Carrier and pseudo code combined synchronization method and system based on optoelectronic phase control

Abstract

The application relates to a carrier and pseudo-code combined synchronization method and system based on photoelectric phase regulation, and the method comprises the following steps: S1, acquiring a first laser and a second laser of homologous laser output; S2, modulating a spread spectrum signal onto the first laser as a carrier signal; S3, taking the second laser as an optical local oscillator, regulating a local pseudo-code sequence onto the second laser to obtain an encoded optical local oscillator; S4, performing analog domain calculation on the carrier signal and the encoded optical local oscillator, demodulating the calculation result, and obtaining an optical domain despreading signal; and S5, performing digital signal processing on the optical domain despreading signal to obtain a demodulation signal of the spread spectrum signal. The application can meet the spread spectrum communication, combine the characteristics of optical domain coding and analog domain calculation, and give consideration to the spread spectrum bandwidth and the synchronization speed.

Description

Technical Field

[0001] This invention relates to the fields of ultra-wideband spread spectrum communication and microwave photonics technology, specifically to a carrier and pseudo-code joint synchronization method and system based on photoelectric phase modulation. Background Technology

[0002] In ultra-wideband spread spectrum communication, spread spectrum technology uses pseudo-random sequences as the basic signal to spread and modulate the signal, making the bandwidth used for information transmission much larger than the bandwidth of the information itself. This reduces the requirements for the signal-to-noise ratio of the input information while ensuring a low error rate in system signal transmission. Achieving signal synchronization between the transmitting and receiving ends is a key issue in spread spectrum technology research. The dynamic nature of both ends can lead to significant frequency offsets, making spread spectrum signal synchronization difficult. From the perspective of spread spectrum signal reception, under low dynamic conditions, the impact of carrier frequency offset on system reception performance is usually ignored, and only pseudo-code synchronization is considered. However, under high dynamic conditions, carrier frequency offset can have a decisive impact on the pseudo-code correlation output; therefore, the impact of both carrier offset and pseudo-code offset on system reception performance must be considered simultaneously.

[0003] To overcome signal frequency spread and time-domain distortion caused by uncertain distances between the transmitting and receiving ends, transmission delays, noise, and interference at the receiving end, and to accurately recover the transmitting information, fast and reliable pseudocode synchronization capabilities are essential. However, traditional radio frequency communication systems based on purely electrical domain methods are constrained by limitations in electronic components and digital processing, resulting in limited operating frequency range, transmission signal bandwidth, anti-interference, and anti-interception capabilities.

[0004] Carrier and pseudocode synchronization is crucial for the implementation of spread spectrum transmission systems, and the quality of synchronization directly affects the overall performance of the system. In traditional digital communication systems, due to the low spreading bandwidth and relatively low code rate, the carrier frequency offset can generally be estimated digitally, and carrier recovery can be achieved through digital frequency offset compensation. However, for high code rates, especially with a 10 GHz spreading bandwidth (up to 100 ps), it is difficult to directly obtain the frequency offset value digitally under high dynamic conditions. Therefore, ultra-wideband photonic spread spectrum systems supporting 10 GHz spreading bandwidth and dynamic transmission links pose significant challenges to the processing bandwidth, acquisition speed, and reliability of the synchronization system, requiring a new method to achieve both carrier synchronization and pseudocode synchronization. Summary of the Invention

[0005] To address the shortcomings of traditional spread spectrum communication systems based on pure electrical domain methods, this invention proposes a carrier and pseudocode joint synchronization method and system based on photoelectric phase modulation.

[0006] To achieve the aforementioned objectives of this invention, in a first aspect, embodiments of this invention propose a carrier-pseudocode joint synchronization method based on photoelectric phase modulation, comprising:

[0007] S1, acquire the first and second laser beams from the same source laser output;

[0008] S2, modulate the spread spectrum signal onto the first laser beam as a carrier signal;

[0009] S3, using the second laser as the optical local oscillator, modulate the local pseudocode sequence onto the second laser to obtain the encoded optical local oscillator;

[0010] S4, perform analog domain calculations on the carrier signal and the encoded optical local oscillator, and demodulate the calculation results to obtain the optical domain despread signal;

[0011] S5, perform digital signal processing on the optical domain despread signal to obtain the demodulated signal of the spread spectrum signal.

