All-optical microwave photon vector network analysis device and microwave device scattering parameter measurement method

Abstract

An all-optical microwave photon vector network analyzer device includes an optical pulse train generation module, an optical pulse repetition rate conversion and locking module, a tunable microwave photon frequency generation module, a signal loading module, an optical sampling and digitization module, and a signal processing module. The optical pulse train generation module and the input of the optical pulse repetition rate conversion and locking module are connected; the first and second outputs of the optical pulse repetition rate conversion and locking module are connected to the optical inputs of the microwave photon frequency generation module and the optical sampling and digitization module, respectively. This device avoids spectrum leakage and other problems caused by asynchronous sampling, further improving the measurement accuracy of a vector network analyzer.

Description

Technical Field

[0001] The present invention relates to optical information processing technology, in particular to an all-optical microwave photon vector network analysis device and a microwave device scattering parameter measurement method. Background Art

[0002] Vector network analyzers are essential test instruments in electronics and communications, primarily used to measure the scattering parameters, or S-parameters, of microwave devices. However, today's microwave devices have limited bandwidth, and the frequency of signals generated by signal sources is constrained by the characteristics of the electronic devices. Furthermore, using traditional transmitters and receivers requires complex phase-locked circuits to ensure synchronization between transmission and reception (Ghelfi P, Laghezza F, Scotti F, et al. A fully photonics-based coherent radar system [J]. Nature, 2014, 507(7492): 341-345).

[0003] Photonic devices offer advantages over electronic devices, such as wide bandwidth, high precision, and low jitter. Microwave photonics technology combines the strengths of photonics and electronics, and has great potential to break through the "electronic bottleneck" of traditional microwave measurement and signal processing. At present, a variety of microwave measurement and signal processing schemes based on photonic technology have been proposed, such as optical analog-to-digital converters (Su F, Wu G, Ye L, et al. Effects of the photonic sampling pulse width and the photodetection bandwidth on the channel response of photonic ADCs[J]. Optics Express, 2016, 24(2): 924.) and the ultra-wideband microwave photonic vector network analyzer based on optical sampling proposed by Min Ding (Ding M, Jin Z, Chen J, et al. Photonic Network Analyzer Based on OpticalSampling[J]. IEEE Photonics Technology Letters, 2020, 32(4): 212-215.). However, their transmitters still require a high-frequency signal source, which is limited by the aforementioned "electronic bottleneck", and the transmitter and receiver still require complex phase-locked circuits to achieve synchronization.

[0004] Existing photogenerated microwave technologies are mainly divided into direct modulation method (Liu X, Pan W, Zou X, et al. Areconfigurable optoelectronic oscillator based on cascaded coherence-controllable recirculating delay lines [J]. Optics express, 2012, 20 (12): 13296-13301.), optoelectronic oscillator method (Wang T, Chen H, Chen M, et al. High-spectral-purity millimeter-wave signal optical generation [J]. Journal of lightwave technology, 2009, 27 (12): 2044-2051.) and optical heterodyne method (Guan BO, Zhang Y, Zhang LW, et al. Electrically tunable microwave generation using compact dual-polarization fiber laser [J]. IEEE Photonics Technology Letters, 2009, 21(11): 727-729.) Although these methods can generate signals with high spectral purity, there is still much room for improvement in terms of tunability. Mode-locked lasers play a huge role in microwave photonics. If we can achieve a wide range of continuously tunable photogenerated microwaves based on the stability of mode-locked lasers, we can maintain signal stability and achieve synchronization of transmission and reception in microwave photon measurement and signal processing. Summary of the Invention

[0005] To address the shortcomings of the above-mentioned prior art, the present invention provides an all-optical microwave photonic vector network analyzer and a method for measuring the scattering parameters of microwave devices. The device uses a sequence of optical pulses homologous to the receiving end to generate a single-frequency sinusoidal signal. This single-frequency signal is used as the excitation source for the microwave device to obtain the scattering signal of the microwave device under test. The scattered signal is then directly sampled and frequency-converted using optical sampling technology at the receiving end. This abandons the purely electronic device structure of traditional vector network analyzers and replaces the complex phase-locked synchronization circuit with a homologous method at the transmitting and receiving ends. This all-optical structure avoids problems such as image frequency interference while increasing the measurement frequency range and reducing system cost and power consumption.

[0006] The technical solutions of the present invention are as follows:

[0007] An all-optical microwave photon vector network analysis device is characterized in that it includes an optical pulse sequence generation module, an optical pulse repetition rate conversion and locking module, a tunable microwave photon frequency generation module, a signal loading module, an optical sampling and digitization module, and a signal processing module. The optical pulse sequence generation module and the input end of the optical pulse repetition rate conversion and locking module are connected; the first output end and the second output end of the optical pulse repetition rate conversion and locking module are respectively connected to the optical input ends of the microwave photon frequency generation module and the optical sampling and digitization module;

[0008] The optical output end of the microwave photon frequency generating module is connected to the optical input end of the signal loading module, the output end of the signal loading module is connected to the radio frequency input end of the optical sampling and digitization module, the output end of the optical sampling and digitization module is connected to the input end of the signal processing module, the output end of the signal processing module is connected to the control end of the tunable microwave photon frequency generating module, and the two test ports of the signal loading module are connected to the two ends of the device under test.

