Microwave source phase noise measurement method, device, system and signal processing circuit

Abstract

The application provides a microwave source phase noise measurement method, device, system and signal processing circuit, and relates to the technical field of microwave source phase noise measurement. The system outputs a main optical signal, a first slave optical signal and a second slave optical signal through a first optical phase-locked loop and a second optical phase-locked loop in the signal processing circuit. The difference between the frequencies of the main optical signal and the first slave optical signal and the difference between the frequencies of the main optical signal and the second slave optical signal are both the sum of the frequency of the microwave signal to be measured and a intermediate frequency. The microwave signal to be measured is modulated onto the main optical signal to obtain a modulated optical signal. According to a first microwave signal obtained by photoelectric conversion after the modulated optical signal and the first slave optical signal are combined and a second microwave signal obtained by photoelectric conversion after the modulated optical signal and the second slave optical signal are combined, the phase noise of the microwave signal to be measured is obtained. The application can reduce the complexity of the high-frequency signal measurement process, improve the measurement sensitivity, shorten the operation time, and is easy to produce and popularize.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microwave source phase noise measurement, and particularly relates to a microwave source phase noise measurement method, device, system and signal processing circuit. BACKGROUND

[0002] With the continuous development of microwave oscillator technology, microwave signal synthesis technologies capable of generating ultra-high frequency and low phase noise microwave signals are constantly emerging, such as optoelectronic oscillators (OEO) and electrical-optical frequency division, etc. The synthesized microwave signals have very high signal frequencies, which poses great challenges to existing microwave signal phase noise measurement technologies.

[0003] Among the current main phase noise measurement methods, the direct spectrum method is the simplest and most direct, which inputs the signal to be measured into a spectrum analyzer to measure the power spectral density of the oscillator, but this method cannot distinguish between amplitude noise and phase noise. The phase discrimination method can overcome the above problems, which converts the phase difference of two input signals into the voltage at the output end of the phase discriminator, but its sensitivity and test bandwidth are limited by the reference source. The frequency discrimination method based on optical delay line does not need to set a reference source, which can overcome the problem of test bandwidth limited by the reference source, and has low power loss and high theoretical sensitivity, but in practical application, there are additional phase noise of the link amplifier, Rayleigh scattering noise in the optical fiber, and the long optical fiber delay line is greatly affected by the environment, which is inconvenient in practical application. In addition, although the long delay line can improve the sensitivity, it limits the maximum bias frequency (the difference between the actual output frequency and the set value). On this basis, a commonly used improved method is the heterodyne phase discriminator method for measuring microwave source phase noise. A specific example is the Keysight E5052B signal source analyzer, which uses the heterodyne phase discriminator method to measure the microwave source phase noise, and combines the double-channel cross-correlation technology to measure the microwave phase noise. This method has a wide phase noise measurement range, does not require an analog delay line, and the double-channel cross-correlation technology does not require very good hardware performance to achieve excellent measurement sensitivity, effectively suppressing the noise of the low noise amplifier (LNA) and the analog to digital converter (ADC) in the link. However, in order to measure high frequency signals, it is necessary to pre-divide the frequency band for down-conversion, which makes the structure complex, and the increase of the cross-correlation order will affect the measurement speed.

[0004] As can be seen, the current microwave source phase noise measurement method is greatly limited in the phase noise measurement range, even if it can measure high frequency signals, the measurement process is relatively complex, and it will affect the measurement speed. In addition, due to the complexity of the phase noise measurement process of high frequency signals, the related measurement equipment is also relatively expensive, and it is difficult to be popularized. SUMMARY

[0005] The application provides a microwave source phase noise measurement method, device, system and signal processing circuit, which solves the defects of complex phase noise measurement process of high frequency signal and large noise measurement range limitation in the prior art microwave source phase noise measurement, and achieves the purpose of reducing the complexity of high frequency signal measurement process and improving the measurement speed under the condition of ensuring high measurement sensitivity.

[0006] The application provides a microwave source phase noise measurement method, device, system and signal processing circuit, which solves the defects of complex phase noise measurement process of high frequency signal and large noise measurement range limitation in the prior art microwave source phase noise measurement, and achieves the purpose of reducing the complexity of high frequency signal measurement process and improving the measurement speed under the condition of ensuring high measurement sensitivity.

[0007] receive the first microwave signal and the second microwave signal from the signal processing circuit; wherein the signal processing circuit comprises a heterodyne phase-locked sub-circuit and a modulation down-conversion sub-circuit, the heterodyne phase-locked sub-circuit comprising a master laser, a first photodetector, a first frequency divider, a first frequency discriminator, a first crystal oscillator, a first loop filter, a first slave laser, a second photodetector, a second frequency divider, a second frequency discriminator, a second crystal oscillator, a second loop filter, a second slave laser, a first branch optical coupler, a first combining optical coupler and a second combining optical coupler, a first output end of the master laser is divided into a first branch output end and a second branch output end through the first branch optical coupler, the first branch output end and a first output end of the first slave laser are connected to an input end of the first combining optical coupler, an output end of the first combining optical coupler is connected to an input end of the first slave laser in sequence through the first photodetector, the first frequency divider, the first frequency discriminator and the first loop filter, to form a first optical phase-locked loop, wherein an input end of the first frequency discriminator is connected to an output end of the first crystal oscillator; the second branch output end and a first output end of the second slave laser are connected to an input end of the second combining optical coupler, an output end of the second combining optical coupler is connected to an input end of the second slave laser in sequence through the second photodetector, the second frequency divider, the second frequency discriminator and the second loop filter, to form a second optical phase-locked loop, wherein an input end of the second frequency discriminator is connected to an output end of the second crystal oscillator; based on the first optical phase-locked loop, a frequency difference between a first slave optical signal output by a second output end of the first slave laser and a master optical signal output by a second output end of the master laser is a set frequency; based on the second optical phase-locked loop, a frequency difference between the master optical signal output by the second output end of the master laser and a second slave optical signal output by a second output end of the second slave laser is the set frequency; the set frequency is a sum of a microwave signal frequency of the microwave signal to be measured and a set intermediate frequency; the modulation down-conversion sub-circuit comprises a phase modulator, a second branch optical coupler, a third combining optical coupler, a fourth combining optical coupler, a third photodetector and a fourth photodetector, an input end of the phase modulator is connected to the second output end of the master laser, an output end of the phase modulator is divided into a third branch output end and a fourth branch output end through the second branch optical coupler, the third branch output end and the second output end of the first slave laser are connected to an input end of the third combining optical coupler, the fourth branch output end and the second output end of the second slave laser are connected to an input end of the fourth combining optical coupler, an output end of the third combining optical coupler is connected to the third photodetector, and an output end of the fourth combining optical coupler is connected to the fourth photodetector; the phase modulator is used for receiving the microwave signal to be measured and modulating the microwave signal to be measured on the master optical signal output by the second output end of the master laser, the third photodetector is used for outputting the first microwave signal, and the fourth photodetector is used for outputting the second microwave signal; obtain N first sampling results of sampling the first microwave signal and N second sampling results of sampling the second microwave signal;Where N is a positive integer and N≥2; Fourier transforms are performed on the N first sampling results and N second sampling results, and cross-correlation power spectral density estimation is performed on the Fourier transform results. The phase noise of the microwave signal under test is output based on the calculation results.

[0008] According to the present invention, a microwave source phase noise measurement method is provided, where N≥100.

[0009] According to the present invention, a microwave source phase noise measurement method is provided, which involves performing Fourier transform on the N first sampling results and the N second sampling results, and performing cross-correlation power spectral density estimation on the Fourier transform results, including: performing cross-correlation power spectral density estimation on the N first sampling results and the N second sampling results based on a graphics processing unit (GPU).

[0010] The present invention also provides a microwave source phase noise measurement device, comprising the following modules: a receiving module, a sampling module, and a processing module.

[0011] The receiving module is used for receiving the first microwave signal and the second microwave signal from the signal processing circuit; wherein the signal processing circuit comprises a heterodyne phase-locked sub-circuit and a modulation down-conversion sub-circuit, the heterodyne phase-locked sub-circuit comprises a master laser, a first photodetector, a first frequency divider, a first frequency discriminator, a first crystal oscillator, a first loop filter, a first slave laser, a second photodetector, a second frequency divider, a second frequency discriminator, a second crystal oscillator, a second loop filter, a second slave laser, a first shunt optical coupler, a first combiner optical coupler and a second combiner optical coupler, a first output end of the master laser is divided into a first branch output end and a second branch output end through the first shunt optical coupler, the first branch output end and a first output end of the first slave laser are connected to an input end of the first combiner optical coupler, an output end of the first combiner optical coupler is connected to an input end of the first slave laser in sequence through the first photodetector, the first frequency divider, the first frequency discriminator and the first loop filter, so as to constitute a first optical phase-locked loop, wherein an input end of the first frequency discriminator is connected to an output end of the first crystal oscillator; the second branch output end and a first output end of the second slave laser are connected to an input end of the second combiner optical coupler, an output end of the second combiner optical coupler is connected to an input end of the second slave laser in sequence through the second photodetector, the second frequency divider, the second frequency discriminator and the second loop filter, so as to constitute a second optical phase-locked loop, wherein an input end of the second frequency discriminator is connected to an output end of the second crystal oscillator; based on the first optical phase-locked loop, a frequency difference between a first slave optical signal output by a second output end of the first slave laser and a master optical signal output by a second output end of the master laser is a set frequency; based on the second optical phase-locked loop, a frequency difference between the master optical signal output by the second output end of the master laser and a second slave optical signal output by a second output end of the second slave laser is the set frequency; the set frequency is a sum of a microwave signal frequency of the microwave signal to be measured and a set intermediate frequency; the modulation down-conversion sub-circuit comprises a phase modulator, a second shunt optical coupler, a third combiner optical coupler, a fourth combiner optical coupler, a third photodetector and a fourth photodetector, an input end of the phase modulator is connected to the second output end of the master laser, an output end of the phase modulator is divided into a third branch output end and a fourth branch output end through the second shunt optical coupler, the third branch output end and the second output end of the first slave laser are connected to an input end of the third combiner optical coupler, the fourth branch output end and the second output end of the second slave laser are connected to an input end of the fourth combiner optical coupler, an output end of the third combiner optical coupler is connected to the third photodetector, and an output end of the fourth combiner optical coupler is connected to the fourth photodetector; the phase modulator is used for receiving the microwave signal to be measured and modulating the microwave signal to be measured on the master optical signal output by the second output end of the master laser, the third photodetector is used for outputting the first microwave signal, and the fourth photodetector is used for outputting the second microwave signal.

