An ultra-deep space high-sensitivity remote control system and signal detection method

Abstract

The present invention belongs to the field of electronics and aerospace measurement and control communication technology, and relates to an ultra-deep space high-sensitivity remote control system and a signal detection method. The system includes: a ground station transmitter, an ultra-deep space transponder and a satellite service terminal deployed on a satellite; the ground station transmitter adopts a synchronous mode under a strong level to transmit a PCM / PSK / PM modulation signal with adjustable power; it is also used to switch to a single-tone mode to transmit a single-tone system signal with adjustable power; the ultra-deep space transponder adopts a superheterodyne and zero intermediate frequency architecture, in the synchronous mode, receives the PCM / PSK / PM modulation signal, achieves time synchronization between the sender and the receiver through compensation, and then switches to the single-tone mode; in the single-tone mode, receives the single-tone system signal and demodulates it; the satellite service terminal receives and detects the demodulated single-tone system signal sent by the ultra-deep space transponder, performs a spectrum analysis of an ultra-long FFT, demaps it back to the remote control command according to the detected frequency, and performs error judgment.

Description

Technical Field

[0001] The present invention relates to the field of electronics and aerospace measurement, control and communication technology, and in particular to an ultra-deep space high-sensitivity remote control system and a signal detection method. Background Art

[0002] As deep space exploration gradually advances into ultra-deep space, the problem of extremely low detection signal-to-noise ratio becomes increasingly apparent, and communication technology is being pushed to its limits. Compared with telemetry, the problem of remote control receiving sensitivity is more challenging. Received signal sensitivity is an important indicator of a transponder, which measures the ability of a receiver to receive weak signals under certain conditions. In traditional unified measurement and control system digital receivers, the capture of the main carrier and the recovery of the data stream clock usually require the use of phase-locked loop technology. These processes limit the current receiver sensitivity to: -157dBm carrier lock, -145dBm command reception at a minimum rate of 7.8125bps.

[0003] In the future, my country will realize deep space exploration beyond Jupiter or the boundary of the solar system. It is necessary to overcome the limit of demodulation sensitivity of the traditional unified measurement and control system and increase the sensitivity of the receiver by one to two orders of magnitude. Therefore, how to effectively detect useful signals from extremely weak signals with long delays is a key technology that must be solved for ultra-deep space exploration. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and propose an ultra-deep space high-sensitivity remote control system and a signal detection method.

[0005] In order to achieve the above-mentioned purpose, the present invention proposes an ultra-deep space high-sensitivity remote control system, comprising: a ground station transmitter and an ultra-deep space transponder and a satellite service terminal deployed on a satellite; wherein:

[0006] The ground station transmitting end is used to adopt a synchronous mode to transmit a PCM / PSK / PM modulation signal with adjustable power under a strong level; and is also used to switch to a single-tone mode to transmit a single-tone system signal with adjustable power;

[0007] The ultra-deep space transponder adopts a superheterodyne and zero intermediate frequency architecture, and is used to receive PCM / PSK / PM modulated signals in synchronous mode, achieve time synchronization between the sender and the receiver through compensation, and then switch to single-tone mode; and is also used to receive single-tone system signals in single-tone mode and demodulate them;

[0008] The satellite service terminal is used to receive and detect the demodulated single-tone system signal sent by the ultra-deep space transponder, perform ultra-long FFT spectrum analysis, demap back the remote control command according to the detected frequency, and perform error judgment.

[0009] Preferably, the PCM / PSK / PM modulation signal is: the remote control PCM signal performs PSK modulation on the subcarrier, and the modulated subcarrier then performs PM modulation on the main carrier;

[0010] The single-tone signal adopts frequency shift keying modulation, the keying time interval is 1 to 512 seconds, and the keying time is adjustable; each tone represents an uplink carrier signal, corresponding to an uplink remote control instruction, and its carrier frequency is adjustable within the kHz range.

[0011] Preferably, the ground station transmitter includes: an intermediate frequency board, a radio frequency integration board, a high-stability reference source, a local oscillator, a mixer and an attenuator; wherein,

[0012] The intermediate frequency board is used to generate PCM / PSK / PM modulation signals in synchronous mode and single-tone system signals in single-tone mode, and is also used to interact with the radio frequency integration board;

[0013] The radio frequency integrated board is used to generate a first-level radio frequency signal;

[0014] The highly stable reference source is used to provide a clock reference;

[0015] The local oscillator is used to provide a local oscillator signal for the mixer;

[0016] The mixer is used for up-conversion;

[0017] The attenuator adopts a combination of a fixed attenuator and an adjustable attenuator to achieve adjustable power of the transmission signal within a set power range.

