Phase coded signal generation system

Abstract

The invention provides a phase coded signal generation system, which relates to the technical field of wireless, and comprises a light source used for generating an optical carrier; at least one signal processing module; wherein the at least one signal processing module comprises a radio frequency signal generator used for generating a radio frequency signal; the pulse sequence generator is used for generating a pulse sequence; the modulator is used for loading the radio frequency signal and the pulse sequence on an optical carrier and outputting a first optical signal; wherein the direct-current bias phase of the modulator is related to a second-order dispersion coefficient, the transmission distance of a dispersion optical fiber and the angular frequency of a radio-frequency signal; the system further comprises a dispersion optical fiber for transmitting an optical signal related to the first optical signal; and the photoelectric detector is used for generating a phase-coded signal based on an input optical signal related to the first optical signal. According to the invention, the DC bias phase of the modulator is designed, so that the anti-dispersion transmission phase-coded signal can be generated, and the performance of the phase-coded signal generation system is improved.

Description

Technical Field

[0001] The present application relates to the field of wireless technology, and in particular to a phase coding signal generation system. Background Art

[0002] Pulse compression technology is widely used in modern radar systems to achieve high range resolution while breaking the limitation of signal peak power. In pulse compression radar, microwave signals are usually phase-coded signals or frequency chirped signals to improve pulse compression ratio and signal-to-noise ratio. Traditionally, phase-coded signals are generated by electronic technology or equipment. However, due to the relatively low operating frequency and the electronic bottleneck of complex implementation methods, the phase-coded signals generated in the electrical domain have the problem of insufficient time-bandwidth product (TBWP). Due to the advantages of huge transmission bandwidth, extremely high transmission frequency, small size, extremely low transmission loss, strong electromagnetic interference resistance, no external electromagnetic wave radiation, improved confidentiality, and no electromagnetic pollution, the photon generation of phase-coded microwave signals has aroused great interest in the industry.

[0003] On this basis, industry insiders proposed a method to generate phase-coded signals. However, when the generated phase-coded signals are transmitted from the base station to the radar antenna through the optical fiber, the signal will be distorted in the optical fiber due to the dispersion property of the optical fiber. As people's requirements for radar continue to increase, resisting power fading caused by dispersion has also become a point worthy of attention in phase-coded signals. Summary of the invention

[0004] The embodiment of the present application provides a phase coded signal generation system, which solves the problem of power fading caused by dispersion during the transmission of phase coded signals.

[0005] In a first aspect, in order to achieve the above-mentioned object, an embodiment of the present application provides a phase coding signal generation system, comprising:

[0006] A light source for generating an optical carrier;

[0007] At least one signal processing module; wherein the at least one signal processing module comprises:

[0008] A radio frequency signal generator, used for generating a radio frequency signal;

[0009] A pulse train generator, used for generating a pulse train;

[0010] A modulator, used to load the radio frequency signal and the pulse sequence onto the optical carrier and output a first optical signal; wherein the DC bias phase of the modulator is related to the second-order dispersion coefficient, the transmission distance of the dispersive optical fiber and the angular frequency of the radio frequency signal;

[0011] The phase encoding signal generation system further comprises:

[0012] a dispersive optical fiber, used for transmitting an optical signal related to the first optical signal;

[0013] A photodetector is used to generate a phase encoding signal based on an input optical signal related to the first optical signal.

[0014] Optionally, the DC bias phase of the modulator is expressed as: in, represents the DC bias phase of the modulator, z represents the transmission distance of the dispersive optical fiber, β represents the second-order dispersion coefficient, and ω represents the angular frequency of the radio frequency signal.

[0015] Optionally, the radio frequency signal is expressed as: V RF cos(ωt); where V RF represents the amplitude of the radio frequency signal, and ω represents the angular frequency of the radio frequency signal.

[0016] Optionally, when the phase-encoded signal generating system includes a plurality of the signal processing modules, the angular frequencies of the radio frequency signals generated by the radio frequency signal generators of different signal processing modules are different.

[0017] Optionally, the modulator is a dual-drive Mach-Zehnder modulator DD-MZM.