[0012] A sampling module is configured to obtain N first sampling results of the first microwave signal and N second sampling results of the second microwave signal, wherein N is a positive integer and N≥2.

[0013] A processing module is configured to perform Fourier transform on the N first sampling results and the N second sampling results, perform cross-correlation power spectral density estimation operation on the Fourier transform results, and output the phase noise of the to-be-measured microwave signal according to the operation results.

[0014] The application further provides a signal processing circuit applied to the microwave source phase noise measurement method, comprising: a heterodyne phase-locked sub-circuit and a modulation down-conversion sub-circuit, wherein the heterodyne phase-locked sub-circuit comprises a master laser, a first photodetector, a first frequency divider, a first frequency discriminator, a first crystal oscillator, a first loop filter, a first slave laser, a second photodetector, a second frequency divider, a second frequency discriminator, a second crystal oscillator, a second loop filter, a second slave laser, a first branch optical coupler, a first combining optical coupler and a second combining optical coupler; a first output end of the master laser is divided into a first branch output end and a second branch output end through the first branch optical coupler; the first branch output end and a first output end of the first slave laser are connected to an input end of the first combining optical coupler; an output end of the first combining optical coupler is connected to an input end of the first slave laser in sequence through the first photodetector, the first frequency divider, the first frequency discriminator and the first loop filter, so as to form a first optical phase-locked loop, wherein an input end of the first frequency discriminator is connected to an output end of the first crystal oscillator; the second branch output end and a first output end of the second slave laser are connected to an input end of the second combining optical coupler; an output end of the second combining optical coupler is connected to an input end of the second slave laser in sequence through the second photodetector, the second frequency divider, the second frequency discriminator and the second loop filter, so as to form a second optical phase-locked loop, wherein an input end of the second frequency discriminator is connected to an output end of the second crystal oscillator; based on the first optical phase-locked loop, a frequency difference between a first slave optical signal output by a second output end of the first slave laser and a master optical signal output by a second output end of the master laser is a set frequency; based on the second optical phase-locked loop, a frequency difference between the master optical signal output by the second output end of the master laser and a second slave optical signal output by a second output end of the second slave laser is the set frequency; the set frequency is a sum of a microwave signal frequency of the microwave signal to be measured and a set intermediate frequency; the modulation down-conversion sub-circuit comprises a phase modulator, a second branch optical coupler, a third combining optical coupler, a fourth combining optical coupler, a third photodetector and a fourth photodetector; an input end of the phase modulator is connected to the second output end of the master laser; an output end of the phase modulator is divided into a third branch output end and a fourth branch output end through the second branch optical coupler; the third branch output end and the second output end of the first slave laser are connected to an input end of the third combining optical coupler; the fourth branch output end and the second output end of the second slave laser are connected to an input end of the fourth combining optical coupler; an output end of the third combining optical coupler is connected to the third photodetector; and an output end of the fourth combining optical coupler is connected to the fourth photodetector; the phase modulator is used for receiving the microwave signal to be measured and modulating the microwave signal to be measured on the master optical signal output by the second output end of the master laser; the third photodetector is used for outputting a first microwave signal; and the fourth photodetector is used for outputting a second microwave signal.The first microwave signal is sampled to obtain N first sampling results, and the second microwave signal is sampled to obtain N second sampling results, the N first sampling results and the N second sampling results are used to perform Fourier transform to obtain a Fourier transform result, and the Fourier transform result is used to perform cross-correlation power spectral density estimation operation to obtain the phase noise of the microwave signal to be measured, wherein N is a positive integer and N is greater than or equal to 2.

[0015] The application further provides an electronic device, including a memory, a processor and a computer program stored in the memory and executable on the processor, and the processor implements the microwave source phase noise measurement method as described above when executing the computer program.

[0016] The application further provides a non-transitory computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the microwave source phase noise measurement method as described above.

[0017] The application further provides a computer program product, which includes a computer program, and the computer program is executed by a processor to implement the microwave source phase noise measurement method as described above.

[0018] The application provides a microwave source phase noise measurement method, device, system and signal processing circuit, wherein the signal processing circuit comprises a heterodyne phase-locked subcircuit and a modulation down-conversion subcircuit; the heterodyne phase-locked subcircuit comprises a master laser, a first photodetector, a first frequency divider, a first frequency discriminator, a first crystal oscillator, a first loop filter, a first slave laser, a second photodetector, a second frequency divider, a second frequency discriminator, a second crystal oscillator, a second loop filter, a second slave laser, a first shunt optical coupler, a first combiner optical coupler and a second combiner optical coupler; a first output end of the master laser is divided into a first branch output end and a second branch output end through the first shunt optical coupler; the first branch output end and a first output end of the first slave laser are connected to an input end of the first combiner optical coupler; an output end of the first combiner optical coupler is sequentially connected to an input end of the first slave laser through the first photodetector, the first frequency divider, the first frequency discriminator and the first loop filter, so as to form a first optical phase-locked loop, wherein an input end of the first frequency discriminator is connected to an output end of the first crystal oscillator; the second branch output end and a first output end of the second slave laser are connected to an input end of the second combiner optical coupler; an output end of the second combiner optical coupler is sequentially connected to an input end of the second slave laser through the second photodetector, the second frequency divider, the second frequency discriminator and the second loop filter, so as to form a second optical phase-locked loop, wherein an input end of the second frequency discriminator is connected to an output end of the second crystal oscillator; based on the first optical phase-locked loop, a frequency difference between a first slave optical signal output by a second output end of the first slave laser and a master optical signal output by a second output end of the master laser is a set frequency; based on the second optical phase-locked loop, a frequency difference between the master optical signal output by the second output end of the master laser and a second slave optical signal output by a second output end of the second slave laser is the set frequency; the set frequency is a sum of a microwave signal frequency of the microwave signal to be measured and a set intermediate frequency; the modulation down-conversion subcircuit comprises a phase modulator, a second shunt optical coupler, a third combiner optical coupler, a fourth combiner optical coupler, a third photodetector and a fourth photodetector; an input end of the phase modulator is connected to the second output end of the master laser; an output end of the phase modulator is divided into a third branch output end and a fourth branch output end through the second shunt optical coupler; the third branch output end and the second output end of the first slave laser are connected to an input end of the third combiner optical coupler; the fourth branch output end and the second output end of the second slave laser are connected to an input end of the fourth combiner optical coupler; an output end of the third combiner optical coupler is connected to the third photodetector; and an output end of the fourth combiner optical coupler is connected to the fourth photodetector; the phase modulator is used for receiving the microwave signal to be measured and modulating the microwave signal to be measured on the master optical signal output by the second output end of the master laser; the third photodetector is used for outputting a first microwave signal; and the fourth photodetector is used for outputting a second microwave signal.Based on the first microwave signal and the second microwave signal output by the signal processing circuit, N first sampling results of sampling the first microwave signal and N second sampling results of sampling the second microwave signal are obtained; wherein N is a positive integer and N is greater than or equal to 2; Fourier transform is performed on the N first sampling results and the N second sampling results, cross-correlation power spectrum density estimation operation is performed on the Fourier transform results, and the phase noise of the to-be-measured microwave signal is output according to the operation results. The signal processing circuit for microwave source phase noise measurement in the embodiment of the present application has a simple structure, and is relatively simple to manufacture and implement, and is easy to produce and popularize. The processing process of the first microwave signal and the second microwave signal output by the signal processing circuit is simple and efficient, thereby solving the defects that the phase noise measurement process of the high-frequency signal in the microwave source phase noise measurement in the prior art is relatively complex and the noise measurement range is relatively large, achieving the purpose of reducing the complexity of the high-frequency signal measurement process and improving the measurement speed while ensuring high measurement sensitivity, and being easy to produce and popularize. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0020] Figure 1 is a structural schematic diagram of the microwave source phase noise measurement system provided by the present application.

[0021] Figure 2 is a structural schematic diagram of the microwave source phase noise measurement device provided by the present application.

[0022] Figure 3 is an output result diagram of the microwave source phase noise measurement system provided by the present application.

[0023] Figure 4 is a flowchart of the microwave source phase noise measurement method provided by the present application.

[0024] Figure 5 is a circuit structure schematic diagram of the signal processing circuit for microwave source phase noise measurement provided by the present application.

[0025] Figure 6 is a structural schematic diagram of the electronic device provided by the present application. DETAILED DESCRIPTION

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] First, the microwave source phase noise measurement system provided in the embodiments of the present invention will be introduced. For example... Figure 1 As shown, the microwave source phase noise measurement system 10 provided in this embodiment of the invention includes a signal processing circuit 11 and a microwave source phase noise measurement device 12.

[0028] Specifically, such as Figure 1 As shown, the signal processing circuit 11 includes a heterodyne phase-locked loop sub-circuit 111 and a modulation down-conversion sub-circuit 112.

[0029] The heterodyne phase-locked loop circuit 111 includes a master laser 11101, a first photodetector 11102, a first frequency divider 11103, a first frequency and phase detector 11104, a first crystal oscillator 11105, a first loop filter 11106, a first slave laser 11107, a second photodetector 11108, a second frequency divider 11109, a second frequency and phase detector 11120, a second crystal oscillator 11121, a second loop filter 11122, a second slave laser 11123, a first splitting optical coupler 11124, a first combining optical coupler 11125, and a second combining optical coupler 11126.

