Frequency control array MIMO signal generation system and method based on photon phase modulation

Abstract

The invention discloses a frequency control array MIMO signal generation system and method based on photon phase modulation, and the system outputs an optical carrier wave through a laser, the optical carrier wave is divided into two paths through a first optical splitter: one path loads a radio frequency signal through a carrier wave suppression single side band modulation module, and after a specific frequency optical signal is generated, the optical signal is divided into N paths through a third optical splitter; and the other path is divided into N paths of optical carriers through a second optical splitter, and the N paths of optical carriers are input into a phase modulation module. The phase modulation module loads a quadrature phase coding signal and a sawtooth wave signal to the optical carrier to form a phase modulation signal. And after the optical coupling module couples the two paths of signals, the photoelectric detection module performs beat frequency to generate N channels of FDA-MIMO signals. The system has the characteristics of large bandwidth, flexible and adjustable frequency offset and phase encoding format, strong channel expansibility, simple structure and the like.

Description

Technical Field

[0001] The present application relates to the technical fields of microwave photonics and frequency diverse array MIMO, and particularly relates to a frequency diverse array MIMO signal generation system and method based on photon phase modulation. Background Art

[0002] As a key technology widely used in fields such as radar and communication, the beam pointing characteristics of a phased array antenna are mainly related to the angle and independent of the distance. With the continuous development of radar technology, the frequency diverse array (FDA) antenna, as a new type of antenna technology, has emerged. By introducing a frequency offset between adjacent antenna elements, the FDA antenna successfully realizes the dual correlation of the transmit beam pattern with both the angle and the distance, thus overcoming the limitation that the beam pointing of the traditional phased array antenna is independent of the distance.

[0003] The FDA antenna with a fixed frequency offset forms a periodically repeated "S"-shaped strip beam pattern in space, and its period is closely related to the frequency offset between adjacent elements. In addition, due to the time periodicity of the array factor, a single frequency offset format of the transmit waveform can achieve full-spatial scanning, which significantly improves the scanning ability of the radar. Further, when the FDA antenna is combined with the multiple input multiple output (MIMO) radar technology, the FDA-MIMO radar system is formed. This system uses the orthogonality of the MIMO signals at the receiving end to separate the echo signals in multiple channels, thereby obtaining an additional degree of freedom in the range dimension. This characteristic enables the FDA-MIMO radar to show great potential in realizing two-dimensional estimation of the target's angle and range, anti-main lobe interference, etc.

[0004] However, the traditional digital array-based FDA-MIMO signal generation technology faces many challenges. Since the bandwidth of the generated signal is strictly limited by the sampling rate of the analog-to-digital converter, with the increasing demand for bandwidth in systems such as radar and communication, the digital array signal FDA-MIMO signal generation technology gradually exposes problems such as rate bottlenecks, frequency dependence, and electromagnetic interference. These problems not only limit the performance improvement of the radar system but also restrict its application in complex electromagnetic environments. Summary of the Invention

[0005] Aiming at the technical bottlenecks in the generation of existing digital array signal FDA-MIMO signals, this application aims to provide a frequency-controlled array MIMO signal generation system and method based on photon phase modulation. Based on a Dual-Parallel Mach-Zehnder Modulator (DPMZM) and a Phase Modulator (PM), it can significantly improve the signal bandwidth, reduce spurious distortion, enhance the frequency offset tuning ability, and reduce electromagnetic interference between multiple channels.

[0006] To achieve the above technical objectives, this application is mainly realized through the following technical solutions:

[0007] In one aspect of this application, a frequency-controlled array MIMO signal generation system based on photon phase modulation is provided, including:

[0008] A laser for outputting an optical carrier;

[0009] A first optical splitter that receives the optical carrier output by the laser and splits it into a first optical path and a second optical path;

[0010] A carrier-suppressed single-sideband modulation module that receives a radio frequency signal and the optical carrier of the first optical path for carrier-suppressed single-sideband modulation and outputs an optical signal of a specific frequency;

[0011] A second optical splitter that receives the optical carrier of the second optical path and splits it into N optical carriers;

[0012] A third optical splitter that receives the optical signal output by the dual-parallel Mach-Zehnder modulator and splits it into N optical signals;

[0013] A phase modulation module with N channels, each channel correspondingly receiving one optical carrier split by the second optical splitter, and loading an orthogonal phase encoding signal and a sawtooth wave signal on the optical carrier of each channel to form a phase modulation signal;

[0014] An optical coupling module with N channels, each channel correspondingly receiving one optical signal split by the third optical splitter and the phase modulation signal formed by the modulation module;

[0015] An optoelectronic detection module with N channels, each channel correspondingly receiving the phase modulation signal output by the optical coupling module to output an FDA-MIMO signal.