[0009] The first output end and the second output end of the optical pulse repetition frequency conversion and locking module are synchronously locked with the input of the optical pulse repetition frequency conversion and locking module.

[0010] The tunable microwave photon frequency generating module is used to output a single-frequency signal with a wide range of continuously adjustable amplitude and frequency.

[0011] The tunable microwave photon frequency generation module includes an optical splitter, a first optical filter, a second optical filter, a frequency source, an optical frequency shifter, an optical combiner and a photodetector;

[0012] The input end of the optical splitter is connected to the output end of the optical pulse repetition rate conversion and locking module, the output end of the optical splitter is respectively connected to the input ends of the first optical filter and the second optical filter, the output end of the second optical filter is connected to the optical input end of the optical frequency shifter, and the radio frequency input end of the optical frequency shifter is connected to the output end of the frequency source; the output end of the first optical filter and the output end of the optical frequency shifter are respectively connected to the two input ends of the optical combiner, the output end of the optical combiner is connected to the input end of the photodetector, and the output end of the photodetector is connected to the signal loading module;

[0013] The input signal of the tunable microwave photon frequency generation module is a light pulse sequence, the repetition frequency of the light pulse sequence is greater than or equal to the minimum bandwidth of the first optical filter and the second optical filter, and the center frequency and bandwidth of the first optical filter or the second optical filter are adjustable;

[0014] The maximum output frequency of the frequency source is greater than or equal to half of the minimum bandwidth of the first optical filter and the second optical filter; the frequency shift range of the optical frequency shifter is greater than or equal to the maximum output frequency of the frequency source.

[0015] The optical pulse repetition frequency conversion and locking module performs repetition frequency conversion and locking on the optical pulse sequence generated by the optical pulse sequence generation module, generating two synchronously locked optical pulse sequences, which serve as optical pulse sources for the optical sampling and digitization module and the adjustable microwave photon frequency generation module, respectively, to achieve synchronization between the signal source and the receiver;

[0016] The signal processing module controls the center frequency and bandwidth of the first optical filter or the second optical filter to achieve large-step tuning of the frequency of the single-tone signal, and controls the output frequency of the frequency source to achieve small-range and small-step tuning of the frequency of the single-tone signal; the single-tone signal is frequency-scanned within a measurement range at a frequency resolution set by the signal processing module, and the signal processing module calculates characteristic parameters of the device under test.

[0017] The signal loading module includes a power splitter, a microwave switch, a first directional coupler and a second directional coupler;

[0018] The optical sampling and digitization module includes a first optical coupler, a second optical coupler, a reference branch modulator, a first test branch modulator, a second test branch modulator, a photoelectric detection module, an electrical analog-to-digital converter and a synchronization module;

[0019] The input end of the power divider is connected to the output end of the microwave photon frequency generating module, the first output end of the power divider is connected to the RF input end of the reference branch modulator, the second output end of the power divider is connected to the input end of the microwave switch, the first output end of the microwave switch is connected to the input end of the first directional coupler, the through end of the first directional coupler is connected to a port of the device under test, and the coupling end of the first directional coupler is connected to the RF input end of the first test branch modulator; the second output end of the microwave switch is connected to the input end of the second directional coupler, the through end of the second directional coupler is connected to another port of the device under test, and the coupling end of the second directional coupler is connected to the RF input end of the second test branch modulator; the second output end II of the optical pulse repetition rate conversion and locking module is connected to the input end of the first optical coupler, and the first output end of the first optical coupler is connected to the input end of the first optical coupler. The end is connected to the input end of the second optical coupler, and the three output ends of the second optical coupler are respectively connected to the optical input ends of the reference branch modulator, the first test branch modulator and the second test branch modulator. The output ends of the reference branch modulator, the first test branch modulator and the second test branch modulator are respectively connected to the input ends of the photodetectors of the respective branches in the photoelectric detection module. The output ends of each photodetector in the photoelectric detection module are respectively connected to the input ends of the electrical analog-to-digital converters of the respective branches in the electrical analog-to-digital converter. The electrical analog-to-digital converter starts sampling after receiving the pulse excitation signal and stops sampling before the pulse excitation signal ends. The output ends of the electrical analog-to-digital converter are respectively connected to the signal processing module. The second output end of the first optical coupler has the same repetition frequency of the optical pulse sequence output by the optical pulse sequence generating module of the synchronization module.

[0020] A method for testing scattering parameters of a device under test using an all-optical microwave photon vector network analyzer comprises the following steps:

[0021] 1) Connect the two ports of the device under test to the two test ports of the signal loading module respectively, and input the measured scattering parameters into the signal processing module in the frequency range of f min ~f max and frequency scanning step Δf;

[0022] 2) The optical pulse sequence generation module generates a repetition frequency of f s The optical pulse sequence is input into the optical pulse repetition frequency conversion and locking module, and the first output end and the second output end of the optical pulse repetition frequency conversion and locking module respectively output optical pulse sequences with repetition frequencies f1 and f2;

[0023] 3) The signal processing module sets the bandwidth of the first optical filter or the second optical filter to the minimum value; if f min<f1 / 2, the center frequency f of the first optical filter or the second optical filter is ch2 Set to the center frequency f of the first optical filter or the second optical filter ch1 The same; otherwise, let f ch2 =f ch1 +REM(f min / f1) or f ch2 =f ch1 -REM(f min / f1), where REM(*) represents the remainder operation;