[0018] Optionally, when the phase coding signal generating system includes a first signal processing module and a second signal processing module, the phase coding signal generating system further includes:

[0019] a polarization rotator connected to the second signal processing module and configured to adjust a linear polarization direction of a first optical signal output by a modulator in the second signal processing module;

[0020] The polarization multiplexer is used to combine the first optical signal output by the modulator in the first signal processing module and the first optical signal adjusted by the polarization rotator, and output an optical signal related to the first optical signal.

[0021] Optionally, the modulator in the first signal processing module, the modulator in the second signal processing module, the polarization rotator and the polarization multiplexer constitute a dual-polarization binary phase-shift keying DP-BPSK controller.

[0022] Optionally, the phase coding signal generation system further includes:

[0023] A polarization controller is connected to the light source and is used to adjust the optical path loss of the optical carrier.

[0024] The beneficial effects of the above technical solution of the present application are as follows:

[0025] The phase-coded signal generation system of the embodiment of the present application includes: a light source for generating an optical carrier; at least one signal processing module; wherein the at least one signal processing module includes: a radio frequency signal generator for generating a radio frequency signal; a pulse sequence generator for generating a pulse sequence; a modulator for loading the radio frequency signal and the pulse sequence on the optical carrier to output a first optical signal; wherein the DC bias phase of the modulator is related to the second-order dispersion coefficient, the transmission distance of the dispersion fiber and the angular frequency of the radio frequency signal; the phase-coded signal generation system also includes: a dispersion fiber for transmitting an optical signal related to the first optical signal; a photodetector for generating a phase-coded signal based on the input optical signal related to the first optical signal. By designing the DC bias phase of the modulator to be related to the second-order dispersion coefficient, the transmission distance of the dispersion fiber and the angular frequency of the radio frequency signal, the dispersion only affects the initial phase of the generated phase-coded signal, but has no effect on the power of the phase-coded signal, thereby avoiding the waveform distortion and power attenuation caused by the dispersion properties of the optical fiber to the phase-coded signal, and improving the performance of the phase-coded signal generation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is one of the schematic diagrams of the phase coded signal generating system according to an embodiment of the present application;

[0027] Figure 2 This is a second schematic diagram of the phase coded signal generating system according to an embodiment of the present application;

[0028] Figure 3 This is a schematic diagram of the signal amplitude simulation comparison before and after the dispersion fiber transmission of the embodiment of the present application. DETAILED DESCRIPTION

[0029] In order to make the technical problems, technical solutions and advantages to be solved by the present application clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0030] It should be understood that the references to "one embodiment" or "an embodiment" throughout the specification mean that the specific features, structures, or characteristics associated with the embodiment are included in at least one embodiment of the present application. Therefore, the references to "in one embodiment" or "in an embodiment" appearing throughout the specification do not necessarily refer to the same embodiment. In addition, these specific features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0031] In the various embodiments of the present application, it should be understood that the size of the serial numbers of the following processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0032] Additionally, the terms "system" and "network" are often used interchangeably herein.

[0033] In the embodiments provided in the present application, it should be understood that "B corresponding to A" means that B is associated with A, and B can be determined according to A. However, it should also be understood that determining B according to A does not mean determining B only according to A, and B can also be determined according to A and / or other information.

[0034] The present application embodiment provides a phase coding signal generation system, such as Figure 1 As shown, including:

[0035] Light source 1 is used to generate an optical carrier; for example, light source 1 is a semiconductor laser. Specifically, light source 1 can be a continuous light source, that is, the optical carrier generated by light source 1 is a continuous optical carrier; wherein the optical carrier generated by light source 1 can be expressed as: E in(t) =E 0 exp(jω 0 t); E 0 represents the amplitude of the optical carrier, ω 0 Indicates the angular frequency of the optical carrier;

[0036] At least one signal processing module 2; wherein the at least one signal processing module 2 comprises:

[0037] A radio frequency signal generator 21, used to generate a radio frequency signal;

