Optical-to-digital signal multi-channel tracking demodulation device and method

Abstract

The present invention belongs to the field of communication technology and relates to a multi-channel tracking and demodulation device and method for optical-to-digital signals, comprising a 2U VPX host, a signal processing module and an optical fiber interface assembly; the 2U VPX host realizes synchronous data transmission of multiple optical signals; the multiple optical signals are greater than four; the signal processing module converts the transmitted multiple optical signals into multi-channel digital signals, and performs tracking and demodulation on the multi-channel digital signals to extract multiple groups of azimuth errors and pitch angle errors; the optical fiber interface assembly realizes the transmission of the multiple optical signals and transmits external optical signals to the 2U VPX host; the device solves the problem of simultaneously receiving and demodulating 8 downlink beacon signals and broadband signals emitted by 8 aircraft, providing azimuth and pitch error voltages and locking indications to the antenna control unit, and completing 8-channel angle self-tracking.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular discloses a multi-channel tracking demodulation device and method for optical-to-digital signals. Background Art

[0002] Existing technologies generally use analog-to-digital tracking and demodulation designs, and a set of equipment can only support tracking and demodulating a single target with one antenna. It cannot support simultaneous and relatively independent tracking and demodulating of at least eight targets, and requires converting optical signals into digital signals for tracking and demodulation.

[0003] In view of this, the present invention proposes a multi-channel tracking and demodulation device and method for optical-to-digital signals, which solves the problem of simultaneously receiving and demodulating 8 downlink beacon signals and broadband signals emitted by 8 aircraft, providing azimuth and pitch error voltages and locking indications to the antenna control unit, completing 8-channel angle self-tracking, and each channel is relatively independent; at the same time, the optical signal is converted into a digital signal. Summary of the Invention

[0004] The object of the present invention is to provide a multi-channel tracking and demodulation device for optical-to-digital signals, and the specific scheme is as follows: it includes a 2U VPX host, a signal processing module and an optical fiber interface component; the 2U VPX host realizes the synchronous data transmission of multiple optical signals; the multiple optical signals are greater than four; the signal processing module converts the transmitted multiple optical signals into multi-channel digital signals, and performs tracking demodulation on the multi-channel digital signals to extract multiple groups of azimuth errors and pitch angle errors; the optical fiber interface component realizes the transmission of the multiple optical signals and transmits external optical signals to the 2U VPX host.

[0005] Furthermore, the 2U VPX host adopts a 2U air-cooled chassis, including a device power supply, a main control computer, a VPX slot, an external interface connector and a fan; the front panel of the 2U air-cooled chassis includes an indicator light, a USB interface and a device switch, and the rear panel includes an RJ45 network port, a reference signal input interface, a VGA display interface, a debugging serial port, an extended serial port and a 3-way X8 fiber optic aviation plug interface.

[0006] Furthermore, the signal processing module includes an optical module, an FPGA, a Zynq processor and a computer mainboard, and adopts the Aurora protocol to parse the multi-channel optical signals; the optical module includes two 4-channel signal optical modules, which are respectively used to receive 4-channel sum-difference composite signal inputs and transmit the received sum-difference composite signals to the FPGA; the FPGA processes each sum-difference composite signal in parallel, including sum-difference separation, FFT fast capture and digital AGC; the Zynq processor cooperates with the FPGA to complete sum-difference cross-correlation demodulation and orthogonal phase detection; the computer mainboard is connected to the FPGA and the Zynq processor via Ethernet for monitoring and data processing operations.

[0007] Furthermore, the FPGA includes an AGC loop, a beacon signal angle error demodulation unit and a broadband signal angle error extraction unit; the AGC loop is used to normalize the input signal and provide a stable input for angle error demodulation; the beacon signal angle error demodulation unit demodulates the sum signal, azimuth signal and elevation signal based on sum carrier tracking and orthogonal phase detection, and extracts the azimuth error voltage and elevation error voltage of the beacon signal; the broadband signal angle error extraction unit demodulates the synthetic signal of the broadband signal based on incoherent down-conversion and cross-correlation demodulation, and extracts the azimuth error voltage and elevation error voltage.

[0008] Furthermore, the AGC loop includes an amplitude excitation module, an integral operation module, a loop filtering module, a gain calculation module and a controllable amplifier; the amplitude excitation module receives the original baseband signal and generates an amplitude excitation signal for controlling the gain adjustment of the AGC loop; the integral operation module performs an integral operation on the input signal, extracts the slowly changing component of the signal amplitude, and outputs it to the loop filtering module; the loop filtering module performs a low-pass filter on the output of the integral operation module to filter out high-frequency noise and output a stable amplitude tracking signal; the gain calculation module calculates the gain coefficient based on the output of the loop filtering module and the threshold signal to achieve normalized control of the signal amplitude; the controllable amplifier performs gain adjustment on the input signal based on the output of the gain calculation module, outputs a normalized signal and an original signal, and the normalized signal is used for angle error demodulation processing.

