Microwave signal phase noise measurement system and method

Abstract

The application provides a microwave signal phase noise measurement system applied to the microwave technical field, comprising: a laser for generating a continuous optical carrier; a phase modulator for modulating a to-be-measured microwave signal onto the optical carrier to obtain a first modulation signal; a polarization beam splitter for inputting the first modulation signal into a polarization state beam splitting delay optical fiber link for modulation to obtain a modulated first modulation signal, the modulation comprising delay and control of phase quadrature; a phase modulator for loading a microwave signal onto the modulated first modulation signal to obtain a second modulation signal; an adjustable optical filter for obtaining a to-be-processed optical signal with only positive first-order sideband information; a photoelectric detector for converting the to-be-processed optical signal into an electrical signal; and a signal processing module for performing data processing on the electrical signal to obtain the phase noise of the to-be-measured microwave signal. The application further discloses a microwave signal phase noise measurement method, which avoids the bandwidth limitation caused by electrical devices.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microwave technology, in particular to a microwave signal phase noise measurement system and method. BACKGROUND

[0002] The most commonly used phase noise test methods at present mainly include direct spectrum technology and frequency discrimination technology; according to whether a reference source is needed, the phase discrimination technology is divided into heterodyne frequency discrimination technology and autodyne frequency discrimination technology. The direct spectrum technology calculates the phase noise of the to-be-tested microwave signal by directly performing spectrum analysis on the input microwave signal, and the working bandwidth and minimum noise base of the system are limited by the performance of the spectrum analyzer, and the phase noise and amplitude noise of the to-be-tested source cannot be distinguished. The heterodyne frequency discrimination technology uses a reference source to mix with the to-be-tested source, and the bandwidth and phase noise base of the system are limited by the bandwidth and phase noise indicators of the reference source. The autodyne delay frequency discrimination method uses an electric phase shifter and an electric mixer, and it is difficult to meet the demand of low phase noise measurement in a bandwidth of 12G or above.

[0003] The existing phase noise measurement system based on the cascaded electro-optical modulator structure avoids the use of the electric mixer, but still uses the electric phase shifter, and it is impossible to avoid the bandwidth limitation caused by the electric device, and the existing phase noise measurement system based on the cascaded electro-optical modulator structure uses two electro-optical modulators, which is high in cost. SUMMARY

[0004] The main purpose of the present application is to provide a microwave signal phase noise measurement system and method, which aims to solve the technical problem that the bandwidth limitation caused by the electric device cannot be avoided in the prior art, and effectively reduces the system cost.

[0005] To achieve the above-mentioned purpose, the first aspect of the embodiment of the present application provides a microwave signal phase noise measurement system, comprising:

[0006] A laser is used to generate a continuous optical carrier;

[0007] An optical coupler is used to couple the optical carrier and input the optical carrier into a phase modulator;

[0008] The phase modulator is used to modulate the microwave signal onto the optical carrier to obtain a first modulation signal;

[0009] A polarization beam splitter is used to input the first modulation signal into a delay optical fiber link through polarization state splitting to obtain a modulated first modulation signal, and the modulation includes delay and control of phase quadrature;

[0010] The phase modulator is used to load the microwave signal onto the modulated first modulation signal to obtain a second modulation signal;

[0011] The polarization beam splitter is further configured to split the second modulated signal into the tunable optical filter through polarization state splitting.

[0012] The tunable optical filter is configured to extract a positive first-order sideband of the second modulated signal to obtain a to-be-processed optical signal, and the to-be-processed optical signal has only positive first-order sideband information.

[0013] The photodetector is configured to convert the to-be-processed optical signal into an electrical signal.

[0014] The signal processing module is configured to perform data processing on the electrical signal to obtain phase noise of the microwave signal.

[0015] Optionally, the delay optical fiber link comprises a circulator, a delay optical fiber, a Faraday rotating mirror, a tunable optical fiber delay line, and a phase delay plate.

[0016] The circulator is configured to input the first modulated signal from an a port of the circulator and output the first modulated signal from a b port of the circulator to the delay optical fiber.

[0017] The delay optical fiber is configured to delay the first modulated signal to obtain a delayed first modulated signal.

[0018] The Faraday rotating mirror is configured to reflect the delayed first modulated signal to the circulator, so that a polarization state of the delayed first modulated signal output from a c port of the circulator is consistent with a polarization state of the first modulated signal input from the a port of the circulator.

