Microwave photon frequency measurement method and device based on photoelectric oscillator

Abstract

The invention discloses a microwave photon frequency measurement method and device based on a photoelectric oscillator combined with an I / Q demodulation technology, and belongs to the technical field of microwave photonics. The device is composed of a photoelectric oscillation module based on a stimulated Brillouin scattering effect, a multi-local oscillator group based on a frequency shifter array and an I / Q demodulation module based on a Hartley structure, a low-power radio frequency signal is sensed and amplified by using a photoelectric oscillator, coexistence of a plurality of local oscillator signals is realized by using the frequency shifter array, down-conversion is performed on a received high-frequency signal, and the low-power radio frequency signal is obtained. And then a channelized receiving system is constructed through an I / Q demodulation coherent receiving technology based on a Hartley structure and a multi-local oscillator signal. The advantages of the microwave photon technology in the aspects of broadband microwave signal transmission, processing and the like are fully utilized, a high-performance and multifunctional microwave photon radio frequency signal receiving system for radar, electronic warfare and communication application is achieved, and a new solution thought is provided for comprehensive improvement of the overall performance of the radio frequency signal receiving system.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave photonics, and in particular relates to a microwave photon frequency measurement method and device based on a photoelectric oscillator combined with an I / Q demodulation technology. Background Art

[0002] Microwave frequency measurement is widely used in fields such as communications, electronic warfare, and radar, providing a basic guarantee for subsequent signal processing and playing an important role. A high-performance receiving system should have a large instantaneous detection bandwidth, high resolution, and a large dynamic range, as well as the ability to detect and receive multi-frequency points and multi-form signals arriving at the same time without distortion, and have the function of real-time processing. At the same time, when detecting low-power signals, the improvement in sensitivity can greatly improve the performance of the receiver. Traditional electronic frequency measurement technology is limited by its inherent "electronic bottleneck", and its sensitivity is low, the frequency measurement system is expensive, and it is susceptible to electromagnetic interference. In recent years, as the electromagnetic environment has become increasingly complex and harsh, traditional frequency measurement methods have found it difficult to achieve large-bandwidth, low-error frequency measurements.

[0003] As an emerging technology, microwave photonic technology combines the advantages of microwave technology and photonic technology, bringing new possibilities for the structural design of new instantaneous frequency measurement receivers. It has the potential to provide broadband frequency measurement, low loss, anti-interference, and small and portable system solutions, and has shown advantages different from traditional instantaneous frequency measurement receivers in the fields of broadband microwave signal transmission, perception, and processing. Generally speaking, the signal processing system based on microwave photonics takes advantage of the high bandwidth of optoelectronic devices, and its loss is extremely low, which avoids the electronic bottleneck well. Therefore, microwave photonic frequency measurement technology provides a new idea for the reception and processing of microwave signals, and lays the foundation for my country's comprehensive breakthroughs in modern electronic warfare, wireless communications and other fields. Summary of the invention

[0004] The purpose of the present invention is to provide a microwave photon frequency measurement method and device based on an optoelectronic oscillator. The present invention uses an optoelectronic oscillator to sense and amplify low-power radio frequency signals, adopts a frequency shifter array to realize the coexistence of multiple local oscillator signals, down-converts the received high-frequency signal, and then constructs a channelized receiving system through the I / Q demodulation coherent receiving technology based on the Hartley structure and multiple local oscillator signals, thereby reducing the pressure of signal processing and realizing high-precision reception of low-power microwave signals. The present invention has the characteristics of wide frequency range, high measurement accuracy, large dynamic range, and high sensitivity, and makes full use of the advantages of microwave photon technology in broadband microwave signal transmission and processing, etc., to realize a high-performance, multi-functional microwave photon radio frequency signal receiving system for radar, electronic warfare and communication applications, and provides a new solution for the overall improvement of the overall performance of the radio frequency signal receiving system.

[0005] The microwave photon frequency measurement device based on an optoelectronic oscillator according to the present invention is composed of an optoelectronic oscillation module based on the stimulated Brillouin scattering effect, a multi-local oscillator group based on a frequency shifter array, and an I / Q demodulation module based on a Hartley structure. Its structure is as shown in Figure 1 the figure.

[0006] Among them, the optoelectronic oscillation module based on the stimulated Brillouin scattering effect is composed of a first tunable laser, a first optical coupler, a first polarization controller, a phase modulator, an isolator, a highly nonlinear optical fiber, a circulator, a second tunable laser, a second polarization controller, a first erbium-doped fiber amplifier, a second optical coupler, a second erbium-doped fiber amplifier, a photodetector, a radio frequency amplifier, a microwave signal generator, and a first electrical coupler. The 2-port of the first tunable laser, the first optical coupler, the first polarization controller, the phase modulator, the isolator, the highly nonlinear optical fiber, and the circulator are connected in sequence. The 1-port of the second tunable laser, the second polarization controller, the first erbium-doped fiber amplifier, and the circulator are connected in sequence. The 3-port of the circulator, the second optical coupler, the second erbium-doped fiber amplifier, the photodetector, the radio frequency amplifier, the first electrical coupler, and the phase modulator are connected in sequence. The microwave signal generator is connected to the first electrical coupler.

[0007] The multi-local oscillator group based on the frequency shifter array is composed of an arbitrary waveform generator, a dual-parallel Mach-Zehnder modulator, a first DC voltage stabilizer, a second DC voltage stabilizer, a third DC voltage stabilizer, a first frequency shifter, a second frequency shifter, a third frequency shifter, a fourth frequency shifter, a fifth frequency shifter, a sixth frequency shifter, a third optical coupler, a fifth optical coupler, a seventh optical coupler, and a ninth optical coupler. Among them, the first frequency shifter, the second frequency shifter, the third frequency shifter, the fourth frequency shifter, the fifth frequency shifter, and the sixth frequency shifter are integrated on the same acousto-optic frequency shifter component and act as a 6-channel frequency shifter array in the multi-local oscillator group. The dual-parallel Mach-Zehnder modulator is composed of a first Mach-Zehnder modulator, a second Mach-Zehnder modulator, and a third Mach-Zehnder modulator. The first Mach-Zehnder modulator and the second Mach-Zehnder modulator are embedded as two branch signal modulators on the two interference arms of the third Mach-Zehnder modulator. Electrical signals generated by the first output channel and the second output channel of the arbitrary waveform generator are respectively input through the first drive port and the second drive port to drive the first Mach-Zehnder modulator and the second Mach-Zehnder modulator. The first DC voltage stabilizer, the second DC voltage stabilizer, and the third DC voltage stabilizer respectively provide bias voltages for the first Mach-Zehnder modulator, the second Mach-Zehnder modulator, and the third Mach-Zehnder modulator to control the working states of the corresponding Mach-Zehnder modulators and further control the working state of the dual-parallel Mach-Zehnder modulator.

