electro-optic intensity modulator 310. The fourth electro-optic intensity modulator 310 is double sideband modulated under the modulation of the strong local oscillator sweeping signal (i = 1, 2,..., n) to generate a strong local oscillator sideband f LO(i) ±f C ±f LO(i)(i = 1, 2, ..., n). The fourth electro-optic intensity modulator 310 can also use other modulation methods to modulate the unknown high-power high-frequency microwave electric field, such as single-sideband modulation, carrier-suppressed double-sideband modulation, carrier-suppressed single-sideband modulation, etc., the specific modulation method is determined according to actual needs. The output terminal of the fourth electro-optic intensity modulator 310 is connected to one of the input terminals of the 2×1 fiber coupler 311. The local oscillator light output from the fourth electro-optic intensity modulator 310 is input to the 2×1 fiber coupler 311.

[0086] Specifically, the 2×1 fiber optic coupler 311 outputs the signals received from the two input terminals to the second low-speed photodetector 312, and outputs a mixed signal after photoelectric conversion by the second low-speed photodetector 312 which has a square law characteristic.

[0087] like Figure 6 The diagram shows the detection component 104 in embodiment 2 when f RF >f B The frequency distribution diagram when the microwave signal under test is not detected indicates that the condition |f is not met. RF -f P |=f B The unknown microwave signal sideband has not yet been amplified, and the difference frequency signal |f generated by the mixing and downconversion is... RF -f LO |≠f IF Therefore, the mixing signal output by the detection component 104 does not generate a frequency of f. IF The target intermediate frequency signal.

[0088] like Figure 7 The diagram shows the detection component 104 in embodiment 2 when f RF >f B The frequency distribution diagram when the microwave signal under test is scanned at this time satisfies the condition |f RF -f P |=f B The sideband of the unknown microwave signal is amplified, and the difference frequency signal |f generated by the mixing and downconversion is... RF -f LO |=f IF Therefore, the mixing signal output by the detection component 104 generates a frequency of f. IF The target intermediate frequency signal.

[0089] This invention also provides a measurement method based on an unknown high-power high-frequency microwave electric field measuring device, such as... Figure 8 As shown, the specific measurement method is as follows:

[0090] S1: Basic parameter measurement and setting.

[0091] The measurement accuracy of the detection assembly 104 is calibrated by using a standard electric field, forming calibration data and determining the optimal value during calibration. The intensity of the local signal and the pump signal are set at the optimal value. The Brillouin frequency shift value f B of the optical fiber used to generate stimulated Brillouin scattering in the detection assembly 104 is measured by using a spectrum analyzer LO . Let the frequency of the local signal be f RF , the frequency of the unknown microwave signal be f IF , the frequency of the intermediate frequency signal after mixing of the two be f RF = |f LO -f P |, the frequency of the pump signal be f RF , and the condition for the sideband of the unknown microwave signal on the optical carrier to be amplified with the maximum gain be |f P -f B |= f IF . Let the frequency of the intermediate frequency signal f LO(0) be a constant value (e.g. 10 MHz) in the range of kHz to MHz.

[0092] S2: System initialization.

[0093] The reflective optical electric field sensing probe in the detection assembly 104 is placed in the electric field of the unknown microwave signal, and the measurement device is started. The sweep assembly 103 sends a set of local signals and pump signals with frequencies f P(0) and f IF to the detection assembly 104. The signal acquisition unit 105 receives the mixed frequency signals output by the detection assembly 104 and sends them to the data processing unit 101, realizing the initialization of the measurement device.

[0094] S3: The intensity I IF of the intermediate frequency signal with frequency f IF is monitored by the data processing unit 101.

[0095] S31: If the intensity I IF of the intermediate frequency signal and the intensity I noise of the noise satisfy I IF >I noise , it is proved that the unknown microwave signal is detected. Then, the frequency f RF and the intensity I RF of the unknown microwave signal are demodulated and output according to the frequency relationship between the signals in the foregoing S1. The intensity I RF is positively correlated with I IF , and the specific value is determined according to the calibration data. If the measurement of the unknown microwave signal is completed, the measurement device stops working. If the measurement still needs to continue, the value of I IF is continuously monitored according to step S3.

[0096] S32: If the intensity I IFWith noise intensity I noise Satisfy I IF ≤I noise If the result is positive, it proves that no unknown microwave signal was detected, and proceed to step S4.

[0097] S4: Measuring f IF Is there a difference frequency signal (Δf) within the range of ±Δf? <f IF (To be determined based on actual needs and circumstances).

[0098] S41: If the frequency of occurrence is f IF The difference frequency signal of ', the data processing unit 101 according to f IF '=|f RF -f LO The frequency f is calculated based on the frequency relationship between '| and S1 mentioned above. IF The target intermediate frequency signal requires the local oscillator frequency f LO(M) and pump signal frequency f P(M) , where f LO 'for f IF The local oscillator signal frequency at that time is determined. Subsequently, the data processing unit 101 sends a corresponding command to the control component 102 based on the processing result. The control component 102 then controls the frequency sweep component 103 to send the target frequency to the detection component 104 according to the received command. At this time, the unknown microwave signal sideband is amplified and down-converted to a frequency of f. IF The intermediate frequency signal is used to output unknown microwave signal parameters. If the measurement of the unknown microwave signal is completed, the measuring device stops working. If further measurement is required, monitoring I continues according to step S3. IF value.