[0019] The circulator is further configured to output the delayed first modulated signal to the tunable optical fiber delay line.

[0020] The tunable optical fiber delay line is configured to adjust a time for the delayed first modulated signal to reach the phase modulator, so that the second modulated signal output by the phase modulator is in phase quadrature with the first modulated signal.

[0021] The phase delay plate is configured to make the polarization state of the delayed first modulated signal orthogonal to the polarization state of the first modulated signal to obtain the modulated first modulated signal.

[0022] Optionally, an optical isolator is further arranged between the laser and the optical coupler.

[0023] The optical isolator is configured to prevent reflected light from entering the laser.

[0024] Optionally, a working bandwidth of the phase modulator is higher than an output frequency of the microwave signal.

[0025] Optionally, the operating range of the tunable filter covers the positive first-order sideband of the microwave signal after modulation.

[0026] Optionally, the analog bandwidth of the photodetector is greater than twice the frequency offset of the phase noise of the microwave signal.

[0027] A second aspect of this invention provides a method for measuring microwave signal phase noise, comprising:

[0028] Generates continuous optical carrier waves;

[0029] The microwave signal is modulated onto the optical carrier to obtain the first modulation signal;

[0030] The first modulation signal is modulated by a polarization-state beam splitter input delay fiber link to obtain a modulated first modulation signal, wherein the modulation includes delay and control of phase orthogonality;

[0031] The microwave signal is loaded onto the modulated first modulation signal to obtain the second modulation signal;

[0032] Extract the positive first-order sideband of the second modulation signal to obtain the optical signal to be processed. The sideband information of the optical signal to be processed consists only of the positive first-order sideband information.

[0033] The optical signal to be processed is converted into an electrical signal;

[0034] The electrical signal is processed to obtain the phase noise of the microwave signal.

[0035] Optionally, the time-delay fiber link includes: a circulator, a time-delay fiber, a Faraday rotating mirror, an adjustable fiber delay line, and a phase delay plate;

[0036] The circulator is used to allow the first modulation signal to enter from port a of the circulator and output to the delay fiber from port b of the circulator;

[0037] The first modulated signal is delayed by the delay fiber to obtain the delayed first modulated signal;

[0038] A Faraday rotating mirror is used to reflect the delayed first modulation signal to the circulator, so that the polarization state of the delayed first modulation signal output from port c of the circulator is consistent with the polarization state of the first modulation signal input from port a of the circulator.

[0039] The delayed first modulation signal is output from port C of the circulator to the adjustable fiber delay line via the circulator.

[0040] The time when the delayed first modulation signal reaches the phase modulator is adjusted by an adjustable optical fiber delay line, so that the second modulation signal output by the phase modulator and the first modulation signal are kept in phase quadrature.

[0041] The polarization state of the delayed first modulation signal and the first modulation signal are made orthogonal by a phase delay sheet, so as to obtain the modulated first modulation signal.

[0042] Optionally, the working bandwidth of the phase modulator is higher than the output frequency of the microwave signal.

[0043] From the above embodiments of the present application, the microwave signal phase noise measurement system and method provided by the present application have the following advantages: on the one hand, the system has low cost and does not need to use a high-speed detector and multiple modulators; on the other hand, the system has large test bandwidth, and the working bandwidth of the microwave signal phase noise measurement system is not limited by the working bandwidth of any electrical device, but is determined by the working bandwidth of the phase modulator. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0045] Figure 1 The structural schematic diagram of the microwave signal phase noise measurement system provided by an embodiment of the present application is shown in the figure.

[0046] Figure 2 The flowchart of the microwave signal phase noise measurement method provided by an embodiment of the present application is shown in the figure.

[0047] LEGEND OF THE DRAWINGS

[0048] 1-laser; 2-optical isolator; 3-optical coupler; 4-microwave signal; 5-phase modulator; 6-polarization beam splitter; 7-circulator; 8-delay optical fiber; 9-Faraday rotating mirror; 10-adjustable optical fiber delay line; 11-phase delay sheet; 12-adjustable optical filter; 13-photoelectric detector; 14-signal processing module. DETAILED DESCRIPTION

[0049] In order to make the inventive purposes, features and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present application.