[0016] In one embodiment, each channel of the phase modulation module includes two cascaded phase modulators PM i,1 and PM i,2 , and the phase modulators PM i,1 and PM i,2 are independently driven by an orthogonal phase encoding signal and a sawtooth wave signal respectively.

[0017] In one embodiment, the phase modulation module has a single-phase modulator structure per channel, and the single-phase modulator structure is driven by a coupled signal of an orthogonal phase encoding signal and a sawtooth wave signal.

[0018] In one embodiment, the carrier-suppressed single-sideband modulation module employs a Dual-Parallel Mach-Zehnder Modulator (DPMZM).

[0019] In one embodiment, the carrier-suppressed single-sideband modulation module uses a Mach-Zehnder Modulator (MZM) to generate double-sideband modulation, and then filters out the target single-sideband frequency through an optical filter.

[0020] In one embodiment, the radio frequency signal includes a single-frequency signal, a chirp signal, a phase encoding signal, or a vector modulation signal.

[0021] In one embodiment, the orthogonal phase encoding signal loaded into the phase modulation module is selected from a binary encoding or a quaternary encoding format.

[0022] In another aspect of the present application, there is provided a method for generating a frequency-controlled array MIMO signal based on photon phase modulation, including the following steps:

[0023] S1: Divide an optical carrier with a frequency of f c into a first optical path and a second optical path;

[0024] S2: Load a radio frequency signal with a frequency of f0 to perform carrier-suppressed single-sideband modulation on the optical carrier of the first optical path, generate an optical signal with a frequency of f c + f0, and divide it into N optical signals;

[0025] S3: Divide the second optical path into N optical carriers, and load an orthogonal phase encoding signal and a sawtooth wave signal to the i-th optical carrier to generate a phase-controlled optical signal for the i-th channel; where i = 1…N;

[0026] S4: Couple the i-th optical signal among the N optical signals with the phase-controlled optical signal of the i-th channel, and generate an i-th channel FDA-MIMO signal through photoelectric conversion and beat frequency.

[0027] In one embodiment, step S3 includes:

[0028] Load an orthogonal phase encoding signal to the i-th optical carrier for phase modulation to generate an optical signal with a frequency of f c and a phase varying with the orthogonal phase encoding signal;

[0029] Continue to load a sawtooth wave signal for phase modulation to shift the frequency by f i, generating a phase-modulated optical signal of the i-th channel with a frequency of (f c + f i ), and the phase varying with the quadrature phase-coded signal.

[0030] In one embodiment, the orthogonality between the FDA-MIMO signals of each channel is adjusted by controlling the code length and phase coding format of the quadrature phase-coded signals applied to each optical carrier.

[0031] In one embodiment, by controlling at least one parameter among the repetition rate, polarity, and amplitude of the sawtooth wave signals applied to each optical carrier, the frequency shift amount of each optical carrier is adjusted, and further the frequency offset of the FDA-MIMO signals of each channel is changed.