[0038] The pulse sequence generator 22 is used to generate a pulse sequence; here, the pulse sequence is specifically a coded sequence voltage signal; here, the pulse sequence generated by the pulse sequence generator 22 can be expressed as: VS(t), wherein V represents the amplitude of the pulse sequence, and S(t) represents the polarity of the pulse sequence; specifically, S(t)={1,-1}; that is, the pulse sequence includes a pulse with an amplitude of V and a pulse with an amplitude of -V; specifically, the arrangement order of V and -V can be set based on the coding requirements, so the pulse sequence can also be called a coded sequence signal;

[0039] A modulator 23, used to load the radio frequency signal and the pulse sequence onto the optical carrier and output a first optical signal; wherein the DC bias phase of the modulator 23 is related to the second-order dispersion coefficient, the transmission distance of the dispersive optical fiber 3 and the angular frequency of the radio frequency signal;

[0040] The phase encoding signal generation system further comprises:

[0041] a dispersive optical fiber 3, used for transmitting an optical signal related to the first optical signal; here, the optical signal related to the first optical signal may specifically be the first optical signal itself (such as when the phase-coded signal generation system includes one signal processing module), or an optical signal after processing a plurality of first optical signals (such as when the phase-coded signal generation system includes two or more signal processing modules);

[0042] The photodetector 4 is configured to generate a phase encoding signal based on an input optical signal related to the first optical signal.

[0043] The phase-coded signal generating system of an embodiment of the present application includes: a light source 1 for generating an optical carrier; at least one signal processing module 2; wherein the at least one signal processing module 2 includes: a radio frequency signal generator 21 for generating a radio frequency signal; a pulse sequence generator 22 for generating a pulse sequence; a modulator 23 for loading the radio frequency signal and the pulse sequence on the optical carrier and outputting a first optical signal; wherein the DC bias phase of the modulator 23 is related to the second-order dispersion coefficient, the transmission distance of the dispersive optical fiber 3 and the angular frequency of the radio frequency signal; the phase-coded signal generating system also includes: a dispersive optical fiber 3 for transmitting an optical signal related to the first optical signal; and a photodetector 4 for generating a phase-coded signal based on an input optical signal related to the first optical signal. In the above-mentioned structure of the embodiment of the present application, by designing the DC bias phase of the modulator 23 to be related only to the second-order dispersion coefficient, the transmission distance of the dispersive optical fiber and the angular frequency of the radio frequency signal, the dispersion only affects the initial phase of the generated phase-coded signal, but has no effect on the power of the phase-coded signal, thereby avoiding the waveform distortion and power attenuation of the phase-coded signal caused by the dispersion properties of the optical fiber, and improving the performance of the phase-coded signal generation system.

[0044] As a specific implementation, the radio frequency signal is expressed as: V RF cos(ωt); where V RF Represents the amplitude of the RF signal, and ω represents the angular frequency of the RF signal. That is to say, the initial phase of the RF signal is 0. Here, it should be noted that the value of the initial phase of the RF signal will only affect the initial phase of the phase-encoded signal, and will not affect the overall phase-encoded signal. For simplicity, the initial phase of the RF signal is set to 0 here.

[0045] As a specific implementation, the DC bias phase of the modulator 23 is expressed as: in, represents the DC bias phase of the modulator, z represents the transmission distance of the dispersive fiber, β represents the second-order dispersion coefficient, and ω represents the angular frequency of the RF signal. It should be noted that the relationship between the DC bias phase and the transmission distance, the second-order dispersion coefficient and the angular frequency is based on the purpose of achieving anti-dispersion, based on the dispersion fiber's effect on the optical carrier and the RF signal (V RF The dispersion phase is determined by the ±1st order sidebands of cos(ωt).

[0046] As an optional implementation, when the phase-coded signal generation system includes a plurality of the signal processing modules 2, the angular frequencies of the RF signals generated by the RF signal generators of different signal processing modules 2 are different, so that the phase-coded signal finally generated can be suitable for multi-band radar. In which, taking the case where the phase-coded signal generation system includes two signal processing modules 2 as an example, the RF signal generated by one of the RF signal generators 21 is expressed as: V RF1 cos(ω 1 t); another RF signal generator 21 generates a RF signal represented by: V RF2 cos(ω 2 t); where ω 1 and ω 2 Different, V RF1 and V RF2 They may be the same or different, and the initial phases of the RF signals generated by the two RF signal generators are both 0.

