Multistage modulation microwave signal phase noise measurement system and method

Abstract

The invention discloses a multistage modulation microwave signal phase noise measurement system and method, and the system comprises a laser light source module which is used for generating an optical carrier signal; the microwave signal module is used for generating a first path of microwave signal and a second path of microwave signal which are the same; the first input end of the first-stage modulation module is connected with the output end of the laser light source module, the second input end of the first-stage modulation module is connected with the output end of the microwave signal module, and the first-stage modulation module is used for loading the first microwave signal to the optical carrier signal to generate a first-stage modulation signal; the input end of the second-stage modulation module is connected with the output end of the first-stage modulation module, and the second-stage modulation module is used for carrying out time delay, phase orthogonality and polarization state modulation on the first-stage modulation signal and loading the second-path microwave signal to the modulated first-stage modulation signal; and the input end of the signal processing module is connected with the output end of the secondary modulation module, and the signal processing module is used for processing the secondary modulation signal to obtain the phase noise of the microwave signal.

Description

Technical Field

[0001] The present disclosure relates to the field of microwave signal phase noise measurement and microwave photon technology, and in particular to a multi-level modulated microwave signal phase noise measurement system and method. Background Art

[0002] Currently, the most commonly used phase noise test methods include direct spectrum technology and frequency detection technology. Depending on whether a reference source is required, phase detection technology is divided into heterodyne frequency detection technology and self-heterodyne frequency detection technology.

[0003] Direct spectrum technology calculates the phase noise of the microwave signal to be measured by directly performing spectrum analysis on the microwave signal. The system's operating bandwidth and minimum noise floor are limited by the performance of the spectrum analyzer, and the phase noise and amplitude noise of the source to be measured cannot be distinguished. Heterodyne demodulation technology uses a reference source to mix with the source to be measured. The bandwidth and phase noise floor of the system are limited by indicators such as the bandwidth and phase noise of the reference source. The self-heterodyne delay demodulation method uses an electrical phase shifter and an electrical mixer, which is difficult to meet the measurement requirements of low phase noise at bandwidths above 12G.

[0004] The phase noise measurement system based on the cascaded electro-optical modulator structure avoids the use of an electrical mixer, but still uses an electrical phase shifter and fails to avoid the bandwidth limitation caused by the electrical phase shifter. Summary of the invention

[0005] The main purpose of the present invention is to provide a multi-level modulated microwave signal phase noise measurement system and method, which can effectively improve the accuracy of the measurement system and reduce the noise floor of the phase noise measurement system through multi-level modulation; use optically controlled phase orthogonality to avoid the bandwidth limitation caused by electrical phase shifters, reduce costs, and enhance anti-interference capabilities.

[0006] To achieve the above-mentioned purpose, the first aspect of an embodiment of the present invention provides a microwave signal phase noise measurement system based on all-optical multi-level modulation, including: a laser light source module, used to generate an optical carrier signal; a microwave signal module, used to generate the same first microwave signal and second microwave signal; a primary modulation module, whose first input end is connected to the output end of the laser light source module, and whose second input end is connected to the output end of the microwave signal module, and is used to load the first microwave signal onto the optical carrier signal to generate a primary modulation signal; a secondary modulation module, whose input end is connected to the output end of the primary modulation module, and is used to delay, phase orthogonalize and polarization modulate the primary modulation signal, and load the second microwave signal onto the modulated primary modulation signal; a signal processing module, whose input end is connected to the output end of the secondary modulation module, and is used to perform signal processing on the secondary modulation signal to obtain the phase noise of the microwave signal.

[0007] Optionally, the laser light source module includes: a laser, used to generate the optical carrier signal; and an optical isolator, whose input end is connected to the output end of the laser, and is used to isolate interference signals on the transmission path of the laser.

[0008] Optionally, the microwave signal module includes: a microwave signal generating device, used to generate a microwave signal; and a microwave power splitter, whose input end is connected to the output end of the microwave signal generating device, used to split the microwave signal into the first microwave signal and the second microwave signal.

[0009] Optionally, the primary modulation module includes: a Mach-Zehnder modulator, whose first input end is connected to the output end of the laser light source module, whose second input end is connected to the first output end of the microwave signal module, and whose third input end is connected to the output end of the bias point controller, and is used to load the first microwave signal onto the optical carrier signal to generate the primary modulation signal; an optical beam splitter, whose input end is connected to the output end of the Mach-Zehnder modulator, and is used to divide the primary modulation signal into two paths, one path entering the bias point controller, and the other path entering the secondary modulation module; a bias point controller, whose input end is connected to the output end of the optical beam splitter, and is used to control the Mach-Zehnder modulator to perform carrier suppression output on the primary modulation signal through feedback from the primary modulation signal.