[0018] Preferably, for the synchronous mode, the ground station transmitter further comprises: a ground time counter framing module, a scrambling module, a rate conversion module and a modulation module deployed on the intermediate frequency board; wherein,

[0019] The ground time counter framing module is used to complete the framing of the ground counter; the frame format includes a 2-byte frame header, a 32-bit second count and a 10-bit ms count, and a 2-byte CRC check, a total of 74 bits; wherein the second count and the ms count are the values ​​of the current frame sending time;

[0020] The scrambling module is used to complete the scrambling of the ground time counter frame and send the scrambled data to the rate conversion module;

[0021] The rate conversion module is used to complete the read and write rate conversion of data using FIFO, the write clock is the transmission signal sampling clock, and the read clock is the baseband data stream clock;

[0022] The modulation module is used to modulate the baseband data output by the rate conversion module according to the PCM / BPSK / PM modulation method, and output it to the radio frequency integration board.

[0023] Preferably, for the single-tone mode, the ground station transmitter further comprises: a single-tone symbol deframing module and a single-tone modulation module deployed on the intermediate frequency board; wherein,

[0024] The single tone symbol deframing module is used to receive a frame containing a single tone symbol sent by a host computer or a serial port, and cyclically send the parsed single tone symbol to the single tone modulation module; the bit width of the single tone symbol is determined by the complex signal bandwidth and the frequency slot width f bin Determine; each frame contains M single-tone symbols, the symbol period T is the time interval between the current symbol and the next symbol, and the symbol period T is online adjustable;

[0025] The single tone modulation module is used to complete the mapping of the single tone symbol value to the frequency control word, and the frequency slot width f bin Adjustable online.

[0026] Preferably, the radio frequency signal power range generated by the transmitting end of the ground station is -100 to -180 dBm, with an adjustable step of ≤1 dB; the uplink signal frequency band is S or X band.

[0027] Preferably, the ultra-deep space transponder comprises: a low noise amplifier, a bandpass filter, a local oscillator, a high-stability reference source, an intermediate frequency board and a radio frequency integration board; wherein,

[0028] The low noise amplifier adopts a two-stage cascade connection, and an isolator is arranged between the two stages to limit the gain fluctuation caused by possible self-excitation and in-band VSWR fluctuation;

[0029] The bandpass filter is used to suppress the image frequency at the receiving end;

[0030] The mixer is used for up-conversion;

[0031] The highly stable reference source is used to provide a clock reference;

[0032] The radio frequency integrated board is used to convert the received radio frequency signal to an intermediate frequency;

[0033] The intermediate frequency board is used to complete the digital signal processing of the intermediate frequency signal, including carrier synchronization, timing synchronization and demodulation of PCM / PSK / PM signals, and preprocessing of single-tone system signals.

[0034] Preferably, for the synchronous mode, the ultra-deep space transponder further comprises: a main carrier acquisition and tracking module, a remote control demodulation module, a frame synchronization module, a descrambling module, a CRC check module and a time synchronization compensation module deployed on the intermediate frequency board; wherein,

[0035] The main carrier capture and tracking module adopts a phase-locked loop structure, including an in-phase branch and an orthogonal branch; the in-phase branch is used to provide automatic gain control and main carrier locking state quantity, and the orthogonal branch is used to lock the phase of the main carrier signal;

[0036] The remote control demodulation module is used to complete the tracking of the remote control subcarrier and the demodulation of the remote control signal, and output the demodulated baseband data and the subcarrier locking state quantity;

[0037] The frame synchronization module is used to receive the baseband data stream output by the remote control demodulation module, complete the frame synchronization of the fixed-length frame shielding the frame header, and is also used to resolve the phase ambiguity caused by BPSK demodulation and output it to the descrambling module, and output the current frame synchronization lock, phase ambiguity and frame synchronization header count state;

[0038] The descrambling module is used to perform descrambling processing on the data after frame synchronization and output it to the CRC check module;

[0039] The CRC check module is used to perform CRC check on the descrambled data stream. When the CRC check succeeds, the time timer of the set bit in the current frame, that is, the clock of the ground station transmitter, is extracted and output to the time synchronization compensation module; and the CRC check correct frame count, the CRC check error frame count, the current frame CRC check correct / error state quantity and the initial synchronization state quantity are output;

[0040] The time synchronization compensation module is used to complete the time synchronization compensation between the sender and the receiver. When the CRC check is successful for the first time, the local second count and ms count values ​​are set to the values ​​in the transmission frame, and the compensation value is added.