[0008] The I / Q demodulation module based on the Hartley structure consists of six demodulation channels. Each channel includes a 90-degree optical coupler, two balanced detectors, and a 90-degree electrical coupler. That is, the first demodulation channel of the present invention is composed of a first 90-degree optical coupler, a first balanced detector, a second balanced detector, and a first 90-degree electrical coupler. The first balanced detector and the second balanced detector are connected in parallel between the first 90-degree optical coupler and the first 90-degree electrical coupler; the second demodulation channel is composed of a second 90-degree optical coupler, a third balanced detector, a fourth balanced detector, and a second 90-degree electrical coupler. The third balanced detector and the fourth balanced detector are connected in parallel between the second 90-degree optical coupler and the second 90-degree electrical coupler; the third demodulation channel is composed of a third 90-degree optical coupler, a fifth balanced detector, a sixth balanced detector, and a third 90-degree electrical coupler. The fifth balanced detector and the sixth balanced detector are connected in parallel between the third 90-degree optical coupler and the third 90-degree electrical coupler; the fourth demodulation channel is composed of a fourth 90-degree optical coupler, a seventh balanced detector, an eighth balanced detector, and a fourth 90-degree electrical coupler. The seventh balanced detector and the eighth balanced detector are connected in parallel between the fourth 90-degree optical coupler and the fourth 90-degree electrical coupler; the fifth demodulation channel is composed of a fifth 90-degree optical coupler, a ninth balanced detector, a tenth balanced detector, and a fifth 90-degree electrical coupler. The ninth balanced detector and the tenth balanced detector are connected in parallel between the fifth 90-degree optical coupler and the fifth 90-degree electrical coupler; the sixth demodulation channel is composed of a sixth 90-degree optical coupler, an eleventh balanced detector, a twelfth balanced detector, and a sixth 90-degree electrical coupler. The eleventh balanced detector and the twelfth balanced detector are connected in parallel between the sixth 90-degree optical coupler and the sixth 90-degree electrical coupler; in each channel, the 90-degree optical coupler outputs a pair of in-phase signals and a pair of quadrature signals. The two pairs of signals are respectively beat by two balanced detectors to obtain the in-phase demodulation signal I and the quadrature demodulation signal Q, and then the demodulation signal is obtained through the coupling of the 90-degree electrical coupler; the second optical coupler is connected to the first 90-degree optical coupler through the fourth optical coupler, the fourth optical coupler is connected to the second 90-degree optical coupler through the sixth optical coupler, the sixth optical coupler is connected to the third 90-degree optical coupler through the eighth optical coupler, the eighth optical coupler is connected to the fourth 90-degree optical coupler through the tenth optical coupler, and the tenth optical coupler is connected to the fifth 90-degree optical coupler and the sixth 90-degree optical coupler through the twelfth optical coupler; the first frequency shifter is respectively connected to the first 90-degree optical coupler and the second frequency shifter through the third optical coupler, the second frequency shifter is respectively connected to the second 90-degree optical coupler and the third frequency shifter through the fifth optical coupler, the third frequency shifter is respectively connected to the third 90-degree optical coupler and the fourth frequency shifter through the seventh optical coupler, the fourth frequency shifter is respectively connected to the fourth 90-degree optical coupler and the fifth frequency shifter through the ninth optical coupler, the fifth frequency shifter is respectively connected to the fifth 90-degree optical coupler and the sixth frequency shifter through the eleventh optical coupler, and the sixth frequency shifter is connected to the sixth 90-degree optical coupler.

[0009] When the system starts to work, a continuous light beam with a frequency of f c is emitted by the first tunable laser as an optical carrier, and is split into a first branch signal and a second branch optical signal by the first optical coupler. The first branch signal aligns the polarization state of the optical signal with the main axis of the phase modulator through the first polarization controller, and then is input into the phase modulator for external modulation; the radio frequency signal with adjustable frequency and adjustable power generated by the microwave signal generator, that is, the unknown signal f x is input into the first electrical coupler as a modulation signal, and then is input into the radio frequency port of the phase modulator to participate in electro-optic modulation, obtaining the phase modulation signals f c and f c ±f x ; the output signal f c 、f c ±f x (as shown in Figure 2 (1)) of the phase modulator enters the highly nonlinear fiber after passing through the isolator (the function of the isolator is to ensure the unidirectional transmission of the optical signal and prevent damage to the device), and participates in the stimulated Brillouin scattering effect as the probe light; the second tunable laser is set to the frequency-sweeping mode, and outputs a frequency-sweeping optical signal containing the frequency f p as the third branch signal. The third branch signal passes through the second polarization controller to make the polarization states of the first branch signal and the third branch signal as consistent as possible to reduce the optical power loss; the output optical signal of the second polarization controller undergoes power compensation through the first erbium-doped fiber amplifier, and then is input to port 1 of the circulator and output from port 2 into the highly nonlinear fiber, and participates in the stimulated Brillouin scattering effect as the pump light; when the frequency difference between the pump light and the probe light is the Brillouin frequency shift amount V B , the pump light power slowly increases until it exceeds the Brillouin threshold, and then the stimulated Brillouin scattering effect occurs inside the highly nonlinear fiber. A Lorentz-shaped gain spectrum is generated at a distance of one Brillouin frequency shift amount V p from the pump frequency f B in the lower sideband direction. At the same time, a loss spectrum is generated at a distance of one Brillouin frequency shift amount V p from the pump frequency f B in the upper sideband direction (as shown in Figure 2 (2), the dotted line represents the f p frequency-sweeping process, and the dotted line spectrum moves towards the solid line spectrum. When the solid line is aligned with the center of the gain spectrum and the modulation sideband). When the probe light sidebands output by the phase modulator are within the gain spectrum and the loss spectrum, the balance of the probe light sidebands will be broken (as shown in Figure 2(As shown in (3), the sidebands in the gain spectrum are amplified, and the sidebands in the loss spectrum are suppressed). This process is the process of converting phase modulation into intensity modulation. Since both the gain spectrum and the loss spectrum are Lorentz-shaped spectral lines, during the frequency scanning process of the second tunable laser, the change in the position of the gain spectrum will cause a change in the amplitude of the sidebands of the probe light. When a microwave signal with an unknown frequency of f x modulates the optical carrier, the gain spectrum generated by the stimulated Brillouin scattering effect will generate gain for the probe light during the frequency scanning process, that is, at f c -f x =f p -V B . After being processed by the stimulated Brillouin scattering effect, the frequencies that break the sideband balance are f c , f c -f x (amplified by the gain spectrum), f c +f x (suppressed by the loss spectrum). The Stokes light enters the second port of the circulator and exits from the third port, and then enters the second optical coupler and is divided into a fourth branch signal and a fifth branch signal (the two signals are the same). The fourth branch signal is amplified by the second erbium-doped fiber amplifier and then input into the photodetector for photoelectric conversion. The beat frequency obtains an electrical signal with the same frequency of f x . This electrical signal is then amplified by the RF amplifier and enters the first electrical coupler; the microwave signal to be measured with a frequency of f x generated by the microwave signal generator is input into the first electrical coupler. After being combined with the electrical signal output by the RF amplifier, it is used as a modulation signal and input into the RF port of the phase modulator for secondary modulation to complete the closed-loop of the feedback loop. The main function of the RF amplifier is to compensate for the loop attenuation of the fourth branch signal, make the closed-loop gain of the optoelectronic oscillation module greater than 1, so that the optoelectronic oscillation module can have a stable oscillation output signal f c , f c -f x , f c +f x , that is, the optical carrier radio frequency signal of the fifth branch, as Figure 3(1). The fifth branch signal is input into the fourth optical coupler and is divided into an eighth branch signal and a ninth branch signal. The eighth branch signal, as the first optical carrier radio frequency signal, is input into the radio frequency port of the first 90-degree optical coupler and enters the first demodulation channel to participate in demodulation; the ninth branch signal is input into the sixth optical coupler and is divided into a twelfth branch signal and a thirteenth branch signal. The twelfth branch signal, as the second optical carrier radio frequency signal, is input into the radio frequency port of the second 90-degree optical coupler and enters the second demodulation channel to participate in demodulation; the thirteenth branch signal is input into the eighth optical coupler and is divided into a sixteenth branch signal and a seventeenth branch signal. The sixteenth branch signal, as the third optical carrier radio frequency signal, is input into the radio frequency port of the third 90-degree optical coupler and enters the third demodulation channel to participate in demodulation; the seventeenth branch signal is input into the tenth optical coupler and is divided into a twentieth branch signal and a twenty-first branch signal. The twentieth branch signal, as the fourth optical carrier radio frequency signal, is input into the radio frequency port of the fourth 90-degree optical coupler and enters the fourth demodulation channel to participate in demodulation; the twenty-first branch signal is input into the twelfth optical coupler and is divided into a twenty-fourth branch signal and a twenty-fifth branch signal. The twenty-fourth branch signal, as the fifth optical carrier radio frequency signal, is input into the radio frequency port of the fifth 90-degree optical coupler and enters the fifth demodulation channel to participate in demodulation; the twenty-fifth branch signal, as the sixth optical carrier radio frequency signal, is input into the radio frequency port of the sixth 90-degree optical coupler and enters the sixth demodulation channel to participate in demodulation.