[0010] Optionally, the secondary modulation module includes: an optical fiber delay module, whose input end is connected to the output end of the primary modulation module, for delaying the primary modulation signal; an adjustable optical fiber delay line, whose input end is connected to the output end of the optical fiber delay module, for phase modulating the delayed primary modulation signal, so that the phase-modulated primary modulation signal is orthogonal to the second microwave signal; a polarization controller, whose input end is connected to the output end of the adjustable optical fiber delay line, for changing the polarization state of the primary modulation signal; a phase modulator, whose input end is connected to the output end of the polarization controller, for modulating the second microwave signal onto the primary modulation signal that has been delayed, phase-orthogonalized and polarization-state modulated, to generate a secondary modulation signal.

[0011] Optionally, the signal processing module includes: an adjustable optical filter, whose input end is connected to the output end of the secondary modulation module, for filtering out the center carrier signal and other sideband signals in the secondary modulation signal, and retaining the positive first-order sideband signal; a photodetector, whose input end is connected to the output end of the adjustable optical filter, for performing photoelectric conversion on the positive first-order sideband signal to generate an electrical signal to be measured; and a data processing module, whose input end is connected to the output end of the photodetector, for filtering, amplifying and data processing the electrical signal to be measured to obtain the phase noise of the microwave signal.

[0012] Optionally, the laser is a narrow-linewidth semiconductor laser with continuous light output.

[0013] Optionally, the length of the delay optical fiber of the optical fiber delay module satisfies Wherein, L represents the length of the delay fiber, c represents the speed of light, n represents the refractive index of the delay fiber, and p represents the maximum frequency deviation of the microwave signal phase noise.

[0014] Optionally, the analog bandwidth of the photodetector is greater than the maximum frequency deviation of the microwave signal phase noise.

[0015] On the other hand, the present disclosure provides a method for measuring phase noise of a multi-level modulated microwave signal, comprising: generating an optical carrier signal by using a laser light source module; generating the same first microwave signal and second microwave signal by using a microwave signal module; loading the first microwave signal onto the optical carrier signal by using a primary modulation module to obtain a primary modulation signal; delaying, phase orthogonalizing and polarization-state modulating the primary modulation signal by using a secondary modulation module, loading the second microwave signal onto the modulated primary modulation signal to obtain a secondary modulation signal; and processing the secondary modulation signal by using a signal processing module to obtain the phase noise of the microwave signal.

[0016] At least one of the above technical solutions adopted in the embodiments of the present disclosure can achieve the following beneficial effects:

[0017] The disclosed embodiment provides a multi-level modulated microwave signal phase noise measurement system, including: a laser light source module, a microwave signal module, a primary modulation module, a secondary modulation module, and a signal processing module. The microwave signal generated by a microwave signal generating device is loaded onto an optical carrier signal generated by a laser light source by means of a multi-level modulation module, and the modulated signal is sent to the signal processing module for processing to obtain the phase noise of the microwave signal. The disclosed embodiment does not require the use of an electrical mixer, has a large working bandwidth, high in-band flatness, and a simple calibration method. The cascade modulation method is used to effectively improve the accuracy of the measurement system and reduce the noise floor of the phase noise measurement system. The optically controlled phase quadrature is used to avoid the bandwidth limitation caused by the electrical phase shifter, reduce costs, and enhance anti-interference capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1The schematic diagram of a multi-level modulated microwave signal phase noise measurement system provided by an embodiment of the present invention is schematically shown.

[0020] Figure 2 A schematic diagram of a flow chart of a method for measuring phase noise of a multi-level modulated microwave signal provided by another embodiment of the present invention is shown;

[0021] Figure 3 The hardware structure diagram of an electronic device provided by an embodiment of the present invention is schematically shown.