[0050] Please refer to Figure 1 , Figure 1 The structure schematic diagram of the microwave signal phase noise measurement system provided by an embodiment of the present application, the microwave signal phase noise measurement system comprises:

[0051] The laser 1 is used for generating a continuous optical carrier;

[0052] The optical coupler 3 is used for coupling the optical carrier and inputting the optical carrier into the phase modulator 5;

[0053] The phase modulator 5 is used for modulating the microwave signal onto the optical carrier to obtain a first modulation signal;

[0054] The polarization beam splitter 6 is used for inputting the first modulation signal into a delay optical fiber link through polarization state splitting to obtain a modulated first modulation signal, and the modulation includes delay and control of phase quadrature;

[0055] The phase modulator 5 is used for loading the microwave signal onto the modulated first modulation signal to obtain a second modulation signal;

[0056] The polarization beam splitter 6 is also used for inputting the second modulation signal into the tunable optical filter 12 through polarization state splitting;

[0057] The tunable optical filter 12 is used for extracting the positive first-order sideband of the second modulation signal to obtain a to-be-processed optical signal, and the sideband information of the to-be-processed optical signal only has the positive first-order sideband information;

[0058] The photodetector 13 is used for converting the to-be-processed optical signal into an electrical signal;

[0059] The signal processing module 14 is used for performing data processing on the electrical signal to obtain the phase noise of the microwave signal.

[0060] In an embodiment of the present application, the delay optical fiber link comprises a circulator 7, a delay optical fiber 8, a Faraday rotating mirror 9, a tunable optical fiber delay line 10 and a phase retarder 11;

[0061] The circulator 7 is used for outputting the first modulation signal to the delay optical fiber 8;

[0062] The time delay optical fiber 8 is used for time delaying the first modulated signal to obtain a time delayed first modulated signal;

[0063] The Faraday mirror 9 is used for reflecting the time delayed first modulated signal to the circulator 7, so that the polarization state of the time delayed first modulated signal returned to the circulator 7 is consistent with the polarization state of the first modulated signal;

[0064] The circulator 7 is also used for outputting the time delayed first modulated signal to the adjustable optical fiber delay line 10;

[0065] The adjustable optical fiber delay line 10 is used for adjusting the time of the time delayed first modulated signal to reach the phase modulator 5, so that the second modulated signal output by the phase modulator 5 and the first modulated signal are kept in phase quadrature;

[0066] The phase delay plate 11 is used for making the time delayed first modulated signal and the polarization state of the first modulated signal orthogonal to obtain the modulated first modulated signal.

[0067] According to the embodiment of the present application, the microwave signal phase noise measurement system can cyclically use the phase modulator through the method of cyclic modulation and polarization isolation, effectively reduces the system cost, and meanwhile, the system working bandwidth is not limited by the bandwidth limitation of the electrical device.

[0068] The principle of the microwave signal phase noise measurement system provided by the present application is as follows:

[0069] The optical carrier output by the laser 1 is represented as: E in (t)=E c exp(jω c t), wherein E c is the electric field amplitude of the optical carrier, ω c is the angular frequency of the optical carrier, j is the imaginary unit, and t is time.

[0070] The microwave signal 4 can be represented as: , wherein E RF is the amplitude of the microwave signal, ω RF is the angular frequency of the microwave signal, is the phase noise of the microwave signal, and t is time.

[0071] The microwave signal 4 E RF (t) after passing through the phase modulator 5 obtains a first modulated signal represented as: , wherein β0 is the modulation depth of the phase modulator 5, and the modulation depth β0 is determined by the microwave signal amplitude E RF and the half-wave voltage of the phase modulator 5;

[0072] The first modulated signal E out0After passing through the polarization beam splitter 6, the circulator 7, the delay fiber 8, the Faraday mirror 9, the circulator 7, the adjustable fiber delay line 10 and the phase delay plate 11, the first modulated signal E is obtained out1 is expressed as

[0073]

[0074] wherein τ is the total delay provided by the delay fiber 8 and the adjustable fiber delay line 10, and τ can be finely adjusted by the adjustable fiber delay line 10.