[0099] S41: If f IF If there is no difference frequency signal within the range of ±△f, proceed to step S5.

[0100] S5: Initiate frequency shift scanning to locate unknown microwave signals and measure f. IF Is there a difference frequency signal within the range of ±△f? Let f be the local oscillator sweep frequency signal and the pump sweep frequency signal, respectively. LO(i) and f P(i) Where i = 1, 2, ..., n, and the two satisfy the relation |f LO(i) -f P(i) |=f B ±f IF .

[0101] S51: If the frequency of occurrence is f IF The difference frequency signal of ', the data processing unit 101 according to f IF '=|f RF -f LO The frequency f is calculated based on the frequency relationship between '| and S1 mentioned above.IF the target intermediate frequency signal LO(M) and the pump signal frequency f P(M) and sends a corresponding instruction to the control component 102, which controls the sweeping component 103 to send the target frequency to the detection component 104. At this time, the unknown microwave signal sideband is amplified and down-converted to an intermediate frequency signal with a frequency of f IF , and the unknown microwave signal parameters are output. If the unknown microwave signal measurement has been completed, the measurement device ends work. If the measurement still needs to continue, the I IF value is continuously monitored according to step S3.

[0102] S52: If there is no beat signal in the f IF ±△f range, it indicates that the frequency (intensity) of the microwave signal to be measured is out of range or the measurement device is malfunctioning, and the measurement needs to be ended and problems need to be found to perform system debugging.

[0103] Based on the measurement method, the frequency and field intensity of the unknown microwave signal can be measured. If the frequency of the unknown microwave signal changes, the target intermediate frequency signal with a frequency of f IF will not be generated, and the system determines whether the unknown microwave signal needs to be searched again according to the intensity information of the detected target intermediate frequency signal, so as to realize adaptive adjustment of the scanning parameters and long-time measurement.

[0104] The above-described embodiments are only a preferred scheme of the present application, and are not intended to limit the present application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, any technical scheme obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present application.