[0030] like Figure 1 As shown, the first output terminal of the main laser 11101 (i.e. Figure 1 The output terminal on the left side of the main laser 11101, Figure 1 (Not shown in the image) is split into two branch outputs by the first branch optocoupler 11124. These two branch outputs are respectively the first branch output (i.e. Figure 1 The output terminal corresponding to the first branch A11 in the middle, Figure 1 (not shown in the image) and the second branch output terminal (i.e. Figure 1 The output terminal corresponding to the second branch A12 in the middle, Figure 1 (Not shown in the image). The first branch output terminal and the first output terminal of the first slave laser 11107 (i.e., Figure 1 The first output terminal from the left side of laser 11107 Figure 1 (Not shown in the image) Connects to the input terminal of the first combiner optocoupler 11125 (located in...) Figure 1 On the right side of the first combining optical coupler 11125, Figure 1The output end of the first combining optical coupler 11125 (located at the left side of the first combining optical coupler 11125 in the figure) is coupled with the input end of the first slave laser 11107 (located at the upper side of the first slave laser 11107 in the figure) in sequence through the first photodetector 11102, the first frequency divider 11103, the first frequency discriminator 11104 and the first loop filter 11106, to constitute a first optical phase-locked loop. Figure 1 The output end of the first combining optical coupler 11125 (located at the left side of the first combining optical coupler 11125 in the figure) is coupled with the input end of the first slave laser 11107 (located at the upper side of the first slave laser 11107 in the figure) in sequence through the first photodetector 11102, the first frequency divider 11103, the first frequency discriminator 11104 and the first loop filter 11106, to constitute a first optical phase-locked loop. Figure 1 The output end of the first combining optical coupler 11125 (located at the left side of the first combining optical coupler 11125 in the figure) is coupled with the input end of the first slave laser 11107 (located at the upper side of the first slave laser 11107 in the figure) in sequence through the first photodetector 11102, the first frequency divider 11103, the first frequency discriminator 11104 and the first loop filter 11106, to constitute a first optical phase-locked loop. Figure 1 The output end of the first combining optical coupler 11125 (located at the left side of the first combining optical coupler 11125 in the figure) is coupled with the input end of the first slave laser 11107 (located at the upper side of the first slave laser 11107 in the figure) in sequence through the first photodetector 11102, the first frequency divider 11103, the first frequency discriminator 11104 and the first loop filter 11106, to constitute a first optical phase-locked loop. Figure 1 The output end of the first combining optical coupler 11125 (located at the left side of the first combining optical coupler 11125 in the figure) is coupled with the input end of the first slave laser 11107 (located at the upper side of the first slave laser 11107 in the figure) in sequence through the first photodetector 11102, the first frequency divider 11103, the first frequency discriminator 11104 and the first loop filter 11106, to constitute a first optical phase-locked loop.

[0031] The output end of the first combining optical coupler 11125 (located at the left side of the first combining optical coupler 11125 in the figure) is coupled with the input end of the first slave laser 11107 (located at the upper side of the first slave laser 11107 in the figure) in sequence through the first photodetector 11102, the first frequency divider 11103, the first frequency discriminator 11104 and the first loop filter 11106, to constitute a first optical phase-locked loop.

[0032] The output end of the first combining optical coupler 11125 (located at the left side of the first combining optical coupler 11125 in the figure) is coupled with the input end of the first slave laser 11107 (located at the upper side of the first slave laser 11107 in the figure) in sequence through the first photodetector 11102, the first frequency divider 11103, the first frequency discriminator 11104 and the first loop filter 11106, to constitute a first optical phase-locked loop.

[0033] In the first optical phase-locked loop, the main optical signal output from the first output terminal of the main laser 11101 is divided into two identical main optical signals by the first split optical coupler 11124. The two identical main optical signals are output through the first branch A1 and the second branch A2, respectively. The main optical signal output from the first branch A1 and the first slave optical signal output from the first slave laser 11107 are input to the first combiner optical coupler 11125. The first combiner optical coupler 11125 combines the received main optical signal and the first slave optical signal, and outputs the first combined optical signal to the first photodetector 11102. The first photodetector 11102 converts the received first combined optical signal into a corresponding microwave signal. This microwave signal is then output to the first frequency discriminator 11104 after the frequency division factor is adjusted by the first frequency divider 11103 (the frequency division factor is k). Based on the monitoring of the frequency and phase difference of the microwave signal by the first frequency discriminator 11104 and the first crystal oscillator 11105, the microwave signal output by the first frequency discriminator 11104 is input to the first slave laser 11107 after passing through the first loop filter 11106, as a feedback tuning signal for the first slave laser 1107, so that the second output terminal of the first slave laser 11107 (i.e., Figure 1 The first output terminal from the right side of laser 11107 Figure 1 The first output optical signal (not shown in the image) and the second output of the main laser (i.e., ...) Figure 1 The output terminal on the right side of the main laser 11101, Figure 1 The frequency difference between the main optical signal output from the laser (not shown) and the set frequency is the sum of the microwave signal frequency of the microwave signal under test and the set intermediate frequency. In other words, based on the setting of the first optical phase-locked loop, the frequency difference between the first slave optical signal output from the second output terminal of the first slave laser 11107 and the main optical signal output from the second output terminal of the main laser 11101 is a fixed frequency, the magnitude of which is equal to the sum of the microwave signal frequency of the microwave signal under test and the set intermediate frequency.

[0034] Please see Figure 1 It should be noted that the main optical signal output from the first output terminal on the left side of the main laser 11101 is the same as the main optical signal output from the second output terminal on the right side of the main laser 11101. Similarly, the first slave optical signal output from the first output terminal on the left side of the first slave laser 11107 is the same as the first slave optical signal output from the second output terminal on the right side of the first slave laser 11107.

[0035] Please continue reading Figure 1 The second branch A12 and the first output terminal of the second laser 11123 (i.e. Figure 1 The second output from the left side of laser 11123 Figure 1The input end of the second combining optical coupler 11126 (located at the right side of the second combining optical coupler 11126 in FIG. 11) is coupled with the output end of the second optical coupler 11124 (located at the left side of the second optical coupler 11124 in FIG. 11) via a second optical coupler 11125 (not shown in FIG. 11) to constitute a second optical phase-locked loop. Figure 1 The input end of the second combining optical coupler 11126 (located at the right side of the second combining optical coupler 11126 in FIG. 11) is coupled with the output end of the second optical coupler 11124 (located at the left side of the second optical coupler 11124 in FIG. 11) via a second optical coupler 11125 (not shown in FIG. 11) to constitute a second optical phase-locked loop. Figure 1 The output end of the second combining optical coupler 11126 (located at the left side of the second combining optical coupler 11126 in FIG. 11) is coupled with the input end of the second slave laser 11123 (located at the lower side of the second slave laser 11123 in FIG. 11) via a second photoelectric detector 11108, a second frequency divider 11109, a second frequency discriminator 11120 and a second loop filter 11122 in sequence to constitute a second optical phase-locked loop. Figure 1 The output end of the second combining optical coupler 11126 (located at the left side of the second combining optical coupler 11126 in FIG. 11) is coupled with the input end of the second slave laser 11123 (located at the lower side of the second slave laser 11123 in FIG. 11) via a second photoelectric detector 11108, a second frequency divider 11109, a second frequency discriminator 11120 and a second loop filter 11122 in sequence to constitute a second optical phase-locked loop. Figure 1 The output end of the second combining optical coupler 11126 (located at the left side of the second combining optical coupler 11126 in FIG. 11) is coupled with the input end of the second slave laser 11123 (located at the lower side of the second slave laser 11123 in FIG. 11) via a second photoelectric detector 11108, a second frequency divider 11109, a second frequency discriminator 11120 and a second loop filter 11122 in sequence to constitute a second optical phase-locked loop. Figure 1 The output end of the second combining optical coupler 11126 (located at the left side of the second combining optical coupler 11126 in FIG. 11) is coupled with the input end of the second slave laser 11123 (located at the lower side of the second slave laser 11123 in FIG. 11) via a second photoelectric detector 11108, a second frequency divider 11109, a second frequency discriminator 11120 and a second loop filter 11122 in sequence to constitute a second optical phase-locked loop. Figure 1 The output end of the second combining optical coupler 11126 (located at the left side of the second combining optical coupler 11126 in FIG. 11) is coupled with the input end of the second slave laser 11123 (located at the lower side of the second slave laser 11123 in FIG. 11) via a second photoelectric detector 11108, a second frequency divider 11109, a second frequency discriminator 11120 and a second loop filter 11122 in sequence to constitute a second optical phase-locked loop.

[0036] The output end of the second combining optical coupler 11126 (located at the left side of the second combining optical coupler 11126 in FIG. 11) is coupled with the input end of the second slave laser 11123 (located at the lower side of the second slave laser 11123 in FIG. 11) via a second photoelectric detector 11108, a second frequency divider 11109, a second frequency discriminator 11120 and a second loop filter 11122 in sequence to constitute a second optical phase-locked loop.

[0037] The output end of the second combining optical coupler 11126 (located at the left side of the second combining optical coupler 11126 in FIG. 11) is coupled with the input end of the second slave laser 11123 (located at the lower side of the second slave laser 11123 in FIG. 11) via a second photoelectric detector 11108, a second frequency divider 11109, a second frequency discriminator 11120 and a second loop filter 11122 in sequence to constitute a second optical phase-locked loop.

[0038] In the second optical phase-locked loop, the main optical signal output on the second branch A2 and the second slave optical signal output on the second slave laser 11123 are input to the second combining optical coupler 11126, the second combining optical coupler 11126 combines the received main optical signal and the first slave optical signal, and outputs a second combined optical signal to the second photodetector 11108. The second photodetector 11108 converts the received second combined optical signal into a corresponding microwave signal. The microwave signal is input to the second frequency divider (with a frequency division factor of k) 11109, and the frequency division factor is adjusted. The microwave signal output by the second frequency divider 11109 is input to the second frequency discriminator 11120 after passing through the second loop filter 11122. The second frequency discriminator 11120 and the second crystal oscillator 11121 monitor the frequency and phase difference of the microwave signal. The microwave signal output by the second frequency discriminator 11120 is input to the second slave laser 11123 after passing through the second loop filter 11122, serving as a feedback tuning signal for the second slave laser 11123. The second output end (located on the right side of the second slave laser 11123 in FIG. 11) of the second slave laser 11123 outputs a second slave optical signal. The frequency difference between the second slave optical signal output by the second output end of the second slave laser 11123 and the main optical signal output by the second output end A2 of the main laser 11101 is a set frequency, which is the sum of the microwave signal frequency of the microwave signal to be measured and a set intermediate frequency. Figure 1 The second slave laser 11123 is located on the right side of the second slave laser 11123 in FIG. 11. Figure 1 The frequency difference between the second slave optical signal output by the second output end of the second slave laser 11123 and the main optical signal output by the second output end A2 of the main laser 11101 is a set frequency, which is the sum of the microwave signal frequency of the microwave signal to be measured and a set intermediate frequency. That is, based on the setting of the second optical phase-locked loop, the frequency difference between the second slave optical signal output by the second output end of the second slave laser 11123 and the main optical signal output by the second output end of the main laser 11101 is a fixed frequency, and the size of the fixed frequency is equal to the sum of the microwave signal frequency of the microwave signal to be measured and the set intermediate frequency.