[0022] Description of reference numerals:

[0023] 1-laser; 2-optical isolator; 3-Mach-Zehnder modulator; 4-1:99 optical beam splitter; 5-optical fiber delay module; 6-microwave signal generating device; 7-microwave power divider; 8-bias point controller; 9-photodetector; 10-data processing module; 11-tunable optical filter; 12-phase modulator; 13-polarization controller; 14-tunable optical fiber delay line. DETAILED DESCRIPTION

[0024] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0025] An embodiment of the present invention provides a multi-level modulated microwave signal phase noise measurement system, which uses a laser light source module to generate an optical carrier signal; uses a microwave signal module to generate the same first microwave signal and second microwave signal; uses a primary modulation module to load the first microwave signal onto the optical carrier signal to obtain a primary modulation signal; uses a secondary modulation module to delay, phase orthogonalize and polarization modulate the primary modulation signal, and loads the second microwave signal onto the modulated primary modulation signal to obtain a secondary modulation signal; uses a signal processing module to process the secondary modulation signal to obtain the microwave signal phase noise.

[0026] Figure 1 A schematic diagram of a multi-level modulated microwave signal phase noise measurement system provided by an embodiment of the present invention is schematically shown.

[0027] like Figure 1 As shown, an embodiment of the present invention provides a multi-level modulated microwave signal phase noise measurement system, including: a laser light source module, a microwave signal module, a primary modulation module, a secondary modulation module, and a signal processing module.

[0028] In an embodiment of the present invention, a laser light source module is used to generate an optical carrier signal; a microwave signal module is used to generate the same first microwave signal and second microwave signal; a primary modulation module is used to load the first microwave signal onto the optical carrier signal to generate a primary modulation signal; a secondary modulation module is used to delay, phase orthogonalize and polarization modulate the primary modulation signal, and load the second microwave signal onto the modulated primary modulation signal; and a signal processing module is used to perform signal processing on the secondary modulation signal to obtain the phase noise of the microwave signal.

[0029] Furthermore, the laser light source module may also include: a laser 1 for generating an optical carrier signal; an optical isolator 2 , whose input end is connected to the output end of the laser 1 and is used to isolate interference signals on the transmission path of the laser 1 .

[0030] Furthermore, the microwave signal module may also include: a microwave signal generating device 6 for generating a microwave signal; a microwave power divider 7, whose input end is connected to the output end of the microwave signal generating device 6, for dividing the microwave signal into a first microwave signal and a second microwave signal.

[0031] Furthermore, the primary modulation module may also include: a Mach-Zehnder modulator 3, whose first input end is connected to the output end of the laser light source module, whose second input end is connected to the first output end of the microwave signal module, and whose third input end is connected to the output end of the bias point controller 8, for loading the first microwave signal onto the optical carrier signal to generate a primary modulation signal; an optical beam splitter 4, whose input end is connected to the output end of the Mach-Zehnder modulator 3, for dividing the primary modulation signal into two paths, with a splitting ratio of 1:99, one path with 1% power entering the bias point controller, and one path with 99% power entering the secondary modulation module; a bias point controller 8, whose input end is connected to the output end of the optical beam splitter 4, and feeds back the Mach-Zehnder modulator 3 through the primary modulation signal, so that the Mach-Zehnder modulator 3 performs carrier suppression output on the primary modulation signal.

[0032] Furthermore, the secondary modulation module may also include: an optical fiber delay module 5, whose input end is connected to the output end of the primary modulation module, for delaying the primary modulation signal; an adjustable optical fiber delay line 14, whose input end is connected to the output end of the optical fiber delay module 5, for phase modulating the delayed primary modulation signal, so that the phase-modulated primary modulation signal is orthogonal to the second microwave signal; a polarization controller 13, whose input end is connected to the output end of the adjustable optical fiber delay line 14, for changing the polarization state of the primary modulation signal; a phase modulator 12, whose input end is connected to the output end of the polarization controller 13, for modulating the second microwave signal onto the primary modulation signal that has been delayed, phase-orthogonal and polarization-state modulated, to generate a secondary modulation signal.

[0033] Furthermore, the signal processing module may also include: an adjustable optical filter 11, whose input end is connected to the output end of the secondary modulation module, for filtering out the central carrier signal and other sideband signals in the secondary modulation signal, and retaining the positive first-order sideband signal; a photodetector 9, whose input end is connected to the output end of the adjustable optical filter 11, for performing photoelectric conversion on the positive first-order sideband signal to generate an electrical signal to be measured; a data processing module 10, whose input end is connected to the output end of the photodetector 9, for filtering, amplifying and data processing the electrical signal to be measured to obtain the phase noise of the microwave signal.

[0034] In the embodiment of the present invention, the laser 1 may be a narrow linewidth semiconductor laser with continuous light output.