[0024] 4) If |f min -|f ch2 -f ch1 ||<f1 / 2, the signal processing module sets the output frequency of the frequency source to f0=|f min -|f ch2 -f ch1 ||, otherwise, set the output frequency of the frequency source to f0=|f min -|f ch2 -f ch1 ||-f1 / 2; set the frequency sweep step of the frequency source to Δf;

[0025] 5) The signal processing module obtains the data output by the optical sampling and digitization module and calculates the frequency of the device under test at the frequency point f = f min The scattering parameters at ;

[0026] 6) If the optical frequency shifter is in frequency right shift mode (taking an optical signal with a frequency greater than the input frequency of the optical frequency shifter), the signal processing module sets the output frequency of the frequency source to f0 = f0 + Δf. If f0 + |f ch2 -f ch1 |≥f max , go to step 8), otherwise, determine whether f0 is greater than f1 / 2. If so, the optical frequency shifter changes to a frequency left shift mode (taking an optical signal with a frequency less than the optical frequency of the optical frequency shifter input optical frequency) and modifies the center frequency of the first optical filter or the second optical filter to f ch2 =f ch2 +f1; If the optical frequency shifter is in frequency left shift mode, the signal processing module sets the output frequency of the frequency source to f0 = f0-Δf, if |f ch2 -f ch1 |-f0≥f max , go to step 8), otherwise, determine whether f0 is less than 0, if so, the optical frequency shifter changes to frequency right shift mode, and modifies the center frequency of the first optical filter or the second optical filter to f ch2 =f ch2 -f1;

[0027] 7) The signal processing module obtains the data output by the optical sampling and digitization module and calculates the scattering parameters of the device under test at the frequency point f=f+Δf; repeat step 6);

[0028] 8) After the test is completed, the measured scattering parameters are calibrated according to the known calibration parameters and the corresponding calibration method.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] Using optoelectronic hybrid technology, a single-frequency microwave signal with a continuously adjustable frequency range can be generated from a frequency source in a lower frequency range. The frequency range of the frequency source only needs to cover 0 to half of the minimum bandwidth of a commercial optical filter. The lowest frequency of the generated single-frequency microwave signal is the same as that of the frequency source, and the highest frequency is equal to the bandwidth of the photodetector used in the tunable microwave photon frequency generation module.

[0031] The optical sampling and digitization module is cognately locked to the single-frequency microwave signal generated by the tunable microwave photon frequency generation module, which can obtain a digital signal with accurate frequency, avoid problems such as spectrum leakage caused by asynchronous sampling, and further improve the measurement accuracy of the vector network analyzer. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the modules of the all-optical microwave photon vector network analysis device of the present invention.

[0033] Figure 2 This is a schematic diagram of the module structure of the tunable microwave photon frequency generation of the present invention.

[0034] Figure 3 This is a structural diagram of Example 1 of the all-optical microwave photon vector network analysis device of the present invention.

[0035] Figure 4 This is a structural diagram of Example 2 of the all-optical microwave photon vector network analysis device of the present invention.

[0036] Figure 5 This is a schematic structural diagram of Example 3 of the all-optical microwave photon vector network analysis device of the present invention. DETAILED DESCRIPTION

[0037] The following is combined with Figure 3-5 Three preferred embodiments of the present invention are given. The preferred embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0038] Example 1:

[0039] An embodiment of the all-optical microwave photon vector network analysis device of the present invention is shown in FIG. Figure 3 As can be seen from the figure, the all-optical microwave photon vector network analysis device of this embodiment includes an optical pulse sequence generation module 1, an optical pulse repetition rate conversion and locking module 2, a tunable microwave photon frequency generation module 3, a signal loading module 4, an optical sampling and digitization module 5, and a signal processing module 6. The two output terminals I and II of the optical pulse repetition rate conversion and locking module 2 are respectively connected to the optical input terminals of the tunable microwave photon frequency generation module 3 and the optical sampling and digitization module 5; the two test ports of the signal loading module 4 are connected to the two ends of the device under test; and the output terminal of the signal processing module 6 is connected to the control terminal of the tunable microwave photon frequency generation module 3.

[0040] The optical pulse repetition rate conversion and locking module 2 includes an optical coupler 2-1, a wavelength division multiplexer 2-2, an optical fiber delay line 2-3 and a wavelength division multiplexer 2-4; the adjustable microwave photon frequency generation module 3 includes a first optical coupler 3-1, an optical filter 3-2, an adjustable optical filter 3-3, a frequency source 3-4, a carrier suppressed single sideband modulator 3-5, a second optical coupler 3-6 and a photodetector 3-7;