[0012] Preferably, in step S2, the spread spectrum signal is generated by frequency modulation of the optical frequency comb and pseudo-code encoded optical frequency comb.

[0013] Preferably, in step S3, after the local pseudocode sequence is modulated onto the second laser, time delay is also controlled by optical domain code synchronization, so that the encoded optical local oscillator pseudocode is synchronized with the signal pseudocode.

[0014] Preferably, in step S4, after the demodulation calculation result, a pilot signal can also be obtained. A preset intermediate frequency signal is used as a reference signal to perform frequency and phase discrimination with the pilot signal to obtain the frequency deviation of the pilot signal. The encoded optical local oscillator is then adjusted according to the frequency deviation to form a closed-loop control.

[0015] Preferably, in step S4, the pilot signal and the reference signal are frequency and phase discriminated in a phase-locked loop, and the carrier frequency of the encoded optical local oscillator is controlled by the PID control loop of the phase-locked loop.

[0016] Preferably, in step S5, after digital signal processing, an autocorrelation signal can be obtained, and the autocorrelation signal is fed back to the encoded optical local oscillator. The delay amount of the optical delay line is adjusted according to the autocorrelation signal to adjust the pseudocode sequence of the encoded optical local oscillator.

[0017] Secondly, embodiments of the present invention provide a carrier and pseudo-code joint synchronization system based on photoelectric phase modulation, comprising:

[0018] The same-source laser output module is used to output the same-source optical carrier and optical local oscillator, which are used to load spread spectrum signals and load codes, respectively.

[0019] An optical carrier spread spectrum signal generation module is used to modulate the received spread spectrum signal onto the optical carrier.

[0020] The encoded optical local oscillator generation module is used to load the local despreading code onto the optical local oscillator to obtain the encoded optical local oscillator;

[0021] The optical domain code synchronization module is used to perform phase modulation on the encoded optical local oscillator;

[0022] The optical domain despreading module is used to convolve the optical carrier spread spectrum signal output by the optical carrier spread spectrum signal generation module with the coded optical local oscillator output by the optical domain code synchronization module in the analog domain to obtain the despread radio frequency signal.

[0023] The digital signal processing module is used to convert the optical domain despread radio frequency signal into an analog-to-digital signal and perform digital processing to output a digital signal and the processing result, thereby realizing signal despreading.

[0024] The carrier and pseudocode joint synchronization method and system based on photoelectric phase modulation of the present invention, compared with the prior art, after acquiring the first and second laser beams from the laser source, modulates the spread spectrum communication signal onto the first laser beam as the carrier signal. Simultaneously, the second laser beam generates an optical local oscillator, and the local pseudocode sequence is modulated onto the optical local oscillator. Analog domain calculations are performed on the carrier signal and the coded optical local oscillator, and the calculation results are demodulated to obtain the carrier frequency offset and the optical domain despread signal. Thus, while satisfying the requirements of spread spectrum communication, the characteristics of optical domain coding and analog domain calculation are combined to balance the spread spectrum bandwidth and synchronization speed. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the carrier and pseudocode joint synchronization system based on photoelectric phase modulation according to the present invention;

[0027] Figure 2 This is a schematic diagram of a preferred embodiment of the carrier and pseudocode joint synchronization system based on photoelectric phase modulation of the present invention;

[0028] Figure 3 This is a schematic diagram illustrating the principle of spread spectrum signal generation based on optical frequency comb coding according to an embodiment of the present invention;

[0029] Figure 4 This is a flowchart illustrating the carrier and pseudocode joint synchronization method based on photoelectric phase modulation, according to an embodiment of the present invention. Detailed Implementation

[0030] The description of the embodiments in this specification should be taken in conjunction with the accompanying drawings, which should form part of the complete specification. In the drawings, the shape or thickness of the embodiments may be exaggerated and may be indicated in a simplified or convenient manner. Furthermore, parts of the various structures in the drawings will be described separately; it is worth noting that elements not shown in the figures or not described in words are in a form known to those skilled in the art.