[0035] In the embodiment of the present invention, the length of the delay optical fiber of the optical fiber delay module 5 satisfies Wherein, L represents the length of the delay fiber, c represents the speed of light, n represents the refractive index of the delay fiber, and p represents the maximum frequency deviation of the microwave signal phase noise.

[0036] In the embodiment of the present invention, the analog bandwidth of the photodetector 9 is greater than the maximum frequency deviation of the microwave signal phase noise.

[0037] In the embodiment of the present invention, the data processing module 10 converts the output electrical signal of the photodetector 9 into a digital signal through low-pass filtering, amplification, high-pass filtering, and amplification, and then enters the data acquisition card to perform data processing to obtain the phase noise of the microwave signal to be measured.

[0038] In the embodiment of the present invention, the operating bandwidth of the Mach-Zehnder modulator 3 is higher than the output frequency of the microwave signal to be measured.

[0039] In the embodiment of the present invention, the working bandwidth of the microwave power divider 7 is higher than the output frequency of the microwave signal to be measured.

[0040] In the embodiment of the present invention, the working bandwidth of the phase modulator 12 is higher than the output frequency of the microwave signal to be measured.

[0041] In the embodiment of the present invention, the tunable optical filter 11 is an optical bandpass filter with an adjustable center frequency.

[0042] The embodiment of the present invention provides a multi-level modulated microwave signal phase noise measurement principle.

[0043] The optical signal output by laser 1 is expressed as:

[0044] E in (t) = E c exp(jω c t) (1)

[0045] Where E0 is the electric field amplitude of the optical signal, ω c is the angular frequency of the optical carrier, j is the imaginary unit, and t is the time.

[0046] The microwave signal output by the microwave signal generating device 6 can be expressed as:

[0047]

[0048] In the formula, 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 to be measured, and t is the time.

[0049] The microwave signal generating device 6 outputs a microwave signal which passes through the Mach-Zehnder modulator 3 and is expressed as:

[0050]

[0051] Wherein β0 is the modulation depth of the Mach-Zehnder modulator 3, the modulation depth β0 is determined by the amplitude of the microwave signal passing through the microwave power divider 7 and the half-wave voltage of the Mach-Zehnder modulator 3, Δθ is the bias point control voltage of the Mach-Zehnder modulator 3, and θ is the phase difference of the microwave signal entering the two arms of the Mach-Zehnder modulator 3.

[0052] After passing through the optical fiber delay module 5 and the adjustable optical fiber delay line 14, the output signal is expressed as:

[0053]

[0054] In the formula, τ is the total delay provided by the optical fiber delay module 5 and the adjustable optical fiber delay line 14 , and τ can be fine-tuned by the adjustable optical fiber delay line 14 .

[0055] After passing through the phase modulator 12, the expression of the output signal is expressed as:

[0056]

[0057]

[0058] Wherein β1 is the modulation depth of the phase modulator 12 , and the modulation depth β1 is determined by the amplitude of the microwave signal passing through the microwave power divider 7 and the half-wave voltage of the phase modulator 12 .

[0059] The signal output by the phase modulator 12 is expanded by the Bessel function:

[0060]

[0061] Simplifying the above formula, we can get:

[0062]

[0063] After passing through the tunable optical filter 11, the negative first-order sideband and the center carrier generated by the two modulations are filtered out, and the positive first-order sideband is retained. At this time, the output signal of the above formula a=0, b=1 and a=1, b=0 after passing through the tunable optical filter 11 can be expressed as:

[0064]

[0065] The photodetector 9 receives the optical signal filtered by the tunable optical filter 11, and outputs an electrical signal as follows:

[0066] E out =η·|E out+1 | 2 =(Ae jα +Be jβ )(Ae jα +Be jβ ) * (9)

[0067] Where: A = J0(β0)·J1(β1)·(1+e jΔθ ) (10)

[0068] B=J1(β0)J0(β1)·(e jθ +e jΔθ ) (11)

[0069]

[0070]

[0071] The output signal of the photodetector 9 can be expressed as:

[0072]

[0073] The signal output by the photoelectric detector 9 is low-pass filtered, amplified, high-pass filtered, amplified, and then enters the data acquisition card and is converted into a digital signal:

[0074]

[0075] The K factor in the above formula can be obtained by changing the delay amount of the adjustable optical fiber delay line 14 before measurement.