[0075] The first modulated signal E out1 After passing through the phase modulator 5, the second modulated signal E out2 is expressed as

[0076]

[0077] The second modulated signal E out2 After the Bessel function expansion:

[0078]

[0079] Simplifying the above formula, we can obtain

[0080]

[0081] The second modulated signal E out2 After passing through the adjustable optical filter 12, the negative first-order sideband and the center carrier generated by twice modulation are filtered out, and the positive first-order sideband is retained. At this time, n=0, m=1 and n=1, m=0 in the above formula, and the to-be-processed optical signal E out3 can be expressed as

[0082]

[0083] The photodetector 13 converts the to-be-processed optical signal E out3 into an electrical signal E out , and the electrical signal E out is

[0084]

[0085] That is, the electrical signal E out output by the photodetector 13 can be expressed as

[0086]

[0087] The signal output by the photodetector 13 passes through low-pass filtering, amplification, high-pass filtering and amplification, and then enters the data acquisition card to be converted into a digital signal E:

[0088]

[0089] It can be understood that the K factor in the above formula can be obtained by changing the delay amount of the adjustable optical fiber delay line 10 before measurement; the phase noise of the microwave signal to be measured is obtained by adjusting the delay amount of the adjustable optical fiber delay line 10 to make The electrical signal is subjected to fast Fourier transformation by the signal processing module 14 to obtain the power spectral density

[0090] The phase noise S(f) of the microwave signal to be measured is generally expressed as a single sideband phase noise power spectral density: Therefore, the phase noise of the microwave signal to be measured can be obtained from the obtained power spectral density:

[0091]

[0092] Please refer to Figure 2 , Figure 2 The flowchart of the microwave signal phase noise measurement method provided by an embodiment of the present application can be applied to Figure 1 The microwave signal phase noise measurement system shown in the figure, and the method mainly includes the following operations:

[0093] S201, generating a continuous optical carrier;

[0094] S202, modulating the microwave signal onto the optical carrier to obtain a first modulation signal;

[0095] S203, modulating the first modulation signal through a polarization state beam splitting input delay optical fiber link to obtain a modulated first modulation signal;

[0096] S204, loading the microwave signal onto the modulated first modulation signal to obtain a second modulation signal;

[0097] S205, extracting the positive first-order sideband of the second modulation signal to obtain a to-be-processed optical signal, and the sideband information of the to-be-processed optical signal only has positive first-order sideband information;

[0098] S206, converting the to-be-processed optical signal into an electrical signal;

[0099] S207, performing data processing on the electrical signal to obtain the phase noise of the microwave signal.

[0100] It can be understood that operation S210 can be implemented by a laser and a microwave signal, and the laser is used to generate a continuous optical carrier. An optical coupler is used to couple the optical carrier and input the optical carrier into a phase modulator. Operations S202 and S204 can be implemented by the phase modulator. Operation S205 can be implemented by an adjustable optical filter. Operation S206 can be implemented by a photodetector. Operation S207 can be implemented by a signal processing module.

[0101] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the term "includes" and tautological expressions thereof, such as "including," "includes," "include," "contains," "containing," and so forth, mean the term "comprises."

[0102] Similarly, in the descriptions above of exemplary embodiments of the disclosure, various features of the disclosure are sometimes grouped together. However, this should not be interpreted as intending that any of the claimed embodiments require more features than are expressly identified in connection with each claim. Reference to an "example," "some examples," "exemplary," "specific examples," or "some examples" in the description is not necessarily to the same example or to one example.

[0103] It should be noted that each functional module in each embodiment of the disclosure can be integrated in one processing module, or each module can exist physically alone, or two or more modules can be integrated in one module. The integrated module can be realized in the form of hardware or in the form of a software functional module.

[0104] When the integrated module is realized in the form of a software functional module and sold or used as an independent product, it can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the disclosure can be embodied in the form of a software product, essentially or in the form of a part or all of the technical solutions of the disclosure.

[0105] It should be noted that, for each method embodiment described above, in order to simplify the description, each is described as a combination of a series of actions, but those skilled in the art should know that the present application is not limited by the order of the actions described, because according to the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to the present application.

[0106] In the above embodiments, the description of each embodiment is focused on, and the parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0107] The above is the description of the microwave signal phase noise measurement system and method provided by the application. For those skilled in the art, according to the idea of the embodiments of the application, the specific implementation and application range can be changed. In summary, the content of the specification should not be understood as a limitation of the application.

