Microwave signal phase noise measurement system and method

Abstract

The invention provides a microwave signal phase noise measurement system, which is applied to the technical field of microwaves, and comprises a laser, a signal processing module and a signal processing module, the phase modulator is used for modulating a microwave signal to be measured onto an optical carrier to obtain a first modulation signal; the polarization beam splitter is used for inputting the first modulation signal into the time-delay optical fiber link for modulation through polarization-state beam splitting to obtain a modulated first modulation signal, and modulation comprises time delay and phase orthogonality control; the phase modulator is used for loading the microwave signal to the modulated first modulation signal to obtain a second modulation signal; the adjustable optical filter is used for obtaining to-be-processed optical signals with sideband information only containing positive first-order sideband information; the photoelectric detector is used for converting a to-be-processed optical signal into an electric signal; and the signal processing module is used for performing data processing on the electric signal to obtain the phase noise of the microwave signal to be detected. The invention further discloses a microwave signal phase noise measuring method, and bandwidth limitation caused by electrical devices is avoided.

Description

Technical Field

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

[0002] At present, the most commonly used phase noise test methods are direct spectrum technology and frequency discrimination technology; depending on whether a reference source is required, phase discrimination technology is divided into heterodyne frequency discrimination technology and self-differential frequency discrimination technology. Direct spectrum technology directly performs spectrum analysis on the microwave signal of the input microwave signal to obtain the phase noise of the microwave signal to be measured. The system's operating bandwidth and minimum noise floor are limited by the performance of the spectrum analyzer, and cannot distinguish between the phase noise and amplitude noise of the source to be measured. Heterodyne frequency discrimination technology uses a reference source to mix with the source to be measured. The bandwidth and phase noise base of the system are limited by indicators such as the bandwidth and phase noise of the reference source. The self-differential delay frequency discrimination method uses an electrical phase shifter and an electrical mixer. It is difficult to meet the measurement requirements of low phase noise at bandwidths above 12G.

[0003] The existing 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, which cannot avoid the bandwidth limitation caused by electrical devices. In addition, the existing phase noise measurement system based on the cascaded electro-optical modulator structure uses two electro-optical modulators, which is expensive. Summary of the invention

[0004] The main purpose of the present invention is to provide a microwave signal phase noise measurement system and method, aiming to solve the technical problem of bandwidth limitation caused by electrical devices that cannot be avoided in the prior art, and effectively reduce the system cost.

[0005] To achieve the above object, a first aspect of an embodiment of the present invention provides a microwave signal phase noise measurement system, comprising:

[0006] A laser for generating a continuous optical carrier wave;

[0007] An optical coupler, used for coupling the optical carrier and inputting 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 modulated signal;

[0009] A polarization beam splitter, used to modulate the first modulated signal through a polarization state splitting input delay optical fiber link to obtain a modulated first modulated signal, wherein the modulation includes delay and controlling phase orthogonality;

[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 used to split the second modulated signal into an adjustable optical filter through polarization state;

[0012] The tunable optical filter is used to extract the positive first-order sideband of the second modulated signal to obtain an optical signal to be processed, wherein the sideband information of the optical signal to be processed only has positive first-order sideband information;

[0013] A photoelectric detector, used for converting the optical signal to be processed into an electrical signal;

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

[0015] Optionally, the delay optical fiber link includes: a circulator, a delay optical fiber, a Faraday rotation mirror, an adjustable optical fiber delay line, and a phase delay plate;

[0016] The circulator is used to allow the first modulated signal to enter through the port a of the circulator, and output from the port b of the circulator to the delay optical fiber;

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

[0018] A Faraday rotator reflector, used for reflecting the delayed first modulated signal to the circulator, so that the polarization state of the delayed first modulated signal output from the circulator c port is consistent with the polarization state of the first modulated signal input from the circulator a port;

[0019] The circulator is further used to output the delayed first modulated signal to the adjustable optical fiber delay line;

[0020] An adjustable optical fiber delay line, used for adjusting the time when the delayed first modulated signal reaches the phase modulator, so that the second modulated signal output by the phase modulator maintains a phase quadrature with the first modulated signal;

[0021] The phase delay plate is used to make the polarization states of the delayed first modulation signal and the first modulation signal orthogonal to obtain the modulated first modulation signal.