[0010] The second branch signal is used as a carrier and input into the first Mach-Zehnder modulator and the second Mach-Zehnder modulator. The first output channel of the arbitrary waveform generator outputs a radio frequency local oscillator signal f with adjustable frequency lo , which is used as a modulation signal and input into the first drive port of the first Mach-Zehnder modulator to participate in modulation; the second output channel of the arbitrary waveform generator outputs a radio frequency local oscillator signal f lo ' with a phase difference of π / 2 from f lo , which is used as a modulation signal and input into the second drive port of the second Mach-Zehnder modulator to participate in modulation; adjust the output voltages of the first DC regulated power supply and the second DC regulated power supply to make the first Mach-Zehnder modulator and the second Mach-Zehnder modulator work at the minimum transmission point, realizing the double-sideband modulation state with suppressed carrier. At this time, the carrier is effectively suppressed; set the output voltage of the third DC regulated power supply to control the third Mach-Zehnder modulator to work at the quadrature bias point, so as to shift the output optical signal of the second Mach-Zehnder modulator by 90 degrees and then combine it with the output optical signal of the first Mach-Zehnder modulator and enter the third Mach-Zehnder modulator, making the dual-parallel Mach-Zehnder modulator work in the single-sideband modulation state with suppressed carrier. The single-sideband modulation signal f c -f lo (as shown in Figure 3 (2), the carrier f cis effectively suppressed) as the optical local oscillator signal. The suppressed-carrier single-sideband modulation signal (optical local oscillator signal) undergoes a first down-conversion through the first frequency shifter, and its frequency becomes f c -f lo -ΔV (ΔV is the fixed frequency shift amount of the frequency shifter), and then it is input into the third optical coupler and divided into a sixth branch signal and a seventh branch signal. The sixth branch signal is used as the first local oscillator signal and is input into the local oscillator port of the first 90-degree optical coupler and then enters the first demodulation channel to participate in demodulation; the seventh branch signal undergoes another down-conversion through the second frequency shifter, and its frequency becomes f c -f lo -2ΔV and then is input into the fifth optical coupler and divided into a tenth branch signal and an eleventh branch signal. The tenth branch signal is used as the second local oscillator signal and is input into the local oscillator port of the second 90-degree optical coupler and then enters the second demodulation channel to participate in demodulation; the eleventh branch signal undergoes another down-conversion through the third frequency shifter, and its frequency becomes f c -f lo -3ΔV and then is input into the seventh optical coupler and divided into a fourteenth branch signal and a fifteenth branch signal. The fourteenth branch signal is used as the third local oscillator signal and is input into the local oscillator port of the third 90-degree optical coupler and then enters the third demodulation channel to participate in demodulation; the fifteenth branch signal undergoes another down-conversion through the fourth frequency shifter, and its frequency becomes f c -f lo -4ΔV and then is input into the ninth optical coupler and divided into an eighteenth branch signal and a nineteenth branch signal. The eighteenth branch signal is used as the fourth local oscillator signal and is input into the local oscillator port of the fourth 90-degree optical coupler and then enters the fourth demodulation channel to participate in demodulation; the nineteenth branch signal undergoes another down-conversion through the fifth frequency shifter, and its frequency becomes f c -f lo -5ΔV and then is input into the eleventh optical coupler and divided into a twenty-second branch signal and a twenty-third branch signal. The twenty-second branch signal is used as the fifth local oscillator signal and is input into the local oscillator port of the fifth 90-degree optical coupler and then enters the fifth demodulation channel to participate in demodulation; the twenty-third branch signal undergoes another down-conversion through the sixth frequency shifter, and its frequency becomes f c -f lo -6ΔV to obtain a twenty-sixth branch signal. The twenty-sixth branch signal is used as the sixth local oscillator signal and is input into the local oscillator port of the sixth 90-degree optical coupler and then enters the sixth demodulation channel to participate in demodulation; each group of local oscillator signals and the optical carrier radio frequency signal are paired with demodulation devices to form a demodulation channel (as shown in Figure 3 (3), where f 1 、f 2 、f 3 、f 4 、f 5 、f 6The frequencies of the sixth branch signal, the tenth branch signal, the fourteenth branch signal, the eighteenth branch signal, the twenty-second branch signal, and the twenty-sixth branch signal respectively serve as the local oscillators of 6 channels).

[0011] The sixth branch signal serves as the first local oscillator signal (with a frequency of f c -f lo -ΔV), and the eighth branch signal serves as the first optical carrier radio frequency signal (E RF , with a frequency of f c 、f c -f x 、f c +f x ) are respectively input from the local oscillator port and the signal port of the first 90-degree optical coupler, and then are divided into four paths inside the 90-degree optical coupler and phase-shifted respectively (f lo-1 、f lo-2 、f lo-3 、f lo-4 ). The phase differences with the first local oscillator signal are 0, π / 2, π, and 3π / 2 respectively; the first optical carrier radio frequency signal is respectively coupled with f lo-1 、f lo-2 、f lo-3 、f lo-4 and outputs two groups of signals. One group of signals is the in-phase signals I 11 (E RF +f lo-1 ) and I 12 (E RF +f lo-3 ), and one group of signals is the quadrature signals Q 11 (E RF +f lo-2 ) and Q 12 (E RF +f lo-4 );The in-phase signals I 11 、the quadrature signals Q 11 、the in-phase signals I 12 、the quadrature signals Q 12 are respectively output from the four output ports of the first 90-degree optical coupler; the in-phase signals I 11 、I 12 have the same phase and are respectively input from the two optical input ports of the first balanced detector. The beat frequency output obtains an electrical signal, namely I 1 , with a frequency of f x -f lo -ΔV (the beat frequency results with other sidebands of the first optical carrier radio frequency signal are discarded). Similarly, the quadrature signals Q 11 、Q 12The phases are orthogonal and are respectively input from the two optical input ports of the second balanced detector. The beat frequency output obtains an electrical signal, namely Q 1 , with the same frequency f x -f lo -ΔV; I 1 、Q 1 The two signals have the same frequency, but the phase difference is π / 2. I 1 、Q 1 The two intermediate frequency signals are input into the first 90-degree electrical coupler for coupling, and the output obtains the output signal of the first demodulation channel, that is, the first demodulation signal f IF1 , with the frequency of f x -f lo -ΔV.

[0012] The signal of the tenth branch is used as the second local oscillator signal (frequency f c -f lo -2ΔV), and the signal of the twelfth branch is used as the second optical carrier radio frequency signal (E RF , with the frequency of f c 、f c -f x 、f c +f x ), and are respectively input from the signal port and the local oscillator port of the second 90-degree optical coupler. Similar to the first demodulation channel, a group of in-phase signals I 21 、I 22 are output, and a group of quadrature signals Q 21 、Q 22 . The in-phase signals I 21 、I 22 are input into the third balanced detector, and the beat frequency output obtains the electrical signal I 2 ; the quadrature signals Q 21 、Q 22 are input into the fourth balanced detector, and the beat frequency output obtains the electrical signal Q 2 . I 2 、Q 2 The two signals are input into the second 90-degree electrical coupler for coupling, and the output obtains the output signal of the second demodulation channel, that is, the second demodulation signal f IF2 , with the frequency of f x -f lo -2ΔV.

[0013] The signal of the fourteenth branch is used as the third local oscillator signal (frequency f c -f lo -3ΔV), and the signal of the sixteenth branch is used as the third optical carrier radio frequency signal (E RF , with the frequency of f c 、f c -f x 、f c +fx ) are respectively input from the signal port and the local oscillator port of the third 90-degree optical coupler, which is the same as the first demodulation channel, and a group of in-phase signals I 31 and I 32 are output, and a group of quadrature signals Q 31 and Q 32 . The in-phase signals I 31 and I 32 are input into the fifth balanced detector, and the beat frequency output obtains the electrical signal I 3 ; the quadrature signals Q 31 and Q 32 are input into the sixth balanced detector, and the beat frequency output obtains the electrical signal Q 3 . The two signals of I 3 and Q 3 are input into the third 90-degree electrical coupler for coupling, and the output obtains the output signal of the third demodulation channel, that is, the third demodulation signal f IF3 , with a frequency of f x - f lo - 3ΔV.

[0014] The eighteenth branch signal is used as the fourth local oscillator signal (with a frequency of f c - f lo - 4ΔV), and the twentieth branch signal is used as the fourth optical carrier radio frequency signal (E RF , with a frequency of f c , f c - f x , f c + f x ), and are respectively input from the signal port and the local oscillator port of the fourth 90-degree optical coupler, which is the same as the first demodulation channel, and a group of in-phase signals I 41 and I 42 are output, and a group of quadrature signals Q 41 and Q 42 . The in-phase signals I 41 and I 42 are input into the seventh balanced detector, and the beat frequency output obtains the electrical signal I 4 ; the quadrature signals Q 41 and Q 42 are input into the eighth balanced detector, and the beat frequency output obtains the electrical signal Q 4 . The two signals of I 4 and Q 4 are input into the fourth 90-degree electrical coupler for coupling, and the output obtains the output signal of the fourth demodulation channel, that is, the fourth demodulation signal f IF4 , with a frequency of f x - f lo - 4ΔV.

