CN114499690A - Ground simulation device for satellite-borne laser communication terminal - Google Patents
Ground simulation device for satellite-borne laser communication terminal Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/61—Coherent receivers
- H04B10/616—Details of the electronic signal processing in coherent optical receivers
- H04B10/6164—Estimation or correction of the frequency offset between the received optical signal and the optical local oscillator
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/548—Phase or frequency modulation
- H04B10/556—Digital modulation, e.g. differential phase shift keying [DPSK] or frequency shift keying [FSK]
- H04B10/5563—Digital frequency modulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/61—Coherent receivers
- H04B10/64—Heterodyne, i.e. coherent receivers where, after the opto-electronic conversion, an electrical signal at an intermediate frequency [fIF] is obtained
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/30—Monitoring; Testing of propagation channels
- H04B17/391—Modelling the propagation channel
- H04B17/3912—Simulation models, e.g. distribution of spectral power density or received signal strength indicator [RSSI] for a given geographic region
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/18578—Satellite systems for providing broadband data service to individual earth stations
- H04B7/18582—Arrangements for data linking, i.e. for data framing, for error recovery, for multiple access
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2656—Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe synchronisation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2657—Carrier synchronisation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2657—Carrier synchronisation
- H04L27/2659—Coarse or integer frequency offset determination and synchronisation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
- H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
- H04L27/38—Demodulator circuits; Receiver circuits
- H04L27/3845—Demodulator circuits; Receiver circuits using non - coherent demodulation, i.e. not using a phase synchronous carrier
- H04L27/3854—Demodulator circuits; Receiver circuits using non - coherent demodulation, i.e. not using a phase synchronous carrier using a non - coherent carrier, including systems with baseband correction for phase or frequency offset
Abstract
The invention discloses a ground simulation device of a satellite-borne laser communication terminal, which comprises: the laser signal detection module receives a laser signal, the laser signal is converted into an intermediate frequency signal and is input into the signal processing board card, the intermediate frequency signal is demodulated according to demodulation parameters issued by the upper computer of the analog device, distance information carried by the intermediate frequency signal is resolved, demodulated data stream, distance information and other state information are transmitted back to the upper computer of the analog device through the ten-gigabit network card and are displayed on the upper computer of the analog device in real time. The invention discloses a ground simulation device of a satellite-borne laser communication terminal, which realizes laser signal demodulation and communication distance measurement and calculation under laboratory conditions, realizes inter-satellite communication with a communication terminal to be tested and simulates the distance measurement process.
Description
Technical Field
The invention relates to the technical field of satellite laser communication, in particular to a ground simulation device of a satellite-borne laser communication terminal.
Background
The operational performance and the main index of the satellite laser communication terminal must be verified before transmission. Therefore, a corresponding laboratory ground simulation verification platform should be established at the same time of developing the satellite laser communication terminal or in advance. A satellite laser communication terminal is generally composed of two basic systems, i.e., a laser communication system for information transmission of two satellites and an optical tracking system for aiming, acquisition and tracking between them. Correspondingly, the detection of the laser communication terminal is also divided into two aspects, namely the verification of the communication performance of the laser communication terminal and the detection and verification of the optical aiming, capturing and tracking performances.
Because the research on satellite laser communication is started late in China, the development of the satellite laser communication terminal ground detection equipment in China is not complete. At present, ground detection equipment of satellite laser communication terminals in China mostly aims at simulation verification equipment of tracking performance and laser signal beam quality after long-distance transmission of the communication terminals in a motion state, and lacks simulation verification equipment aiming at communication and distance measurement performance of a laser communication system.
At present, the detection of the communication and ranging performance of a laser communication terminal is generally realized by combining optical delay equipment with a communication terminal self-closed loop test mode. The optical signal output by the transmitting end of the communication terminal is input into the optical delay equipment, and is transmitted to the receiving end of the communication terminal for demodulation and ranging after optical delay. However, the cost of the optical delay device is high, and the optical delay device is not suitable for simulating signal transmission delay of a communication distance of tens of thousands of kilometers between satellites. The self-sending and self-receiving test method of the communication terminal cannot fully simulate the working state of the communication terminal for establishing a laser communication link with other satellite communication terminals and executing an inter-satellite ranging task. Due to the uniqueness and complexity of satellite platforms, interactive verification testing using real satellites is complicated and costly.