[0076] By adjusting the delay of the optical fiber delay line 14,

[0077]

[0078] The output signal is subjected to a fast Fourier transform by the data processing module 10 to obtain the power spectrum density of the output signal:

[0079]

[0080] The phase noise of the microwave signal generating device 6 is generally expressed as a single sideband phase noise power spectrum density:

[0081]

[0082] The phase noise of the microwave signal can be obtained from the required power spectral density:

[0083]

[0084] The disclosed multi-level modulated microwave signal phase noise measurement system does not require an electrical mixer and has the characteristics of large working bandwidth, high in-band flatness and simple calibration method.

[0085] The present invention discloses a microwave signal phase noise measurement system with multi-stage modulation, which can effectively improve the accuracy of the measurement system and reduce the noise floor of the microwave signal phase noise measurement system through a multi-stage cascade modulation method. Figure 2 A schematic diagram schematically shows a flow chart of a method for measuring phase noise of a multi-level modulated microwave signal provided by another embodiment of the present invention

[0086] like Figure 2 As shown, a multi-level modulated microwave signal phase noise measurement method of this embodiment includes S1 to S5, which is applied to Figure 1 The multi-level modulated microwave signal phase noise measurement system is shown.

[0087] S1, using a laser light source module to generate an optical carrier signal.

[0088] S2, using a microwave signal module to generate the same first microwave signal and second microwave signal.

[0089] S3, using a primary modulation module to load the first microwave signal onto the optical carrier signal to obtain a primary modulation signal.

[0090] S4, using the secondary modulation module to delay, phase orthogonalize and polarization-state modulate the primary modulation signal, and loading the second microwave signal onto the modulated primary modulation signal to obtain a secondary modulation signal.

[0091] S5, using a signal processing module to perform signal processing on the secondary modulation signal to obtain a microwave signal phase noise.

[0092] In the embodiment of the present invention, the data processing module is an electronic device. Figure 3 , Figure 3The hardware structure diagram of an electronic device is schematically shown.

[0093] The electronic device described in this embodiment includes:

[0094] The memory 31, the processor 32 and the computer program stored in the memory 31 and executable on the processor, when the processor executes the program, the aforementioned Figure 1 The method for constructing a user psychological model described in the illustrated embodiment.

[0095] Furthermore, the electronic device also includes:

[0096] At least one input device 33 ; at least one output device 34 .

[0097] The memory 31 , processor 32 , input device 33 and output device 34 are connected via a bus 35 .

[0098] The input device 33 may specifically be a photoelectric detector 9 .

[0099] The output device 34 may specifically be a display screen.

[0100] The memory 31 may be a high-speed random access memory (RAM) memory or a non-volatile memory, such as a disk memory. The memory 31 is used to store a set of executable program codes, and the processor 32 is coupled to the memory 31 .

[0101] Furthermore, an embodiment of the present invention further provides a computer-readable storage medium, which may be provided in the terminal in the above embodiments. Figure 3 The computer readable storage medium stores a computer program, which, when executed by the processor, implements the aforementioned Figure 1 The method for constructing a user psychological model described in the illustrated embodiment. Furthermore, the computer storage medium may also be a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, or other medium that can store program codes.

[0102] In the multiple embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the embodiments described above are only schematic. For example, the division of the modules is only a logical function division. There may be other division methods in actual implementation, such as multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication link shown or discussed can be through some interfaces, and the indirect coupling or communication link of the modules can be electrical, mechanical or other forms.

[0103] The modules described as separate components may or may not be physically separated, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed on multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0104] In addition, each functional module in each embodiment of the present invention may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of software functional modules.

[0105] It should be noted that, for the convenience of description, the aforementioned method embodiments are all described as a series of action combinations, but those skilled in the art should be aware that the present invention is not limited by the described action sequence, because according to the present invention, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present invention.

[0106] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0107] The above is a description of the method, device, electronic device and storage medium for constructing the user psychological model provided by the present invention. For those skilled in the art, according to the ideas of the embodiments of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

[0108] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0109] Similarly, in order to simplify the present disclosure and help understand one or more of the various disclosed aspects, in the above description of the exemplary embodiments of the present disclosure, the various features of the present disclosure are sometimes grouped together into a single embodiment, figure, or description thereof. The description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0110] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present disclosure in detail. It should be understood that the above are only specific embodiments of the present disclosure and are not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A multi-level modulated microwave signal phase noise measurement system, characterized in that: include: A laser light source module, used for generating an optical carrier signal; A microwave signal module, used for generating the same first microwave signal and second microwave signal; A primary modulation module, whose first input end is connected to the output end of the laser light source module, and whose second input end is connected to the output end of the microwave signal module, and is used to load the first microwave signal onto the optical carrier signal to generate a primary modulation signal; A secondary modulation module, whose input end is connected to the output end of the primary modulation module, is used to delay, phase orthogonalize and polarization modulate the primary modulation signal, and load the second microwave signal onto the modulated primary modulation signal; A signal processing module, whose input end is connected to the output end of the secondary modulation module, is used to perform signal processing on the secondary modulation signal to obtain microwave signal phase noise.