[0041] The output end of the optical pulse sequence generator 1-1 is connected to the input end of the optical coupler 2-1, the output end I of the optical coupler 2-1 is connected to the input end of the wavelength division multiplexer 2-2, the output end of the wavelength division multiplexer 2-2 is respectively connected to one end of the optical fiber delay line 2-3 of different lengths of the branch where each wavelength is located, the other end of the optical fiber delay line 2-3 is connected to the branch of the corresponding wavelength of the wavelength division multiplexer 2-4, the output end of the wavelength division multiplexer 2-4 is connected to the first optical coupler 3-1, the output end of the first optical coupler 3-1 is respectively connected to the input end of the optical filter 3-2 and the tunable optical filter 3-3, the output end of the tunable optical filter 3-3 is connected to the carrier suppressed single sideband modulator The optical input end of the frequency source 3-4 is connected to the RF input end of the carrier suppressed single sideband modulator 3-5; the optical input ends of the optical filter 3-2 and the carrier suppressed single sideband modulator 3-5 are respectively connected to the two input ends of the second optical coupler 3-6, along the output end direction of the second optical coupler 3-6, there are the photodetector 3-7 and the power divider 4-1 in sequence, the first output end of the power divider 4-1 is connected to the RF input end of the reference branch modulator 5-3, the second output end of the power divider 4-1 is connected to the input end of the microwave switch 4-2, the first output end ① of the microwave switch 4-2 is connected to the input end of the first directional coupler 4-3, The through end of the first directional coupler 4-3 is connected to one port of the device under test, and the coupling end of the first directional coupler 4-3 is connected to the RF input end of the first test branch modulator 5-4; the second output end ② of the microwave switch 4-2 is connected to the input end of the second directional coupler 4-4, the through end of the second directional coupler 4-4 is connected to another port of the device under test, and the coupling end of the second directional coupler 4-4 is connected to the RF input end of the second test branch modulator 5-5; the output end II of the optical coupler 2-1 is connected to the input end of the first optical coupler 5-1, the first output end of the first optical coupler 5-1 is connected to the input end of the second optical coupler 5-2, and the second output end of the optical coupler 2-1 is connected to the input end of the second optical coupler 5-2. The three output ends of the second optical coupler 5-2 are respectively connected to the optical input ends of the reference branch modulator 5-3, the first test branch modulator 5-4 and the second test branch modulator 5-5, the output ends of the three modulators are respectively connected to the input ends of the photoelectric detectors of the respective branches in the photoelectric detection module 5-6, the output ends of the photoelectric detectors in the photoelectric detection module 5-6 are respectively connected to the input ends of the electrical analog-to-digital converters of the respective branches in the electrical analog-to-digital converter 5-7, the electrical analog-to-digital converter 5-7 starts sampling after receiving the pulse excitation signal and stops sampling before the pulse excitation signal ends, and the output ends of the electrical analog-to-digital converters are respectively connected to the signal processing module 6;The second output end of the first optical coupler 5-1 is connected to the analog-to-digital converter 5-7 of the synchronization module 5-8, so that the sampling rate of the analog-to-digital converter 5-7 is the same as the repetition frequency of the optical pulse sequence output by the optical pulse sequence generator 1-1.

[0042] The testing process of this embodiment includes the following steps:

[0043] 1) Connect the two ports of the device under test to the two test ports of the signal loading module 4 respectively, and set the frequency range of the measured scattering parameter to be f min ~f max In this embodiment, f min =0;

[0044] 2) The optical pulse sequence generator 1-1 generates a repetition frequency of f s The delay time of the optical fiber delay line 2-2 is set to 1 / mf s 、2 / mf s ,…,1 / f s The optical pulse repetition frequency conversion and locking module multiplies the optical pulse repetition frequency to mf s , where m = 1, 2, 3, ...;

[0045] 3) The bandwidth of the tunable optical filter 3-3 is set to the minimum value and the center frequency f through the signal processing module 6. ch2 Set to the center frequency f of optical filter 3-2 ch1 Same, define n=(f ch2 -f ch1 ) / mf s , k = 0, wherein the initial value of n is 0, k is the modulation mode of the carrier suppressed single sideband modulator 3-5, k = 0 is lower sideband modulation, k = 1 is upper sideband modulation; the frequency of the single optical frequency comb output by the tunable optical filter 3-3 is modulated by the carrier suppressed single sideband modulator 3-5 by the frequency source 3-4, and the frequency of the frequency source output signal is set to f i ;

[0046] 4) Set the test range of frequency source 3-4 to 0~mf through signal processing module 6 s / 2, the resolution is Δf; when k=0, let f i =mf s / 2, and adjust the bias point of the carrier suppressed single sideband modulator 3-5 to make the modulation mode lower sideband modulation; when k = 1, let f i =0, and adjust the bias point of the carrier suppressed single sideband modulator 3-5 so that the modulation mode is upper sideband modulation;

[0047] 5) Calculate n = (fch2 -f ch1 ) / mf s The tunable microwave photon frequency generating module 3 outputs a single-frequency signal, the frequency of the single-frequency signal is f0 = f i +(2n-1)mf s / 2, the single-frequency signal is divided into two paths by the power divider 4-1: one path is input to the RF input port of the reference branch modulator 5-3 of the optical sampling and digitization module 5, and the other path is loaded into the input end of the microwave switch 4-2;

[0048] 6) The microwave switch 4-2 is switched to the first output terminal, and the input signal is loaded onto the first port of the device under test via the first directional coupler 4-3. The signal transmitted through the device under test is input to the RF input port of the second test branch modulator 5-5 via the second directional coupler 4-4; the signal reflected by the device under test is input to the RF input port of the first test branch modulator 5-4 via the first directional coupler 4-3;