[0022] Optionally, an optical isolator is further provided between the laser and the optical coupler;

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

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

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

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

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

[0028] Generate a continuous optical carrier;

[0029] Modulating the microwave signal onto the optical carrier to obtain a first modulated signal;

[0030] Modulating the first modulated signal through a polarization state splitting input delay optical fiber link to obtain a modulated first modulated signal, wherein the modulation includes delay and controlling phase orthogonality;

[0031] Loading the microwave signal onto the modulated first modulation signal to obtain a second modulation signal;

[0032] Extracting the positive first-order sideband of the second modulated signal to obtain an optical signal to be processed, wherein the sideband information of the optical signal to be processed only includes positive first-order sideband information;

[0033] Converting the optical signal to be processed into an electrical signal;

[0034] The electrical signal is subjected to data processing to obtain the phase noise of the microwave signal.

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

[0036] Through the circulator, the first modulated signal enters from the port a of the circulator and is output from the port b of the circulator to the delay optical fiber;

[0037] Delaying the first modulated signal through the delay optical fiber to obtain a delayed first modulated signal;

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

[0039] Outputting the delayed first modulated signal from the c port of the circulator to the adjustable optical fiber delay line through the circulator;

[0040] The time when the delayed first modulated signal reaches the phase modulator is adjusted by an adjustable optical fiber delay line, so that the second modulated signal output by the phase modulator maintains a phase quadrature with the first modulated signal;

[0041] The phase retarder is used to make the polarization states of the delayed first modulation signal and the first modulation signal orthogonal to obtain the modulated first modulation signal.

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

[0043] It can be seen from the above embodiments of the present invention that the microwave signal phase noise measurement system and method provided by the present invention, on the one hand, has low system cost and does not require the use of high-speed detectors and multiple modulators. On the other hand, the system has a large test bandwidth, and the working bandwidth of the microwave signal phase noise measurement system is not limited to the working bandwidth of any electrical device, but is only determined by the working bandwidth of the phase modulator. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] 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.

[0045] Figure 1 A schematic diagram of the structure of a microwave signal phase noise measurement system provided by an embodiment of the present invention;

[0046] Figure 2 A schematic diagram of a flow chart of a microwave signal phase noise measurement method provided by an embodiment of the present invention;

[0047] [Description of Reference Numerals]

[0048] 1-Laser; 2-Optical isolator; 3-Optical coupler; 4-Microwave signal; 5-Phase modulator; 6-Polarization beam splitter; 7-Circulator; 8-Delay fiber; 9-Faraday rotation mirror; 10-Adjustable fiber delay line; 11-Phase delay plate; 12-Adjustable optical filter; 13-Photodetector; 14-Signal processing module. DETAILED DESCRIPTION

[0049] 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.

[0050] See also Figure 1 , Figure 1 A schematic diagram of the structure of a microwave signal phase noise measurement system provided in one embodiment of the present invention, wherein the microwave signal phase noise measurement system comprises:

[0051] Laser 1, used for generating a continuous optical carrier;

[0052] An optical coupler 3 is used to couple the optical carrier and input the optical carrier into a phase modulator 5;

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

[0054] A polarization beam splitter 6, used for modulating the first modulated signal through a polarization state splitting input delay optical fiber link to obtain a modulated first modulated signal, wherein the modulation includes delay and controls phase orthogonality;

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

[0056] The polarization beam splitter 6 is further used to split the second modulated signal into an adjustable optical filter 12 through polarization state;

[0057] The tunable optical filter 12 is used to extract the positive first-order sideband of the second modulated signal to obtain an optical signal to be processed, wherein the sideband information of the optical signal to be processed only has positive first-order sideband information;

[0058] A photoelectric detector 13, used for converting the optical signal to be processed into an electrical signal;