[0032] The beneficial effects of this application are as follows:

[0033] This application utilizes microwave photonics technology. Through carrier-suppressed single-sideband modulation of the input radio frequency signal, which is then power-divided into N paths and coupled with the phase modulation signals of the corresponding optical paths, FDA-MIMO signals with different frequency offsets and different phase coding formats are obtained through photoelectric detection, having characteristics such as large bandwidth, flexible adjustability of frequency offset and phase coding format, strong channel scalability, and simple structure. Description of the Drawings

[0034] Figure 1 It is a schematic diagram of a frequency-controlled array MIMO signal generation system based on photon phase modulation according to an embodiment of this application;

[0035] Figure 2 It is a spectrogram of the carrier-suppressed single-sideband CS-SSB optical signal output by the DPMZM in an embodiment of this application;

[0036] Figure 3 It is a spectrogram of the optical signal output by the first PM in the first path in an embodiment of this application;

[0037] Figure 4 It is a spectrogram of the optical signal output by the second PM in the first path in an embodiment of this application;

[0038] Figure 5 It is a time domain and partial region enlarged view of the electrical signal output after beat frequency of the first PD in an embodiment of this application;

[0039] Figure 6 It is a phase change diagram of the electrical signal output after beat frequency of the first PD and the first path quadrature phase-coded signal in an embodiment of this application. Detailed Embodiments

[0040] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0041] Introducing microwave photon technology into the field of FDA-MIMO signal generation has become a highly potential solution. Microwave photon technology, with its inherent advantages such as large bandwidth, electromagnetic interference resistance, and low frequency dependence, provides the possibility to break through the bottleneck of digital array signal generation technology. By utilizing microwave photon technology, the signal bandwidth can be significantly increased, spurious distortion can be reduced, frequency offset tuning ability can be enhanced, and electromagnetic interference between multiple channels can be effectively reduced. However, there has been no report on the method for generating microwave photon FDA-MIMO signals. Therefore, developing a system and method for generating FDA-MIMO signals based on microwave photon technology has important research significance and application value.

[0042] In an embodiment of the present application, a microwave photon FDA-MIMO signal generation system based on a dual-parallel Mach-Zehnder modulator and a phase modulator is provided.

[0043] Referring to Figure 1 as shown, the device in this embodiment includes a laser, one DPMZM, 2×N PMs (N is the number of FDA-MIMO signal paths), one radio frequency (RF) source, N sawtooth wave generators, N arbitrary wave generators (AWGs), three optical splitters (OSs), N optical couplers (OCs), and N photodiodes (PDs).

[0044] Specifically, the output port of the laser is connected to the input end of the optical splitter OS1; the two output ends of OS1 are respectively connected to the optical signal input end of the DPMZM and the input end of the optical splitter OS2; the output end of the DPMZM is connected to the input end of the optical splitter OS3; the i-th (i = 1…N) output end of OS2 is connected to the input end of the phase modulator PM i,1 ; the output end of PM i,1 is connected to the input end of the phase modulator PM i,2 ; the output end of PM i,2 and the i-th output end of OS3 are correspondingly connected to the two input ends of the optical coupler OC i ; the output end of the optical coupler OC i is respectively connected to PD iInput terminal; PD i Output the required i-th FDA-MIMO radio frequency signal (RF i ); The RF source is connected to the RF input port of the DPMZM, and the i-th channel quadrature phase encoding signal is connected to the PM i1 RF input port, and the i-th channel sawtooth wave signal is connected to the PM i,2 RF input port.

[0045] In some embodiments, the method for implementing carrier-suppressed single-sideband modulation is not limited to DPMZM, and methods such as using MZM to generate double-sideband modulation and filtering out the required frequency with an optical filter can also be adopted.

[0046] In some embodiments, the number of optical power splitting paths and the number of PDs N of OS2 and OS3 in the invention can be determined according to actual needs, and after signal power splitting, the power can be compensated by adding an optical power amplifier to optimize the signal-to-noise ratio of the generated signal.

[0047] In some embodiments, the signal loaded into the DPMZM is not limited to a single-frequency signal, and can also be other signals such as radar and communication signals, such as chirp signals, phase encoding signals, or vector modulation signals.

[0048] In some embodiments, the MIMO signal loaded into the PM i,1 is not limited to the four-phase encoding format, and can also be other formats of MIMO signals such as binary encoding.

[0049] In some embodiments, each channel of the phase modulation module has two PMs, which respectively load the quadrature phase encoding signal and the sawtooth wave signal to achieve optical carrier frequency shift and phase modulation. Alternatively, the quadrature phase encoding signal and the sawtooth wave signal can be coupled and input into one PM to simultaneously achieve the functions of optical carrier frequency shift and phase modulation in one PM.