[0039] It should be noted that the second slave optical signal output by the first output end of the second slave laser 11123 is the same as the second slave optical signal output by the second output end of the second slave laser 11123.

[0040] In specific implementations, the main laser 11101 can be a continuous wave (CW) laser, for example, a CW narrow linewidth laser. The first slave laser 11107 and the second slave laser 11123 can be tunable narrow linewidth lasers.

[0041] The following describes the principle of making the frequency difference between the main optical signal output by the main laser and the first slave optical signal output by the first slave laser a set frequency based on the first optical phase-locked loop, and the principle of making the frequency difference between the main optical signal output by the main laser and the second slave optical signal output by the second slave laser a set frequency based on the second optical phase-locked loop.

[0042] Specifically, in the heterodyne phase-locked subcircuit 11, the main optical signal output by the first output end and the second output end of the main laser 11101 It can be calculated using the following formula:

[0043] ;

[0044] in, It is the electric field amplitude of the main optical signal. It is the relative intensity noise of the main optical signal. It is the angular frequency of the main optical signal output by the main laser. It is the phase jitter of the main optical signal output by the main laser. Represents the phase of a complex number.

[0045] After passing through the heterodyne phase-locked loop circuit, the first slave optical signal output by the first slave laser 11107 is... The second optical signal output from the second laser 11123 It can be calculated using the following formula:

[0046] ;

[0047] ;

[0048] in, It is the relative intensity noise of the first slave optical signal output from the first slave laser 11107. The first is the electric field amplitude of the optical signal. It is the angular frequency of the first optical signal output from the first laser 11107. The phase jitter of the first slave optical signal output from the first slave laser 11107; It is the relative intensity noise of the second optical signal output from the second laser 11123. It is the electric field amplitude of the second optical signal. It is the angular frequency of the second optical signal output from the second laser 11123. The phase jitter of the second slave optical signal output from the second slave laser 11123.

[0049] After phase locking via the first and second optical phase-locked loops, the following relationship can be satisfied for the angular frequency: the angular frequency of the first microwave signal... The angular frequency of the second microwave signal ;in, , It is the angular frequency of the second crystal oscillator, and k is the frequency division factor of the first and second optical phase-locked loops; the phase jitter can satisfy the following relationship: the phase jitter of the first microwave signal Phase jitter of the second microwave signal ;in, This refers to the phase jitter of the first crystal oscillator. For the phase jitter of the second crystal oscillator, the combination of Figure 1 It can be seen that by controlling the frequency division multiple k in the first optical phase-locked loop and the second optical phase-locked loop, the frequency difference between the main optical signal output by the main laser after phase locking and the first slave optical signal output by the first slave laser is the sum of the microwave signal frequency of the microwave signal to be measured and a set intermediate frequency frequency, that is, ; wherein, , is the microwave signal frequency of the microwave signal to be measured, is the set intermediate frequency frequency.

[0050] It should be noted that the set intermediate frequency frequency can be set by those skilled in the art according to the actual situation, and the embodiment of the present application does not limit it.

[0051] Please continue to refer to Figure 1 , the modulation down-conversion sub-circuit 112 includes a phase modulator 11201, a second branch optical coupler 11202, a third branch optical coupler 11203, a fourth branch optical coupler 11204, a third photodetector 11205 and a fourth photodetector 11206. The input end of the phase modulator 11201 (located on the left side of the phase modulator 11201 in Figure 1 , not shown in Figure 1 ) is connected to the second output end of the main laser 11101, and the output end of the phase modulator 11201 (located on the right side of the phase modulator 11201 in Figure 1 , not shown in Figure 1 ) is divided into a third branch output end (i.e. the output end corresponding to the third branch D11 in Figure 1 , not shown in Figure 1 ) and a fourth branch output end (i.e. the output end corresponding to the fourth branch D12 in Figure 1 , not shown in Figure 1 ) through the second branch optical coupler 11202, the third branch output end and the second output end of the first slave laser 11107 are connected to the input end (located on the left side of the third branch optical coupler 11203 in Figure 1 , not shown in Figure 1 ) of the third branch optical coupler 11203, and the fourth branch output end and the second output end of the second slave laser 11123 are connected to the input end (located on the left side of the fourth branch optical coupler 11204 in Figure 1 , not shown in Figure 1 ) of the fourth branch optical coupler 11204, the output end of the third branch optical coupler 11203 (located on the right side of the third branch optical coupler 11203 in Figure 1 , not shown in Figure 1 ) is connected to the third photodetector 11205, and the output end of the fourth branch optical coupler 11204 (located on the right side of the fourth branch optical coupler 11204 inFigure 1 The fourth light detector 11206 is connected to the right side of the fourth combiner optical coupler 11204. Figure 1

[0052] As shown in Figure 1 , the phase modulator 11201 is configured to receive the microwave signal to be measured and modulate the microwave signal to be measured on the main optical signal output by the second output end of the main laser 11101, the third light detector 11205 is configured to output the first microwave signal, and the fourth light detector 11206 is configured to output the second microwave signal.

[0053] Referring to Figure 1 , the main optical signal output by the second output end of the main laser 11101 is input to the phase modulator 11201, and the phase modulator 11201 also receives the microwave signal to be measured. The phase modulator 11201 modulates the microwave signal to be measured on the main optical signal received by the phase modulator 11201 to output a modulated optical signal. The modulated optical signal is output from the third branch output end and the fourth branch output end after passing through the second combiner optical coupler 11202. The modulated optical signal output on the third branch D11 and the first slave optical signal output by the second output end of the first slave laser are input to the third combiner optical coupler 11203 for combination. The third combiner optical coupler 11203 outputs the combined third combined optical signal to the third light detector 11205. The third light detector 11205 converts the received third combined optical signal into a corresponding microwave signal to obtain the first microwave signal and output the first microwave signal. The modulated optical signal on the fourth branch D12 and the second slave optical signal output by the second output end of the second slave laser are input to the fourth combiner optical coupler 11204 for combination. The fourth combiner optical coupler 11204 outputs the combined fourth combined optical signal to the fourth light detector 11206. The fourth light detector 11206 converts the received fourth combined optical signal into a corresponding microwave signal to obtain the second microwave signal and output the second microwave signal. Thus, the first microwave signal and the second microwave signal can be obtained. Based on the first microwave signal and the second microwave signal, the phase noise of the microwave signal to be measured can be obtained.

[0054] The principle of obtaining the phase noise of the microwave signal to be measured based on the first microwave signal and the second microwave signal will be introduced below.

[0055] First, the process of obtaining the expression of the first microwave signal and the second microwave signal will be introduced. Please continue to refer to Figure 1 In the modulation down-conversion sub-circuit 112, the phase modulator 11201 receives the microwave signal to be measured and modulates the microwave signal to be measured on the main optical signal output by the main laser to obtain a modulated optical signal The modulated optical signal can be represented by the following formula:

[0056] ​ ;

[0057] wherein, is the insertion loss of the phase modulator 11201, is the modulation coefficient of the phase modulator, , is the modulation signal amplitude, is the half-wave voltage of the phase modulator, is the angular frequency of the microwave signal to be measured, is the phase jitter of the microwave signal to be measured. The negative first-order sideband expression can be obtained from the Jacobi-Anger expansion as follows:

[0058] .

[0059] wherein J1 is the first-order Bessel function.

[0060] Based on the above calculation results, the photoelectric current signal (first microwave signal) output by the third photoelectric detector 11205 is as follows:

[0061] ；

[0062] .

[0063] Similarly, the photoelectric current signal (second microwave signal) output by the fourth photoelectric detector 11206 is as follows:

[0064] .

[0065] After introducing the expression obtaining process of the first microwave signal and the second microwave signal, the process of obtaining the phase noise of the microwave signal to be measured based on the first microwave signal and the second microwave signal is introduced.

[0066] Please continue to refer to Figure 1 , in the embodiment of the application, the microwave source phase noise measurement device 12 receives the first microwave signal and the second microwave signal, and obtains the phase noise of the microwave signal to be measured according to the first microwave signal and the second microwave signal.

[0067] As shown in Figure 1 , the microwave source phase noise measurement device 200 comprises a receiving module 201, a sampling module 202 and a processing module 203.

[0068] The receiving module 201 is used for receiving the first microwave signal and the second microwave signal from the signal processing circuit.

[0069] Specifically, the signal processing circuit, i.e., the signal processing circuit 11 in the above embodiment, the circuit structure, and the obtaining process of the first microwave signal and the second microwave signal can refer to the corresponding description in the above embodiment, which will not be repeated here.

[0070] The sampling module 22 is configured to obtain N first sampling results of the first microwave signal and N second sampling results of the second microwave signal, where N is a positive integer and N≥2.

[0071] As shown in FIG. 1, the microwave source phase noise measurement device 12 can sample the first microwave signal based on the ADC to obtain N first sampling results, and sample the second microwave signal based on the ADC to obtain N second sampling results. Figure 1

[0072] In some embodiments, N≥100 to ensure that the phase noise obtained in the subsequent module (corresponding to the processing module 23) has higher accuracy.

[0073] The processing module 23 is configured to perform Fourier transform on the N first sampling results and the N second sampling results, perform cross-correlation power spectral density estimation operation on the Fourier transform results, and output the phase noise of the to-be-measured microwave signal according to the operation results.