Claims

1. A microwave signal phase noise measurement system, characterized in that, include: Lasers are used to generate continuous optical carriers; An optical coupler is used to couple the optical carrier and input the optical carrier into a phase modulator; The phase modulator is used to modulate the microwave signal onto the optical carrier to obtain a first modulated signal; A polarization beam splitter is used to modulate the first modulation signal by inputting the polarization state beam splitter into a time-delayed optical fiber link to obtain a modulated first modulation signal, wherein the modulation includes delay and control of phase orthogonality. The phase modulator is used to load the microwave signal onto the modulated first modulated signal to obtain a second modulated signal; The polarization beam splitter is also used to split the second modulation signal into a tunable filter through polarization beam splitting; The tunable optical filter is used to extract the positive first-order sideband of the second modulation signal to obtain the optical signal to be processed. The sideband information of the optical signal to be processed consists only of the positive first-order sideband information. A photodetector is used to convert the optical signal to be processed into an electrical signal; The signal processing module is used to process the electrical signal to obtain the phase noise of the microwave signal. The time-delay fiber link includes: a circulator, a time-delay fiber, a Faraday rotating mirror, an adjustable fiber delay line, and a phase delay plate; The circulator is used to allow the first modulation signal to enter from port a of the circulator and output it to the delay fiber from port b of the circulator; The delay fiber is used to delay the first modulation signal to obtain the delayed first modulation signal; A Faraday rotating mirror is used to reflect the delayed first modulation signal to the circulator so that the polarization state of the delayed first modulation signal output from port c of the circulator is consistent with the polarization state of the first modulation signal input from port a of the circulator. The circulator is also used to output the delayed first modulation signal to the adjustable fiber delay line; An adjustable fiber delay line is used to adjust the time when the delayed first modulation signal arrives at the phase modulator, so that the second modulation signal output by the phase modulator and the first modulation signal remain in phase orthogonal. A phase delay plate is used to make the polarization states of the delayed first modulation signal orthogonal to those of the first modulation signal, thereby obtaining the modulated first modulation signal.

2. The microwave signal phase noise measurement system according to claim 1, characterized in that, An optical isolator is also provided between the laser and the optical coupler; The optical isolator is used to prevent reflected light from entering the laser.

3. The microwave signal phase noise measurement system according to claim 1, characterized in that, The operating bandwidth of the phase modulator is higher than the frequency of the microwave signal.

4. The microwave signal phase noise measurement system according to claim 1, characterized in that, The operating range of the tunable filter covers the positive first-order sideband of the microwave signal after modulation.

5. The microwave signal phase noise measurement system according to claim 1, characterized in that, The 3dB bandwidth of the photodetector is greater than the maximum frequency deviation of the phase noise of the microwave signal.

6. A method for measuring phase noise of microwave signals, characterized in that, include: Generates continuous optical carrier waves; The microwave signal is modulated onto the optical carrier to obtain the first modulation signal; The first modulation signal is modulated by a polarization-state beam splitter input delay fiber link to obtain a modulated first modulation signal, wherein the modulation includes delay and control of phase orthogonality; The microwave signal is loaded onto the modulated first modulation signal to obtain the second modulation signal; Extract the positive first-order sideband of the second modulation signal to obtain the optical signal to be processed. The sideband information of the optical signal to be processed consists only of the positive first-order sideband information. The optical signal to be processed is converted into an electrical signal; The electrical signal is processed to obtain the phase noise of the microwave signal; The time-delay fiber link includes: a circulator, a time-delay fiber, a Faraday rotating mirror, an adjustable fiber delay line, and a phase delay plate; The circulator is used to allow the first modulation signal to enter from port a of the circulator and output to the delay fiber from port b of the circulator; The first modulated signal is delayed by the delay fiber to obtain the delayed first modulated signal; A Faraday rotating mirror is used to reflect the delayed first modulation signal to the circulator, so that the polarization state of the delayed first modulation signal output from port c of the circulator is consistent with the polarization state of the first modulation signal input from port a of the circulator. The delayed first modulation signal is output from port C of the circulator to the adjustable fiber delay line via the circulator. The arrival time of the delayed first modulation signal at the phase modulator is adjusted by an adjustable fiber delay line, so that the second modulation signal output by the phase modulator and the first modulation signal remain in phase orthogonal. The first modulated signal is obtained by making the polarization states of the delayed first modulated signal and the first modulated signal orthogonal by using a phase delay plate.

7. The microwave signal phase noise measurement method according to claim 6, characterized in that, The operating bandwidth of the phase modulator is higher than the frequency of the microwave signal.

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