[0015] The twenty-second branch signal is used as the fifth local oscillator signal (with a frequency of fc -f lo -5ΔV), the twenty-fourth branch signal is used as the fifth optical carrier radio frequency signal (E RF , with a frequency of f c 、f c -f x 、f c +f x ), and are respectively input from the signal port and the local oscillator port of the fifth 90-degree optical coupler. Similar to the first demodulation channel, a set of in-phase signals I 51 、I 52 and a set of quadrature signals Q 51 、Q 52 are output. The in-phase signals I 51 、I 52 are input into the ninth balanced detector, and the beat frequency output obtains the electrical signal I 5 ; the quadrature signals Q 51 、Q 52 are input into the tenth balanced detector, and the beat frequency output obtains the electrical signal Q 5 . The two signals I 5 、Q 5 are input into the fifth 90-degree electrical coupler for coupling, and the output signal of the fifth demodulation channel is output, that is, the fifth demodulation signal f IF5 , with a frequency of f x -f lo -5ΔV.

[0016] The twenty-sixth branch signal is used as the sixth local oscillator signal (with a frequency of f c -f lo -6ΔV), the twenty-fifth branch signal is used as the sixth optical carrier radio frequency signal (E RF , with a frequency of f c 、f c -f x 、f c +f x ), and are respectively input from the signal port and the local oscillator port of the sixth 90-degree optical coupler. Similar to the first demodulation channel, a set of in-phase signals I 61 、I 62 and a set of quadrature signals Q 61 、Q 62 are output. The in-phase signals I 61 、I 62 are input into the eleventh balanced detector, and the beat frequency output obtains the electrical signal I 6 ; the quadrature signals Q 61 、Q 62 are input into the twelfth balanced detector, and the beat frequency output obtains the electrical signal Q 6 . The two signals I 6 、Q 6Two signals are input into the sixth 90-degree electrical coupler for coupling, and the output signal of the sixth demodulation channel is obtained, that is, the sixth demodulation signal f IF6 , with a frequency of f x -f lo -6ΔV.

[0017] This system can construct six channels to obtain six demodulation signals. Therefore, signals within 6 ΔV bandwidths can be processed simultaneously. By adjusting the frequency f lo of the local oscillator signal, frequency domain division can be achieved, and the frequency measurement of wideband microwave signals can be completed, that is, f x =f IFn +f lo +nΔV, where n = 1 to 6.

[0018] For the frequency measurement device of the present invention, after demodulating to obtain the intermediate frequency signal f IFn (the intermediate frequency signal f IF refers to f IF1 ~f IF6 ), it is also necessary to consider the interference of the image signal (when an unknown signal enters the channel, it will beat with the local oscillator of the corresponding channel to obtain the correct result, and it will also beat with the local oscillator of the next channel to obtain an incorrect result. However, this incorrect result is only incorrect relative to the current unknown signal. It will cause interference when the unknown signal beats with the local oscillator of the next channel to obtain the same result as the unknown signal in the next channel. At this time, it can be regarded as the image signal of the next channel) on the measurement result. The frequency of the image signal f IM is less than the frequency of the local oscillator signal and satisfies f x -f lo' =f lo' -f IM (f lo' =f lo -n×ΔV), that is, the image signal and the radio frequency signal to be measured have equal intervals from the local oscillator signal of the channel (as shown in Figure 4 (1), the local oscillator f c -f lo’ of the channel is the frequency-shifted local oscillator f c -f lo frequency-shifted n times; f c -f x and f c -f IM are the modulation sidebands of the signal to be measured and the image signal respectively). Therefore, when the signal input to the system is the image signal f IM , the same demodulation result as when the signal to be measured f x is input to the system will still be obtained, that is, the intermediate frequency signal f IFn (as shown in Figure 4(as shown in (2)). Therefore, in the present invention, the power of the image signal is suppressed by means of I / Q demodulation coherent reception. That is, when the signal to be measured and the image signal are simultaneously input into the system, the I-channel signal obtained by beat frequency of the upper path balanced detector in the demodulation module is the sum of the signal to be measured and the image signal (as shown in Figure 5 (1)), and the Q-channel signal obtained by beat frequency of the lower path balanced detector is the result of adding the signal to be measured with a phase lag of π / 2 and the image signal with a phase advance of π / 2 (as shown in Figure 5 (2)); after the I and Q channel signals are input into the 90-degree electrical coupler, the Q-channel signal is phase-shifted by 90 degrees and then coupled with the I-channel signal (as shown in Figure 5 (3)), so that the image signal can be reversed and cancelled (as shown in Figure 5 (4)). After image rejection, the interference of the image signal is excluded, and a unique mapping relationship can be established between the intermediate frequency signal obtained from this channel and the signal to be measured. According to the output channel number n and the frequency shift local oscillator signal f lo the frequency of the unknown signal can be inversely calculated as f x = f IFn + f lo + nΔV.

[0019] The present invention selects a tunable laser with a wavelength of 1530 nm to 1565 nm as the continuous wave light source; the first optical coupler is a 2:8 coupler; other optical couplers are 5:5 couplers; the bandwidth of the phase modulator is 32 GHz; the isolation degree of the isolator is greater than 40 dB; the bandwidth of the dual-parallel Mach-Zehnder modulator is 25 GHz; the bandwidth of the balanced photodetector is 22 GHz; the bandwidth of the photodetector is 40 GHz; the maximum gain of the erbium-doped fiber amplifier is 17 dB; the output bit rate of the arbitrary waveform generator can reach up to 65 Gb / s at most, and data can be output from four output channels simultaneously at most; the amplitudes of the output voltages of the first DC regulated power supply, the second DC regulated power supply, and the third DC regulated power supply are adjustable from 1 V to 20 V; the working frequency band of the RF amplifier is 50 kHz to 20 GHz, and the gain is 28 dB; the output frequency range of the microwave signal generator is 1 GHz to 70 GHz; the fixed frequency shift amount of the frequency shifter assembly is 500 MHz; the working wavelength of the 90-degree optical coupler is 1520 to 1570 nm; the working frequency of the 90-degree electrical coupler is 0.1 GHz to 0.605 GHz; the length of the highly nonlinear optical fiber is 5 km; the amplitude of the output voltage of the DC regulated power supply is adjustable from 1 V to 20 V.

[0020] The characteristics of the device of the present invention:

[0021] 1. This device constructs an optoelectronic oscillator by utilizing the stimulated Brillouin scattering (SBS) effect. The narrowband frequency selection of the SBS effect is used to avoid the use of radio frequency filters, and at the same time, it brings greater gain to the optoelectronic oscillator loop, enhancing the optoelectronic oscillator's ability to sense low-power radio frequency signals.

[0022] 2. Six local oscillator signals are generated using a dual-parallel Mach-Zehnder modulator and a frequency shifter array, thereby constructing six channels. While completing the down-conversion of the signal, the spectrum is divided, reducing the requirements for data acquisition and processing devices.

[0023] 3. The I / Q demodulation coherent reception module constructed using the Hartley structure can complete the suppression of image signals, achieving a single mapping relationship between the demodulated signal frequency value and the frequency value of the signal to be measured. Description of the Drawings

[0024] Figure 1 : Schematic diagram of the structure of a microwave photon frequency measurement device based on an optoelectronic oscillator;

[0025] Figure 2 : Spectral schematic diagram of the process of converting phase modulation into intensity modulation by the stimulated Brillouin scattering effect;

[0026] Figure 3 : Spectral schematic diagram of the channelized frequency measurement process using multiple local oscillator signals;

[0027] Figure 4 : Schematic diagram of the process of the image signal affecting the measurement result;

[0028] Figure 5 : Schematic diagram of the process of eliminating and suppressing the image signal by the I / Q demodulation module based on the Hartley structure;

[0029] Figure 6 : Electrical spectrogram of the image signal suppression result;

[0030] Figure 7 : Electrical spectrogram of the demodulated signals of six channels;

[0031] Figure 8 : Measurement error curve within the range of 2 GHz to 18 GHz for the microwave signal to be measured;

[0032] Figure 9 : Output power curve for each frequency point within the range of 2 GHz to 18 GHz when the input power is a small signal of -65 dBm.

[0033] Table 1: Channels corresponding to the frequency-shifted local oscillator frequencies and the frequency measurement ranges.