Disclosure of Invention
The invention aims to solve the problems of complex satellite interaction and strict test and high cost in the prior art, and provides a ground simulation device for a satellite-borne laser communication terminal, which can simulate and generate laser signals of a corresponding communication system carrying signal propagation distance information under laboratory conditions, and realize inter-satellite communication and simulation of a ranging process with a tested communication terminal; the method can be used as ground detection equipment for verifying the communication and ranging performance of the satellite-borne laser communication terminal. The invention aims to realize the purpose by adopting a heterodyne detection and coherent communication system and combining a ranging communication integrated signal processing technology.
The invention provides a ground simulation device of a satellite-borne laser communication terminal, which comprises:
the laser signal processing subsystem: the system comprises a digital signal processing subsystem, a laser communication terminal, a computer subsystem and a laser communication terminal, wherein the digital signal processing subsystem is used for receiving a received optical signal input by the laser communication terminal to be tested, receiving a laser control instruction transmitted by the computer subsystem, converting the received optical signal into an intermediate frequency signal according to the laser control instruction, transmitting the intermediate frequency signal to the digital signal processing subsystem, receiving a baseband signal transmitted by the digital signal processing subsystem and converting the baseband signal into an emitting optical signal;
the digital signal processing subsystem: the laser signal processing subsystem is used for receiving an intermediate frequency signal transmitted by the laser signal processing subsystem, receiving internal transmission data and a control command transmitted by the computer control subsystem, generating a baseband signal according to the internal transmission data, demodulating the intermediate frequency signal according to the control command to generate a feedback signal, and transmitting the feedback signal to the computer control subsystem;
the computer control subsystem: the system comprises a laser signal processing subsystem, a digital processing subsystem and a data processing subsystem, wherein the laser signal processing subsystem is used for receiving external transmission data input by an external data source, transmitting a laser control instruction to the laser signal processing subsystem, transmitting internal transmission data and a control command to the digital processing subsystem and receiving and displaying a feedback signal transmitted by the digital signal processing subsystem.
The invention relates to a ground simulation device of a satellite-borne laser communication terminal, and as a preferred mode, a laser signal processing subsystem comprises:
the laser signal modulation module: the system comprises a digital signal processing subsystem, a light source laser, a communication system and a communication system, wherein the digital signal processing subsystem is used for receiving a baseband signal transmitted by the digital signal processing subsystem and modulating the baseband signal to the optical carrier to generate a transmitting optical signal;
laser signal detection module: the system comprises a computer subsystem, a laser communication terminal, a digital signal processing subsystem and a signal processing subsystem, wherein the computer subsystem is used for receiving a received optical signal input by the laser communication terminal to be tested, receiving local oscillator light transmitted by a light source laser, receiving a laser control instruction transmitted by the computer subsystem, converting the laser signal into an intermediate frequency signal by means of coherent heterodyne detection according to the laser control instruction, and transmitting the intermediate frequency signal to the digital signal processing subsystem;
a light source laser: the optical carrier is used for sending optical carrier to the laser signal modulation module and the local oscillator light is used for sending local oscillator light to the laser signal detection module.
The invention relates to a ground simulation device of a satellite-borne laser communication terminal, which is used as an optimal mode, and a calculation and control subsystem comprises the following components:
ten thousand million network cards: the system comprises a control computer, a digital processing subsystem, an analog device upper computer and a digital processing subsystem, wherein the control computer is used for receiving internal transmission data transmitted by the digital processing subsystem, receiving external transmission data input by an external data source, receiving a control command transmitted by the analog device upper computer, and transmitting demodulated state information to the analog device upper computer, and the state information comprises data stream and distance information;
an upper computer of the simulation device: the control command is sent to the gigabit network card, the control command is sent to the digital signal processing subsystem, the laser control command is sent to the laser signal processing subsystem, the state information demodulated by the gigabit network card is received and displayed in real time, and laser signal demodulation and communication distance measurement and calculation are achieved.