2. The system according to claim 1, characterized in that The laser light source module comprises: A laser (1) for generating the optical carrier signal; An optical isolator (2) has an input end connected to the output end of the laser (1) and is used to isolate interference signals on the transmission path of the laser (1).

3. The system according to claim 1, characterized in that The microwave signal module comprises: A microwave signal generating device (6), used for generating a microwave signal; A microwave power splitter (7) has an input end connected to the output end of the microwave signal generating device (6) and is used to split the microwave signal into the first microwave signal and the second microwave signal.

4. The system according to claim 1, characterized in that The primary modulation module comprises: A Mach-Zehnder modulator (3), whose first input end is connected to the output end of the laser light source module, whose second input end is connected to the first output end of the microwave signal module, and whose third input end is connected to the output end of the bias point controller (8), is used to load the first microwave signal onto the optical carrier signal to generate the primary modulation signal; An optical beam splitter (4), whose input end is connected to the output end of the Mach-Zehnder modulator (3), and is used to split the primary modulation signal into two paths, one path entering the bias point controller and the other path entering the secondary modulation module; A bias point controller (8) has an input end connected to the output end of the optical beam splitter (4) and feeds back the Mach-Zehnder modulator (3) through the primary modulation signal, so that the Mach-Zehnder modulator (3) performs carrier suppression output on the primary modulation signal.

5. The system according to claim 1, characterized in that The secondary modulation module comprises: An optical fiber delay module (5), whose input end is connected to the output end of the primary modulation module and is used to delay the primary modulation signal; An adjustable optical fiber delay line (14), whose input end is connected to the output end of the optical fiber delay module (5), and is used to perform phase modulation on the delayed primary modulation signal so that the phase-modulated primary modulation signal is orthogonal to the second microwave signal; A polarization controller (13), whose input end is connected to the output end of the adjustable optical fiber delay line (14) and is used to change the polarization state of the primary modulation signal; The phase modulator (12) has an input end connected to the output end of the polarization controller (13) and is used to modulate the second microwave signal onto the first-level modulation signal that has been subjected to time delay, phase orthogonalization and polarization state modulation to generate a second-level modulation signal.

6. The system according to claim 1, characterized in that The signal processing module comprises: An adjustable optical filter (11), whose input end is connected to the output end of the secondary modulation module, is used to filter out the central carrier signal and other sideband signals in the secondary modulation signal and retain the positive first-order sideband signal; A photodetector (9), whose input end is connected to the output end of the tunable optical filter (11), and is used to perform photoelectric conversion on the positive first-order sideband signal to generate an electrical signal to be measured; A data processing module (10) has an input end connected to the output end of the photodetector (9) and is used to filter, amplify and perform data processing on the electrical signal to be measured to obtain the phase noise of the microwave signal.

7. The system according to claim 2, characterized in that The laser (1) is a narrow-linewidth semiconductor laser that outputs continuous light.

8. The system according to claim 5, characterized in that The length of the delay optical fiber of the optical fiber delay module (5) satisfies Wherein, L represents the length of the delay fiber, c represents the speed of light, n represents the refractive index of the delay fiber, and p represents the maximum frequency deviation of the microwave signal phase noise.

9. The system according to claim 6, characterized in that The analog bandwidth of the photoelectric detector (9) is greater than the maximum frequency deviation of the microwave signal phase noise.

10. A method for measuring phase noise of a multi-level modulated microwave signal, applied to the multi-level modulated microwave signal phase noise measurement system as claimed in any one of claims 1 to 9, characterized in that: include: Using a laser light source module to generate an optical carrier signal; Generate the same first microwave signal and second microwave signal by using a microwave signal module; Using a primary modulation module to load the first microwave signal onto the optical carrier signal to obtain a primary modulation signal; Using a secondary modulation module to perform time delay, phase orthogonal and polarization state modulation on the primary modulation signal, and loading the second microwave signal onto the modulated primary modulation signal to obtain a secondary modulation signal; The signal processing module is used to perform signal processing on the secondary modulation signal to obtain microwave signal phase noise.

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