[0074] As shown in FIG. 1, the microwave source phase noise measurement device 12 can perform Fourier transform (FFT) on the N first sampling results and the N second sampling results obtained by the ADC sampling, and perform digital signal processing (Digital Signal Processing, DSP) on the Fourier transform results. Figure 1 When performing digital signal processing on the Fourier transform results, the GPU can be used to perform cross-correlation power spectral density estimation operation on the N first sampling results and the N second sampling results. For the Mth first sampling result and the Mth second sampling result obtained at the same time, N≥M≥1, the Mth first sampling result and the Mth second sampling result are corresponding, to obtain a sampling pair, the cross-correlation power spectral density estimation operation is performed on the sampling pair, to obtain the operation result corresponding to the sampling pair, and the calculation of each sampling pair is recorded as one calculation. For the N first sampling results and the N second sampling results, N sampling pairs can be obtained, and the GPU can be used to perform parallel calculation on the N sampling pairs, to improve the operation efficiency.

[0075]

[0076] ​​Of course, it is understandable that the cross-correlation power spectral density estimation of the N first sampling results and the N second sampling results can be performed in other ways (such as by a central processing unit (CPU)) to obtain the calculation results.

[0077] It should be noted that the phase noise of the microwave source under test is included in the phase of the first and second microwave signals. After sampling by the ADC, since the amplitude of the electrical signal is a slowly changing variable and the signal is single-frequency within a measurement time period, the phase of the first and second microwave signals can be solved using Hilbert transform. After removing the phase of the intermediate frequency signal (i.e., the signal corresponding to the intermediate frequency set above) from the obtained phase, the resulting phase includes the phase of the microwave source under test and the noise term. (i.e., the phase jitter of the microwave signal under test), the phase jitter of the first microwave signal Phase jitter of the second microwave signal Other phase noise introduced by the first and second optical phase-locked loops, noise introduced by photodetectors (including the first, second, third, and fourth photodetectors), quantization noise generated by the ADC, and aperture jitter noise, etc. By performing power spectral density estimation on the first and second microwave signals using cross-correlation techniques, uncorrelated noise can be canceled. As the number of cross-correlations increases to m (i.e., N=m), the mean power spectral density of the uncorrelated interference term decreases. Therefore, the noise of the first optical phase-locked loop, the second optical phase-locked loop, the photodetector, and the noise introduced by the ADC can be effectively suppressed, thereby reducing the noise floor and improving measurement sensitivity.

[0078] Finally, as Figure 1 Based on the calculation results, a corresponding phase noise image is generated and displayed. For example, taking N=10 and N=100, the output can be as follows: Figure 1 The phase noise measurement results are shown. Figure 1 In SUT, phase noise refers to phase noise.

[0079] In this embodiment of the invention, since the microwave signal to be measured is loaded onto the optical signal for measurement, the high frequency range of the optical signal itself can overcome the current limitation that it is impossible to measure noise in high-frequency signals, thus broadening the noise measurement range. At the same time, the signal processing circuit for microwave source phase noise measurement in this embodiment of the invention has a simple structure, is relatively simple to manufacture and implement, and is easy to produce and popularize.

[0080] The application provides a microwave source phase noise measurement system and device, and the signal processing circuit comprises a heterodyne phase-locked subcircuit and a modulation down-conversion subcircuit. The heterodyne phase-locked subcircuit comprises a main laser, a first photodetector, a first frequency divider, a first frequency discriminator, a first crystal oscillator, a first loop filter, a first slave laser, a second photodetector, a second frequency divider, a second frequency discriminator, a second crystal oscillator, a second loop filter, a second slave laser, a first shunt optical coupler, a first combiner optical coupler and a second combiner optical coupler. The first output end of the main laser is divided into a first branch output end and a second branch output end through the first shunt optical coupler. The first branch output end and the first output end of the first slave laser are connected to the input end of the first combiner optical coupler. The output end of the first combiner optical coupler is connected to the input end of the first slave laser in sequence through the first photodetector, the first frequency divider, the first frequency discriminator and the first loop filter, so as to form a first optical phase-locked loop. The input end of the first frequency discriminator is connected to the output end of the first crystal oscillator. The second branch output end and the first output end of the second slave laser are connected to the input end of the second combiner optical coupler. The output end of the second combiner optical coupler is connected to the input end of the second slave laser in sequence through the second photodetector, the second frequency divider, the second frequency discriminator and the second loop filter, so as to form a second optical phase-locked loop. The input end of the second frequency discriminator is connected to the output end of the second crystal oscillator. Based on the first optical phase-locked loop, the frequency difference between the first slave optical signal output by the second output end of the first slave laser and the main optical signal output by the second output end of the main laser is a set frequency. Based on the second optical phase-locked loop, the frequency difference between the main optical signal output by the second output end of the main laser and the second slave optical signal output by the second output end of the second slave laser is the set frequency. The set frequency is the sum of the microwave signal frequency of the microwave signal to be measured and a set intermediate frequency. The modulation down-conversion subcircuit comprises a phase modulator, a second shunt optical coupler, a third combiner optical coupler, a fourth combiner optical coupler, a third photodetector and a fourth photodetector. The input end of the phase modulator is connected to the second output end of the main laser. The output end of the phase modulator is divided into a third branch output end and a fourth branch output end through the second shunt optical coupler. The third branch output end and the second output end of the first slave laser are connected to the input end of the third combiner optical coupler. The fourth branch output end and the second output end of the second slave laser are connected to the input end of the fourth combiner optical coupler. The output end of the third combiner optical coupler is connected to the third photodetector. The output end of the fourth combiner optical coupler is connected to the fourth photodetector. The phase modulator is used for receiving the microwave signal to be measured and modulating the microwave signal on the main optical signal output by the second output end of the main laser. The third photodetector is used for outputting a first microwave signal. The fourth photodetector is used for outputting a second microwave signal.Based on the first microwave signal and the second microwave signal output by the signal processing circuit, N first sampling results of sampling the first microwave signal and N second sampling results of sampling the second microwave signal are obtained; wherein N is a positive integer and N is greater than or equal to 2; Fourier transform is performed on the N first sampling results and the N second sampling results, cross-correlation power spectral density estimation operation is performed on the Fourier transform results, and the phase noise of the to-be-measured microwave signal is output according to the operation results. The signal processing circuit structure for microwave source phase noise measurement in the embodiment of the present application is simple, and the manufacturing and implementation are relatively simple, easy to produce and popularize. The processing process of the first microwave signal and the second microwave signal output by the signal processing circuit is simple and efficient, thereby solving the defects that the phase noise measurement process of the high-frequency signal in the microwave source phase noise measurement in the prior art is relatively complex and the noise measurement range is limited, achieving the purpose of reducing the complexity of the high-frequency signal measurement process and improving the measurement speed while ensuring high measurement sensitivity, and being easy to produce and popularize.

[0081] The microwave source phase noise measurement method provided by the present application will be described below, and the microwave source phase noise measurement described below can be mutually corresponding with the microwave source phase noise measurement device described above.

[0082] Figure 1 is a flowchart of the microwave source phase noise measurement method provided by the embodiment of the present application. As shown in Figure 1 , the method comprises the following S410-S430.

[0083] S410: receiving the first microwave signal and the second microwave signal from the signal processing circuit.

[0084] The signal processing circuit comprises a heterodyne phase-locked sub-circuit and a modulation down-conversion sub-circuit. The heterodyne phase-locked sub-circuit comprises a main laser, a first photodetector, a first frequency divider, a first frequency discriminator, a first crystal oscillator, a first loop filter, a first slave laser, a second photodetector, a second frequency divider, a second frequency discriminator, a second crystal oscillator, a second loop filter, a second slave laser, a first shunt optical coupler, a first combiner optical coupler and a second combiner optical coupler. A first output end of the main laser is divided into a first branch output end and a second branch output end through the first shunt optical coupler. The first branch output end and a first output end of the first slave laser are connected to an input end of the first combiner optical coupler. An output end of the first combiner optical coupler is connected to an input end of the first slave laser in sequence through the first photodetector, the first frequency divider, the first frequency discriminator and the first loop filter, so as to form a first optical phase-locked loop. An input end of the first frequency discriminator is connected to an output end of the first crystal oscillator. The second branch output end and a first output end of the second slave laser are connected to an input end of the second combiner optical coupler. An output end of the second combiner optical coupler is connected to an input end of the second slave laser in sequence through the second photodetector, the second frequency divider, the second frequency discriminator and the second loop filter, so as to form a second optical phase-locked loop. An input end of the second frequency discriminator is connected to an output end of the second crystal oscillator. A frequency difference between a first slave optical signal output by a second output end of the first slave laser and a main optical signal output by a second output end of the main laser is a set frequency based on the first optical phase-locked loop. A frequency difference between the main optical signal output by the second output end of the main laser and a second slave optical signal output by a second output end of the second slave laser is the set frequency based on the second optical phase-locked loop. The set frequency is a sum of a microwave signal frequency of the microwave signal to be detected and a set intermediate frequency. The modulation down-conversion sub-circuit comprises a phase modulator, a second shunt optical coupler, a third combiner optical coupler, a fourth combiner optical coupler, a third photodetector and a fourth photodetector. An input end of the phase modulator is connected to the second output end of the main laser. An output end of the phase modulator is divided into a third branch output end and a fourth branch output end through the second shunt optical coupler. The third branch output end and the second output end of the first slave laser are connected to an input end of the third combiner optical coupler. The fourth branch output end and the second output end of the second slave laser are connected to an input end of the fourth combiner optical coupler. An output end of the third combiner optical coupler is connected to the third photodetector. An output end of the fourth combiner optical coupler is connected to the fourth photodetector. The phase modulator is used for receiving the microwave signal to be detected and modulating the microwave signal to be detected on the main optical signal output by the second output end of the main laser. The third photodetector is used for outputting a first microwave signal. The fourth photodetector is used for outputting a second microwave signal.

[0085] S420: obtain N first sampling results of sampling the first microwave signal and N second sampling results of sampling the second microwave signal; wherein N is a positive integer and N≥2.

[0086] S430: perform Fourier transform on the N first sampling results and the N second sampling results, perform cross-correlation power spectral density estimation operation on the Fourier transform results, and output the phase noise of the microwave signal to be measured according to the operation results.