The invention relates to a ground simulation device of a satellite-borne laser communication terminal, which is a preferred mode.A digital signal processing subsystem is a signal processing board card adopting a structure combining an FPGA (field programmable gate array), an ADC (analog to digital converter) and a DAC (digital to analog converter), the signal processing board card demodulates an intermediate-frequency signal according to demodulation parameters issued by an upper computer of the simulation device, simultaneously demodulates distance information carried by the intermediate-frequency signal, transmits the demodulated state information to a gigabit network card, and converts internally transmitted data input by the gigabit network card into baseband signals carrying the distance information and transmits the baseband signals to a laser signal modulation module.
Inputting an intermediate frequency signal of the signal processing board card, obtaining an intermediate frequency signal sampling sequence after ADC sampling, and processing the intermediate frequency signal sampling sequence by using a digital signal processing platform; in order to obtain a relatively stable intermediate frequency, an intermediate frequency signal sampling sequence output by the ADC is divided into two paths, one path is demodulated, and the other path is used for frequency offset estimation of the intermediate frequency signal.
And performing FFT (fast Fourier transform) on the intermediate-frequency signal subjected to frequency offset estimation to obtain the central frequency of the intermediate-frequency signal and transmitting the central frequency to an upper computer of the analog device, and if the central frequency is deviated from the central frequency set by the upper computer of the analog device, performing local oscillator optical frequency offset adjustment by the upper computer of the analog device through a laser control instruction to maintain the frequency offset of the intermediate frequency within a frequency range in which the system can realize demodulation.
The intermediate frequency signal to be demodulated is processed by digital down-conversion DDC, the frequency band signal is converted into a baseband signal, because the analog device needs to realize multi-level communication rate, in order to conveniently process signals with different rates in a unified way, the sampling sequence is resampled by an interpolation filter in the process of digital down-conversion to ensure that the sampling points of baseband code element signals with different rates are consistent, the resampled baseband signal obtains the optimal sampling point position by timing synchronization, after the residual frequency offset is eliminated by utilizing carrier synchronization, the number of the received complete data frames is confirmed by frame synchronization, and after decoding and descrambling, the data information is demodulated. Thereby achieving demodulation of the laser signal.
The measurement and calculation of the communication distance are completed by a method of acquiring time information carried by signals in the signal synchronization process, the data frame length Tframe, the code element length Tbit and the code element phase Nphase are used as units for measuring the delay time, the frame length and the code element length correspond to the measurement of integral multiple of the code element length delay, the code element phase corresponds to decimal time of the code element length delay measurement, the number of received data frames and the number of code elements can be obtained in a frame synchronization link, the code element phase can be obtained in a phase accumulator in a timing synchronization loop, a delay value corresponding to the current communication distance can be obtained by a formula T (Nframe Tframe + Nbit Tbit + Nphase Tbit), and the measurement and calculation of the current communication distance can be realized by multiplying the delay value by the light speed C in a simulation environment.
The invention relates to a ground simulation device of a satellite-borne laser communication terminal, as an optimal mode, a digital signal processing subsystem further comprises:
the coding module: the scrambling module is used for encoding the intermediate frequency signals and the internal transmission data according to the communication protocol of the satellite communication terminal to generate encoded data and inputting the encoded data into the scrambling module;
a scrambling module: the system comprises a scrambling module, a frame identification mark, a rate switching module and a frame identification mark, wherein the scrambling module is used for receiving encoded data sent by the scrambling module, scrambling the encoded data and taking frame length scrambled data to generate scrambled data, and the frame identification mark is added before the scrambled data to be used as a frame header to form frame data which is used for transmitting the frame data into the rate switching module;
a rate switching module: the system comprises a scrambling module, a resampling module, a data processing module and a data processing module, wherein the scrambling module is used for receiving a frame of data transmitted by the scrambling module, generating a baseband signal sampling sequence of a corresponding communication rate from the frame of data according to the communication rate to be realized currently, and inputting the baseband signal sampling sequence into the resampling module;
a resampling module: the analog device takes rectangular wave as a code element waveform of a baseband signal, and generates a rectangular wave baseband signal in a mode of generating a plurality of sampling points with the same value for the same code element signal; when the sampling rate is fixed, the number of sampling points forming the waveform of the code element signal is different, the generated baseband signal rate is different, but in a multi-rate communication system, the rate of the baseband signal and the sampling rate are not always in integral multiple relation, at this time, the method can not be directly used for generating the baseband signal with the corresponding rate, the generated integral multiple sampling rate frequency division rate baseband signal sampling sequence is resampled by an interpolation filter, and the baseband signal with the speed of non-integral multiple sampling clock frequency division is generated;
DAC digital-to-analog conversion module: and the distance simulation module is used for receiving the signal propagation distance input by the distance simulation module and performing digital-to-analog conversion on the signal propagation distance to generate a baseband signal with distance information.