[0049] 7) The repetition frequency of the output of the optical pulse sequence generator 1-1 is f s The optical pulse sequence is divided into three paths by the output terminal II of the optical coupler 2-1, the first output terminal of the first optical coupler 5-1 and the second optical coupler 5-2, respectively serving as sampling pulse sequences of the reference branch, the first test branch and the second test branch; the reference branch modulator 5-3 directly samples the frequency signal output from the first output terminal of the power divider 5-4; the first test branch modulator 5-4 and the second test branch modulator 5-5 respectively sample the reflected and transmitted signals of the device under test; the three sampling signals are sent to the signal processing module 6 by the photoelectric detection module 5-6 and the electrical analog-to-digital conversion module 5-7 to obtain corresponding digital sampling results;

[0050] 8) The signal processing module 6 calculates the signal amplitude A of the first test branch 11 , and the phase difference θ between the signal of the second test branch and the reference branch signal 11 , get the S11 parameters of the device under test at this frequency: Wherein j is an imaginary unit; the signal processing module 6 calculates the signal amplitude A of the first test branch; 21 , and the phase difference θ between the signal of the second test branch and the reference branch signal 21 , get the S21 parameter of the device under test at this frequency: Where j is the imaginary unit;

[0051] 9) When f0≤f max , go to the next step, otherwise go to step 11);

[0052] 10) When k = 0, let f i =f i -Δf, when f i ≥0, return to step 4), otherwise when f i <0, let k=1, return to step 4); when k=1, let f i =f i +Δf, when f i ≤mf s / 2, return to step 4), otherwise when f i >mf s / 2, let k = 0, f ch2 =f ch2 +mf s Return to step 4);

[0053] 11) Switch the microwave switch 4-2 to the second output terminal and repeat the above measurement steps to obtain the S12 and S22 parameters of the device under test;

[0054] 12) Calibrate the measured S11, S12, S21, and S22 parameters according to known calibration parameters and corresponding calibration methods.

[0055] Example 2:

[0056] The optical pulse repetition rate conversion and locking module 2 includes an optical coupler 2-1 and an optical switch 2-2; the output terminal I of the optical coupler 2-1 is directly connected to the output terminal of the optical coupler 3-2, the output terminal II is connected to the input terminal of the optical switch 2-2, and the output terminal of the optical switch 2-2 is connected to the input terminal of the first optical coupler 5-1; the other structures and connections are the same as those in Example 1.

[0057] The testing process of this embodiment includes the following steps:

[0058] Steps 2), 3), 4), 5), 7), and 10) of the test process of Example 1 are modified as follows, and the other steps are the same as those of Example 1:

[0059] 2) The optical pulse sequence generator 1-1 generates a repetition frequency of f s The optical pulse sequence is set to f s / m, the output repetition frequency is f s / m optical pulse sequence, the optical pulse sequence and repetition frequency is f s The optical pulse sequence is used as the input of the first optical coupler 5-1 and the first optical coupler 3-1 respectively to achieve the synchronous locking of the tunable microwave photon frequency generation module 3 and the optical sampling and digitization module 5; the repetition frequency is f sThe optical pulse sequence is connected to the output end of the optical filter 3-2 and the output end of the tunable optical filter 3-3 by the two output ends of the first optical coupler 3-1, respectively. The optical filter 3-2 outputs a single optical frequency comb with a fixed frequency, and the tunable optical filter 3-3 filters out a single optical frequency comb with a frequency determined by the center frequency of the tunable optical filter 3-3.

[0060] 3) The bandwidth of the tunable optical filter 3-3 is set to the minimum value and the center frequency f through the signal processing module 6. ch2 Set to the center frequency f of optical filter 3-2 ch1 Same, define n=(f ch2 -f ch1 ) / f s , k = 0, wherein the initial value of n is 0, k is the modulation mode of the carrier suppressed single sideband modulator 3-5, k = 0 is lower sideband modulation, k = 1 is upper sideband modulation; the frequency of the single optical frequency comb output by the tunable optical filter 3-3 is modulated by the carrier suppressed single sideband modulator 3-5 by the frequency source 3-4, and the frequency of the frequency source output signal is set to f i ;

[0061] 4) Set the test range of frequency source 3-4 to 0~f through signal processing module 6 s / 2, the resolution is Δf; when k=0, let f i =f s / 2, and adjust the bias point of the carrier suppressed single sideband modulator 3-5 to make the modulation mode lower sideband modulation; when k = 1, let f i =0, and adjust the bias point of the carrier suppressed single sideband modulator 3-5 so that the modulation mode is upper sideband modulation;

[0062] 5) Calculate n = (f ch2 -f ch1 ) / f s The tunable microwave photon frequency generating module 3 outputs a single-frequency signal, the frequency of the single-frequency signal is f0 = f i +(2n-1)f s / 2, the single-frequency signal is divided into two paths by the power divider 4-1: one path is input to the RF input port of the reference branch modulator 5-3 of the optical sampling and digitization module 5, and the other path is loaded into the input end of the microwave switch 4-2;

[0063] 7) The repetition frequency of the output of the optical switch 2-2 is f sThe optical pulse sequence of / m is split into three paths by the output terminal II of the optical coupler 2-1, the first output terminal of the first optical coupler 5-1 and the second optical coupler 5-2, respectively serving as sampling pulse sequences of the reference branch, the first test branch and the second test branch; the reference branch modulator 5-3 directly samples the frequency signal output from the first output terminal of the power divider 5-4; the first test branch modulator 5-4 and the second test branch modulator 5-5 respectively sample the reflected and transmitted signals of the device under test; the three sampling signals are sent to the signal processing module 6 by the photoelectric detection module 5-6 and the electrical analog-to-digital conversion module 5-7 to obtain corresponding digital sampling results;