[0050] In another embodiment of the present application, a method for generating a microwave photonics FDA-MIMO signal based on a dual-parallel Mach-Zehnder modulator and a phase modulator is provided, including the following steps:

[0051] 1) Output an optical carrier with a frequency of f c from the laser and input it into OS1;

[0052] 2) OS1 divides the injected optical carrier into two paths, one path is input into the DPMZM, and the other path is input into OS2;

[0053] 3) Modulate the optical carrier with an RF signal with a frequency of f0 in the DPMZM to achieve carrier-suppressed single-sideband modulation, and then the DPMZM outputs an optical signal with a frequency of f c + f0;

[0054] 4) The optical signal output by the DPMZM is input to the OS3, and the optical signal is split into N paths;

[0055] 5) The OS2 splits the injected optical carrier into N paths, and the i-th path is correspondingly input to the PM i,1 ;

[0056] 6) The i-th path of quadrature phase-encoded signal drives the PM i,1 to perform phase modulation on the optical carrier, modulate the i-th path of quadrature phase-encoded signal onto the optical carrier, and then the PM i,1 outputs an optical signal with a frequency of f c , and the phase varies with the input i-th path of quadrature phase-encoded signal;

[0057] 7) The optical signal output by the PM i,1 is injected into the PM i,2 , the repetition rate of the i-th sawtooth wave signal is f i , drives the PM i,2 to perform sawtooth wave phase modulation on the optical signal, realizing a frequency shift of f i , and then the PM i,2 outputs a phase modulation signal with a frequency of f c + f i , and the phase varies with the input i-th path of quadrature phase-encoded signal;

[0058] 8) The i-th path of optical signal split by the OS3 and the phase modulation signal output by the PM i,2 are coupled through the OC i and input to the PD i for beat frequency to obtain the i-th channel FDA-MIMO signal RF i with a frequency of f0 - f i .

[0059] By controlling the code length and phase encoding format of each path of quadrature phase-encoded signal, phase encoding signal generation modulation with different degrees of orthogonality can be realized, and then the orthogonality between each channel FDA-MIMO signals can be changed.

[0060] By controlling the repetition rate, polarity, and amplitude of each path of sawtooth wave signal, the frequency shift amount of the optical carrier can be adjusted, and then the frequency offset of the i-th channel FDA-MIMO signal RF i can be changed;

[0061] Exemplary Embodiment

[0062] Adopt as Figure 1For the described device, N is taken as 4, and it generates 4-channel FDA-MIMO signals. The device includes: a semiconductor laser, a dual-parallel Mach-Zehnder modulator (DPMZM), 8 phase modulators (PM), 4 PDs, a radio frequency signal source, a 4-channel sawtooth wave generator, a 4-channel quadrature phase encoding generator, 3 optical splitters (OS), and 4 optical couplers (OC). The output port of the semiconductor laser is connected to the optical input port of OS1 through a polarization-maintaining fiber. The two optical output ports of OS1 are respectively connected to the optical input port of DPMZM and the optical input port of OS2. The 4 optical input ports of OS2 are respectively connected to the optical input ports of PM 1,1 to PM 4,1 ; the optical output ports of PM 1,1 to PM 4,1 are respectively connected to the optical input ports of PM 1,2 to PM 4,2 ; the optical output ports of PM 1,2 to PM 4,2 are respectively connected in pairs to the 16 optical output ports of OS3 and then connected to the optical input ports of OC1 to OC4. The optical output ports of OC1 to OC4 are respectively connected to the optical input ports of 4 PDs; the output port of the radio frequency signal source is connected to the radio frequency input port of DPMZM; the 4-channel quadrature phase encoding signals are respectively connected to the radio frequency ports of the corresponding PM i1 ; the output ports of the 4-channel sawtooth wave generator are respectively connected to the radio frequency ports of the corresponding PM i,2 .