A distance simulation module: delaying the generated baseband signal sampling sequence, and inputting the corresponding signal propagation distance after delaying into a DAC module; the distance simulation module realizes the time delay of two ranges of thickness, and the signal processing board card works with a clock and a counter to realize the coarse precision time delay to simulate the coarse precision large-range communication distance; a sampling clock and a fractional delay filter are utilized to realize high-precision delay to simulate a fine-precision small-range communication distance; inputting the generated baseband signal carrying the distance information into a laser signal modulation module as a modulation signal, and modulating a signal light source to generate a corresponding communication system laser signal carrying the distance information;
DAC digital-to-analog conversion module: the distance simulation module is used for receiving the signal propagation distance input by the distance simulation module and performing digital-to-analog conversion on the signal propagation distance to generate a baseband signal with distance information.
As a preferred mode, the ground simulation device for the satellite-borne laser communication terminal according to the present invention further includes:
Mach-Zehnder modulator: the function of simulating the laser signal and the communication distance of the satellite-borne laser communication terminal is realized;
a bias controller: the device is used for controlling the bias point of the Mach-Zehnder modulator within the range of the bias point required by the corresponding communication system to generate the laser signal of the corresponding communication system carrying the distance information;
a radio frequency amplifier: and the laser modulator is used for improving the driving capability of a baseband signal through a radio frequency amplifier to be used as an optical modulation signal and modulating and inputting the laser signal of the Mach-Zehnder modulator.
The invention relates to a ground simulation device of a satellite-borne laser communication terminal, and as an optimal mode, a laser signal detection module comprises:
an optical mixer: the optical frequency mixing device is used for mixing the received laser signal with local oscillator light generated by a light source laser to generate an optical frequency mixing signal;
balancing the detector: and the optical mixing signal is subjected to photoelectric conversion by a balanced detector to generate an intermediate frequency signal.
The invention has the beneficial effects that:
1) the optical signal modulation module modulates the received baseband signal to an optical carrier to generate an optical signal of a corresponding communication system, and the laser signal detection module converts the received optical signal into an electric intermediate frequency signal in a coherent heterodyne detection mode so that the digital signal processing subsystem realizes coherent demodulation to generate a laser communication signal of a coherent communication system and a multi-gear communication rate. The communication performance of a satellite laser communication system of a coherent communication system can be verified in a laboratory environment;
2) the invention further adopts a signal processing board card working clock counter in the distance simulation module to realize the large-range coarse precision simulation of the laser signal communication distance; and a sampling clock and a fractional delay filter are adopted to realize large-range high-precision simulation of the communication distance of the laser signal. The satellite laser communication system ranging performance of a coherent communication system can be verified in a laboratory environment;
3) the invention further uses the digital signal processing subsystem to receive the test data transmitted by the upper computer of the analog device through the optical fiber gigabit network card, the data is processed correspondingly to generate corresponding baseband signals which are sent to the laser signal modulation module to be used as optical carrier modulation signals, the digital signal processing subsystem receives intermediate frequency signals output by the laser signal detection module, coherent demodulation is carried out on the analog signals, data obtained by demodulation are transmitted to an upper computer of an analog device through a gigabit network, generates baseband signals, completes the simulation and measurement of communication distance in the process of demodulating intermediate frequency signals, meanwhile, the method receives the upper computer control instruction of the analog device, realizes corresponding signal processing operation, transmits a feedback signal capable of reflecting the current communication and ranging states, can detect and demodulate a coherent communication system and laser signals with multi-gear communication speed, and can measure and calculate the communication distance of the laser signals. The method can realize inter-satellite communication and distance measurement process simulation with the tested communication terminal under the laboratory condition.