[0064] 10) When k = 0, let f i =f i -Δf, when f i ≥0, return to step 4), otherwise when f i <0, let k=1, return to step 4); when k=1, let f i =f i +Δf, when f i ≤f s / 2, return to step 4), otherwise when f i >f s / 2, let k = 0, f ch2 =f ch2 +f s Return to step 4);

[0065] Example 3:

[0066] The optical pulse repetition rate conversion and locking module 2 includes an optical coupler 2-1 and an optical pulse sequence generator 2; the output end I of the optical coupler 2-1 is connected to the output end of the optical pulse sequence generator 2, the output end of the optical pulse sequence generator 2 is connected to the input end of the first optical coupler 3-1, and the output end II of the optical coupler is connected to the input end of the first optical coupler 5-1; the other structures and connections are the same as those in Example 1.

[0067] The testing process of this embodiment includes the following steps:

[0068] Steps 2), 3), 4), 5), 7), and 10) of the test process of Example 1 are modified as follows, and the other steps are the same as those of Example 1:

[0069] 2) The optical pulse sequence generator generates a repetition frequency of f s1 The optical pulse sequence is used as the seed light input of the tunable microwave photon frequency generation module and the optical pulse sequence generator 2, and the optical pulse sequence generator 2 outputs a repetition frequency multiplied to f s2The optical pulses are de-sequenced to achieve synchronous locking of the two modules; the repetition frequency is f s2 The optical pulse sequence is connected to the output of the optical filter and the output of the tunable optical filter via the two output ends of the optical coupler, respectively. The optical filter outputs a single optical frequency comb with a fixed frequency, and the tunable optical filter filters out a single optical frequency comb with a frequency determined by the center frequency of the tunable optical filter.

[0070] 3) Setting the bandwidth of the tunable optical filter to the minimum value and the center frequency f through the signal processing module ch2 Set to the center frequency f of the optical filter ch1 Same, define n=(f ch2 -f ch1 ) / f s2 , k = 0, where the initial value of n is 0, k is the modulation mode of the carrier suppressed single sideband modulator, k = 0 is lower sideband modulation, k = 1 is upper sideband modulation; the frequency of the single optical frequency comb output by the tunable optical filter is modulated by the frequency source of the carrier suppressed single sideband modulator, and the frequency of the output signal of the frequency source is set to f i ;

[0071] 4) Set the test range of the frequency source to 0~f through the signal processing module s2 / 2, the resolution is Δf; when k=0, let f i =f s2 / 2, and adjust the bias point of the carrier suppressed single sideband modulator to make the modulation mode lower sideband modulation; when k = 1, let f i =0, and adjust the bias point of the carrier suppressed single sideband modulator to make the modulation mode upper sideband modulation;

[0072] 5) Calculate n = (f ch2 -f ch1 ) / f s2 The tunable microwave photon frequency generating module outputs a single-frequency signal, the frequency of the single-frequency signal is f0 = f i +(2n-1)f s2 / 2, the single frequency signal is divided into two paths by the power divider: one path is input to the RF input port of the reference branch modulator of the optical sampling and digitization module, and the other path is loaded into the input end of the microwave switch;

[0073] 7) The repetition frequency is f s1The optical pulse sequence is split into three paths by the optical coupler through the output end (II) of the optical coupler and the first output end of the optical coupler, respectively serving as sampling pulse sequences of the reference branch, the first test branch, and the second test branch; the reference branch modulator directly samples the frequency signal output from the first output end of the power splitter; the first test branch modulator and the second test branch modulator respectively sample the reflected and transmitted signals of the device under test; the three sampling signals are sent to the signal processing module through the photoelectric detection module and the electrical analog-to-digital conversion module to obtain corresponding digital sampling results;

[0074] 10) When k = 0, let f i =f i -Δf, when f i ≥0, return to step 4), otherwise when f i <0, let k=1, return to step 4); when k=1, let f i =f i +Δf, when f i ≤f s2 / 2, return to step 4), otherwise when f i >f s2 / 2, let k = 0, f ch2 =f ch2 +f s2 Return to step 4).

[0075] The above embodiment realizes the generation of a single-frequency microwave signal with a continuously adjustable frequency over a wide range by automatically controlling the device parameters in each module and utilizing a frequency source in a relatively low frequency range.

[0076] The above embodiments respectively adopt different optical pulse repetition frequency conversion and locking module structures to generate two synchronous optical pulse sequences with different repetition frequencies. The optical pulse sequence input to the tunable microwave photon frequency generation module is greater than or equal to the minimum bandwidth of the optical filter, while the repetition frequency of the optical pulse sequence input to the optical sampling and digitization module is lower, thereby reducing the requirements for the sampling rate and bandwidth of the electrical analog-to-digital converter.