[0063] The specific process of generating the FDA-MIMO signals is as follows:

[0064] Step 1: Connect the device of the embodiment in the simulation software, and set the average power of the continuous optical carrier generated by the semiconductor laser to be 3.2 mW and the frequency to be 193.5100 THz; the half-wave voltage of DPMZM and PM is about 5 V, and the extinction ratio is about 35 dB;

[0065] Step 2: Use OS1 to split the input optical carrier power into two paths and inject them into DPMZM and OS2 respectively;

[0066] Step 3: The radio frequency signal source generates a single-frequency signal with a frequency of 10 GHz and a power of 13 dBm to drive DPMZM. DPMZM operates in the suppressed-carrier single-sideband mode to generate a carrier-suppressed single-sideband signal, as Figure 2 shown;

[0067] Step 4: Inject the generated carrier-suppressed single-sideband signal into OS3, and use OS3 to split the carrier-suppressed single-sideband signal into 4 paths;

[0068] Step 5: OS2 further divides the split laser source into 4 paths. Taking the first path as an example, the first path of 4 orthogonal phase-encoded signals has 128 symbols, and the 4 phases are represented by symbols 0, 1, 2, and 3 respectively. Input PM 1,1 , and set the phase offset parameter of PM 1,1 to 90°, which means that an input voltage of 1v can shift the optical carrier frequency by 90°. Symbols 0, 1, 2, and 3 can achieve 0°, 90°, 180°, and 270° for the optical carrier respectively. The optical signal output after phase modulation is as shown in Figure 3 .

[0069] Step 6: Input the optical signal output by PM 1,1 into PM 1,2 . The actual frequency offset between the FDA-MIMO array elements is small, so as to directly observe the frequency shift effect of the output signal of PM 1，2 . Set the phase offset parameter of PM 1,2 to 90°, which means that an input voltage of 1v can shift the optical carrier frequency by 90°. Set the frequency of the sawtooth wave signal to 1GHz, the amplitude to 2v, and the symmetry to 0%. Input it into PM 1,2 to achieve sawtooth frequency shift. The frequency of the phase modulation signal output by PM 1,2 is 193.51THz + 1GHz. The phase modulation signal output after sawtooth frequency shift is as shown in Figure 4 ;

[0070] Step 7: Couple the first path split by OS3 and the phase modulation signal output by PM 1,2 through OC1 and inject it into the first path PD for beat frequency. The time domain is as shown in Figure 5 . The enlarged view shows its internal variation with the first path MIMO orthogonal phase-encoded signal. Phase changes can be observed at 17, 18, and 20ns. Figure 5 shows the time domain characteristics of the four-path FDA-MIMO, roughly showing its internal variation with the orthogonal phase-encoded signal, indicating that the orthogonal phase-encoded signal is modulated into the FDA signal through PM. To more clearly observe whether the phase change in each path of the FDA-MIMO signal is consistent with the change in the MIMO orthogonal phase-encoded signal, the Hilbert transform is performed on the generated first-channel FDA-MIMO signal below to observe the phase change of the first-channel FDA-MIMO signal and compare it with the MIMO orthogonal phase-encoded signal. As shown in Figure 6 , the phase change of the generated first-channel FDA-MIMO signal is consistent with the designed first-path 128-bit orthogonal phase-encoded signal, that is, a path of FDA-MIMO signal is successfully generated using the proposed architecture.

[0071] Step 8: Similarly, for each optical carrier split from OS2, apply sawtooth signals with different polarities and repetition rates, as well as different quadrature phase encoding signals, to tune the frequency offset and phase of the optical carrier respectively. Finally, after coupling with the optical signals split from OS3 and beating, multi-channel FDA-MIMO signals with different frequency shifts and phase encodings can be obtained.

[0072] The above-described embodiments are only examples of the present invention and are not intended to limit the protection scope of the present invention only. It should be noted that for those of ordinary skill in the art, several equivalent deformations and substitutions can be made on the basis of the content disclosed in the present invention. The radio frequency signal format (carrier frequency, bandwidth, signal format), optical carrier parameters (frequency and power), the formation method of carrier-suppressed single sideband modulation, the number of channels, etc. can all be changed. These equivalent deformations, substitutions, and parameter adjustments should also be regarded as the protection scope of the present invention.