[0087] The application provides a microwave source phase noise measurement method, and a signal processing circuit comprises a heterodyne phase-locked subcircuit and a modulation down-conversion subcircuit. The heterodyne phase-locked subcircuit comprises a main laser, a first photodetector, a first frequency divider, a first frequency discriminator, a first crystal oscillator, a first loop filter, a first slave laser, a second photodetector, a second frequency divider, a second frequency discriminator, a second crystal oscillator, a second loop filter, a second slave laser, a first branch optical coupler, a first combining optical coupler and a second combining optical coupler. A first output end of the main laser is divided into a first branch output end and a second branch output end through the first branch optical coupler. The first branch output end and a first output end of the first slave laser are connected to an input end of the first combining optical coupler. An output end of the first combining optical coupler is sequentially connected to an input end of the first slave laser through the first photodetector, the first frequency divider, the first frequency discriminator and the first loop filter to form a first optical phase-locked loop. An input end of the first frequency discriminator is connected to an output end of the first crystal oscillator. A second branch output end and a first output end of the second slave laser are connected to an input end of the second combining optical coupler. An output end of the second combining optical coupler is sequentially connected to an input end of the second slave laser through the second photodetector, the second frequency divider, the second frequency discriminator and the second loop filter to form a second optical phase-locked loop. The second frequency discriminator is coupled to the second crystal oscillator. Based on the first optical phase-locked loop, a frequency difference between a first slave optical signal output by a second output end of the first slave laser and a main optical signal output by a second output end of the main laser is a set frequency. Based on the second optical phase-locked loop, a frequency difference between the main optical signal output by the second output end of the main laser and a second slave optical signal output by a second output end of the second slave laser is the set frequency. The set frequency is a sum of a microwave signal frequency of the microwave signal to be measured and a set intermediate frequency. The modulation down-conversion subcircuit comprises a phase modulator, a second branch optical coupler, a third combining optical coupler, a fourth combining optical coupler, a third photodetector and a fourth photodetector. An input end of the phase modulator is connected to the second output end of the main laser. An output end of the phase modulator is divided into a third branch output end and a fourth branch output end through the second branch optical coupler. The third branch output end and the second output end of the first slave laser are connected to an input end of the third combining optical coupler. The fourth branch output end and the second output end of the second slave laser are connected to an input end of the fourth combining optical coupler. An output end of the third combining optical coupler is connected to the third photodetector. An output end of the fourth combining optical coupler is connected to the fourth photodetector. The phase modulator is used for receiving the microwave signal to be measured and modulating the microwave signal to be measured on the main optical signal output by the second output end of the main laser. The third photodetector is used for outputting a first microwave signal. The fourth photodetector is used for outputting a second microwave signal. Based on the first microwave signal and the second microwave signal output by the signal processing circuit, N first sampling results of sampling the first microwave signal and N second sampling results of sampling the second microwave signal are obtained.Wherein, N is a positive integer and N>=2;The Fourier transform is carried out to N first sampling result and N second sampling result, and the phase noise of the microwave signal to be measured is output according to the operation result.This embodiment of the present application has simple structure of signal processing circuit for microwave source phase noise measurement, and is relatively simple in manufacturing and implementation, easy to produce and popularize, and the processing process of the first microwave signal and the second microwave signal output by the signal processing circuit is simple and efficient, thereby solving the defects that the phase noise measurement process of high-frequency signal in the microwave source phase noise measurement in the prior art is relatively complex and the noise measurement range is limited, achieving the purpose of reducing the complexity of high-frequency signal measurement process and improving the measurement speed under the condition of ensuring high measurement sensitivity, and being easy to produce and popularize.

[0088] The present application also provides a signal processing circuit. Figure 1 As shown in the figure, the signal processing circuit 11 provided by the present application comprises a heterodyne phase-locked sub-circuit 111 and a modulation down-conversion sub-circuit 112.

[0089] The heterodyne phase-locked sub-circuit 111 comprises a main laser 11101, a first photodetector 11102, a first frequency divider 11103, a first frequency discriminator 11104, a first crystal oscillator 11105, a first loop filter 11106, a first slave laser 11107, a second photodetector 11108, a second frequency divider 11109, a second frequency discriminator 11120, a second crystal oscillator 11121, a second loop filter 11122, a second slave laser 11123, a first shunt optical coupler 11124, a first combiner optical coupler 11125 and a second combiner optical coupler 11126.

[0090] The modulation down-conversion sub-circuit 112 comprises a phase modulator 11201, a second shunt optical coupler 11202, a third combiner optical coupler 11203, a fourth combiner optical coupler 11204, a third photodetector 11205 and a fourth photodetector 11206.

[0091] The connection mode of each element in the heterodyne phase-locked sub-circuit 111 and the modulation down-conversion sub-circuit 112 and the signal processing process can refer to the related description in the above-mentioned introduction part of the signal processing circuit 11 in the embodiment of the microwave source phase noise measurement system, which will not be repeated here.

[0092] The third photodetector 11205 is configured to output a first microwave signal, and the fourth photodetector 11206 is configured to output a second microwave signal. The first microwave signal is configured to be sampled to obtain N first sampling results, and the second microwave signal is configured to be sampled to obtain N second sampling results. The N first sampling results and the N second sampling results are configured to be subjected to Fourier transform to obtain a Fourier transform result. The Fourier transform result is configured to be subjected to cross-correlation power spectral density estimation operation to obtain the phase noise of the microwave signal to be measured. N is a positive integer and N≥2.

[0093] The application provides a signal processing circuit for microwave source phase noise measurement, and the signal processing circuit comprises a heterodyne phase-locked subcircuit and a modulation down-conversion subcircuit. The heterodyne phase-locked subcircuit comprises a main laser, a first photodetector, a first frequency divider, a first frequency discriminator, a first crystal oscillator, a first loop filter, a first slave laser, a second photodetector, a second frequency divider, a second frequency discriminator, a second crystal oscillator, a second loop filter, a second slave laser, a first branch optical coupler, a first combining optical coupler and a second combining optical coupler. A first output end of the main laser is divided into a first branch output end and a second branch output end through the first branch optical coupler. The first branch output end and a first output end of the first slave laser are connected to an input end of the first combining optical coupler. An output end of the first combining optical coupler is connected to an input end of the first slave laser in sequence through the first photodetector, the first frequency divider, the first frequency discriminator and the first loop filter to form a first optical phase-locked loop. An input end of the first frequency discriminator is connected to an output end of the first crystal oscillator. The second branch output end and a first output end of the second slave laser are connected to an input end of the second combining optical coupler. An output end of the second combining optical coupler is connected to an input end of the second slave laser in sequence through the second photodetector, the second frequency divider, the second frequency discriminator and the second loop filter to form a second optical phase-locked loop. An input end of the second frequency discriminator is connected to an output end of the second crystal oscillator. A frequency difference between a first slave optical signal output by a second output end of the first slave laser and a main optical signal output by a second output end of the main laser is a set frequency based on the first optical phase-locked loop. A frequency difference between the main optical signal output by the second output end of the main laser and a second slave optical signal output by a second output end of the second slave laser is the set frequency based on the second optical phase-locked loop. The set frequency is a sum of a microwave signal frequency of the microwave signal to be measured and a set intermediate frequency. The modulation down-conversion subcircuit comprises a phase modulator, a second branch optical coupler, a third combining optical coupler, a fourth combining optical coupler, a third photodetector and a fourth photodetector. An input end of the phase modulator is connected to the second output end of the main laser. An output end of the phase modulator is divided into a third branch output end and a fourth branch output end through the second branch optical coupler. The third branch output end and the second output end of the first slave laser are connected to an input end of the third combining optical coupler. The fourth branch output end and the second output end of the second slave laser are connected to an input end of the fourth combining optical coupler. An output end of the third combining optical coupler is connected to the third photodetector. An output end of the fourth combining optical coupler is connected to the fourth photodetector. The phase modulator is used for receiving the microwave signal to be measured and modulating the microwave signal to be measured on the main optical signal output by the second output end of the main laser. The third photodetector is used for outputting a first microwave signal. The fourth photodetector is used for outputting a second microwave signal.Based on the first microwave signal and the second microwave signal output by the signal processing circuit, N first sampling results of sampling the first microwave signal and N second sampling results of sampling the second microwave signal are obtained; wherein N is a positive integer and N≥2; Fourier transform is performed on the N first sampling results and the N second sampling results, cross-correlation power spectral density estimation operation is performed on the Fourier transform results, and the phase noise of the microwave signal to be measured is output according to the operation results. The signal processing circuit structure for microwave source phase noise measurement in the embodiment of the application is simple, and manufacturing and implementation are relatively simple, easy to produce and popularize. The processing process of the first microwave signal and the second microwave signal output by the signal processing circuit is simple and efficient, thereby solving the defects that the phase noise measurement process of the high-frequency signal in the microwave source phase noise measurement in the prior art is relatively complex and the noise measurement range is relatively large, achieving the purpose of reducing the complexity of the high-frequency signal measurement process and improving the measurement speed while ensuring high measurement sensitivity, and being easy to produce and popularize.