[0009] Furthermore, the beacon signal angle error demodulation unit includes a sum path processing module, a difference path processing module and a low-pass filtering module; the sum path processing module filters and gain controls the sum signal, and outputs the phase-shifted sum path reference signal through the carrier synchronization module; the difference path processing module filters and gain controls the azimuth difference path signal and the elevation difference path signal respectively, and performs coherent detection with the sum path reference signal to extract angle error information; the low-pass filtering module performs low-pass filtering on the detection signal output by the coherent detection, and outputs the azimuth error voltage and the elevation error voltage for antenna closed-loop control.

[0010] Furthermore, the broadband signal angle error extraction unit includes an AGC amplification module, an incoherent down-conversion module, a phase-shift demodulation module, a cross-correlation processing module and a low-pass and gain adjustment module; the AGC amplification module performs AGC amplification on the synthesized signal to generate an AGC control voltage to ensure signal amplitude stability and provide a normalized input for subsequent processing; the incoherent down-conversion module uses DDS to perform incoherent down-conversion on the synthesized signal; the phase-shift demodulation module phase-shifts and filters the azimuth signal and the pitch signal respectively to match the broadband signal characteristics; the cross-correlation processing module performs cross-correlation operation on the phase-shifted signal to extract angle error information; the low-pass and gain adjustment module performs low-pass filtering and gain adjustment on the related signals obtained by the cross-correlation operation to output the azimuth angle error voltage and the pitch angle error voltage.

[0011] Furthermore, the optical fiber interface assembly includes multiple optical fiber links, including GYM12K1AN-2LC-2S0.8 / 0.3, GYM12KT1ANF2-J599 / 26KB02B1N F2-C5*2-S2 and J599 / 20KB02A1N-2LC-S2-L0.8; one end of the GYM12K1AN-2LC-2S0.8 / 0.3 is a GYM12KF1AN socket, and the other end is 2 LC plugs. The main cable uses a 12-core single-mode ribbon cable, and the branch uses an armored bundle tube.

[0012] The present invention also provides a multi-channel tracking and demodulation method for optical-to-digital signals, comprising: receiving a multi-channel sum-and-difference synthesized optical signal through an optical fiber interface component, converting it into a digital signal through an optical module, and parsing it using the Aurora protocol to achieve channel synchronization processing; the multi-channel sum-and-difference synthesized optical signal is greater than four channels; performing amplitude tracking on the input multi-channel sum-and-difference synthesized optical signal in an FPGA, and controlling the signal power at a fixed level through integration operation, loop filtering, and gain calculation to provide a stable input for angular error demodulation; performing angular error demodulation processing on the angular input signal to obtain an azimuth error voltage and a pitch angle error voltage; the angular input signal includes a beacon signal and a broadband signal.

[0013] Furthermore, the beacon signal is subjected to angular error demodulation processing, including: carrier synchronization of the sum-path signal to generate a phase-shifted sum-path reference signal; filtering and gain control of the azimuth difference path signal and the elevation difference path signal, and performing coherent detection with the sum-path reference signal, and outputting the azimuth error voltage and the elevation error voltage through low-pass filtering; the broadband signal is subjected to angular error demodulation processing, including: after AGC amplification of the synthesized signal, non-coherent down-conversion using DDS, phase-shifting and filtering the azimuth signal and the elevation signal respectively; performing cross-correlation operation on the phase-shifted signal, and outputting the azimuth error voltage and the elevation error voltage through low-pass filtering and gain adjustment.

[0014] The present invention has the following advantages and beneficial effects:

[0015] The high-precision AGC loop in the amplitude tracking technology proposed in this invention uses a "quantity" within the loop to track the input signal amplitude. After achieving amplitude tracking, the gain coefficient is calculated from the ratio of the obtained amplitude to the desired threshold, thereby achieving signal normalization. This approach completely solves the linear system problem of the AGC loop and realizes high-precision normalized control of signal power.