[0041] Preferably, for the single-tone mode, the ultra-deep space transponder further comprises: a single-tone signal preprocessing module and a timing pulse generating module deployed on the intermediate frequency board; wherein,

[0042] The single-tone signal preprocessing module is used to down-convert, filter and down-sample the received single-tone system signal, and send it to the satellite service terminal;

[0043] The timing pulse generating module is used to determine the symbol boundary, generate a timing pulse with a period of a single-tone symbol period T, and output it to the satellite service terminal.

[0044] On the other hand, the present invention proposes a signal detection method, which is implemented based on the ultra-deep space high-sensitivity remote control system, and includes:

[0045] Under strong level, the synchronous mode is adopted, the ground station transmitter transmits PCM / BPSK / PM signal, and the ultra-deep space transponder processes the signal and completes time synchronization;

[0046] When it is detected that the synchronization mode has been completed, the ground station transmitter adjusts the attenuation to reduce the signal to a weak level, switches to single-tone mode, and transmits a single-tone system signal; the ultra-deep space transponder completes the reception and demodulation processing;

[0047] The satellite service terminal performs ultra-long FFT spectrum analysis on the received demodulated single-tone signal, compares the single-tone symbol output by the detection with the single-tone symbol transmitted by the ground station, and makes error judgment.

[0048] Compared with the prior art, the advantages of the present invention are:

[0049] 1. The present invention proposes an ultra-deep space high-sensitivity remote control system and an ultra-deep space high-sensitivity remote control signal detection method. By constructing an ultra-deep space transponder with a new single-tone system including a synchronous mode and a single-tone mode, the receiver sensitivity is improved by one to two orders of magnitude, and its sensitivity is better than -175dBm;

[0050] 2. The satellite service terminal CPU of the present invention is an ARM CPU built into the ZYNQ FPGA, which has the ability to analyze ultra-long sampling spectra, is simple to implement and has low cost.

[0051] 3. The various command parameters of the ultra-deep space high-sensitivity remote control system of the present invention can be adjusted online and the state quantities can be monitored in real time. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 is a structural block diagram of the ultra-deep space high-sensitivity remote control system of the present invention;

[0053] Figure 2 It is a schematic diagram of a single-tone remote control signal system;

[0054] Figure 3 This is a functional block diagram of the transmitter end of the ultra-deep space high-sensitivity remote control signal detection method of the present invention;

[0055] Figure 4 is the ground time counter frame format of the present invention;

[0056] Figure 5 It is the monophonic symbol frame format of the present invention;

[0057] Figure 6 It is a functional block diagram of the receiving end of the ultra-deep space high-sensitivity remote control signal detection method of the present invention;

[0058] Figure 7 It is a flow chart of the signal detection method operation of the present invention. DETAILED DESCRIPTION

[0059] The purpose of the present invention is to overcome the demodulation sensitivity limit of the traditional unified measurement and control system, propose an ultra-deep space high-sensitivity remote control system, and also propose an ultra-deep space high-sensitivity remote control signal detection method to construct an ultra-deep space transponder with a new single-tone system, thereby improving the receiver sensitivity by one to two orders of magnitude.

[0060] An ultra-deep space high-sensitivity remote control system has a synchronous mode and a single-tone mode. The system includes: a ground station transmitter and an ultra-deep space transponder and a satellite service terminal deployed on a satellite.

[0061] 1. Ground station transmitter

[0062] It consists of an IF board, an RF integrated board, a high-stability reference source, a local oscillator (LO), a mixer, an attenuator, etc. It is used to generate RF signals with adjustable power. The signal systems include PCM / BPSK / PM modulation signals and single-tone system signals.

[0063] As an improvement of the above-mentioned remote control system, the high-stable reference source of the ground station transmitter is used to provide a clock reference, and the intermediate frequency board, the radio frequency integrated board, the local oscillator, the mixer and the attenuator are used to generate a radio frequency signal with adjustable power; the power range of the radio frequency signal is between -100 and -180dBm, and the adjustable step is ≤1dB; the power adjustment adopts the method of multiple frequency conversion and multiple attenuation to overcome the problem of nonlinear decrease of signal power with increasing attenuation caused by leakage generated when the attenuation of the radio frequency band exceeds 100dB.