[0047] As a specific implementation, the modulator 23 is a dual-drive Mach-Zehnder modulator DD-MZM.

[0048] As an optional implementation, Figure 2 As shown, when the phase coded signal generating system includes a first signal processing module 210 and a second signal processing module 220, here, the first signal processing module 210 and the second signal processing module 220 have the same structure, both including a radio frequency signal generator 21, a pulse sequence generator 22 and a modulator 23, and the phase coded signal generating system also includes:

[0049] A polarization rotator 5 connected to the second signal processing module 220, specifically connected to the modulator 23 in the second signal processing module 220, for adjusting the linear polarization direction of the first optical signal output by the modulator 23 in the second signal processing module 220; here, the polarization rotator 5 is specifically a 90° polarization rotator;

[0050] The polarization multiplexer 6 is used to combine the first optical signal output by the modulator 23 in the first signal processing module 210 and the first optical signal adjusted by the polarization rotator 5, and output an optical signal related to the first optical signal.

[0051] As a specific implementation method, the modulator 23 in the first signal processing module 210, the modulator 23 in the second signal processing module 220, the polarization rotator 5 and the polarization multiplexer 6 constitute a dual-polarization binary phase shift keying (DP-BPSK) controller.

[0052] Further, as an optional implementation, the phase coding signal generation system further includes:

[0053] The polarization controller 7 is connected to the light source 1 and is used to adjust the optical path loss of the optical carrier, so as to minimize the loss of the optical carrier input to the signal processing module 2, thereby improving the system performance to a certain extent.

[0054] Based on this, the phase coding signal generation system in the embodiment of the present application includes two signal processing modules 2 (such as Figure 2 In the case of (as shown in the figure), the structure of the system and the functions of each component specifically include:

[0055] A light source 1 for generating an optical carrier wave, wherein the light source 1 is a semiconductor laser, and the light generated by the light source 1 is a continuous light. The continuous light output by the semiconductor laser can be expressed as: E in(t) =E 0 exp(jω 0 t); E 0 represents the amplitude of the optical carrier, ω 0 Indicates the angular frequency of the optical carrier;

[0056] A polarization controller 7 connected to the output end of the light source 1 and used to adjust the optical path loss of the optical carrier output by the light source 1;

[0057] Two modulators 23 are respectively connected to the output end of the polarization controller 7, wherein the optical carrier processed by the polarization controller 7 is divided into two paths and respectively input to the two modulators 23;

[0058] Two RF signal generators 21, wherein one RF signal generator 21 is connected to a RF port of a modulator 23, so that the RF signal generated by the RF signal generator 21 (respectively represented as V RF1 cos(ω 1 t) and V RF2 cos(ω 2t)) driving the RF port connected thereto;

[0059] Two pulse sequence generators 22, wherein one pulse sequence generator 22 is connected to another RF port of a modulator, so that the pulse sequence generated by the pulse sequence generator 22 (respectively represented as V 1 S 1 (t) and V 2 S 2 (t), S 1 (t) = {1, -1}, S 2 (t) = {1, -1}) drives the RF port connected to it;

[0060] In this way, the two modulators 23 load the radio frequency signal and the pulse sequence onto the optical carrier to output the first optical signal; wherein the first optical signal output by the two modulators 23 can be expressed as:

[0061]

[0062] Among them, m 1 and m 2 Represents the modulation index of the two RF signals, m 1 =πV RF1 / V π , m 2 =πV RF2 / V π ; γ 1 and γ 2 Represents the modulation index of two pulse sequences (coded sequence signals), and γ 1 =πV 1 / V π , γ 2 =πV 2 / V π ; and represents the DC bias phase of the two modulators 23, Among them, V DC1 and V DC2 Respectively represent the DC bias voltages of the two modulators 23, V π is the half-wave voltage of the modulator 23;

[0063] Furthermore, the first optical signals output by the two modulators 23 can be expressed as follows according to the Bessel function expansion in the case of small signal modulation:

[0064]