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

[0060] In one embodiment of the present invention, the delay optical fiber link comprises: a circulator 7, a delay optical fiber 8, a Faraday rotation mirror 9, an adjustable optical fiber delay line 10, and a phase delay plate 11;

[0061] The circulator 7 is used to output the first modulated signal to the delay optical fiber 8;

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

[0063] A Faraday reflector 9, used for reflecting the delayed first modulated signal to the circulator 7, so that the polarization state of the delayed first modulated signal returning to the circulator 7 is consistent with the polarization state of the first modulated signal;

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

[0065] The adjustable optical fiber delay line 10 is used to adjust the time when the delayed first modulated signal reaches the phase modulator 5, so that the second modulated signal output by the phase modulator 5 maintains a phase orthogonality with the first modulated signal;

[0066] The phase delay plate 11 is used to make the polarization states of the delayed first modulation signal and the first modulation signal orthogonal to obtain the modulated first modulation signal.

[0067] According to an embodiment of the present invention, the microwave signal phase noise measurement system provided by the present invention can cyclically use the phase modulator through cyclic modulation and polarization isolation methods, thereby effectively reducing the system cost, and at the same time the system operating bandwidth is not limited by the bandwidth limitation of electrical devices.

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

[0069] The optical carrier output by laser 1 is expressed as: E in (t) = E c exp(jω c t), where 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 the time.

[0070] The microwave signal 4 can be expressed as: 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, t is the time;

[0071] Microwave Signal 4 E RF (t) After passing through the phase modulator 5, the first modulated signal is expressed as: Where β 0 is the modulation depth of the phase modulator 5, the modulation depth β 0 The microwave signal amplitude E RF and the half-wave voltage of the phase modulator 5;

[0072] The first modulation signal E out0 After passing through the polarization beam splitter 6, the circulator 7, the delay optical fiber 8, the Faraday reflector 9, the circulator 7, the adjustable optical fiber delay line 10 and the phase delay plate 11, the modulated first modulation signal E is obtained. out1 It is expressed as:

[0073]

[0074] Herein, τ is the total delay provided by the delay optical fiber 8 and the adjustable optical fiber delay line 10 , and τ can be fine-tuned by the adjustable optical fiber delay line 10 .

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

[0076]

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

[0078]

[0079] Simplifying the above formula, we can get:

[0080]

[0081] The second modulation signal E out2 After passing through the adjustable optical filter 12, 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, n=0, m=1 and n=1, m=0 in the above formula, the optical signal to be processed E out3 It can be expressed as:

[0082]

[0083] The photodetector 13 converts the optical signal E to be processed out3 Converted into electrical signal E out , electrical signal E out for:

[0084]

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

[0086]

[0087] The signal output by the photoelectric detector 13 is low-pass filtered, amplified, high-pass filtered, amplified, and then enters the data acquisition card and is 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 electrical signal is processed by the signal processing module 14 to perform a fast Fourier transform to obtain a power spectrum density.

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

[0091]

[0092] See also Figure 2 , Figure 2 A flow chart of a microwave signal phase noise measurement method provided by an embodiment of the present invention, which can be applied to Figure 1 The microwave signal phase noise measurement system shown in the figure 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 modulated signal;

[0095] S203, modulating the first modulated signal through a polarization state splitting input delay optical fiber link to obtain a modulated first modulated 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 modulated signal to obtain an optical signal to be processed, wherein the sideband information of the optical signal to be processed only includes positive first-order sideband information;

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

[0099] S207: Perform data processing on the electrical signal to obtain 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. The 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 a 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 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.

[0102] 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.

[0103] It should be noted that the functional modules in the various embodiments of the present disclosure 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 modules may be implemented in the form of hardware or in the form of software functional modules.

[0104] If the integrated module is implemented in the form of a software function 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 solution of the present invention is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product.

[0105] It should be noted that, for the above-mentioned method embodiments, for the sake of simplicity of description, they are all described as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the described order of actions, because according to the present invention, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also know 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 a microwave signal phase noise measurement system and method provided by the present invention. For technicians in this field, 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.