[0064] As an improvement of the above-mentioned remote control system, the frequency band of the radio frequency signal at the transmitting end of the ground station is: according to Recommendation SFCG 7-1R6, TRANSPONDER TURNAROUND FREQUENCY RATIOS AND RADIO FREQUENCY CHANNELPLANS FOR SPACE RESEARCH, CATEGORY B in the SFCG (SPACE FREQUENCY COORDINATION GROUP) recommendation, the selectable ground station-aircraft uplink signal frequency band is S or X band.

[0065] As an improvement of the above remote control system, the radio frequency signal system of the ground station transmitter includes a PCM / BPSK / PM modulation signal and a single-tone system signal;

[0066] PCM / PSK / PM modulation mode belongs to residual carrier modulation mode, that is, the remote control PCM signal performs PSK modulation on the subcarrier, and the modulated subcarrier then performs PM modulation on the main carrier;

[0067] The single-tone signal is frequency shift keying (FSK) modulation, and the keying time interval is 1 to 512 seconds, and the keying time is adjustable; each tone represents an uplink carrier signal, and its carrier frequency is adjustable in the kHz range, and its frequency is precisely controlled. Each tone corresponds to an uplink remote control command.

[0068] 1) Synchronous mode

[0069] The transmitter includes:

[0070] The ground time counter framing module is used to complete the framing of the ground time counter. The frame format includes a 2-byte frame header, a 32-bit second count, a 10-bit ms count, and a 2-byte CRC checksum, a total of 74 bits; the second count and ms count are the values ​​of the current frame sending time;

[0071] The scrambling module is used to complete the scrambling of the ground time counter frame and send the scrambled data to the rate conversion module;

[0072] The rate conversion module uses FIFO to complete the data read and write rate conversion. The write clock is the transmission signal sampling clock, and the read clock is the baseband data stream clock.

[0073] The modulation module is used to modulate the baseband data output by the rate conversion module according to the PCM / BPSK / PM modulation method and output it to the RF integration board.

[0074] 2) Single tone mode

[0075] The transmitter includes:

[0076] The single tone symbol de-framing module is used to receive the frame containing the single tone symbol sent by the front end (host computer or serial port), and send the parsed single tone symbol to the single tone modulation module in a loop; the bit width of the single tone symbol is determined by the complex signal bandwidth and the frequency slot f bin The width (minimum frequency interval) is determined; each frame contains M single-tone symbols, and the symbol period T is the time interval between the current symbol and the next symbol, that is, the duration of the current symbol, and the symbol period T is online adjustable;

[0077] The single tone modulation module is used to complete the mapping of the single tone symbol value to the frequency control word, and the frequency slot f bin The width is adjustable online.

[0078] 2. Ultra-deep space transponder

[0079] It adopts the architecture of superheterodyne and zero intermediate frequency, and is composed of low noise amplifier (LNA), bandpass filter (BPF), local oscillator (LO), high stability reference source, intermediate frequency board and RF integration board, etc. It is used to receive the RF signal transmitted by the ground station, and after amplification, filtering, frequency conversion to intermediate frequency and AD acquisition, it completes signal demodulation and synchronization functions;

[0080] As an improvement of the above remote control system, the high-stability reference source of the ultra-deep space transponder is used to provide a clock reference;

[0081] The mixer is used for up-conversion; the LNA adopts two-stage cascade amplification to meet the gain requirements, and the noise coefficient NF of the ultra-deep space transponder is better than 2dB;

[0082] An isolator is used between the two-stage LNA to limit the gain fluctuation caused by possible self-excitation and in-band voltage standing wave ratio (VSWR) fluctuation;

[0083] The bandpass filter is used to suppress the image frequency at the receiving end;

[0084] The RF integration board converts the received RF signal to an intermediate frequency;

[0085] The IF board is used to complete the digital signal processing of the IF signal, including carrier synchronization, timing synchronization and demodulation of PCM / PSK / PM signals, and pre-processing of single-tone signals.