[0094] Figure 1 An example of a schematic diagram of the physical structure of an electronic device is shown in FIG. 1. Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 FigureAs shown, the electronic device can include a processor 610, a communications interface 620, a memory 630, and a communications bus 640, wherein the processor 610, the communications interface 620, and the memory 630 complete mutual communication through the communications bus 640. The processor 610 can invoke a logic instruction in the memory 630 to execute a microwave source phase noise measurement method, which includes receiving a first microwave signal and a second microwave signal from a signal processing circuit; wherein the signal processing circuit includes a heterodyne phase-locked sub-circuit and a modulation down-conversion sub-circuit, the heterodyne phase-locked sub-circuit includes a master laser, a first photodetector, a first frequency divider, a first frequency discriminator, a first crystal oscillator, a first loop filter, a first slave laser, a second photodetector, a second frequency divider, a second frequency discriminator, a second crystal oscillator, a second loop filter, a second slave laser, a first shunt optical coupler, a first combining optical coupler, and a second combining optical coupler, a first output end of the master laser is divided into a first branch output end and a second branch output end through the first shunt optical coupler, the first branch output end and a first output end of the first slave laser are connected to an input end of the first combining optical coupler, an output end of the first combining optical coupler is connected to an input end of the first slave laser in sequence through the first photodetector, the first frequency divider, the first frequency discriminator, and the first loop filter, to constitute a first optical phase-locked loop, wherein an input end of the first frequency discriminator is connected to an output end of the first crystal oscillator; the second branch output end and a first output end of the second slave laser are connected to an input end of the second combining optical coupler, an output end of the second combining optical coupler is connected to an input end of the second slave laser in sequence through the second photodetector, the second frequency divider, the second frequency discriminator, and the second loop filter, to constitute a second optical phase-locked loop, wherein an input end of the second frequency discriminator is connected to an output end of the second crystal oscillator; based on the first optical phase-locked loop, a frequency difference between a first slave optical signal output by a second output end of the first slave laser and a master optical signal output by a second output end of the master laser is a set frequency; based on the second optical phase-locked loop, a frequency difference between the master optical signal output by the second output end of the master laser and a second slave optical signal output by a second output end of the second slave laser is the set frequency; the set frequency is a sum of a microwave signal frequency of the microwave signal to be measured and a set intermediate frequency frequency;The modulation down-conversion sub-circuit comprises a phase modulator, a second branch optical coupler, a third branch optical coupler, a fourth branch optical coupler, a third photodetector and a fourth photodetector, the input end of the phase modulator is connected with the second output end of the master laser, the output end of the phase modulator is divided into a third branch output end and a fourth branch output end through the second branch optical coupler, the third branch output end is connected with the input end of the third branch optical coupler and the second output end of the first slave laser, the fourth branch output end is connected with the input end of the fourth branch optical coupler and the second output end of the second slave laser, the output end of the third branch optical coupler is connected with the third photodetector, and the output end of the fourth branch optical coupler is connected with the fourth photodetector; the phase modulator is used for receiving the microwave signal to be measured and modulating the master optical signal output by the second output end of the master laser, the third photodetector is used for outputting a first microwave signal, and the fourth photodetector is used for outputting a second microwave signal; N first sampling results of sampling the first microwave signal and N second sampling results of sampling the second microwave signal are obtained; wherein N is a positive integer and N is greater than or equal to 2; Fourier transform is performed on the N first sampling results and the N second sampling results, cross-correlation power spectral density estimation operation is performed on the Fourier transform results, and the phase noise of the microwave signal to be measured is output according to the operation results.

[0095] In addition, the logic instructions in the memory 630 described above can be implemented in the form of a software function unit and sold or used as an independent product, which can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application essentially or part of the prior art that contributes or part of the technical solutions can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a plurality of instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute all or part of the steps of the methods described in various embodiments of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various media that can store program codes.

[0096] In another aspect, the present application also provides a computer program product, which comprises a computer program, the computer program being stored in a non-transitory computer readable storage medium, and the computer program being capable of executing the microwave source phase noise measurement method provided by the above-mentioned methods when executed by a processor, the method comprising: receiving a first microwave signal and a second microwave signal from a signal processing circuit; wherein the signal processing circuit comprises a heterodyne phase-locked sub-circuit and a modulation down-conversion sub-circuit, the heterodyne phase-locked sub-circuit comprising a master laser, a first photodetector, a first frequency divider, a first frequency discriminator, a first crystal oscillator, a first loop filter, a first slave laser, a second photodetector, a second frequency divider, a second frequency discriminator, a second crystal oscillator, a second loop filter, a second slave laser, a first shunt optical coupler, a first combiner optical coupler, and a second combiner optical coupler, a first output end of the master laser being divided into a first branch output end and a second branch output end through the first shunt optical coupler, the first branch output end and a first output end of the first slave laser being connected to an input end of the first combiner optical coupler, an output end of the first combiner optical coupler being connected to an input end of the first slave laser in sequence through the first photodetector, the first frequency divider, the first frequency discriminator, and the first loop filter, to constitute a first optical phase-locked loop, wherein an input end of the first frequency discriminator is connected to an output end of the first crystal oscillator; the second branch output end and a first output end of the second slave laser being connected to an input end of the second combiner optical coupler, an output end of the second combiner optical coupler being connected to an input end of the second slave laser in sequence through the second photodetector, the second frequency divider, the second frequency discriminator, and the second loop filter, to constitute a second optical phase-locked loop, wherein an input end of the second frequency discriminator is connected to an output end of the second crystal oscillator; a frequency difference between a first slave optical signal outputted by a second output end of the first slave laser and a master optical signal outputted by a second output end of the master laser being a set frequency based on the first optical phase-locked loop; a frequency difference between the master optical signal outputted by the second output end of the master laser and a second slave optical signal outputted by a second output end of the second slave laser being the set frequency based on the second optical phase-locked loop; the set frequency being a sum of a microwave signal frequency of the microwave signal to be measured and a set intermediate frequency frequency; the modulation down-conversion sub-circuit comprising a phase modulator, a second shunt optical coupler, a third combiner optical coupler, a fourth combiner optical coupler, a third photodetector, and a fourth photodetector, an input end of the phase modulator being connected to the second output end of the master laser, an output end of the phase modulator being divided into a third branch output end and a fourth branch output end through the second shunt optical coupler, the third branch output end and the second output end of the first slave laser being connected to an input end of the third combiner optical coupler, the fourth branch output end and the second output end of the second slave laser being connected to an input end of the fourth combiner optical coupler, an output end of the third combiner optical coupler being connected to the third photodetector, and an output end of the fourth combiner optical coupler being connected to the fourth photodetector.The phase modulator is used for receiving the microwave signal to be measured and modulating the microwave signal on the main optical signal outputted by the second output end of the main laser, the third photodetector is used for outputting the first microwave signal, and the fourth photodetector is used for outputting the second microwave signal; N first sampling results of sampling the first microwave signal and N second sampling results of sampling the second microwave signal are obtained; wherein N is a positive integer and N is greater than or equal to 2; Fourier transform is performed on the N first sampling results and the N second sampling results, cross-correlation power spectral density estimation operation is performed on the Fourier transform results, and the phase noise of the microwave signal to be measured is outputted according to the operation results.

[0097] In yet another aspect, the present application also provides a non-transitory computer readable storage medium having stored thereon a computer program, which, when executed by a processor, implements the method for measuring microwave source phase noise provided by any of the above methods, the method comprising: receiving a first microwave signal and a second microwave signal from a signal processing circuit; wherein the signal processing circuit comprises a heterodyne phase-locked sub-circuit and a modulation down-conversion sub-circuit, the heterodyne phase-locked sub-circuit comprising a master laser, a first photodetector, a first frequency divider, a first frequency discriminator, a first crystal oscillator, a first loop filter, a first slave laser, a second photodetector, a second frequency divider, a second frequency discriminator, a second crystal oscillator, a second loop filter, a second slave laser, a first branching optical coupler, a first combining optical coupler, and a second combining optical coupler, a first output end of the master laser being split into a first branch output end and a second branch output end through the first branching optical coupler, the first branch output end and a first output end of the first slave laser connecting an input end of the first combining optical coupler, an output end of the first combining optical coupler being coupled to an input end of the first slave laser through the first photodetector, the first frequency divider, the first frequency discriminator, and the first loop filter in sequence, to form a first optical phase-locked loop, wherein an input end of the first frequency discriminator is connected to an output end of the first crystal oscillator; the second branch output end and a first output end of the second slave laser connecting an input end of the second combining optical coupler, an output end of the second combining optical coupler being coupled to an input end of the second slave laser through the second photodetector, the second frequency divider, the second frequency discriminator, and the second loop filter in sequence, to form a second optical phase-locked loop, wherein an input end of the second frequency discriminator is connected to an output end of the second crystal oscillator; based on the first optical phase-locked loop, a frequency difference between a first slave optical signal output from a second output end of the first slave laser and a master optical signal output from a second output end of the master laser is a set frequency; based on the second optical phase-locked loop, a frequency difference between the master optical signal output from the second output end of the master laser and a second slave optical signal output from a second output end of the second slave laser is the set frequency; the set frequency is a sum of a microwave signal frequency of the microwave signal to be measured and a set intermediate frequency frequency; the modulation down-conversion sub-circuit comprises a phase modulator, a second branching optical coupler, a third combining optical coupler, a fourth combining optical coupler, a third photodetector, and a fourth photodetector, an input end of the phase modulator being connected to the second output end of the master laser, an output end of the phase modulator being split into a third branch output end and a fourth branch output end through the second branching optical coupler, the third branch output end and the second output end of the first slave laser connecting an input end of the third combining optical coupler, the fourth branch output end and the second output end of the second slave laser connecting an input end of the fourth combining optical coupler, an output end of the third combining optical coupler being connected to the third photodetector, and an output end of the fourth combining optical coupler being connected to the fourth photodetector.The phase modulator is used for receiving the microwave signal to be measured and modulating the microwave signal to be measured on the main optical signal output by the second output end of the main laser; the third photodetector is used for outputting the first microwave signal, and the fourth photodetector is used for outputting the second microwave signal; N first sampling results of sampling the first microwave signal and N second sampling results of sampling the second microwave signal are obtained; wherein N is a positive integer and N≥2; Fourier transform is performed on the N first sampling results and the N second sampling results, cross-correlation power spectral density estimation operation is performed on the Fourier transform results, and the phase noise of the microwave signal to be measured is output according to the operation results.

[0098] The device embodiments described above are merely illustrative, wherein the units described as separate components can or can not be physically separated, and the components displayed as units can or can not be physical units, i.e., can be located in one place or distributed on multiple network units. Part or all of the modules can be selected to achieve the purpose of the embodiment scheme according to actual needs. Those skilled in the art can understand and implement without creative labor.

[0099] Through the description of the above embodiments, those skilled in the art can clearly understand that the embodiments can be realized by means of software and necessary general hardware platforms, and of course can also be realized by hardware. Based on such understanding, the above technical solutions can be embodied in the form of software products, which can be stored in a computer readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and include a plurality of instructions to make a computer device (which can be a personal computer, server, or network device, etc.) execute the methods described in each embodiment or some parts of the embodiments.