[0016] The optical-to-digital signal 8-channel tracking and demodulation device proposed in the present invention can achieve simultaneous tracking of 8 targets without increasing the number of devices, thereby significantly reducing the corresponding cost and the size of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is an exemplary diagram of a multi-channel tracking demodulation device for optical-to-digital signals provided by the present invention;

[0018] Figure 2 An exemplary schematic diagram of a signal processing module provided by the present invention;

[0019] Figure 3 An exemplary signal flow diagram of the signal processing module provided by the present invention;

[0020] Figure 4 An exemplary schematic diagram of an AGC ring provided by the present invention;

[0021] Figure 5 An exemplary schematic diagram of a beacon signal angle error demodulation unit provided by the present invention;

[0022] Figure 6 This is an exemplary schematic diagram of the broadband signal angle error extraction unit provided by the present invention. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0024] Figure 1 This is an exemplary diagram of a multi-channel tracking demodulation device for optical-to-digital signals provided by the present invention. Figure 1 As shown, the optical-to-digital signal multi-channel tracking demodulation device provided by the present invention includes a 2U VPX host, a signal processing module, an optical fiber interface component and integrated management software.

[0025] The 2U VPX mainframe implements synchronous data transmission of multiple optical signals. Multiple optical signals refer to eight or more sum-and-difference optical signals, each containing independent azimuth and elevation error information, enabling parallel tracking of multiple targets. For example, this can be used to track eight satellites or radio targets. Synchronous transmission involves processing and transmitting multiple optical signals in parallel with a time accuracy of 1μs or less, ensuring timing consistency across all channels and enabling real-time, high-precision multi-target tracking. The 2U VPX mainframe utilizes a 2U air-cooled chassis that complies with the VPX standard. It integrates a device power supply, a main control computer, VPX slots, external interface connectors, and a fan. The device power supply provides power, while the VPX slots ensure high-speed, synchronous transmission of multiple signals. The front panel features indicators, a USB port, and a device switch. The rear panel includes an RJ45 network port, a 10MHz reference signal input, a VGA display port, a debug serial port, a 422 expansion serial port, and three X8 fiber optic aviation connectors. Indicators indicate device operating status. The 3-channel X8 fiber optic aviation plug interface supports 8-channel optical signal transmission to meet multi-channel tracking requirements.

[0026] The signal processing module converts the transmitted multiple optical signals into multi-channel digital signals and performs tracking demodulation on each of these multi-channel digital signals to extract multiple sets of azimuth and elevation errors. The VPX signal processing module conforms to the standard 6U air-cooled VPX form factor. The VPX signal processing module is responsible for signal processing and can be interconnected with other boards via the VPX backplane. Multi-channel digital signals are parallel digital signal streams generated by the optical modules (e.g., two 4-channel QSFP+ optical modules) in the signal processing module, corresponding to the multiple (8) sum and difference optical signals. These signals are recognized and processed by the FPGA. Each digital signal contains independent sum, azimuth, and elevation error information for subsequent angular error demodulation, ensuring parallel tracking of multiple targets. Azimuth error refers to the angular deviation between the actual target azimuth and the antenna's pointing direction. This error is calculated by demodulating the azimuth error path signals from the beacon signal and the broadband signal. It is output as a voltage and used to control the antenna's horizontal adjustment to ensure alignment with the target. The pitch angle error refers to the angular deviation between the actual pitch of the target and the pitch of the antenna. It is obtained by demodulating the pitch difference signal and is used to control the vertical adjustment of the antenna. The two together realize the two-dimensional closed-loop tracking of the antenna on the target.

[0027] The optical module uses two 4-channel QSFP+ optical modules to receive 8-channel sum and difference composite optical signals. Each signal is a sum and difference composite signal synthesized according to the Aurora protocol. After passing through the optical module, the sum and difference signals are separated inside the FPGA and then sent to the terminal receiving demodulation circuit. For more information about the signal processing module, see Figure 2 and Figure 3 .

[0028] The fiber optic interface assembly transmits multiple optical signals, transferring external optical signals to the 2U VPX host. The assembly includes multiple fiber optic links, including GYM12K1AN-2LC-2S0.8 / 0.3, GYM12KT1ANF2-J599 / 26KB02B1N F2-C5*2-S2, and J599 / 20KB02A1N-2LC-S2-L0.8. The GYM12K1AN-2LC-2S0.8 / 0.3 has a GYM12KF1AN socket on one end and two LC plugs on the other. The main cable uses a 12-core single-mode ribbon cable, and the branches use 1.8mm diameter armored bundle tubes. The total length is 0.8 meters, with branches 0.3 meters long.

[0029] The sum and difference signals sent from the RF front end pass through the optical receiver module and are separated into the sum path and the difference path (azimuth and elevation) within the FPGA. The FFT fast capture circuit enables rapid carrier tracking loop lock. The AGC control signal sent to the difference path (azimuth and elevation) is generated by the sum path, normalizing the amplitude of the difference path signal.