[0065] A polarization rotator 5 connected to an output end of one of the modulators 23, and used to adjust the linear polarization direction of the first optical signal output by one of the modulators 23;

[0066] a polarization multiplexer 6 connected to the polarization rotator 5 and another modulator 23, and configured to combine the adjusted first optical signal output by the polarization rotator 5 and the first optical signal output by another modulator 23 to generate an optical signal related to the first optical signal;

[0067] The dispersion optical fiber 3 is connected to the polarization multiplexer 6 and is used to transmit the optical signal related to the first optical signal, wherein the transmitted optical signal is represented as:

[0068]

[0069] Among them, the dispersion fiber has a great influence on the carrier and V RF1 cos(ω 1 t) ±1st order sidebands and V RF2 cos(ω 2 The dispersion phases introduced by the ±1st order sidebands of t) are: 0 = zβ 0 , and Among them, β 0 , β 1 and β 2 are the 0th, 1st and 2nd order dispersion coefficients respectively; z is the transmission distance of the dispersive optical fiber;

[0070] The photodetector 4 is connected to the dispersion optical fiber 3 and is used to convert the optical signal transmitted by the dispersion optical fiber 3 into an electrical signal to obtain a phase coded signal, wherein the electrical signal generated by the photodetector 4 can be expressed as:

[0071]

[0072] In combination with the above formula, it can be known that in order to achieve the generated phase coded signal to resist dispersion transmission, the DC bias phase of the two modulators 23 is and Should meet the following requirements: Right now,

[0073] Furthermore, based on the electrical signal generated by the photodetector 4, the phase encoding signal finally generated can be expressed as:

[0074]

[0075] Combination Figure 3From the simulation diagram of signal amplitude comparison before and after dispersion fiber transmission and the above formula, it can be seen that dispersion has no effect on the power of the two generated bands of signals, but only affects the initial phase of the phase-coded signal. Therefore, the generation of a dual-band phase-coded signal that can resist dispersion transmission is achieved.

[0076] Taking the phase coding signal generation system including the DP-BPSK controller as an example, the generation process of the phase coding signal is described as follows:

[0077] First, the semiconductor laser (light source 1) generates continuous light, which is regulated by the polarization controller 7 and divided into two paths, one of which is input to the first DD-MZM (one of the modulators 23) located in the upper arm of the DP-BPSK modulator, and the other is input to the second DD-MZM (another modulator 23) located in the lower arm of the DP-BPSK modulator;

[0078] Second, the first RF signal generator (one of the RF signal generators 21) generates a first RF signal, and the generated first RF signal is connected to a RF port of the first DD-MZM; the first pulse sequence generator (one of the pulse sequence generators 22) generates a first coding sequence signal (pulse sequence), and the generated first coding sequence voltage signal is connected to another RF port of the first DD-MZM;

[0079] Third, the second RF signal generator (another RF signal generator 21) generates a second RF signal, and the generated second RF signal drives a RF port of the second DD-MZM; the second pulse sequence generator (another pulse sequence generator 22) generates a second coded sequence signal, and the generated second coded sequence signal drives another RF port of the second DD-MZM;

[0080] Fourth, the second DD-MZM output port is connected to the 90° polarization rotator (polarization rotator 5) input port;

[0081] Fifth, the optical path (first optical signal) output by the first DD-MZM and the optical path output by the 90° polarization rotator are combined through the polarization multiplexer 6;

[0082] Sixth, the synthesized optical path is transmitted through a single-mode optical fiber (dispersion optical fiber 3);

[0083] Seventh, the transmitted optical path is converted into an electrical signal after passing through the photodetector 4, thereby obtaining a dual-band phase-coded microwave signal that can resist dispersion transmission;

[0084] The amplitude of the DC bias of the first DD-MZM is set to V DC1 , the phase is set to: The DC bias of the second DD-MZM is set to V DC2 , the phase is set to:

[0085] Compared with the existing phase coding signal generation scheme, the phase coding signal generation system of the embodiment of the present application generates a limit coding signal with a simple structure and easy operation, so that the generated phase coding signal does not have the problem of power fading when transmitted in the optical fiber, and solves the waveform distortion and power fading phenomenon caused by the dispersion properties of the optical fiber after the traditional phase coding signal is generated. By setting two signal processing modules in the phase coding signal generation system, and setting the angular frequencies of the RF signals generated by the RF signal generators in the two signal processing modules to different angular frequencies, the generated phase coding signal can be simultaneously applicable to multi-band radars, has a wider range of application scenarios, greatly improves the performance of generating phase coding signals based on the modulator, and has the advantages of simple structure and easy operation.