[0077] The present invention utilizes photogenerated microwave technology based on optical pulse sequences to tune the amplitude and frequency of the generated single-frequency signal in the optical domain, breaking through the traditional signal source frequency range limited by electronic devices and increasing the test bandwidth of the system at the transmitting end. The present invention utilizes optical sampling technology for direct reception, abandoning the superheterodyne and / or direct conversion receiver structure, effectively reducing the system's power consumption and directly avoiding problems such as image frequency suppression. By utilizing the principle of homologous transmission and reception, the problem of spectrum leakage of digital signals caused by synchronous transmission and reception is fundamentally solved, and the measurement accuracy of the scattering parameters of the vector network is fundamentally improved. Utilizing mature commercial optoelectronic devices, the system is low-cost, relatively simple to implement, and easy to integrate.

Claims

1. An all-optical microwave photon vector network analysis device, characterized in that: The optical pulse sequence generating module (1), an optical pulse repetition frequency conversion and locking module (2), a tunable microwave photon frequency generating module (3), a signal loading module (4), an optical sampling and digitizing module (5), and a signal processing module (6); the optical pulse sequence generating module (1) and the input end of the optical pulse repetition frequency conversion and locking module (2) are connected; the first output end (I) and the second output end (II) of the optical pulse repetition frequency conversion and locking module (2) are respectively connected to the optical input end of the microwave photon frequency generating module (3) and the optical sampling and digitizing module (5); The optical output end of the microwave photon frequency generating module (3) is connected to the optical input end of the signal loading module (4), the output end of the signal loading module (4) is connected to the radio frequency input end of the optical sampling and digitizing module (5), the output end of the optical sampling and digitizing module (5) is connected to the input end of the signal processing module (6), the output end of the signal processing module (6) is connected to the control end of the tunable microwave photon frequency generating module (3), and the two test ports of the signal loading module (4) are connected to the two ends of the device under test; The tunable microwave photon frequency generating module (3) is used to output a single-frequency signal with a wide range of continuously adjustable amplitude and frequency; The tunable microwave photon frequency generation module (3) comprises an optical splitter (3-1), a first optical filter (3-2), a second optical filter (3-3), a frequency source (3-4), an optical frequency shifter (3-5), an optical combiner (3-6) and a photodetector (3-7); The input end of the optical splitter (3-1) is connected to the output end of the optical pulse repetition frequency conversion and locking module (2); the output end of the optical splitter (3-1) is respectively connected to the input ends of the first optical filter (3-2) and the second optical filter (3-3); the output end of the second optical filter (3-3) is connected to the optical input end of the optical frequency shifter (3-5); the radio frequency input end of the optical frequency shifter (3-5) is connected to the output end of the frequency source (3-4); the output end of the first optical filter (3-2) and the output end of the optical frequency shifter (3-5) are respectively connected to the two input ends of the optical combiner (3-6); the output end of the optical combiner (3-6) is connected to the input end of the photodetector (3-7); the output end of the photodetector (3-7) is connected to the signal loading module (4); The input signal of the tunable microwave photon frequency generating module (3) is a light pulse sequence, the repetition frequency of the light pulse sequence is greater than or equal to the minimum bandwidth of the first optical filter (3-2) and the second optical filter (3-3), and the center frequency and bandwidth of the first optical filter (3-2) or the second optical filter (3-3) are adjustable; The maximum output frequency of the frequency source (3-4) is greater than or equal to half of the minimum bandwidth of the first optical filter (3-2) and the second optical filter (3-3); the frequency shift range of the optical frequency shifter (3-5) is greater than or equal to the maximum output frequency of the frequency source (3-4).

2. The all-optical microwave photon vector network analysis device according to claim 1, characterized in that: The first output end (I) and the second output end (II) of the optical pulse repetition frequency conversion and locking module (2) are synchronously locked with the input of the optical pulse repetition frequency conversion and locking module (2).

3. The all-optical microwave photon vector network analysis device according to claim 1, characterized in that: The optical pulse repetition frequency conversion and locking module (2) performs repetition frequency conversion and locking on the optical pulse sequence generated by the optical pulse sequence generation module (1), thereby generating two synchronously locked optical pulse sequences, which serve as optical pulse sources for the optical sampling and digitization module (5) and the adjustable microwave photon frequency generation module (3), respectively, to achieve synchronization between the signal source and the receiver; The signal processing module (6) controls the center frequency and bandwidth of the first optical filter (3-2) or the second optical filter (3-3) to achieve large-step tuning of the frequency of the single-tone signal, and the signal processing module (6) controls the output frequency of the frequency source (3-4) to achieve small-range and small-step tuning of the frequency of the single-tone signal; the single-tone signal is frequency-scanned within a measurement range at a frequency resolution set by the signal processing module (6), and the characteristic parameters of the device under test are calculated by the signal processing module (6).