Claims

1. A frequency control array MIMO signal generation system based on photon phase modulation, characterized in that, Including: A laser for outputting an optical carrier; A first optical splitter that receives the optical carrier output by the laser and splits it into a first optical path and a second optical path; A carrier-suppressed single-sideband modulation module that receives a radio frequency signal and the optical carrier of the first optical path for carrier-suppressed single-sideband modulation and outputs an optical signal of a specific frequency; A second optical splitter that receives the optical carrier of the second optical path and splits it into N optical carriers; A third optical splitter that receives the optical signal output by the dual-parallel Mach-Zehnder modulator and splits it into N optical signals; A phase modulation module having N channels, each channel correspondingly receiving one optical carrier split by the second optical splitter, and loading an orthogonal phase encoding signal and a sawtooth wave signal on the optical carrier of each channel to form a phase modulation signal; An optical coupling module having N channels, each channel correspondingly receiving one optical signal split by the third optical splitter and the phase modulation signal formed by the modulation module; An optoelectronic detection module having N channels, each channel correspondingly receiving the phase modulation signal output by the optical coupling module and outputting an FDA-MIMO signal.

2. The frequency control array MIMO signal generation system according to claim 1, wherein Each channel of the phase modulation module includes two cascaded phase modulators PM i,1 and PM i,2 , and the phase modulators PM i,1 and PM i,2 are independently driven by an orthogonal phase encoding signal and a sawtooth wave signal respectively.

3. The frequency-controlled array MIMO signal generation system according to claim 1, wherein Each channel of the phase modulation module has a single-phase modulator structure, and the single-phase modulator structure is driven by a coupling signal of an orthogonal phase encoding signal and a sawtooth wave signal.

4. The frequency control array MIMO signal generation system according to claim 1, wherein The carrier-suppressed single-sideband modulation module uses a dual-parallel Mach-Zehnder modulator; or the carrier-suppressed single-sideband modulation module uses a Mach-Zehnder modulator to generate a double-sideband modulation and then filters out the target single-sideband frequency through an optical filter.

5. The frequency control array MIMO signal generation system according to claim 1, wherein The radio frequency signal includes a single-frequency signal, a chirp signal, a phase encoding signal, or a vector modulation signal.

6. The frequency control array MIMO signal generation system according to claim 1, wherein The orthogonal phase encoding signal loaded onto the phase modulation module is selected from a binary encoding or a quaternary encoding format.

7. A method for generating frequency-controlled array MIMO signals based on photon phase modulation, characterized in that Including the following steps: S1: Split the optical carrier with frequency f c into a first optical path and a second optical path; S2: Perform carrier-suppressed single-sideband modulation on the optical carrier of the first optical path with a radio frequency signal having a loading frequency of f0 to generate an optical signal having a frequency of f c + f0, and split it into N optical signals; S3: Splitting the second optical path into N optical carriers, and loading an orthogonal phase encoding signal and a sawtooth wave signal on the i-th optical carrier to regulate and generate the phase-regulated optical signal of the i-th channel; where i = 1...N; S4: Coupling the i-th optical signal in the N optical signals with the phase-regulated optical signal of the i-th channel, and generating the FDA-MIMO signal of the i-th channel through optoelectronic conversion and beat frequency.

8. The method for generating a frequency-controlled array MIMO signal based on photon phase modulation according to claim 7, wherein Step S3 includes: Phase-modulate the i-th optical carrier by loading an orthogonal phase-coded signal to generate an optical signal with a frequency of f c and a phase varying with the orthogonal phase-coded signal; Continue to load the sawtooth wave signal for phase modulation to generate a frequency shift f i , and generate the i-th channel phase-controlled optical signal with a frequency of (f c + f i ) and a phase varying with the orthogonal phase encoding signal.

9. The method for generating a frequency-controlled array MIMO signal based on photon phase modulation according to claim 7, wherein Adjusting the orthogonality between the FDA-MIMO signals of each channel by controlling the code length and phase encoding format of the orthogonal phase encoding signal applied to each optical carrier.

10. The method for generating a frequency-controlled array MIMO signal based on photon phase modulation according to claim 7, wherein Adjusting the frequency shift amount of each optical carrier and the frequency offset of the FDA-MIMO signal of each channel by controlling at least one parameter of the repetition rate, polarity, and amplitude of the sawtooth wave signal applied to each optical carrier.

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