[0086] 1) Synchronous mode

[0087] Including those deployed on the IF board:

[0088] The main carrier capture and tracking module adopts a phase-locked loop structure, including an in-phase branch and an orthogonal branch; the in-phase branch provides automatic gain control (AGC) and the main carrier locking state quantity, and the orthogonal branch locks the phase of the main carrier signal;

[0089] The remote control demodulation module is used to complete the tracking of the remote control subcarrier and the demodulation of the remote control signal, and output the demodulated baseband data and the subcarrier locking state quantity;

[0090] The frame synchronization module is used to receive the baseband data stream output by the remote control demodulation module, complete the frame synchronization of the fixed-length frame (74bit) shielded frame header, and also resolve the phase ambiguity of the BPSK demodulation and output it to the descrambling module, and output the current frame synchronization lock, phase ambiguity, and frame synchronization header count status;

[0091] The descrambling module is used to descramble the data after frame synchronization and output it to the CRC check module;

[0092] The CRC check module is used to perform CRC check on the descrambled data stream. After the CRC check is successful, the 42-bit time timer in the current frame, that is, the clock of the ground station transmitter, is extracted and output to the time synchronization compensation module; and the CRC check correct frame count, CRC check error frame count, current frame CRC check correct / error state quantity, and initial synchronization state quantity are output;

[0093] The time synchronization compensation module is used to complete the time synchronization compensation of the sender and the receiver. When the CRC check is successfully detected for the first time, that is, after the initial synchronization, the local second count and ms count values ​​are set to the values ​​in the transmission frame, and the compensation value is added; when the transmission delay is ignored, on the one hand, without knowing the specific delay from the sender to the receiver, the real-time insertion of the compensation value is used to make adjustments to achieve the purpose of time synchronization between the two parties; on the other hand, the functions of the sender and the receiver can be combined to obtain a more accurate compensation value through simulation; finally, by leading out the time pulse signals of the sender and the receiver, it is judged whether synchronization is achieved by observing the two pulse signals.

[0094] 2) Single tone mode

[0095] The single-tone signal preprocessing module is used to down-convert, filter and down-sample the received single-tone system signal, and send it to the satellite service terminal for single-tone signal detection;

[0096] The timing pulse generation module is used to determine the symbol boundary and generate a timing pulse. The timing pulse period is the single-tone symbol period T, which is output to the satellite service terminal for single-tone signal detection. Because when performing single-tone frequency detection, if the symbol boundary is deviated, the peak value after coherent integration will be lost, which is easy to cause misjudgment.

[0097] 3. The satellite service terminal is used to receive the pre-processed single-tone system signal sent by the ultra-deep space transponder, detect the single-tone system signal, demap it back to the remote control command according to the detected frequency, and perform error judgment.

[0098] Single-tone signal detection uses the timing pulse as the boundary, and performs coherent integration, incoherent accumulation, windowing, peak detection, and demapping on the pre-processed single-tone signal; the coherent integration duration is the single-tone symbol period T, which is agreed upon by the sender and the receiver when switching to single-tone mode.

[0099] The present invention also provides an ultra-deep space high-sensitivity remote control signal detection method. Based on the ultra-deep space high-sensitivity remote control system, the method comprises the following steps:

[0100] 1) Under strong power level (signal source power greater than -140dBm), the ground station transmits PCM / BPSK / PM signal, and the ultra-deep space transponder on the satellite performs signal processing to complete time synchronization, that is, synchronous mode;

[0101] Time synchronization principle: align the transmitter time and the receiver time so that both parties have the same time measurement value at the same moment.

[0102] Specific implementation: The sender (ground station) and the receiver (ultra-deep space transponder) each maintain a timer. In the synchronous mode, the onboard transponder receives a frame containing the sender's clock. If the CRC check is correct, the local (receiver) second count and ms count values ​​are set to the time count values ​​in the transmission frame; when setting the values, it is also necessary to compensate for the frame processing duration and the delay of the receiving signal synchronization algorithm (in the ground verification stage, the transmission delay can be ignored) to achieve time synchronization between the sender and the receiver;

[0103] The synchronization of the ultra-deep space transponder is related to the distance delay between the ground station and the transponder on the aircraft. Since the relative distance between the aircraft and the earth is known on the ground, targeted compensation can be made based on the distance delay to ensure that a certain symbol received by the on-board receiver is within the agreed symbol period.

[0104] 2) When it is detected that the synchronization mode has been completed, the ground station transmitter adjusts the attenuation to reduce the signal to a weak level (e.g. -175dBm), and the ground station switches to single-tone mode and sends out a single-tone system signal; the ultra-deep space transponder completes the reception and preprocessing of the single-tone remote control signal;

[0105] 3) The satellite service terminal performs ultra-long FFT spectrum analysis on the received pre-processed single-tone system signal, compares the single-tone symbol output by the detection with the single-tone symbol transmitted by the ground station, and performs error judgment.