4. The all-optical microwave photon vector network analysis device according to claim 1, characterized in that: The signal loading module (4) comprises a power divider (4-1), a microwave switch (4-2), a first directional coupler (4-3) and a second directional coupler (4-4); The optical sampling and digitization module (5) comprises a first optical coupler (5-1), a second optical coupler (5-2), a reference branch modulator (5-3), a first test branch modulator (5-4), a second test branch modulator (5-5), a photoelectric detection module (5-6), an electrical analog-to-digital converter (5-7), and a synchronization module (5-8); The input end of the power divider (4-1) is connected to the output end of the microwave photon frequency generating module (3), the first output end of the power divider (4-1) is connected to the radio frequency input end of the reference branch modulator (5-3), the second output end of the power divider (4-1) is connected to the input end of the microwave switch (4-2), the first output end ① of the microwave switch (4-2) is connected to the input end of the first directional coupler (4-3), the through end of the first directional coupler (4-3) is connected to a port of the device under test, and the coupling end of the first directional coupler (4-3) is connected to the first test The microwave switch (4-2) is connected to the radio frequency input end of the branch modulator (5-4); the second output end ② of the microwave switch (4-2) is connected to the input end of the second directional coupler (4-4), the through end of the second directional coupler (4-4) is connected to the other port of the device under test, and the coupling end of the second directional coupler (4-4) is connected to the radio frequency input end of the second test branch modulator (5-5); the second output end II of the optical pulse repetition frequency conversion and locking module (2) is connected to the input end of the first optical coupler (5-1), and the first output end of the first optical coupler (5-1) is connected to the second optical coupler (5 -2), the three output ends of the second optical coupler (5-2) are respectively connected to the optical input ends of the reference branch modulator (5-3), the first test branch modulator (5-4) and the second test branch modulator (5-5), the output ends of the reference branch modulator (5-3), the first test branch modulator (5-4) and the second test branch modulator (5-5) are respectively connected to the input ends of the photoelectric detectors of their respective branches in the photoelectric detection module (5-6), and the output ends of the photoelectric detectors in the photoelectric detection module (5-6) are respectively connected to the electrical analog-to-digital converter The first optical coupler (5-1) and the second optical coupler (5-7) are connected to the input ends of the electrical analog-to-digital converters of the respective branches in the first optical coupler (5-7), the electrical analog-to-digital converters (5-7) start sampling after receiving the pulse excitation signal and stop sampling before the pulse excitation signal ends, and the output ends of the electrical analog-to-digital converters are respectively connected to the signal processing modules (6); the second output end of the first optical coupler (5-1) is connected to the electrical analog-to-digital converter (5-7) through the synchronization module (5-8), so that the sampling rate of the electrical analog-to-digital converter module (5-7) is the same as the repetition frequency of the optical pulse sequence output by the optical pulse sequence generating module (1).

5. A method for testing scattering parameters of a device under test using the all-optical microwave photon vector network analyzer according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: 1) The two ports of the device under test are connected to the two test ports of the signal loading module (4) respectively, and the frequency range of the measured scattering parameters is input to the signal processing module (6) min ~f max and frequency scanning step Δf; 2) The optical pulse sequence generation module (1) generates a repetition frequency of f s An optical pulse sequence is input into an optical pulse repetition frequency conversion and locking module (2), and a first output end (I) and a second output end (II) of the optical pulse repetition frequency conversion and locking module (2) respectively output optical pulse sequences with repetition frequencies f1 and f2; 3) The signal processing module (6) sets the bandwidth of the first optical filter (3-3) or the second optical filter (3-2) to the minimum value; if f min <f1 / 2, the center frequency f of the first optical filter (3-3) or the second optical filter (3-2) ch2 Set to the center frequency f of the first optical filter (3-3) or the second optical filter (3-2) ch1 The same; otherwise, let f ch2 =f ch1 +REM(f min / f1) or f ch2 =f ch1 -REM(f min / f1), where REM(*) represents the remainder operation; 4) If |f min -|f ch2 -f ch1 ||<f1 / 2, the signal processing module (6) sets the output frequency of the frequency source (3-4) to f0=|f min -|f ch2 -f ch1 ||, otherwise, set the output frequency of the frequency source (3-4) to f0=|f min -|f ch2 -f ch1 ||-f1 / 2; Set the frequency sweep step of the frequency source (3-4) to Δf; 5) The signal processing module (6) obtains the data output by the optical sampling and digitization module (5) and calculates the frequency of the device under test at the frequency point f = f min The scattering parameters at ; 6) If the optical frequency shifter (3-5) is in the frequency right shift mode, that is, taking an optical signal with a frequency greater than the input optical frequency of the optical frequency shifter (3-5), the signal processing module (6) sets the output frequency of the frequency source (3-4) to f0=f0+Δf. If f0+|f ch2 -f ch1 |≥f max , go to step 8), otherwise, determine whether f0 is greater than f1 / 2. If so, the optical frequency shifter (3-5) changes to a frequency left shift mode, that is, taking an optical signal with a frequency less than the input optical frequency of the optical frequency shifter (3-5), and modifying the center frequency of the first optical filter (3-3) or the second optical filter (3-2) to f ch2 =f ch2 +f1; If the optical frequency shifter (3-5) is in the frequency left shift mode, the signal processing module (6) sets the output frequency of the frequency source (3-4) to f0 = f0-Δf, if |f ch2 -f ch1 |-f0≥f max , go to step 8), otherwise, determine whether f0 is less than 0, if so, the optical frequency shifter (3-5) changes to the frequency right shift mode, and modifies the center frequency of the first optical filter (3-3) or the second optical filter (3-2) to f ch2 =f ch2 -f1; 7) The signal processing module (6) obtains the data output by the light sampling and digitization module (5), and calculates the scattering parameters of the device under test at the frequency point f=f+Δf; and repeats step 6); 8) After the test is completed, the measured scattering parameters are calibrated according to the known calibration parameters and the corresponding calibration method.

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