[0030] Considering that the difference channel signal has a lower signal-to-noise ratio than the channel signal and is a broadband signal with suppressed carrier, the difference channel uses quadrature phase detection and filtering of the reference signal acquired by the channel after tracking to derive pitch and azimuth error information, enabling the system to enter self-tracking. The lock indication, digital values ​​of the AGC voltage, and digital values ​​of the angular error voltage are transmitted to the ACU via the serial port. Simultaneously, the lock indication (TTL level), AGC voltage, angular error voltage, and device status monitoring information are transmitted via the Ethernet port to the tracking monitoring software, which monitors the key operating parameters of the tracking receiver.

[0031] The signal processing module (ie, tracking receiver) has the ability to receive various signal forms such as beacon signals and broadband signals. Figure 2 An exemplary schematic diagram of a signal processing module provided by the present invention; Figure 3 : This is an exemplary signal flow diagram of the signal processing module provided by the present invention. Figure 2 and 3 As shown, the signal processing module includes two four-channel optical modules, an FPGA (field programmable gate array, model JFTVX690T20), a Zynq processor (e.g., FMQL45T900), a computer motherboard, and an Ethernet physical layer transceiver (LAN). It uses the Aurora protocol to parse the multi-channel optical signals. The optical modules include two four-channel optical modules, each for receiving four sum-and-difference composite signal inputs and transmitting them to the FPGA. The FPGA processes each sum-and-difference composite signal in parallel, including sum-and-difference separation, fast FFT capture, and digital AGC. The Zynq processor collaborates with the FPGA to perform sum-and-difference cross-correlation demodulation and quadrature phase detection. The computer motherboard communicates with the FPGA and Zynq processor via Ethernet for monitoring and data processing.

[0032] The Xilinx XC7VX690T FPGA performs parallel processing of each sum-and-difference composite signal. This parallel processing includes sum-and-difference separation, fast Fourier transform (FFT) capture, and digital AGC. Sum-and-difference separation separates the sum signal, azimuth error signal, and pitch error signal, providing a clean signal input for subsequent demodulation. Fast Fourier transform (FFT) capture uses the FFT algorithm to lock the carrier and quickly track the signal frequency. The digital AGC extracts the slowly varying component of the signal amplitude through integration, then filters out high-frequency noise through loop filtering. The gain calculation module then calculates the gain coefficient, providing a stable signal amplitude for angle error demodulation.

[0033] The Zynq processor uses the XC7Z045, working in conjunction with the FPGA to perform cross-correlation demodulation and quadrature phase detection. Cross-correlation demodulation performs point-by-point cross-correlation calculations on wideband signals, extracting angle error information without carrier capture, making it suitable for complex signal scenarios. Quadrature phase detection performs coherent detection on beacon signals to output azimuth and elevation angle errors.

[0034] The computer motherboard communicates with the FPGA and Zynq processor via Ethernet, runs monitoring software, displays signal strength and angular error curves in real time, and can dynamically configure demodulation parameters to achieve intelligent management and debugging of the equipment.

[0035] The characteristic of the monopulse tracking method is that the antenna beam is fixed, and the azimuth and elevation angle error information can be generated simultaneously with a single incoming signal. The monopulse self-tracking system has already formed the azimuth (hereinafter referred to as Az) error signal and the elevation (hereinafter referred to as EI) error signal in the antenna channel synthesis (sum channel synthesis and difference channel synthesis) stage. After the downconverter downconverts the signal to a frequency band that can be processed by the tracking receiver, the tracking receiver detects the azimuth error signal Az (e.g., azimuth error voltage ), pitch error signal E1 (eg, pitch error voltage ) and transmits it to the servo system through a certain method. After receiving this error signal, the servo drives the antenna motor in a direction that reduces the error, ensuring that the antenna is always aligned with the target signal. This target signal can be a satellite communication signal or other signal.

[0036] In some embodiments, the FPGA includes an AGC loop, a beacon signal angle error demodulation unit, and a broadband signal angle error extraction unit.

[0037] The AGC loop normalizes the input signal to provide a stable input for angle error demodulation. The input signal is the multi-channel (8-channel) sum-and-difference digital signal input to the FPGA after conversion by the optical module and parsing using the Aurora protocol in the signal processing module. This signal includes the beacon signal, the sum of the broadband signal, the azimuth difference signal, and the elevation difference signal. It is the primary processing target for angle error demodulation. The input signal undergoes a process called amplitude excitation module to generate a reference signal, integration to extract slowly varying amplitude components, loop filtering to remove noise, gain calculation to output coefficients, and controllable amplifier gain adjustment. This process stabilizes the signal amplitude at a fixed level to prevent demodulation errors caused by fluctuations in optical signal strength. The receiver needs to adapt to dynamic signals in the digital domain, requiring an AGC design. The AGC controls the coherent frequency conversion output from the carrier phase-locked loop (PLL). Once the carrier phase-locked loop locks onto the signal, the coherent frequency conversion result reflects a portion of the signal power, thereby enabling signal power control and maintaining a fixed level.