Claims

1. A microwave signal phase noise measurement system, characterized in that: include: A laser for generating a continuous optical carrier wave; An optical coupler, used for coupling the optical carrier and inputting 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, used to modulate the first modulated signal through a polarization state splitting input delay optical fiber link to obtain a modulated first modulated signal, wherein the modulation includes delay and controlling phase orthogonality; The phase modulator is used to load the microwave signal onto the modulated first modulation signal to obtain a second modulation signal; The polarization beam splitter is further used to split the second modulated signal into an adjustable optical filter through polarization state; The tunable optical filter is used to extract the positive first-order sideband of the second modulated signal to obtain an optical signal to be processed, wherein the sideband information of the optical signal to be processed only has positive first-order sideband information; A photoelectric detector, used for converting the optical signal to be processed into an electrical signal; The signal processing module is used to perform data processing on the electrical signal to obtain the phase noise of the microwave signal.

2. The microwave signal phase noise measurement system according to claim 1, characterized in that: The time-delay optical fiber link comprises: a circulator, a time-delay optical fiber, a Faraday rotating reflector, an adjustable optical fiber delay line, and a phase delay plate; The circulator is used to allow the first modulated signal to enter through the port a of the circulator, and output from the port b of the circulator to the delay optical fiber; The delay optical fiber is used to delay the first modulated signal to obtain a delayed first modulated signal; A Faraday rotator reflector, used for reflecting the delayed first modulated signal to the circulator, so that the polarization state of the delayed first modulated signal output from the circulator c port is consistent with the polarization state of the first modulated signal input from the circulator a port; The circulator is further used to output the delayed first modulated signal to the adjustable optical fiber delay line; An adjustable optical fiber delay line, used for adjusting the time when the delayed first modulated signal reaches the phase modulator, so that the second modulated signal output by the phase modulator maintains a phase quadrature with the first modulated signal; The phase delay plate is used to make the polarization states of the delayed first modulation signal and the first modulation signal orthogonal to obtain the modulated first modulation signal.

3. 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.

4. 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.

5. The microwave signal phase noise measurement system according to claim 1, characterized in that: The working range of the tunable optical filter covers the positive first-order sideband after the microwave signal is modulated.

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

7. A method for measuring microwave signal phase noise, characterized in that: include: Generate a continuous optical carrier; Modulating the microwave signal onto the optical carrier to obtain a first modulated signal; Modulating the first modulated signal through a polarization state splitting input delay optical fiber link to obtain a modulated first modulated signal, wherein the modulation includes delay and controlling phase orthogonality; Loading the microwave signal onto the modulated first modulation signal to obtain a second modulation signal; Extracting the positive first-order sideband of the second modulated signal to obtain an optical signal to be processed, wherein the sideband information of the optical signal to be processed only includes positive first-order sideband information; Converting the optical signal to be processed into an electrical signal; The electrical signal is subjected to data processing to obtain the phase noise of the microwave signal.

8. The microwave signal phase noise measurement method according to claim 7, characterized in that: The time-delay optical fiber link comprises: a circulator, a time-delay optical fiber, a Faraday rotating reflector, an adjustable optical fiber delay line, and a phase delay plate; Through the circulator, the first modulated signal enters from the port a of the circulator and is output from the port b of the circulator to the delay optical fiber; Delaying the first modulated signal through the delay optical fiber to obtain a delayed first modulated signal; A Faraday rotating mirror is used to reflect the delayed first modulated signal to the circulator, so that the polarization state of the delayed first modulated signal output from the circulator c port is consistent with the polarization state of the first modulated signal input from the circulator a port; Outputting the delayed first modulated signal from the c port of the circulator to the adjustable optical fiber delay line through the circulator; The time when the delayed first modulated signal reaches the phase modulator is adjusted by an adjustable optical fiber delay line, so that the second modulated signal output by the phase modulator maintains a phase quadrature with the first modulated signal; The phase retarder is used to make the polarization states of the delayed first modulation signal and the first modulation signal orthogonal to obtain the modulated first modulation signal.

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

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