[0034]

[0035] Detailed implementation mode

[0036] Example 1:

[0037] The first tunable laser source is the TSL-510 tunable laser of Santec Corporation, and the wavelength range of the laser is 1510 nm to 1630 nm; the second tunable laser source is the TSL-550 tunable laser of Santec Corporation, and the wavelength range of the first laser is 1260 nm to 1680 nm; the first polarization controller and the second polarization controller are three-ring polarization controllers of Sichuan Ziguan Corporation, and the operating wavelength is 1260 to 1650 nm; the phase modulator is the MPZ-LN-40 of iXblue Corporation, with a bandwidth of 32 GHz, a half-wave voltage of 7 V, and an insertion loss of 2.5 dB; the dual-parallel Mach-Zehnder modulator is the MXIQER-LN-30 of iXblue Corporation, with an operating bandwidth of 25 GHz and an operating wavelength of 1530 - 1580 nm; the arbitrary waveform generator is the M8195A of Keysight Corporation; the first DC regulated power supply, the second DC regulated power supply, and the third DC regulated power supply are all GPS-2303C of GW Instek Corporation, and the output voltage amplitude is adjustable from 1 V to 20 V; the photodetector is the KG-PD-50G-A-FC of Beijing Kangguan Corporation, with a bandwidth of 50 GHz and a conversion rate of 0.55 A / W; the balanced detector is the KG-BPR-20G-A-FC of Beijing Kangguan Corporation, with a bandwidth of 40 GHz; the first electrical coupler is the power splitter AV81311 of the 41st Research Institute of China Electronics Technology Group Corporation, with a frequency range of 0 to 26.5 GHz and a power splitting ratio of 50:50; the first erbium-doped fiber amplifier and the second erbium-doped fiber amplifier are the EDFA-ILA of PulseRay Optoelectronics Corporation, with a maximum output power of 17 dBm; the RF amplifier is the MWLA-000200G28 of Fullwave Electronics Technology Co., Ltd., with a signal gain of 28 dB and an operating frequency band of 50 kHz to 20 GHz; the first optical coupler is a 20:80 single-input dual-output coupler; other optical couplers are 50:50 single-input dual-output couplers; the acousto-optic frequency shifter assembly is the SGY500-C6 of the 29th Research Institute of China Electronics Technology Group Corporation, and the assembly includes 6 frequency shifters. The 6 frequency shifters are independent of each other, with stable performance, an insertion loss between 3.3 and 4.1 dB, and a frequency shift error of each frequency shifter less than 0.1 MHz; the 90-degree optical coupler is the COH24 of Kylia Corporation, with an operating wavelength of 1520 to 1570 nm, and an insertion loss of the signal light and the local oscillator light of 7 dB; the 90-degree electrical coupler is the HC0350W03 of Yantel Corporation, with an operating frequency range of 0.1 GHz to 0.605 GHz, a return loss of 16.5 dB, an insertion loss of 0.8 dB, and a port isolation of 15 dB.

[0038] After the system is connected, turn on the device switch to put the device in the working state. First, the first tunable laser outputs an optical signal with a fixed frequency of f c = 193.414 THz (corresponding to a wavelength of 1550 nm). The optical signal is divided into a first branch signal and a second branch signal through a 20:80 first optical coupler. The first branch signal is input into the phase modulator through the first polarization controller. The microwave signal with a power of 0 dBm generated by the microwave signal generator, f x is involved in modulation. The modulated signal enters the highly nonlinear fiber through the isolator and serves as the probe light for the stimulated Brillouin scattering effect. The second tunable laser outputs a swept-frequency optical signal with a power of 5 mW, f p After being controlled by the second polarization controller, the optical power is compensated to 15 mW through the first erbium-doped fiber amplifier, enters from port 1 of the circulator, and is output from port 2 and enters the highly nonlinear fiber as the pump light for the stimulated Brillouin scattering effect.

[0039] Connect the fourth branch well. The intensity-modulated optical signal f c 、f c ±f x generated by the stimulated Brillouin scattering effect is output from port 3 of the circulator, and after passing through the second optical coupler, it is output as the fourth branch signal. Then, the optical power is amplified to -1 dBm through the second erbium-doped fiber amplifier, beat by the photodetector, and then amplified by the RF amplifier and combined with the microwave signal generated by the microwave signal generator through the first electrical coupler and input into the phase modulator as the modulation signal. Set the second tunable laser to the swept-frequency mode, and the wavelength λ p The scanning range is 1549.9 nm to 1550.2 nm. Manually adjust the frequency of the output signal of the microwave signal generator from 2 GHz in steps of 1 GHz to 18 GHz to measure 17 frequency points. When measuring a single frequency point f x , when the pump light frequency f p is scanned to f x +V B , the negative first-order modulation sideband f c -f x of the optical carrier radio frequency signal is amplified by the Brillouin gain spectrum, and the photodetector beats to obtain the signal to be measured with a frequency of f x and forms a stable oscillation. The optical carrier radio frequency signal output from the fifth branch of the optoelectronic oscillation module is divided into the eighth branch signal, the twelfth branch signal, the sixteenth branch signal, the twentieth branch signal, the twenty-fourth branch signal, and the twenty-fifth branch signal through the fourth optical coupler, the sixth optical coupler, the eighth optical coupler, the tenth optical coupler, and the twelfth optical coupler, and participates in I / Q demodulation.

[0040] The second branch signal enters the dual-parallel Mach-Zehnder modulator and is modulated by the frequency-shifted local oscillator signals with frequencies of 1.4 GHz, 4.4 GHz, 7.4 GHz, 10.4 GHz, 13.4 GHz, and 16.4 GHz generated by an arbitrary waveform generator. The outputs of the first DC voltage stabilizer, the second DC voltage stabilizer, and the third DC voltage stabilizer are set to 6.7 V, 8.0 V, and 7.5 V respectively, so that the dual-parallel Mach-Zehnder modulator operates in the single-sideband suppressed-carrier modulation state. After being modulated by the dual-parallel Mach-Zehnder modulator, the frequency-shifted local oscillator signal with a frequency of 1.4 GHz can generate a lower-sideband optical modulation signal with a frequency difference of 1.4 GHz relative to the optical carrier f c After frequency shifting by the first frequency shifter, the second frequency shifter, the third frequency shifter, the fourth frequency shifter, the fifth frequency shifter, and the sixth frequency shifter, channel local oscillator signals with frequencies of 1.9 GHz, 2.4 GHz, 2.9 GHz, 3.4 GHz, 3.9 GHz, and 4.4 GHz can be generated. The six-channel frequency measurement ranges constructed are 1.9 GHz - 2.4 GHz, 2.4 GHz - 2.9 GHz, 2.9 GHz - 3.4 GHz, 3.4 GHz - 3.9 GHz, 3.9 GHz - 4.4 GHz, and 4.4 GHz - 4.9 GHz. Therefore, the frequency-shifted local oscillator signal with a frequency of 1.4 GHz can measure signals in the range of 1.9 GHz - 4.9 GHz. The 2 GHz signal to be measured will be output at the first demodulation channel; the 3 GHz signal to be measured will be output at the third demodulation channel; the 4 GHz signal to be measured will be output at the fifth demodulation channel (frequency modulation is performed with a 1 GHz step corresponding to the previous text. For the points corresponding to the 1.4 GHz local oscillator, there is no output at the second, fourth, and sixth channels). Correspondingly, the frequency-shifted local oscillator signal with a frequency of 4.4 GHz can generate channel local oscillator signals with frequencies of 4.9 GHz, 5.4 GHz, 5.9 GHz, 6.4 GHz, 6.9 GHz, and 7.4 GHz, and the measurement range is 4.9 GHz - 7.9 GHz; the frequency-shifted local oscillator signal with a frequency of 7.4 GHz corresponds to a frequency measurement range of 7.9 GHz - 10.9 GHz; the upper limits of the frequency measurement ranges corresponding to the frequency-shifted local oscillator signals with frequencies of 10.4 GHz, 13.4 GHz, and 16.4 GHz can exceed 18 GHz, and down-conversion is completed during the demodulation process, and intermediate-frequency signals with frequencies of 0 - 500 MHz are obtained in each channel. The specific correspondence between the frequency-shifted local oscillator and the measurement channels can be seen in Table 1.