[0038] The beacon signal angle error demodulation unit demodulates the sum signal, azimuth signal, and elevation signal based on sum carrier tracking and quadrature phase detection, extracting the azimuth and elevation error voltages of the beacon signal. Sum carrier tracking uses the FFT fast capture algorithm to quickly lock the beacon signal sum carrier frequency and phase, generating a phase-shifted sum reference signal. Quadrature phase detection coherently detects the sum reference signal with the azimuth and elevation difference signals, outputting quadrature I / Q signals, extracting the DC component through low-pass filtering, and converting it into azimuth and elevation error voltages.

[0039] The broadband signal angle error extraction unit demodulates the synthesized signal of the broadband signal based on incoherent down-conversion and cross-correlation demodulation, and extracts the azimuth error voltage and the elevation error voltage. Incoherent down-conversion can refer to the use of DDS (direct digital frequency synthesizer) to generate a local oscillator signal close to the carrier frequency of the input broadband signal, digitally mixing it with the broadband synthesized signal in the FPGA, down-converting the high-frequency broadband signal to the baseband, eliminating the dependence on the signal carrier, and adapting to broadband and carrier-suppressed signal processing. Cross-correlation demodulation refers to the cross-correlation operation of the azimuth and elevation signals after incoherent down-conversion in the FPGA, using the signal autocorrelation to extract the angle deviation information, and outputting the azimuth and elevation angle error voltages after low-pass filtering and gain adjustment to achieve angular error resolution in a carrier-free scenario. For more information about the AGC loop, see Figure 4 For more information about the beacon signal angle error demodulation unit, see Figure 5 For more information about the wideband signal angle error extraction unit, see Figure 6 and its related descriptions.

[0040] Traditional AGC designs utilize feedback from the difference between power measurement and threshold at the back end to control the front-end gain. Because gain control is a multiplication relationship, the AGC control system is a nonlinear system. Compared to linear systems, nonlinear systems lack theoretical support and cannot be designed in detail for response speed and control accuracy. Currently, nonlinear systems increase loop gain to ensure a certain control range and control speed. However, this gain does not decrease linearly as the controlled variable approaches the desired value, resulting in large tracking errors during the loop tracking phase. Therefore, the present invention provides a new AGC loop that solves the linear system problem of the AGC loop and achieves high-precision normalized control of signal power. Figure 4 Schematic diagram of an exemplary AGC ring provided by the present invention. Figure 4 As shown, the AGC loop includes an amplitude excitation module, an integral operation module, a loop filtering module, a gain calculation module and a controllable amplifier.

[0041] The amplitude excitation module receives the raw baseband signal and generates an amplitude excitation signal, which is used to control the gain adjustment of the AGC loop. The raw baseband signal refers to the initial digital baseband signal input to the AGC loop, including the sum path, azimuth difference path, and elevation difference path information of the beacon signal and wideband signal. The amplitude excitation signal is a fixed-amplitude, fixed-frequency digital reference signal generated by the amplitude excitation module within the AGC loop. The gain of the AGC loop refers to the digital gain coefficient output by the AGC loop through the "integration operation → loop filtering → gain calculation" process. For example, the amplitude recording module can generate a 10MHz sine wave reference signal with a fixed amplitude of 1Vpp. This signal is superimposed on the 2.4GHz QPSK input signal output by the optical module to control the gain adjustment of the AGC loop, ensuring that the signal amplitude remains stable during subsequent processing.

[0042] The integration module integrates the input signal, extracting the slowly varying component of the signal amplitude and outputting it to the loop filter module. This slowly varying component refers to the amplitude fluctuation trend of the input signal (the eight-channel sum-and-difference synthesized digital signal) over a longer time scale, reflecting the slowly varying nature of the signal strength. For example, the integration module can integrate a 2.4GHz, 100MHz bandwidth input signal within the FPGA, extracting the slowly varying component of the signal amplitude and providing input to the loop filter.

[0043] The loop filter module performs low-pass filtering on the output of the integral operation module to filter out high-frequency noise and output a stable amplitude tracking signal. For example, the loop filter module can use an 8th-order IIR low-pass filter with a cutoff frequency of 1 kHz to filter out high-frequency noise and output a stable amplitude tracking signal.