Drawings
FIG. 1 is a ground simulation device diagram of a satellite-borne laser communication terminal simulation device;
FIG. 2 is a system configuration diagram of a satellite-borne laser communication terminal simulation device;
FIG. 3 is a hardware architecture diagram of a digital signal processing platform of a satellite-borne laser communication terminal simulation apparatus;
FIG. 4 is a schematic diagram of a laser signal transmission link of a satellite-borne laser communication terminal simulation device;
FIG. 5 is a schematic diagram of a laser signal detection module of a satellite-borne laser communication terminal simulation device;
fig. 6 is a working schematic diagram of a laser signal receiving link of a satellite-borne laser communication terminal simulation device.
Detailed Description
The following description of the embodiments of the present invention is provided in connection with the accompanying drawings.
Example 1
Referring to fig. 1 to 5, the invention provides a ground simulation device for a satellite-borne laser communication terminal, which comprises:
the laser signal processing subsystem: the system comprises a digital signal processing subsystem, a laser communication terminal, a computer subsystem and a signal processing subsystem, wherein the digital signal processing subsystem is used for receiving a received optical signal input by the laser communication terminal to be tested, receiving a laser control instruction transmitted by the computer subsystem, converting the received optical signal into an intermediate frequency signal according to the laser control instruction, transmitting the intermediate frequency signal to the digital signal processing subsystem, and receiving a baseband signal transmitted by the digital signal processing subsystem and converting the baseband signal into an emitting optical signal;
the digital signal processing subsystem: the laser signal processing subsystem is used for receiving an intermediate frequency signal transmitted by the laser signal processing subsystem, receiving internal transmission data and a control command transmitted by the computer control subsystem, generating a baseband signal according to the internal transmission data, demodulating the intermediate frequency signal according to the control command to generate a feedback signal, and transmitting the feedback signal to the computer control subsystem;
the computer control subsystem: the system comprises a laser signal processing subsystem, a digital processing subsystem and a data processing subsystem, wherein the laser signal processing subsystem is used for receiving external transmission data input by an external data source, transmitting a laser control instruction to the laser signal processing subsystem, transmitting internal transmission data and a control command to the digital processing subsystem and receiving and displaying a feedback signal transmitted by the digital signal processing subsystem.
Example 2
Referring to fig. 1, the invention provides a satellite-borne laser communication terminal ground simulation device, which comprises a laser signal processing subsystem, a digital signal processing subsystem and a computer control subsystem, wherein the laser signal processing subsystem comprises a laser signal modulation module, a laser signal detection module and a light source laser, and the laser signal modulation module consists of a herzehnder modulator, a bias voltage controller and a radio frequency amplifier; the laser signal detection module consists of a 90-degree optical mixer and a balance detector; the light source laser is a narrow linewidth frequency stabilized laser.
Referring to fig. 2, the hardware part of the digital signal processing subsystem is an FPGA digital signal processing board card, the board card adopts a framework combining the FPGA, the ADC and the DAC, and the computer control subsystem is composed of an analog device upper computer and a gigabit network card carried on a main board of the analog device upper computer through a PCIE bus.
Referring to fig. 3, which is a working schematic diagram of a laser signal transmitting link, the modules for implementing the laser signal generating and distance simulating functions include a coding module, a scrambling module, a rate switching module, a resampling module, a distance simulating module, a DAC digital-to-analog conversion module, a signal light source laser and a laser modulation module, and the working process is as follows:
s1, the upper computer of the analog device controls the gigabit network card to input externally transmitted data transmitted from the outside of the system through the control software, and the externally transmitted data is input into the digital signal processing platform through the gigabit network interface of the digital signal processing platform;
s2, encoding the incoming data by using an encoding module according to a communication protocol with the satellite communication terminal to generate encoded data;
s3, the coded data generates scrambled data through a scrambling module (pre-scrambling or post-scrambling is selected according to the protocol of the communication terminal), the purpose of scrambling is to avoid the overlong 1 or 0 value in the generated data stream, and when the sent data is maintained at the 1 or 0 value for overlong time, the receiving end can not normally realize timing synchronization, thereby affecting demodulation and ranging.