[0100] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of measuring phase noise of a microwave source, characterized by, The method comprises: The first microwave signal and the second microwave signal are received from the signal processing circuit; wherein the signal processing circuit comprises a heterodyne phase-locked sub-circuit and a modulation down-conversion sub-circuit, the heterodyne phase-locked sub-circuit comprises a master laser, a first photodetector, a first frequency divider, a first frequency discriminator, a first crystal oscillator, a first loop filter, a first slave laser, a second photodetector, a second frequency divider, a second frequency discriminator, a second crystal oscillator, a second loop filter, a second slave laser, a first shunt optical coupler, a first combiner optical coupler and a second combiner optical coupler, a first output end of the master laser is divided into a first branch output end and a second branch output end through the first shunt optical coupler, the first branch output end and a first output end of the first slave laser are connected to an input end of the first combiner optical coupler, an output end of the first combiner optical coupler is connected to an input end of the first slave laser in sequence through the first photodetector, the first frequency divider, the first frequency discriminator and the first loop filter, to constitute a first optical phase-locked loop, wherein an input end of the first frequency discriminator is connected to an output end of the first crystal oscillator; the second branch output end and a first output end of the second slave laser are connected to an input end of the second combiner optical coupler, an output end of the second combiner optical coupler is connected to an input end of the second slave laser in sequence through the second photodetector, the second frequency divider, the second frequency discriminator and the second loop filter, to constitute a second optical phase-locked loop, wherein an input end of the second frequency discriminator is connected to an output end of the second crystal oscillator; based on the first optical phase-locked loop, a frequency difference between a first slave optical signal output from a second output end of the first slave laser and a master optical signal output from a second output end of the master laser is a set frequency; based on the second optical phase-locked loop, a frequency difference between the master optical signal output from the second output end of the master laser and a second slave optical signal output from a second output end of the second slave laser is the set frequency; the set frequency is a sum of a microwave signal frequency of a microwave signal to be measured and a set intermediate frequency; the modulation down-conversion sub-circuit comprises a phase modulator, a second shunt optical coupler, a third combiner optical coupler, a fourth combiner optical coupler, a third photodetector and a fourth photodetector, an input end of the phase modulator is connected to the second output end of the master laser, an output end of the phase modulator is divided into a third branch output end and a fourth branch output end through the second shunt optical coupler, the third branch output end and a second output end of the first slave laser are connected to an input end of the third combiner optical coupler, the fourth branch output end and a second output end of the second slave laser are connected to an input end of the fourth combiner optical coupler, an output end of the third combiner optical coupler is connected to the third photodetector, and an output end of the fourth combiner optical coupler is connected to the fourth photodetector.The phase modulator is used for receiving the microwave signal to be measured and modulating the microwave signal to be measured on the main optical signal output by the second output end of the main laser, the third photodetector is used for outputting the first microwave signal, and the fourth photodetector is used for outputting the second microwave signal. obtaining N first sampling results of sampling the first microwave signal and N second sampling results of sampling the second microwave signal; wherein N is a positive integer and N≥2; performing Fourier transform on the N first sampling results and the N second sampling results, performing cross-correlation power spectral density estimation operation on the Fourier transform results, and outputting the phase noise of the to-be-measured microwave signal according to the operation results.

2. The microwave source phase noise measurement method of claim 1, wherein, N≥100。 3. The microwave source phase noise measurement method of claim 1 or 2, wherein, The Fourier transform on the N first sampling results and the N second sampling results, and the cross-correlation power spectral density estimation operation on the Fourier transform results, comprise: performing cross-correlation power spectral density estimation operation on the N first sampling results and the N second sampling results based on a graphic processing unit (GPU).

4. A microwave source phase noise measurement apparatus, characterized by, The method comprises: The receiving module is used for receiving the first microwave signal and the second microwave signal from the signal processing circuit; wherein the signal processing circuit comprises a heterodyne phase-locked sub-circuit and a modulation down-conversion sub-circuit, the heterodyne phase-locked sub-circuit comprises a main laser, a first photodetector, a first frequency divider, a first frequency discriminator, a first crystal oscillator, a first loop filter, a first slave laser, a second photodetector, a second frequency divider, a second frequency discriminator, a second crystal oscillator, a second loop filter, a second slave laser, a first shunt optical coupler, a first combiner optical coupler and a second combiner optical coupler, a first output end of the main laser is divided into a first branch output end and a second branch output end through the first shunt optical coupler, the first branch output end and a first output end of the first slave laser are connected to an input end of the first combiner optical coupler, an output end of the first combiner optical coupler is sequentially connected to the first photodetector, the first frequency divider, the first frequency discriminator and the first loop filter, and an input end of the first slave laser, so as to constitute a first optical phase-locked loop, wherein an input end of the first frequency discriminator is connected to an output end of the first crystal oscillator; the second branch output end and a first output end of the second slave laser are connected to an input end of the second combiner optical coupler, an output end of the second combiner optical coupler is sequentially connected to the second photodetector, the second frequency divider, the second frequency discriminator and the second loop filter, and an input end of the second slave laser, so as to constitute a second optical phase-locked loop, wherein an input end of the second frequency discriminator is connected to an output end of the second crystal oscillator; based on the first optical phase-locked loop, a frequency difference between a first slave optical signal output from a second output end of the first slave laser and a main optical signal output from a second output end of the main laser is a set frequency; based on the second optical phase-locked loop, a frequency difference between the main optical signal output from the second output end of the main laser and a second slave optical signal output from a second output end of the second slave laser is the set frequency; the set frequency is a sum of a microwave signal frequency of a microwave signal to be measured and a set intermediate frequency; the modulation down-conversion sub-circuit comprises a phase modulator, a second shunt optical coupler, a third combiner optical coupler, a fourth combiner optical coupler, a third photodetector and a fourth photodetector, an input end of the phase modulator is connected to the second output end of the main laser, an output end of the phase modulator is divided into a third branch output end and a fourth branch output end through the second shunt optical coupler, the third branch output end and a second output end of the first slave laser are connected to an input end of the third combiner optical coupler, the fourth branch output end and a second output end of the second slave laser are connected to an input end of the fourth combiner optical coupler, an output end of the third combiner optical coupler is connected to the third photodetector, and an output end of the fourth combiner optical coupler is connected to the fourth photodetector.The phase modulator is used for receiving the microwave signal to be measured and modulating the microwave signal to be measured on the main optical signal output by the second output end of the main laser, the third photodetector is used for outputting the first microwave signal, and the fourth photodetector is used for outputting the second microwave signal. a sampling module configured to obtain N first sampling results of sampling the first microwave signal and N second sampling results of sampling the second microwave signal; wherein N is a positive integer and N≥2; a processing module configured to perform Fourier transform on the N first sampling results and the N second sampling results, perform cross-correlation power spectral density estimation operation on the Fourier transform results, and output the phase noise of the to-be-measured microwave signal according to the operation results.

5. The microwave source phase noise measurement apparatus of claim 4, wherein, N≥100。 6. A signal processing circuit applied to the method of measuring phase noise of a microwave source according to any one of claims 1 to 3, characterized in that, The method comprises: a heterodyne phase-locked sub-circuit and a modulation down-conversion sub-circuit, wherein The heterodyne phase-locked sub-circuit comprises a main laser, a first photodetector, a first frequency divider, a first frequency discriminator, a first crystal oscillator, a first loop filter, a first slave laser, a second photodetector, a second frequency divider, a second frequency discriminator, a second crystal oscillator, a second loop filter, a second slave laser, a first shunt optical coupler, a first combiner optical coupler, and a second combiner optical coupler; a first output end of the main laser is divided into a first branch output end and a second branch output end through the first shunt optical coupler; the first branch output end and a first output end of the first slave laser are connected to an input end of the first combiner optical coupler; an output end of the first combiner optical coupler is connected to an input end of the first slave laser in sequence through the first photodetector, the first frequency divider, the first frequency discriminator, and the first loop filter, so as to form a first optical phase-locked loop, wherein an input end of the first frequency discriminator is connected to an output end of the first crystal oscillator; the second branch output end and a first output end of the second slave laser are connected to an input end of the second combiner optical coupler; an output end of the second combiner optical coupler is connected to an input end of the second slave laser in sequence through the second photodetector, the second frequency divider, the second frequency discriminator, and the second loop filter, so as to form a second optical phase-locked loop, wherein an input end of the second frequency discriminator is connected to an output end of the second crystal oscillator; based on the first optical phase-locked loop, a frequency difference between a first slave optical signal output by a second output end of the first slave laser and a main optical signal output by a second output end of the main laser is a set frequency; based on the second optical phase-locked loop, a frequency difference between the main optical signal output by the second output end of the main laser and a second slave optical signal output by a second output end of the second slave laser is the set frequency; the set frequency is a sum of a microwave signal frequency of a microwave signal to be detected and a set intermediate frequency. The modulation down-conversion sub-circuit comprises a phase modulator, a second branch optical coupler, a third branch optical coupler, a fourth branch optical coupler, a third photodetector and a fourth photodetector, an input end of the phase modulator is connected to a second output end of the master laser, an output end of the phase modulator is divided into a third branch output end and a fourth branch output end through the second branch optical coupler, the third branch output end and a second output end of the first slave laser are connected to an input end of the third branch optical coupler, the fourth branch output end and a second output end of the second slave laser are connected to an input end of the fourth branch optical coupler, an output end of the third branch optical coupler is connected to the third photodetector, and an output end of the fourth branch optical coupler is connected to the fourth photodetector; the phase modulator is used for receiving the microwave signal to be measured and modulating the microwave signal to be measured on a master optical signal output by the second output end of the master laser, the third photodetector is used for outputting a first microwave signal, and the fourth photodetector is used for outputting a second microwave signal; the first microwave signal is used for being sampled to obtain N first sampling results, the second microwave signal is used for being sampled to obtain N second sampling results, the N first sampling results and the N second sampling results are used for being subjected to Fourier transform to obtain Fourier transform results, and the Fourier transform results are used for being subjected to cross-correlation power spectral density estimation operation to obtain phase noise of the microwave signal to be measured; wherein N is a positive integer and N≥2.

7. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the computer program to realize the microwave source phase noise measurement method in any one of claims 1 to 3.

8. A non-transitory computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to realize the microwave source phase noise measurement method in any one of claims 1 to 3.

9. A computer program product comprising a computer program, characterized in that, The computer program is executed by the processor to realize the microwave source phase noise measurement method in any one of claims 1 to 3.

10. A microwave source phase noise measurement system characterized by, Comprise: The microwave source phase noise measurement device in any one of claims 4 to 5 and the signal processing circuit in claim 6.

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