[0031] The descriptions of the embodiments herein, including any references to directions and orientations, are for ease of description only and should not be construed as limiting the scope of the invention. The following description of preferred embodiments involves combinations of features, which may exist independently or in combination; the invention is not particularly limited to the preferred embodiments. The scope of the invention is defined by the claims.

[0032] like Figure 1 The diagram shows a schematic of the carrier and pseudo-code joint synchronization system based on photoelectric phase modulation of the present invention. The system includes: a co-source laser output module for outputting a co-source optical carrier and an optical local oscillator, which are used to load a spread spectrum signal and a code, respectively, and to ensure high coherence between the signal light and the local oscillator light; an optical carrier spread spectrum signal generation module for modulating the received spread spectrum signal onto the optical carrier; a coded optical local oscillator generation module for loading the local despreading code onto the optical local oscillator to obtain a coded optical local oscillator; an optical domain code synchronization module for performing phase modulation on the coded optical local oscillator to achieve optical domain pseudo-code synchronization; an optical domain despreading module for convolving the optical carrier spread spectrum signal output by the optical carrier spread spectrum signal generation module and the coded optical local oscillator output by the optical domain code synchronization module in the analog domain to achieve optical domain despreading of the ultra-wideband spread spectrum signal and output the despread radio frequency signal; and a digital signal processing module for performing analog-to-digital conversion and digital processing on the optical domain despread radio frequency signal to output a digital signal and processing result, thereby achieving signal despreading.

[0033] like Figure 2 The diagram shown is a schematic representation of a typical embodiment of the carrier and pseudo-code joint synchronization system based on photoelectric phase modulation of the present invention. This typical embodiment addresses the higher synchronization performance requirements of 10GHz ultra-wideband spread spectrum communication by specifically arranging the components of the synchronization system to overcome the bottlenecks of traditional electronic devices and digital processing capabilities. In this typical embodiment, the co-source laser output module is configured as a laser, the optical carrier spread spectrum signal generation module is configured as a first electro-optic modulator, the coded optical local oscillator generation module is configured as a second electro-optic modulator, the optical domain code synchronization module is configured as an adjustable optical delay line, the optical domain despreading module is configured as a photodetector, and the digital signal processing module includes analog-to-digital conversion and digital signal processing.

[0034] The spread spectrum signal input to the second electro-optic modulator is generated by the beat frequency of a signal-modulated optical frequency comb and a pseudo-code-encoded optical frequency comb. (See [reference needed]). Figure 3 The spread spectrum signal contains both a broadband spread spectrum signal and an coded frequency comb. This coded optical frequency comb can be used as the pilot signal required for carrier synchronization. The pilot signal is encoded according to the optical spread spectrum code. After encoding, both the pilot signal and the data signal are hidden below the noise, thus achieving a low detection power effect. After analog domain despreading after the photodetector, both the pilot signal and the data signal obtain an N-fold gain (N is the length of the spread spectrum sequence).

[0035] Since the pilot signal power is higher than the data signal power, for concealment purposes, the pilot signal power after optical synchronization and despreading can achieve a sufficiently high signal-to-noise ratio (e.g., 10dB). At this point, a phase-locked loop (see [reference needed]) can be used. Figure 2 The pilot signal is phase-locked. Since the optical domain coding of the pilot signal and the data signal is consistent, a point-frequency signal with a sufficient signal-to-noise ratio after the photodetector assists in achieving phase locking at the transceiver end, simultaneously synchronizing the carrier and pseudocode, thereby decoupling carrier synchronization and pseudocode synchronization.