[0041] After multiple groups of local oscillator signals are constructed, the microwave signal generator is set to generate a microwave signal to be measured with a power of 1 mW and a frequency of 5.6 GHz (there is output at the first channel and the second channel, but at this time the local oscillator of the first channel is 4.9 GHz, so the first demodulation signal is greater than 500 MHz. The purpose of the system down-conversion is to reduce the frequency below 500 MHz). The output second local oscillator signal (f c-5.4 GHz, the signal of the tenth branch) and the radio-over-fiber signal (f output by the optoelectronic oscillation module c -5.6 GHz, the signal of the twelfth branch) are respectively input into the second 90-degree optical coupler of the second demodulation channel from the local oscillator port and the signal port, obtaining a set of in-phase signals and a set of quadrature signals. By beating the obtained set of in-phase signals with a third balanced detector, the I-channel signal can be obtained. By beating the obtained set of quadrature signals with a fourth balanced detector, the Q-channel signal can be obtained (the frequencies of the I and Q channel signals are both 0.2 GHz, but the phases differ by π / 2). Then, after coupling the I and Q channel signals with a second 90-degree electrical coupler, the second demodulation signal with a frequency of 0.2 GHz is finally obtained. Then, a mirror microwave signal with a power of 1 mW and a frequency of 5.2 GHz is respectively generated by a microwave signal generator (the channel local oscillator frequency is 4.4 GHz + 2 * 500 MHz = 5.4 GHz, and the measured signal and the mirror signal have equal frequency intervals from the channel local oscillator). The output signal of the second channel (i.e., the output signal of the second 90-degree electrical coupler) is observed by a spectrum analyzer, and the result is as Figure 6 shown. It can be seen that the measured signal with a frequency of 5.6 GHz and the mirror signal with a frequency of 5.2 GHz are both down-converted and demodulated to obtain the same frequency value. However, the power of the measured signal is -43 dBm, and the power of the mirror signal is -80 dBm. It can be known that the I / Q demodulation technology based on the Hartley structure suppresses the mirror frequency, and the mirror rejection ratio is 37 dB. Then, the microwave signal generator is respectively made to generate six signals with frequencies of 5.3 GHz, 11.9 GHz, 9 GHz, 15.6 GHz, 10.2 GHz, and 7.6 GHz, which are respectively output from the first demodulation channel to the sixth demodulation channel. The final demodulation result is as Figure 7 (1)-(6) shown. It can be seen that the down-conversion function of the system is complete, and each demodulation channel works normally, obtaining an intermediate frequency signal in the range of 0-500 MHz. Then, the frequency measurement error of the present invention is studied. Seventeen frequency points with an interval of 1 GHz from 2 GHz to 18 GHz are respectively measured, and the result is as Figure 8 shown. It can be obtained that the average frequency measurement error of the system of the present invention is 5.44 MHz.

[0042] Finally, the microwave signal generator is adjusted again. The input power of the radio frequency signals at the seventeen frequency points is gradually decreased from 10 dBm in steps of 5 dBm. When it is decreased to -65 dBm, a gain of more than 3 dB for the signal can be ensured, as Figure 9 shown. Therefore, the device of the present invention can measure low-power radio frequency signals with a power of -65 dBm.

Claims

1. A microwave photon frequency measurement device based on an optoelectronic oscillator, characterized in that: The invention is composed of an optoelectronic oscillation module based on stimulated Brillouin scattering effect, a multi-local oscillator group based on a frequency shifter array, and an I / Q demodulation module based on a Hartley structure, wherein the optoelectronic oscillation module based on stimulated Brillouin scattering effect is composed of a first tunable laser, a first optical coupler, a first polarization controller, a phase modulator, an isolator, a highly nonlinear optical fiber, a circulator, a second tunable laser, a second polarization controller, a first erbium-doped optical fiber amplifier, a second optical coupler, a second erbium-doped optical fiber amplifier, a photodetector, a radio frequency amplifier, a microwave signal generator, and a first electric coupler; the first tunable laser, the first optical coupler, the first polarization controller, the phase modulator, the isolator, the highly nonlinear optical fiber, and the 2nd port of the circulator are connected in sequence, the second tunable laser, the second polarization controller, the first erbium-doped optical fiber amplifier, and the 1st port of the circulator are connected in sequence, the 3rd port of the circulator, the second optical coupler, the second erbium-doped optical fiber amplifier, the photodetector, the radio frequency amplifier, the first electric coupler, and the phase modulator are connected in sequence, and the microwave signal generator is connected to the first electric coupler; The multi-local oscillator group based on the frequency shifter array is composed of an arbitrary waveform generator, a dual parallel Mach-Zehnder modulator, a first DC voltage regulator, a second DC voltage regulator, a third DC voltage regulator, a first frequency shifter, a second frequency shifter, a third frequency shifter, a fourth frequency shifter, a fifth frequency shifter, a sixth frequency shifter, a third optical coupler, a fifth optical coupler, a seventh optical coupler, and a ninth optical coupler; the dual parallel Mach-Zehnder modulator is composed of a first Mach-Zehnder modulator, a second Mach-Zehnder modulator, and a third Mach-Zehnder modulator, the first Mach-Zehnder modulator and the second Mach-Zehnder modulator are embedded in two interference arms of the third Mach-Zehnder modulator as two branch signal modulators, and the electrical signals generated by the first output channel and the second output channel of the arbitrary waveform generator are respectively inputted by the first driving port and the second driving port; the first DC voltage regulator, the second DC voltage regulator, and the third DC voltage regulator provide bias voltages for the first Mach-Zehnder modulator, the second Mach-Zehnder modulator, and the third Mach-Zehnder modulator respectively; The I / Q demodulation module based on the Hartley structure is composed of 6 demodulation channels. The first demodulation channel is composed of a first 90-degree optical coupler, a first balanced detector, a second balanced detector and a first 90-degree electrical coupler, and the first balanced detector and the second balanced detector are connected in parallel between the first 90-degree optical coupler and the first 90-degree electrical coupler; the second demodulation channel is composed of a second 90-degree optical coupler, a third balanced detector, a fourth balanced detector and a second 90-degree electrical coupler, and the third balanced detector and the fourth balanced detector are connected in parallel between the second 90-degree optical coupler and the second 90-degree electrical coupler; the third demodulation channel is composed of a third 90-degree optical coupler, a fifth balanced detector, a sixth balanced detector and a third 90-degree electrical coupler, and the fifth balanced detector and the sixth balanced detector are connected in parallel between the third 90-degree optical coupler. and the third 90-degree electrical coupler; the fourth demodulation channel is composed of a fourth 90-degree optical coupler, a seventh balanced detector, an eighth balanced detector and a fourth 90-degree electrical coupler, and the seventh balanced detector and the eighth balanced detector are connected in parallel between the fourth 90-degree optical coupler and the fourth 90-degree electrical coupler; the fifth demodulation channel is composed of a fifth 90-degree optical coupler, a ninth balanced detector, a tenth balanced detector and a fifth 90-degree electrical coupler, and the ninth balanced detector and the tenth balanced detector are connected in parallel between the fifth 90-degree optical coupler and the fifth 90-degree electrical coupler; the sixth demodulation channel is composed of a sixth 90-degree optical coupler, an eleventh balanced detector, a twelfth balanced detector and a sixth 90-degree electrical coupler, and the eleventh balanced detector and the twelfth balanced detector are connected in parallel between the sixth 90-degree optical coupler and the sixth 90-degree electrical coupler; The second optical coupler is connected to the first 90-degree optical coupler through the fourth optical coupler, the fourth optical coupler is connected to the second 90-degree optical coupler through the sixth optical coupler, the sixth optical coupler is connected to the third 90-degree optical coupler through the eighth optical coupler, the eighth optical coupler is connected to the fourth 90-degree optical coupler through the tenth optical coupler, and the tenth optical coupler is connected to the fifth 90-degree optical coupler and the sixth 90-degree optical coupler through the twelfth optical coupler; the first frequency shifter is connected to the first 90-degree optical coupler and the second frequency shifter respectively through the third optical coupler, the second frequency shifter is connected to the second 90-degree optical coupler and the third frequency shifter respectively through the fifth optical coupler, the third frequency shifter is connected to the third 90-degree optical coupler and the fourth frequency shifter respectively through the seventh optical coupler, the fourth frequency shifter is connected to the fourth 90-degree optical coupler and the fifth frequency shifter respectively through the ninth optical coupler, the fifth frequency shifter is connected to the fifth 90-degree optical coupler and the sixth frequency shifter respectively through the eleventh optical coupler, and the sixth frequency shifter is connected to the sixth 90-degree optical coupler.