[0044] The gain calculation module calculates the gain coefficient based on the output of the loop filter module and the threshold signal, achieving normalized signal amplitude control. The threshold signal is a reference level used in the AGC loop to define the target signal amplitude and represents the desired signal power target. For example, when the input signal amplitude is 2V (below the threshold of 3V), the gain coefficient is 1.5. The controllable amplifier amplifies the input signal to a 3V amplitude, achieving normalized signal amplitude control.

[0045] The controllable amplifier adjusts the gain of the input signal based on the output of the gain calculation module, outputting a normalized signal and an original signal. The normalized signal is used for angle error demodulation. The normalized signal is a digital signal whose amplitude is stabilized at a fixed target level after AGC loop gain adjustment. The original signal is the input signal before AGC loop gain adjustment, without amplitude normalization. The normalized signal has a stable amplitude of 3V with an accuracy of ±0.1dB. The normalized signal serves as the input to the angle error demodulation unit, ensuring the stability and accuracy of the demodulation process. The original signal is retained to monitor the original strength of the input signal.

[0046] Figure 5 This is an exemplary schematic diagram of the beacon signal angle error demodulation unit provided by the present invention. The sum path receiver completes the beacon signal frequency guidance and carrier capture tracking. The difference path signal is digitally demodulated and phase-detected with the sum path reference signal to detect the azimuth and pitch angle error information. The phase-detected sum path reference signal is the phase-shifted sum path DCO output signal. The phase shifter and the difference path DCO are integrated into one design. Figure 5 As shown, the beacon signal angle error demodulation unit includes a sum path processing module, a difference path processing module and a low-pass filtering module.

[0047] The sum signal processing module filters and performs gain control on the sum signal, and outputs a phase-shifted sum reference signal through the carrier synchronization module. For example, the sum signal processing module can perform bandpass filtering and gain control on a 2.4 GHz sum signal with a ±50 kHz bandwidth to ensure signal quality. The carrier synchronization module quickly locks to the carrier frequency and phase of the beacon signal, providing a precise phase reference for subsequent quadrature phase detection. The carrier synchronization module uses an FFT algorithm to lock to the carrier and generate a phase-shifted sum reference signal.

[0048] The difference path processing module filters and performs gain control on the azimuth difference path signal and the elevation difference path signal, respectively, and performs coherent detection with the sum path reference signal to extract angular error information. The azimuth difference path signal is a signal generated by the antenna feed network that carries information about the target's horizontal angular deviation (azimuth angle). The elevation difference path signal is a signal generated by the antenna feed network that carries information about the target's vertical angular deviation (pitch angle). For example, the azimuth difference path and elevation difference path processing modules can filter and perform gain control on the azimuth difference path signal and the elevation difference path signal, respectively, before performing coherent detection with the sum path reference signal to output I / Q signals.

[0049] The low-pass filter module performs low-pass filtering on the coherent detection signal, outputting azimuth and elevation error voltages for antenna closed-loop control. Antenna closed-loop control ensures precise antenna pointing to the target through real-time monitoring and adjustment. In the optical-to-digital signal multi-channel tracking demodulation device, the extracted azimuth and elevation error voltages are used to continuously adjust the antenna's azimuth and elevation angles, ensuring constant alignment with the target signal.

[0050] Figure 6This is an exemplary schematic diagram of the broadband signal angular error extraction unit provided by the present invention. The broadband signal angular error extraction adopts the same method, the tracking receiver receives the sum and difference signals, adopts local DDS non-coherent down-conversion, and extracts the error signal after correlating the sum and difference signals. Through angular error extraction, the pitch and azimuth error signals are output and sent to the sky feeding subsystem. The sum and difference cross-correlation algorithm is used to realize the angular error extraction of broadband signals, without the need to complete the capture of the sum signal, and is suitable for the angular error extraction of dual-channel systems in any signal form. In deep space systems, radio star phase correction also completes the angular error extraction of radio sources based on this algorithm. As Figure 6 As shown, the broadband signal angle error extraction unit includes an AGC amplification module, a non-coherent down-conversion module, a phase shift demodulation module, a cross-correlation processing module, and a low-pass and gain adjustment module.

[0051] The AGC amplification module performs AGC amplification on the composite signal, generating an AGC control voltage to ensure signal amplitude stability and provide a normalized input for subsequent processing. AGC voltage control dynamically adjusts the amplitude of the input composite signal through the automatic gain control (AGC) mechanism, generating a digital control voltage representing the signal amplitude to offset amplitude fluctuations during signal transmission and achieve signal amplitude stabilization and normalization. The AGC voltage value sent to the servo and the AGC detection voltage calculated by the FPGA actually represent the signal strength of the current input signal. However, the pre-demodulated signal has already been modulated by the amplifier and does not represent the actual signal strength received by the antenna. The actual signal strength should be the signal size before modulation, that is, the optical input signal size. The servo requires an AGC indicator voltage that reflects this actual signal strength.