[0036] The encoded optical local oscillator at the receiver is modulated onto the optical local oscillator by a local frequency comb, generating an encoded local oscillator optical frequency comb. The number of comb teeth of the local oscillator optical frequency comb is equal to the period of the local pseudocode sequence, and the spacing of the optical frequency comb of the local oscillator optical frequency comb is equal to the digital signal rate.

[0037] In the receiving architecture used in this embodiment, carrier synchronization is implemented based on a broadband optical phase-locked loop, pseudocode synchronization is implemented based on optical domain simulated convolution, and carrier synchronization and pseudocode synchronization can be implemented in parallel.

[0038] The received ultra-wideband spread spectrum signal and the coded optical local oscillator are correlated in the analog domain, and the frequency f' of the carrier pilot signal is obtained through a photodetector. IF (See also) Figure 2 ) and power information, based on the known intermediate frequency signal frequency f IF The optical phase-locked loop (PLL) is used to quickly determine the frequency deviation between the intermediate frequency (IF) and the reference frequency of the signal. The carrier frequency is then promptly restored via the PLL's PID control loop, achieving carrier synchronization. Digital signal processing calculates the power value of the synchronization autocorrelation signal, and the delay of the optical delay line is controlled according to decision conditions to regulate the pseudo-code sequence of the coded optical local oscillator, achieving pseudo-code acquisition and tracking. After pseudo-code synchronization, the correlation signal peak reaches its maximum. The selection of the local oscillator start frequency and the intermediate frequency is based on the principle of facilitating frequency offset estimation and judgment by the PLL, while avoiding aliasing interference in the despread signal.

[0039] The present invention also provides a method based on the above-mentioned carrier and pseudocode joint synchronization system, comprising:

[0040] S1, acquire the first and second laser outputs from the same source laser.

[0041] S2, modulate the spread spectrum signal onto the first laser beam as a carrier signal.

[0042] S3, using the second laser as the optical local oscillator, modulate the local pseudocode sequence onto the second laser to obtain the encoded optical local oscillator.

[0043] S4, perform analog domain calculations on the carrier signal and the encoded optical local oscillator, and demodulate the calculation results to obtain the optical domain despread signal.

[0044] S5, perform digital signal processing on the optical domain despread signal to obtain the demodulated signal of the spread spectrum signal.

[0045] like Figure 4 As shown, the above steps S1-S5 further include two processes: carrier synchronization and pseudocode synchronization.

[0046] Carrier synchronization process: The optical spread spectrum signal is convolved with the optically delayed coded optical local oscillator in the analog domain to obtain the despread electrical signal in the optical domain. This electrical signal contains an intermediate frequency of f'. IF The pilot signal is input into the phase-locked loop for carrier synchronization and synchronized with the preset intermediate frequency signal f. IF Frequency and phase discrimination is performed to quickly determine the frequency deviation between the intermediate frequency of the signal and the reference frequency. The carrier frequency of the encoded optical local oscillator is adjusted through the PID control loop of the phase-locked loop to restore the carrier frequency in a timely manner and achieve carrier synchronization.

[0047] Pseudo-code synchronization process: The optical carrier spread spectrum signal and the optically delayed coded optical local oscillator are convolved in the analog domain to obtain the optically despread electrical signal. This electrical signal is input to the digital signal processing module. After synchronization is achieved, an autocorrelation signal is output and fed back to the optical domain code synchronization module to lock the optical delay, achieving synchronous acquisition and transitioning to the tracking stage. In this embodiment, the optical delay line is adjusted in 1 / 2 chip steps, traversing N frequency domain codes 2N times. Each adjustment provides the current correlation data from the digital signal processing module until an accurate synchronization position is found, achieving synchronous acquisition, stopping the search, and transitioning to the tracking stage. During the tracking process, the offset of the optical delay line is adjusted in real time (it can be adjusted in both left and right directions). Based on the changes in the correlation peak, the position of the optical delay line is adjusted to keep the correlation peak at its maximum value, locking the synchronous tracking state.