2. A microwave photon frequency measurement device based on an optoelectronic oscillator as claimed in claim 1, characterized in that: A tunable laser with a wavelength of 1530nm to 1565nm is selected as a continuous wave light source; the first optical coupler is a 2:8 coupler; the other optical couplers are 5:5 couplers; the bandwidth of the phase modulator is 32GHz; the isolation of the isolator is greater than 40dB; the bandwidth of the dual parallel Mach-Zehnder modulator is 25GHz; the bandwidth of the balanced photodetector is 22GHz; the bandwidth of the photodetector is 40GHz; the maximum gain of the erbium-doped fiber amplifier is 17dB; the output bit rate of the arbitrary waveform generator can reach a maximum of 65Gb / s, and data can be output from up to four output channels at the same time; the The output voltage amplitudes of the first DC voltage stabilizer, the second DC voltage stabilizer and the third DC voltage stabilizer are adjustable from 1V to 20V; the operating frequency band of the RF amplifier is 50kHz to 20GHz, and the gain is 28dB; the output frequency range of the microwave signal generator is 1GHz to 70GHz; the fixed frequency shift of the frequency shifter component is 500MHz; the operating wavelength of the 90-degree optical coupler is 1520 to 1570nm; the operating frequency of the 90-degree electrical coupler is 0.1GHz to 0.605GHz; the length of the high nonlinear optical fiber is 5km; the output voltage amplitude of the DC voltage stabilizer is adjustable from 1V to 20V.