The method comprises the steps that encoded data are added into a frame header serving as a frame identification mark after pseudo-randomization to form frame data, a base band signal sampling sequence is generated through a rate switching module, the rate switching module generates the base band signal sampling sequence of corresponding communication rate according to the communication rate to be realized at present, a simulation device takes rectangular waves as base band signal code element waveforms and generates rectangular wave base band signals in a mode of generating a plurality of same-value sampling points for the same code element signals, and when the sampling rate is fixed, the number of sampling points forming the code element signal waveforms is different, and the base band signal generating rates are different; supposing that the sampling rate of the communication system is 5Gsps, 1 code element signal waveform is formed by 5 sampling points, namely, a communication rate baseband signal of 1Gbps can be generated, but in a multi-rate communication system, the rate of the baseband signal and the sampling rate are not always in integral multiple relation, at this time, the method can not be directly used for generating a baseband signal of corresponding rate, the generated baseband signal sampling sequence of integral multiple sampling rate frequency division rate is resampled by an interpolation filter to generate a baseband signal of which the rate is non-integral multiple sampling clock frequency division frequency, the generated baseband signal sampling sequence is input into a DAC to generate a baseband signal with distance information after the corresponding signal propagation distance is delayed by a distance analog module, wherein the distance analog module can realize the delay of two ranges of thickness, and the large-range communication distance of the thickness precision is simulated by combining a working clock of a signal processing board system with a counter to realize the thickness precision delay, a sampling clock and a fractional delay filter are utilized to realize high-precision delay to simulate a fine-precision small-range communication distance, a baseband signal is used as an optical modulation signal by improving the driving capability of a radio frequency amplifier, and the signal light of the Mach-Zehnder modulator is modulated and input; the bias controller controls the bias point of the Mach-Zehnder modulator within the range of the bias point required by the corresponding communication system so as to obtain good modulation effect and generate the laser signal of the corresponding communication system carrying distance information.
Referring to fig. 4, which is a working schematic diagram of a laser signal receiving link, the main modules of the laser receiving link of the analog device include an ADC digital-to-analog conversion module, a digital down-conversion module, a timing synchronization loop, a carrier synchronization loop, a frame synchronization module, a decoding module, and an descrambling module.
After the laser signal detection module receives the laser signal, the center frequency of the intermediate frequency signal output by the laser signal detection module is adjusted to the intermediate frequency set by the analog device by adjusting the center frequency of the local oscillator light.
Referring to fig. 5, a working principle of a laser signal detection module is that a 90-degree optical mixer is used to mix a received laser signal with local oscillator light generated by a light source laser, four optical mixing signals with phase differences of 0 °, 90 °, 180 °, and 270 ° are output, two pairs of optical mixing signals with phase differences of 180 ° enter two pairs of balance detectors, and after photoelectric conversion by the balance detectors, two paths of electric intermediate frequency signals with phase differences of 90 ° are generated; one path of the input ADC is used for signal demodulation and communication distance measurement, the other path of the input ADC is used for external output, and external instruments such as a frequency spectrograph and the like can be accessed to monitor the center frequency of the intermediate frequency signal.
The intermediate frequency signal sampling sequence output by the ADC is divided into two paths, one path is demodulated, and the other path is used for frequency offset estimation of the intermediate frequency signal, so that the relatively stable intermediate frequency can be obtained.
And performing FFT (fast Fourier transform) on the intermediate-frequency signal subjected to frequency offset estimation to obtain the center frequency of the current intermediate-frequency signal, transmitting the center frequency to an upper computer of the simulation device, and if the center frequency deviates from the center frequency set by the simulation device, adjusting the frequency offset of local oscillator light through a laser control instruction by the upper computer of the simulation device to maintain the frequency offset of the intermediate frequency within the frequency range in which the system can realize demodulation.