[0048] The carrier and pseudocode joint synchronization method and system based on photoelectric phase modulation of the present invention, compared with the prior art, after acquiring the first and second laser beams from the laser source, modulates the spread spectrum communication signal onto the first laser beam as the carrier signal. Simultaneously, the second laser beam generates an optical local oscillator, and the local pseudocode sequence is modulated onto the optical local oscillator. Analog domain calculations are performed on the carrier signal and the coded optical local oscillator, and the calculation results are demodulated to obtain the carrier frequency offset and the optical domain despread signal. Thus, while satisfying the requirements of spread spectrum communication, the characteristics of optical domain coding and analog domain calculation are combined to balance the spread spectrum bandwidth and synchronization speed.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A carrier-pseudocode joint synchronization method based on photoelectric phase modulation, characterized in that, The method includes: S1, acquire the first and second laser beams from the same source laser output; S2, modulate the spread spectrum signal onto the first laser beam as a carrier signal; S3, using the second laser as the optical local oscillator, modulate the local pseudocode sequence onto the second laser to obtain the encoded optical local oscillator; S4, perform analog domain calculations on the carrier signal and the encoded optical local oscillator, and demodulate the calculation results to obtain the optical domain despread signal; After demodulation calculation, a pilot signal can be obtained. Using a preset intermediate frequency signal as a reference signal, frequency and phase discrimination is performed with the pilot signal to obtain the frequency deviation of the pilot signal. The coded optical local oscillator is then adjusted according to the frequency deviation to form a closed-loop control. S5, perform digital signal processing on the optical domain despread signal to obtain the demodulated signal of the spread spectrum signal.

2. The carrier and pseudo-code joint synchronization method based on photoelectric phase modulation according to claim 1, characterized in that, In step S2, the spread spectrum signal is generated by the beat frequency of an optical frequency comb modulated by a signal and an optical frequency comb with pseudo-code encoding.

3. The carrier and pseudo-code joint synchronization method based on photoelectric phase modulation according to claim 1, characterized in that, In step S3, after the local pseudocode sequence is modulated onto the second laser, time delay is also controlled through optical domain code synchronization, so that the encoded optical local oscillator pseudocode is synchronized with the signal pseudocode.

4. The carrier and pseudo-code joint synchronization method based on photoelectric phase modulation according to claim 1, characterized in that, In step S4, the pilot signal and the reference signal are frequency and phase discriminated in a phase-locked loop, and the carrier frequency of the encoded optical local oscillator is adjusted by the PID control loop of the phase-locked loop.

5. The carrier and pseudo-code joint synchronization method based on photoelectric phase modulation according to claim 1, characterized in that, In step S5, after digital signal processing, an autocorrelation signal can be obtained. The autocorrelation signal is fed back to the encoded optical local oscillator. The delay amount of the optical delay line is adjusted according to the autocorrelation signal to control the pseudocode sequence of the encoded optical local oscillator.

6. A carrier and pseudo-code joint synchronization system based on photoelectric phase modulation, characterized in that, The system includes: The same-source laser output module is used to output the same-source optical carrier and optical local oscillator, which are used to load spread spectrum signals and load codes, respectively. An optical carrier spread spectrum signal generation module is used to modulate the received spread spectrum signal onto the optical carrier. The encoded optical local oscillator generation module is used to load the local despreading code onto the optical local oscillator to obtain the encoded optical local oscillator; The optical domain code synchronization module is used to perform phase modulation on the encoded optical local oscillator; The optical domain despreading module is used to convolve the optical carrier spread spectrum signal output by the optical carrier spread spectrum signal generation module with the coded optical local oscillator output by the optical domain code synchronization module in the analog domain to obtain the despread radio frequency signal. After the demodulation calculation result, a pilot signal can also be obtained. Using a preset intermediate frequency signal as a reference signal, frequency and phase discrimination is performed with the pilot signal to obtain the frequency deviation of the pilot signal. The coded optical local oscillator is adjusted according to the frequency deviation to form a closed-loop control. The digital signal processing module is used to convert the optical domain despread radio frequency signal into an analog-to-digital signal and perform digital processing to output a digital signal and the processing result, thereby realizing signal despreading.

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