3. A microwave photon frequency measurement method based on an optoelectronic oscillator, characterized in that: When the system starts working, the first tunable laser emits a beam with a frequency of f c The continuous light is used as an optical carrier and is divided into a first branch signal and a second branch optical signal by a first optical coupler; the polarization state of the first branch signal is aligned with the main axis of the phase modulator by a first polarization controller, and then input into the phase modulator for external modulation; the frequency-adjustable and power-adjustable radio frequency signal generated by the microwave signal generator, that is, the unknown signal f x As a modulated signal, it is input into the first electrical coupler, and then input into the RF port of the phase modulator to participate in electro-optical modulation to obtain a phase modulated signal f c and f c ±f x ; The output signal f of the phase modulator c 、f c ±f x After passing through the isolator, it enters the highly nonlinear optical fiber and participates in the stimulated Brillouin scattering effect as a probe light; The second tunable laser is set to swept mode, and the output contains a frequency of f p The frequency-sweeping optical signal is used as the third branch signal, and the third branch signal passes through the second polarization controller to make the polarization states of the first branch signal and the third branch signal as consistent as possible to reduce the loss of optical power; The output optical signal of the second polarization controller is power compensated by the first erbium-doped fiber amplifier, then input to port 1 of the circulator and output from port 2 into the highly nonlinear optical fiber to participate in the stimulated Brillouin scattering effect as pump light. When the frequency difference between the pump light and the probe light is the Brillouin frequency shift V B When the pump light power increases slowly until it exceeds the Brillouin threshold, stimulated Brillouin scattering occurs inside the highly nonlinear optical fiber, and the distance from the pump frequency f in the lower sideband direction is p A Brillouin frequency shift V B A Lorentzian gain spectrum is generated at the upper sideband direction, and at the same time, the distance from the pump frequency f p A Brillouin frequency shift V B A loss spectrum is generated at the position of the second tunable laser. When the detection light sideband output by the phase modulator is within the gain spectrum and the loss spectrum, the sideband balance of the detection light will be broken. This process is the process of converting phase modulation into intensity modulation. Since both the gain spectrum and the loss spectrum are Lorentz-shaped spectral lines, the position change of the gain spectrum will cause the amplitude change of the detection light sideband during the frequency sweep of the second tunable laser. At the unknown frequency f x When a microwave signal modulates an optical carrier, the gain spectrum generated by the stimulated Brillouin scattering effect will be displayed during the frequency sweep process, that is, f c -f x =f p -V B When the detection light is gained, the frequency of breaking the sideband balance after the stimulated Brillouin scattering effect is f c 、f c -f x 、f c +f x The Stokes light is input from port 2 of the circulator and output from port 3, enters the second optical coupler and is divided into the fourth branch signal and the fifth branch signal; the fourth branch signal is amplified by the second erbium-doped fiber amplifier and input into the photodetector for photoelectric conversion, and the beat frequency is also f x The electrical signal is amplified by the radio frequency amplifier and then enters the first electrical coupler; the frequency generated by the microwave signal generator is f x The microwave signal to be measured is input into the first electric coupler, and after being combined with the electrical signal output by the RF amplifier, it is input into the RF port of the phase modulator as a modulation signal for secondary modulation to complete the closed loop of the feedback loop; the main function of the RF amplifier is to compensate for the loop attenuation of the fourth branch signal, so that the closed loop gain of the optoelectronic oscillation module is greater than 1, so that the optoelectronic oscillation module can have a stable oscillation output signal f c 、f c -f x 、f c +f x , that is, the optically-carried RF signal of the fifth branch; the fifth branch signal is input into the fourth optical coupler and divided into an eighth branch signal and a ninth branch signal, and the eighth branch signal is input into the RF port of the first 90-degree optical coupler as the first optically-carried RF signal to enter the first demodulation channel for demodulation; the ninth branch signal is input into the sixth optical coupler and divided into a twelfth branch signal and a thirteenth branch signal, and the twelfth branch signal is input into the RF port of the second 90-degree optical coupler as the second optically-carried RF signal to enter the second demodulation channel for demodulation; the thirteenth branch signal is input into the eighth optical coupler and divided into a sixteenth branch signal and a seventeenth branch signal, and the sixteenth branch The seventeenth branch signal is input into the tenth optical coupler as the third light-carrying radio frequency signal and is input into the radio frequency port of the third 90-degree optical coupler to enter the third demodulation channel for demodulation; the seventeenth branch signal is input into the tenth optical coupler and is divided into the twentieth branch signal and the twenty-first branch signal, and the twentieth branch signal is input into the radio frequency port of the fourth 90-degree optical coupler as the fourth light-carrying radio frequency signal and is input into the fourth demodulation channel for demodulation; the twenty-first branch signal is input into the twelfth optical coupler and is divided into the twenty-fourth branch signal and the twenty-fifth branch signal, and the twenty-fourth branch signal is input into the radio frequency port of the fifth 90-degree optical coupler as the fifth light-carrying radio frequency signal and is input into the fifth demodulation channel for demodulation; The twenty-fifth branch signal is input as the sixth optically-carried radio frequency signal to the radio frequency port of the sixth 90-degree optical coupler and enters the sixth demodulation channel for demodulation; The second branch signal is input as a carrier into the first Mach-Zehnder modulator and the second Mach-Zehnder modulator, and the first output channel of the arbitrary waveform generator outputs a frequency-adjustable RF local oscillator signal f lo , as the modulation signal input to the first driving port of the first Mach-Zehnder modulator to participate in the modulation; the second output channel of the arbitrary waveform generator outputs a signal that is the same as f lo The RF local oscillator signal f with a phase difference of π / 2 lo ', as a modulation signal input to the second driving port of the second Mach Zehnder modulator to participate in the modulation; adjust the output voltage of the first DC voltage regulator source and the second DC voltage regulator source so that the first Mach Zehnder modulator and the second Mach Zehnder modulator work at the minimum transmission point, and realize the double-sideband modulation state of the carrier is suppressed, and the carrier is effectively suppressed at this time; set the output voltage of the third DC voltage regulator source to control the third Mach Zehnder modulator to work at the orthogonal bias point, so that the output optical signal of the second Mach Zehnder modulator is phase-shifted by 90 degrees and then combined with the output optical signal of the first Mach Zehnder modulator to enter the third Mach Zehnder modulator, so that the dual parallel Mach Zehnder modulator works in the single-sideband modulation state of the carrier is suppressed, and the single-sideband modulation signal f of the carrier suppressed output by the dual parallel Mach Zehnder modulator c -f lo As the optical local oscillator signal; the single-sideband modulated signal (optical local oscillator signal) with suppressed carrier is down-converted once through the first frequency shifter, and the frequency becomes f c -f lo -ΔV is then input into the third optical coupler and divided into the sixth branch signal and the seventh branch signal. ΔV is the fixed frequency shift amount of the frequency shifter. The sixth branch signal is input into the local oscillator port of the first 90-degree optical coupler as the first local oscillator signal and then enters the first demodulation channel for demodulation. The seventh branch signal is down-converted again through the second frequency shifter, and the frequency becomes f c -f lo -2ΔV and then input into the fifth optical coupler to be divided into the tenth branch signal and the eleventh branch signal. The tenth branch signal is input into the local oscillator port of the second 90-degree optical coupler as the second local oscillator signal and then enters the second demodulation channel for demodulation. The eleventh branch signal is down-converted again through the third frequency shifter, and the frequency becomes f c -f lo -3ΔV and then input into the seventh optical coupler to be divided into the fourteenth branch signal and the fifteenth branch signal. The fourteenth branch signal is input into the local oscillator port of the third 90-degree optical coupler as the third local oscillator signal and then enters the third demodulation channel for demodulation. The fifteenth branch signal is down-converted again through the fourth frequency shifter, and the frequency becomes f c -f lo -4ΔV is then input into the ninth optical coupler and divided into the eighteenth branch signal and the nineteenth branch signal. The eighteenth branch signal is input into the local oscillator port of the fourth 90-degree optical coupler as the fourth local oscillator signal and then enters the fourth demodulation channel for demodulation; The nineteenth branch signal is down-converted again through the fifth frequency shifter, and the frequency becomes f c -f lo -5ΔV is then input into the eleventh optical coupler and divided into the twenty-second branch signal and the twenty-third branch signal. The twenty-second branch signal is input into the local oscillator port of the fifth 90-degree optical coupler as the fifth local oscillator signal and then enters the fifth demodulation channel for demodulation. The twenty-third branch signal is down-converted again through the sixth frequency shifter, and the frequency becomes f c -f lo -6ΔV to obtain the twenty-sixth branch signal, the twenty-sixth branch signal is input as the sixth local oscillator signal to the local oscillator port of the sixth 90-degree optical coupler and then enters the sixth demodulation channel for demodulation; each group of local oscillator signals and optically-carried radio frequency signals can form a demodulation channel in combination with a demodulation device; The sixth branch signal is used as the first local oscillator signal (frequency is f c -f lo -ΔV), the eighth branch signal is used as the first optical radio frequency signal (E RF , frequency is f c 、f c -f x 、f c +f x ) are input from the local oscillator port and the signal port of the first 90-degree optical coupler, and then are divided into four paths inside the 90-degree optical coupler and phase-shifted (f lo-1 、f lo-2 、f lo-3 、f lo-4 ), and the phase differences with the first local oscillator signal are 0, π / 2, π, 3π / 2 respectively; the first optical carrier RF signal is respectively coupled to f in the 90-degree optical coupler lo-1 、f lo-2 、f lo-3 、f lo-4 Couple and output two sets of signals, one set of signals is the in-phase signal I 11 (E RF +f lo-1 ) and I 12 (E RF +f lo-3 ), a set of signals is an orthogonal signal Q 11 (E RF +f lo-2 ) and Q 12 (E RF +f lo-4 ); In-phase signal I 11 , orthogonal signal Q 11 , in-phase signal I 12 , orthogonal signal Q 12 The in-phase signal I is outputted from the four output ports of the first 90-degree optical coupler respectively; 11 ,I 12 The phase is the same, and the two optical input ports of the first balanced detector are input respectively, and the beat frequency output is an electrical signal I1 with a frequency of f x -f lo -ΔV (the beat frequency results with other sidebands of the first optically-carried RF signal are discarded); similarly, the orthogonal signal Q 11 , Q 12 The phase is orthogonal, and the two optical input ports of the second balanced detector are input respectively, and the beat frequency output is an electrical signal Q1, with the same frequency f x -f lo -ΔV; The frequencies of the two signals I1 and Q1 are consistent, but the phase difference is π / 2. The two intermediate frequency signals I1 and Q1 are input into the first 90-degree electric coupler for coupling, and the output signal of the first demodulation channel is obtained, that is, the first demodulation signal f IF1 , frequency is f x -f lo -ΔV; The tenth branch signal is used as the second local oscillator signal (frequency is f c -f lo -2ΔV) the twelfth branch signal is used as the second optical radio frequency signal (E RF , frequency is f c 、f c -f x 、f c +f x ), respectively input from the signal port and the local oscillator port of the second 90-degree optical coupler, the same as the first demodulation channel, and output a set of in-phase signals I 21 ,I 22 , and a set of orthogonal signals Q 21 , Q 22 ; In-phase signal I 21 ,I 22 Input into the third balanced detector, the beat frequency output is the electrical signal I2; the orthogonal signal Q 21 , Q 22 The two signals I2 and Q2 are input into the second 90-degree electrical coupler for coupling, and the output signal of the second demodulation channel, i.e., the second demodulation signal f IF2 , frequency is f x -f lo -2ΔV; The fourteenth branch signal is used as the third local oscillator signal (frequency is f c -f lo -3ΔV), the sixteenth branch signal is used as the third optical radio frequency signal (E RF , frequency is f c 、f c -f x 、f c +f x ), respectively input from the signal port and the local oscillator port of the third 90-degree optical coupler, the same as the first demodulation channel, and output a set of in-phase signals I 31 ,I 32 and a set of orthogonal signals Q 31 , Q 32 ; In-phase signal I 31 ,I 32 Input into the fifth balanced detector, the beat frequency output is the electrical signal I3; the orthogonal signal Q 31 , Q 32 The two signals I3 and Q3 are input into the third 90-degree electric coupler for coupling, and the output signal of the third demodulation channel is obtained, that is, the third demodulation signal f IF3 , frequency is f x -f lo -3ΔV; The eighteenth branch signal is used as the fourth local oscillator signal (frequency is f c -f lo -4ΔV), the twentieth branch signal is used as the fourth optical radio frequency signal (E RF , frequency is f c 、f c -f x 、f c +f x ), respectively input from the signal port and the local oscillator port of the fourth 90-degree optical coupler, the same as the first demodulation channel, and output a set of in-phase signals I 41 ,I 42 and a set of orthogonal signals Q 41 , Q 42 ; In-phase signal I 41 ,I 42 Input into the seventh balanced detector, the beat frequency output is the electrical signal I4; the orthogonal signal Q 41 , Q 42 The two signals I4 and Q4 are input into the fourth 90-degree electrical coupler for coupling, and the output signal of the fourth demodulation channel is obtained, that is, the fourth demodulation signal f IF4 , frequency is f x -f lo -4ΔV; The twenty-second branch signal is used as the fifth local oscillator signal (frequency is f c -f lo -5ΔV), the twenty-fourth branch signal is used as the fifth optical radio frequency signal (E RF , frequency is f c 、f c -f x 、f c +f x ), respectively input from the signal port and the local oscillator port of the fifth 90-degree optical coupler, the same as the first demodulation channel, and output a set of in-phase signals I 51 ,I 52 and a set of orthogonal signals Q 51 , Q 52 ; In-phase signal I 51 ,I 52 Input into the ninth balanced detector, the beat frequency output is the electrical signal I5; the orthogonal signal Q 51 , Q 52 The two signals I5 and Q5 are input into the fifth 90-degree electric coupler for coupling, and the output signal of the fifth demodulation channel is obtained, that is, the fifth demodulation signal f IF5 , frequency is f x -f lo -5ΔV; The twenty-sixth branch signal is used as the sixth local oscillator signal (frequency is f c -f lo -6ΔV), the twenty-fifth branch signal is used as the sixth optical radio frequency signal (E RF , frequency is f c 、f c -f x 、f c +f x ), respectively input from the signal port and the local oscillator port of the sixth 90-degree optical coupler, the same as the first demodulation channel, and output a set of in-phase signals I 61 ,I 62 and a set of orthogonal signals Q 61 , Q 62 ; In-phase signal I 61 ,I 62 Input into the eleventh balanced detector, the beat frequency output is the electrical signal I6; the orthogonal signal Q 61 , Q 62 The two signals I6 and Q6 are input into the sixth 90-degree electric coupler for coupling, and the output signal of the sixth demodulation channel, i.e., the sixth demodulation signal f IF6 , frequency is f x -f lo -6ΔV; This completes the broadband microwave signal frequency measurement, i.e. f x =f IFn +f lo +nΔV, n=1~6.

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