The intermediate frequency signal to be demodulated is processed by digital down-conversion DDC, the frequency band signal is converted into a baseband signal, because the analog device needs to realize multi-level communication rate, in order to conveniently process signals with different rates in a unified way, the sampling sequence is resampled by an interpolation filter in the process of digital down-conversion to ensure that the sampling points of baseband code element signals with different rates are consistent, the resampled baseband signal obtains the optimal sampling point position by timing synchronization, after the residual frequency offset is eliminated by utilizing carrier synchronization, the number of the received complete data frames is confirmed by frame synchronization, and after decoding and descrambling, the data information is demodulated. Thereby achieving demodulation of the laser signal.
The measurement and calculation of communication distance are completed by the method of acquiring the time information carried by the signal in the signal synchronization process and by the length T of the data frameframeLength of code element TbitAnd the symbol phase NphaseAs a unit for measuring the delay time, the frame length and the code element length correspond to the measurement of the delay of integral-multiple code element length, and the code element phase corresponds to the delay measurement of decimal-multiple code element length; the number of received data frames and the number of code elements can be obtained in a frame synchronization link, the phase of the code elements can be obtained in a phase accumulator in a timing synchronization loop, and the formula T is equal to Nframe·Tframe+Nbit·Tbit+Nphase·TbitThe time delay value corresponding to the current communication distance can be obtained and multiplied by the light speed C in the simulation environment, so that the current communication distance is measured and calculated, and the demodulated data, the distance measurement information and other related information are transmitted back to the software control subsystem computer through the network port to be displayed.
The foregoing description is intended to be illustrative rather than limiting, and it will be appreciated by those skilled in the art that various modifications, changes, and equivalents may be made without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (7)
1. The utility model provides a satellite-borne laser communication terminal ground analogue means which characterized in that: the method comprises the following steps:
the laser signal processing subsystem: the system comprises a laser communication terminal, a digital signal processing subsystem and a laser communication subsystem, wherein the laser communication terminal is used for receiving a received optical signal input by the laser communication terminal to be tested, receiving a laser control instruction transmitted by the computer subsystem, converting the received optical signal into an intermediate frequency signal according to the laser control instruction, transmitting the intermediate frequency signal to the digital signal processing subsystem, and receiving a baseband signal transmitted by the digital signal processing subsystem and converting the baseband signal into an emitted optical signal;
the digital signal processing subsystem: the system comprises a laser signal processing subsystem, a computer control subsystem and a signal processing subsystem, wherein the laser signal processing subsystem is used for receiving the intermediate frequency signal transmitted by the laser signal processing subsystem, receiving internal transmission data and a control command transmitted by the computer control subsystem, generating the baseband signal according to the internal transmission data, demodulating the intermediate frequency signal according to the control command to generate a feedback signal, and transmitting the feedback signal to the computer control subsystem;
the computer control subsystem: the system comprises a laser signal processing subsystem, a digital processing subsystem and a data processing subsystem, wherein the laser signal processing subsystem is used for receiving external transmission data input by an external data source, transmitting the laser control instruction to the laser signal processing subsystem, transmitting internal transmission data and a control command to the digital processing subsystem, and receiving and displaying the feedback signal transmitted by the digital signal processing subsystem.
2. The ground simulation device of the satellite-borne laser communication terminal according to claim 1, wherein: the laser signal processing subsystem includes:
the laser signal modulation module: the optical signal processing subsystem is used for receiving an optical carrier transmitted by a light source laser, performing corresponding communication system modulation on the optical carrier to generate a laser signal, receiving the baseband signal transmitted by the digital signal processing subsystem, and modulating the baseband signal onto the optical carrier to generate the transmitting optical signal;
laser signal detection module: the receiving computer subsystem is used for receiving the received optical signal input by the laser communication terminal to be detected, receiving the local oscillator light transmitted by the light source laser, receiving the laser control instruction transmitted by the receiving computer subsystem, converting the laser signal into an intermediate frequency signal in a coherent heterodyne detection mode according to the laser control instruction, and transmitting the intermediate frequency signal to the digital signal processing subsystem;
a light source laser: the local oscillator light is used for sending the optical carrier to the laser signal modulation module and sending the local oscillator light to the laser signal detection module.