[0086] The above exemplary embodiments are described with reference to the accompanying drawings, and many different forms and embodiments are feasible without departing from the spirit and teachings of the present application. Therefore, the present application should not be constructed as a limitation of the exemplary embodiments proposed herein. More specifically, these exemplary embodiments are provided so that the present application will be perfect and complete, and the scope of the present application will be conveyed to those who are familiar with the technology. In these figures, the component sizes and relative sizes may be exaggerated for clarity. The terms used here are only based on the purpose of describing specific exemplary embodiments and are not intended to be limiting. As used herein, unless the text clearly indicates otherwise, the singular forms "one", "an" and "the" are intended to include these multiple forms. It will be further understood that the terms "comprising" and / or "including" when used in this specification indicate the presence of the features, integers, steps, operations, components and / or components, but do not exclude the presence or increase of one or more other features, integers, steps, operations, components, components and / or their groups. Unless otherwise indicated, when stated, a range of values ​​includes the upper and lower limits of that range and any subranges therebetween.

[0087] The above is a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles described in the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A phase coded signal generation system, characterized in that: include: A light source for generating an optical carrier; At least one signal processing module; wherein the at least one signal processing module comprises: A radio frequency signal generator, used for generating a radio frequency signal; A pulse train generator, used for generating a pulse train; A modulator, used to load the radio frequency signal and the pulse sequence onto the optical carrier and output a first optical signal; wherein the DC bias phase of the modulator is related to the second-order dispersion coefficient, the transmission distance of the dispersive optical fiber and the angular frequency of the radio frequency signal; The phase encoding signal generation system further comprises: a dispersive optical fiber, used for transmitting an optical signal related to the first optical signal; A photodetector is used to generate a phase encoding signal based on an input optical signal related to the first optical signal.

2. The phase coded signal generation system according to claim 1, characterized in that: The DC bias phase of the modulator is expressed as: in, represents the DC bias phase of the modulator, z represents the transmission distance of the dispersive optical fiber, β represents the second-order dispersion coefficient, and ω represents the angular frequency of the radio frequency signal.

3. The phase coded signal generation system according to claim 1, characterized in that: The RF signal is expressed as: V RF cos(ωt); where V RF represents the amplitude of the radio frequency signal, and ω represents the angular frequency of the radio frequency signal.

4. The phase coded signal generation system according to claim 1 or 3, characterized in that: In the case where the phase encoding signal generating system includes a plurality of the signal processing modules, the angular frequencies of the radio frequency signals generated by the radio frequency signal generators of different signal processing modules are different.

5. The phase coded signal generation system according to claim 1, characterized in that: The modulator is a dual-drive Mach-Zehnder modulator DD-MZM.

6. The phase coded signal generation system according to claim 1, characterized in that: When the phase coding signal generating system includes a first signal processing module and a second signal processing module, the phase coding signal generating system further includes: a polarization rotator connected to the second signal processing module and used to adjust the linear polarization direction of the first optical signal output by the modulator in the second signal processing module; The polarization multiplexer is used to combine the first optical signal output by the modulator in the first signal processing module and the first optical signal adjusted by the polarization rotator, and output an optical signal related to the first optical signal.

7. The phase coded signal generation system according to claim 6, characterized in that: The modulator in the first signal processing module, the modulator in the second signal processing module, the polarization rotator and the polarization multiplexer constitute a dual-polarization binary phase shift keying DP-BPSK controller.

8. The phase coded signal generation system according to claim 1, characterized in that: The phase encoding signal generation system further comprises: A polarization controller is connected to the light source and is used to adjust the optical path loss of the optical carrier.

Images