Claims

1. A measurement method using an unknown high-power high-frequency microwave electric field measurement device based on frequency shift scanning, characterized by, The unknown high-power high-frequency microwave electric field measuring device based on frequency shift scanning comprises a data processing unit (101), a control component (102), a sweep component (103), a detection component (104) and a signal acquisition unit (105); the control component (102) is used for controlling the signal acquisition of the signal acquisition unit (105) and the scanning intensity and frequency of the sweep component (103), and feeding back control information to the data processing unit (101); the sweep component (103) is used for sending local oscillation sweep signals and pump sweep signals to modulate the detection component (104); the detection component (104) is used for receiving unknown microwave signals, and outputting the unknown microwave signals to the signal acquisition unit (105) after Brillouin selective single sideband amplification and frequency mixing conversion; the signal acquisition unit (105) is used for acquiring low-frequency mixing signals output by the detection component (104) and sending the low-frequency mixing signals to the data processing unit (101); the data processing unit (101) is used for receiving signals transmitted back by the signal acquisition unit (105) and extracting intensity information of intermediate frequency signals in a specified frequency range, receiving frequency and intensity information of local oscillation signals and pump signals fed back by the control component (102), processing data and judging whether the frequency of the unknown microwave signal is scanned, sending corresponding instructions to the control component (102) according to the judgment result, and outputting intensity and frequency information of the unknown microwave signal when the frequency of the unknown microwave signal is scanned. The measuring method is specifically as follows: S1: measuring the detection component (104) with a standard electric field to calibrate the measurement accuracy, forming calibration data and determining the optimal value; setting the strength of the local signal and the pump signal at the optimal value; measuring the Brillouin frequency shift value of the optical fiber for generating stimulated Brillouin scattering in the detection component (104) with a spectrum analyzer f B ; the local signal frequency is f LO , the unknown microwave signal frequency is f RF , and the intermediate frequency signal frequency after mixing of the two is f IF = f RF - f LO | the pump signal frequency is f P , and the condition for the unknown microwave signal sideband on the optical carrier to be amplified with the maximum gain is f RF - f P |= f B ; the intermediate frequency signal frequency f IF is a certain constant value in the range of kHz~MHz; S2: put the reflective optical electric field sensing probe in the detection component (104) into the unknown microwave signal electric field, start the measurement device; the sweep component (104) sends a group of frequency of 1 f LO(0) And f P(0) The local oscillator signal and the pump signal to the detection component (104); the signal acquisition unit (105) receives the mixed frequency signal output by the detection component (104) and sends it to the data processing unit (101), realizing the initialization of the measurement device; S3: monitoring the intensity of the intermediate frequency signal with a frequency of f IF S3: monitoring the intensity of the intermediate frequency signal with a frequency of I IF ; S31: if the intermediate frequency signal strength I IF and the noise strength I noise satisfies I IF > I noise , then it is proved that the unknown microwave signal is detected; then the frequency of the unknown microwave signal is demodulated and output according to the frequency relationship between the signals in the aforementioned S1 f RF and the strength I RF ; if the unknown microwave signal measurement has been completed, the measuring device stops working; if it still needs to continue measuring, it continues to monitor according to step S3 I IF ; S32: if the intermediate frequency signal strength I IF with the noise intensity I noise satisfies I IF ≤ I noise then it is proved that the unknown microwave signal is not detected, and step S4 is entered; S4: Measure f IF ±△ f whether there is a beat signal within the range; S41: if the difference frequency signal with frequency f IF ’ is generated, the data processing unit (101) calculates the local oscillator signal frequency f IF ’ f RF f LO ’ and the pump signal frequency f IF needed for generating the target intermediate frequency signal with frequency f LO(M) f P(M) , wherein f LO ’ is the local oscillator signal frequency when f IF ’ ; then the data processing unit (101) sends corresponding instructions to the control component (102) according to the processing result, and the control component (102) controls the sweep component (103) to send the target frequency to the detection component (104) according to the received instructions; at this time, the unknown microwave signal sideband is amplified and down-converted to an intermediate frequency signal with frequency f IF , and the unknown microwave signal parameters are output; if the unknown microwave signal measurement has been completed, the measurement device stops working; if the measurement still needs to continue, the value of I IF is continuously monitored according to step S3.​​​ S42: If f IF ±△ f no beat signal in the range, go to step S5; S5: start frequency shift scanning to find unknown microwave signal, measure f IF ±△ f whether there is a difference frequency signal in the range; set the local frequency sweep signal and the pump sweep signal as f LO(i) and f P(i) , wherein i =1, 2,..., n , both satisfy the relationship f LO(i) - f P(i) |= f B ± f IF ; S51: if the difference frequency signal with frequency f IF ’ is generated, the data processing unit (101) calculates the frequency of the local oscillator signal f IF ’ f RF f LO ’ and the frequency of the pump signal f IF required for generating the target intermediate frequency signal with frequency f LO(M) f P(M) and sends corresponding instructions to the control component (102), which controls the sweep component (103) to send the target frequency to the detection component (104); at this time, the unknown microwave signal sideband is amplified and down-converted to an intermediate frequency signal with frequency f IF , and the unknown microwave signal parameters are output; if the unknown microwave signal measurement has been completed, the measurement device stops working; if the measurement still needs to continue, the value of I IF is continuously monitored according to step S3.​​​ S52: If f IF ±△ f If there is no beat signal in the range, it indicates that the frequency or intensity of the microwave signal to be measured is out of range, or the measurement device is malfunctioning, and the measurement needs to be ended and the problem needs to be found to perform system debugging.

2. The measurement method according to claim 1, characterized in that, The detection component (104) can modulate the unknown microwave signal to the optical carrier to form the unknown microwave signal sideband, and the detection component (104) is modulated by the local oscillation sweep signal and the pump sweep signal to generate the local oscillation sideband and the pump sideband which move on the frequency spectrum, and the pump sideband generates the Stokes gain sideband due to the stimulated Brillouin effect; the unknown microwave signal sideband will be amplified if it is in the Stokes gain sideband, and the amplified or unamplified unknown microwave signal sideband is mixed with the local oscillation sideband to generate a mixing signal and output to the signal acquisition unit (105).

3. The measurement method according to claim 1, characterized in that, The detection component (104) comprises a light source, an electro-optic intensity modulator for modulating the local oscillation signal, an electro-optic intensity modulator for modulating the pump signal, a reflective optical electric field sensing probe for receiving the unknown microwave signal and modulating the unknown microwave signal to the optical carrier, a fiber amplifier for amplifying the pump light, an optical fiber for generating the stimulated Brillouin scattering, an isolator for isolating the forward pump light, and a low-speed photodetector for converting the optical signal into an electrical signal.

4. The measurement method according to claim 3, characterized in that, The optical fiber is a single-mode optical fiber or a high-nonlinear optical fiber with a length of more than 5 km.

5. The measurement method according to claim 3, characterized in that, The electro-optic intensity modulator for modulating the pump signal works in a carrier-suppressed double-sideband modulation mode; the electro-optic intensity modulator for modulating the local oscillation signal and the reflective optical electric field sensing probe work in one of a double-sideband modulation mode, a single-sideband modulation mode, a carrier-suppressed double-sideband modulation mode or a carrier-suppressed single-sideband modulation mode.

6. The measurement method according to claim 3, characterized in that, The electro-optic intensity modulator for modulating the local oscillation signal and the reflective optical electric field sensing probe are connected in a cascade mode or a parallel mode.

7. The method of measuring of claim 1, wherein, The sweep component (103) comprises a first microwave signal source for generating a local signal and a second microwave signal source for generating a pump signal; the local signal generated by the first microwave signal source and the pump signal generated by the second microwave signal source can realize synchronous scanning, and the frequency difference between the two remains unchanged.

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