3. The ground simulation device of the satellite-borne laser communication terminal according to claim 1, wherein: the calculation and control subsystem includes:
ten thousand million network cards: the system comprises a control computer, a digital processing subsystem, an analog device upper computer and a digital processing subsystem, wherein the control computer is used for transmitting internal transmission data to the digital processing subsystem, receiving the external transmission data input by the external data source, receiving a control command transmitted by the analog device upper computer and transmitting demodulated state information to the analog device upper computer, and the state information comprises data stream and distance information;
the upper computer of the simulation device: the control command is sent to the gigabit network card, the control command is sent to the digital signal processing subsystem, the laser control command is sent to the laser signal processing subsystem, and the state information demodulated by the gigabit network card is received and displayed in real time.
4. The ground simulation device of the satellite-borne laser communication terminal according to claim 1, wherein: the digital signal processing subsystem is a signal processing board card adopting a structure combining an FPGA, an ADC and a DAC.
5. The ground simulation device of the satellite-borne laser communication terminal according to claim 1, wherein: the digital signal processing subsystem further comprises:
the coding module: the scrambling module is used for encoding the intermediate frequency signal and the internal transmission data according to a communication protocol of the satellite communication terminal to generate encoded data and inputting the encoded data into the scrambling module;
a scrambling module: the system comprises a scrambling module, a frame identification mark, a frame header and a rate switching module, wherein the scrambling module is used for receiving the coded data sent by the scrambling module, scrambling the coded data and taking the frame length scrambled data to generate scrambled data, and the frame identification mark is added to the front of the scrambled data to be used as the frame header to form frame data which is used for transmitting the frame data into the rate switching module;
a rate switching module: the system comprises a scrambling module, a resampling module, a data processing module and a data processing module, wherein the scrambling module is used for receiving the frame data transmitted by the scrambling module, and generating a baseband signal sampling sequence of a corresponding communication rate according to the communication rate to be realized currently from the frame data, and inputting the baseband signal sampling sequence into the resampling module;
a resampling module: the device comprises a rate switching module, a distance simulation module and a frequency conversion module, wherein the rate switching module is used for receiving the baseband signal sampling sequence transmitted by the rate switching module, resampling the generated baseband signal sampling sequence with the integral multiple sampling rate and the frequency conversion rate through an interpolation filter, generating a baseband signal with the realization rate of non-integral multiple sampling clock frequency conversion, and inputting the baseband signal sampling sequence into the distance simulation module;
a distance simulation module: and the digital-to-analog conversion module is used for delaying the baseband signal sampling sequence to generate a corresponding signal propagation distance and inputting the signal propagation distance into the DAC module.
DAC digital-to-analog conversion module: and the distance simulation module is used for receiving the signal propagation distance input by the distance simulation module and performing digital-to-analog conversion on the signal propagation distance to generate a baseband signal with distance information.
6. The ground simulation device of the satellite-borne laser communication terminal according to claim 2, wherein: the laser signal modulation module further includes:
Mach-Zehnder modulator: the function of simulating the laser signal and the communication distance of the satellite-borne laser communication terminal is realized;
a bias controller: the Mach-Zehnder modulator is used for controlling the bias point of the Mach-Zehnder modulator within the range of the bias point required by the corresponding communication system to generate a corresponding communication system laser signal carrying distance information;
a radio frequency amplifier: and the laser modulator is used for improving the driving capability of a baseband signal through a radio frequency amplifier to be used as an optical modulation signal and modulating and inputting the laser signal of the Mach-Zehnder modulator.
7. The ground simulation device of the satellite-borne laser communication terminal according to claim 2, wherein: the laser signal detection module includes:
an optical mixer: the local oscillator light mixing device is used for mixing the received laser signal with local oscillator light generated by a light source laser to generate a light mixing signal;
balancing the detector: the intermediate frequency signal is generated by photoelectric conversion of the optical mixing signal through a balanced detector.
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