[0052] The non-coherent down-conversion module uses a DDS (direct digital synthesizer) to perform non-coherent down-conversion on the composite signal. The composite signal is a combination of the sum and difference (azimuth and elevation) signals output by the antenna feed network, containing target angle deviation information. The phase-shift demodulation module phase-shifts and filters the azimuth and elevation signals to match broadband signal characteristics. The cross-correlation processing module performs a cross-correlation operation on the phase-shifted signals to extract angular error information. The low-pass and gain adjustment module performs a low-pass filter and gain adjustment on the correlation signals obtained from the cross-correlation operation, outputting azimuth and elevation angle error voltages.

[0053] The present invention also provides a multi-channel tracking demodulation method for optical-to-digital signals, comprising: receiving multi-channel sum-and-difference synthesized optical signals through an optical fiber interface component, converting them into digital signals through an optical module, and using the Aurora protocol for parsing to achieve channel synchronization processing; the multi-channel sum-and-difference synthesized optical signals are greater than four channels.

[0054] The amplitude of the input multi-path sum and difference synthesized optical signals is tracked separately in the FPGA. Through integration operation, loop filtering and gain calculation, the signal power is controlled at a fixed level to provide a stable input for angle error demodulation.

[0055] Angle error demodulation is performed on the angle input signal to obtain an azimuth error voltage and an elevation error voltage; the angle input signal includes a beacon signal and a broadband signal. Specifically, the angle error demodulation of the beacon signal includes: carrier synchronization of the sum-path signal to generate a phase-shifted sum-path reference signal; filtering and gain control of the azimuth difference path signal and the elevation difference path signal, performing coherent detection with the sum-path reference signal, and outputting the azimuth error voltage and the elevation error voltage through low-pass filtering. Angle error demodulation of the broadband signal includes: AGC amplification of the synthesized signal, non-coherent down-conversion using a DDS, phase shifting and filtering the azimuth signal and the elevation signal respectively; cross-correlation calculation of the phase-shifted signals, low-pass filtering and gain adjustment, and outputting the azimuth error voltage and the elevation error voltage.

[0056] The input optical signal is input into the tracking reception processing module through the QSFP+ optical module according to the specific Aurora protocol. The module analyzes the 8 digital signals separately, extracts the AGC voltage and angle error information, and sends the demodulated data as a digital signal.

[0057] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A multi-channel tracking demodulation device for optical-to-digital signals, characterized in that: Includes a 2U VPX host, signal processing module, and fiber optic interface components; The 2U VPX host realizes synchronous data transmission of multiple optical signals; the multiple optical signals are greater than four; The signal processing module converts the transmitted multi-channel optical signals into multi-channel digital signals, and performs tracking demodulation on the multi-channel digital signals to extract multiple groups of azimuth errors and pitch angle errors. The signal processing module includes an optical module, an FPGA, a Zynq processor and a computer motherboard, and uses the Aurora protocol to parse the multi-channel optical signals. The optical module includes two 4-channel signal optical modules, which are respectively used to receive 4-channel sum and difference composite signal inputs and transmit the received sum and difference composite signals to the FPGA. The FPGA processes each sum and difference composite signal in parallel, including sum and difference separation, FFT fast capture and digital AG. C; the Zynq processor cooperates with FPGA to complete sum-difference cross-correlation demodulation and orthogonal phase detection; the computer motherboard is connected to the FPGA and the Zynq processor via Ethernet for monitoring and data processing operations; the FPGA includes an AGC loop, a beacon signal angle error demodulation unit and a broadband signal angle error extraction unit; the AGC loop is used to normalize the input signal to provide a stable input for angle error demodulation; the beacon signal angle error demodulation unit demodulates the sum signal, azimuth signal and pitch signal based on sum carrier tracking and orthogonal phase detection to extract the azimuth error voltage and pitch angle of the beacon signal error voltage; the broadband signal angle error extraction unit demodulates the synthetic signal of the broadband signal based on incoherent down-conversion and cross-correlation demodulation to extract the azimuth error voltage and the pitch error voltage; the AGC loop includes an amplitude excitation module, an integral operation module, a loop filtering module, a gain calculation module and a controllable amplifier; the amplitude excitation module receives the original baseband signal and generates an amplitude excitation signal for controlling the gain adjustment of the AGC loop; the integral operation module performs an integral operation on the input signal, extracts the slowly varying component of the signal amplitude, and outputs it to the loop filtering module; the loop filtering module performs an integral operation on the input of the integral operation module The output is low-pass filtered to filter out high-frequency noise and output a stable amplitude tracking signal; the gain calculation module calculates the gain coefficient according to the output of the loop filter module and the threshold signal to achieve normalized control of the signal amplitude; the controllable amplifier adjusts the gain of the input signal according to the output of the gain calculation module, outputs a normalized signal and an original signal, and the normalized signal is used for angle error demodulation processing; the beacon signal angle error demodulation unit includes a sum path processing module, a difference path processing module and a low-pass filtering module; the sum path processing module filters and gain controls the sum signal, and outputs a phase-shifted sum path reference signal through a carrier synchronization module; The difference path processing module filters and controls the gain of the azimuth difference path signal and the elevation difference path signal respectively, and performs coherent detection with the sum path reference signal to extract the angle error information; the low-pass filtering module performs low-pass filtering on the detection signal output by the coherent detection, and outputs the azimuth error voltage and the elevation error voltage for antenna closed-loop control; the broadband signal angle error extraction unit includes an AGC amplification module, an incoherent down-conversion module, a phase shift demodulation module, a cross-correlation processing module and a low-pass and gain adjustment module; the AGC amplification module performs a coherent detection on the composite signal AGC amplifies and generates an AGC control voltage to ensure signal amplitude stability and provide normalized input for subsequent processing; the non-coherent down-conversion module uses DDS to perform non-coherent down-conversion on the synthesized signal; the phase-shift demodulation module phase-shifts and filters the azimuth signal and the pitch signal respectively to match the broadband signal characteristics; the cross-correlation processing module performs cross-correlation operation on the phase-shifted signal to extract angle error information; the low-pass and gain adjustment module performs low-pass filtering and gain adjustment on the correlation signal obtained by the cross-correlation operation, and outputs the azimuth error voltage and the pitch error voltage; The optical fiber interface assembly realizes the transmission of the multi-channel optical signals and transmits the external optical signals to the 2U VPX host.

2. The optical-to-digital signal multi-channel tracking demodulation device according to claim 1, characterized in that: The 2UVPX host uses a 2U air-cooled chassis, including a device power supply, a main control computer, a VPX slot, an external interface connector and a fan; The front panel of the 2U air-cooled chassis includes indicator lights, a USB port, and a device switch, and the rear panel includes an RJ45 network port, a reference signal input port, a VGA display port, a debug serial port, an extended serial port, and a 3-way X8 optical fiber aviation plug port.

3. The optical-to-digital signal multi-channel tracking demodulation device according to claim 1, characterized in that: The optical fiber interface assembly includes multiple optical fiber links, including GYM12K1AN-2LC-2S0.8 / 0.3, GYM12KT1ANF2-J599 / 26KB02B1N F2-C5*2-S2 and J599 / 20KB02A1N-2LC-S2-L0.8; one end of the GYM12K1AN-2LC-2S0.8 / 0.3 is a GYM12KF1AN socket, and the other end is two LC plugs. The main cable uses a 12-core single-mode ribbon cable, and the branch uses an armored bundle tube.

4. A method for multi-channel tracking and demodulation of optical-to-digital signals applied to an optical-to-digital signal multi-channel tracking and demodulation device according to any one of claims 1 to 3, characterized in that: include: The optical fiber interface component receives multi-channel sum and difference synthesized optical signals, converts them into digital signals through the optical module, and uses the Aurora protocol to analyze and realize channel synchronization processing; The multi-path sum-and-difference synthesized optical signals are greater than four paths; The FPGA tracks the amplitude of the input multi-path sum and difference synthesized optical signals. Through integration, loop filtering, and gain calculation, the signal power is controlled at a fixed level, providing a stable input for angle error demodulation. Performing angle error demodulation processing on the angle input signal to obtain an azimuth error voltage and a pitch angle error voltage; the angle input signal includes a beacon signal and a broadband signal; Angle error demodulation processing, including: Carrier synchronization is performed on the summing-path signal to generate a phase-shifted summing-path reference signal; Filtering and gain controlling the azimuth difference path signal and the elevation difference path signal, performing coherent detection with the sum path reference signal, and outputting the azimuth error voltage and the elevation error voltage through low-pass filtering; Perform angle error demodulation on broadband signals, including: After AGC amplification of the synthesized signal, DDS is used for non-coherent down-conversion, and the azimuth signal and elevation signal are phase-shifted and filtered respectively; The phase-shifted signal is subjected to cross-correlation operation, low-pass filtered and gain adjusted to output azimuth error voltage and elevation error voltage.

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