[0106] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0107] Example 1

[0108] Embodiment 1 of the present invention provides an ultra-deep space high-sensitivity remote control system, including: a ground station transmitter, and an ultra-deep space transponder and a satellite service terminal deployed on a satellite, Figure 1 The figure shows a structural block diagram of an ultra-deep space high-sensitivity remote control system, which shows the connection relationship between the various component modules.

[0109] The ground station transmitter consists of an intermediate frequency board, an integrated RF board, a high-stability reference source, a local oscillator (LO), a mixer, an attenuator, etc., which is used to generate an RF signal with adjustable power. The frequency band is the recommended X-band (7145-7190MHz), and the signal system includes PCM / BPSK / PM modulation signals and single-tone system signals. Figure 1The transmitter of the ground station shown in the figure adopts a solution of multiple frequency conversion and multiple attenuation. On the one hand, it solves the problem that the signal power decreases nonlinearly with the increase of attenuation due to leakage generated when the attenuation of the RF band exceeds 100dB; on the other hand, it also solves the problem that the frequency band of the baseband signal processing chip AD9364 cannot exceed 6GHz.

[0110] The IF board at the transmitting end of the ground station is used to generate PCM / BPSK / PM modulation signals in synchronous mode and single-tone system signals in single-tone mode, and is also used to interact with the RF integration board.

[0111] The core chip of the RF integration board is AD9364, which is used to generate the first-level RF signal. The power adjustment step of the AD9364 transmit signal is 0.25dB, which is finer than the adjustment step of the 1dB adjustable attenuator.

[0112] A highly stable reference source is the key to the ultra-deep space high-sensitivity remote control system. It provides high-precision frequency information that affects the detection level of weak signals, and its stability index is better than 1e-11@100s.

[0113] Mixers are used for frequency up-conversion.

[0114] The external attenuator adopts a combination of a fixed attenuator and an adjustable attenuator, which ultimately makes the power range of the transmitted signal adjustable within -100 to -180dBm.

[0115] The ultra-deep space transponder adopts a superheterodyne and zero intermediate frequency architecture, and consists of a low noise amplifier (LNA), a bandpass filter (BPF), a local oscillator (LO), a high-stable reference source, an intermediate frequency board and an RF integration board. It is used to receive the RF signal transmitted by the ground station, and after amplification, filtering, frequency conversion to intermediate frequency, and AD acquisition, it completes signal demodulation and synchronization functions.

[0116] Among them, the RF integrated board is used to convert the uplink signal into an intermediate frequency.

[0117] A highly stable reference source is used to provide a clock reference.

[0118] Mixers are used for frequency up-conversion.

[0119] The LNA is cascaded in two stages to meet the gain requirement.

[0120] The isolator is used to limit possible self-excitation and gain fluctuations caused by in-band VSWR fluctuations.

[0121] Bandpass filters are used to suppress image frequencies at the receiving end.

[0122] The IF board uses the ZYNQ7000 FPGA development platform to receive and process PCM / PSK / PM signals in synchronous mode, single-tone signals in single-tone mode and time synchronization, and is also used for interaction with the RF integration board.

[0123] The CPU of the satellite service terminal is the ARM CPU built into the ZYNQ7000 FPGA, which uses the calculation library function under Linux or directly performs ultra-long FFT calculations according to the principle of FFT.

[0124] It should be noted that the embodiments are intended to illustrate and verify the system and method of the present invention. The ultra-deep space transponder in the embodiments is not an actual onboard transponder, so a network connection is used between the transponder and the satellite service terminal.

[0125] Ultra-deep space high-sensitivity remote control signal detection methods include: synchronous mode and single-tone mode.

[0126] The signal system in synchronous mode is PCM / PSK / PM modulation, which belongs to residual carrier modulation, that is, the remote control PCM signal performs PSK modulation on the subcarrier, and the modulated subcarrier then performs PM modulation on the main carrier;

[0127] The signal expression of PCM / PM / BPSK modulation is:

[0128] s(t)=sin(ω s t+m CM C(t)sinω CM t)

[0129] Among them, ω s Represents the main carrier (angular) frequency of the signal, ω CM represents the (angular) frequency of the remote control subcarrier, m CM represents the modulation degree of the remote control signal subcarrier, and C(t) represents the remote control baseband signal C(t)∈(1,-1).

[0130] The single-tone signal is frequency shift keying (FSK) with a keying interval of 1 to 512 seconds. Each tone is an uplink carrier signal with its frequency precisely controlled.

[0131] Figure 2 A schematic diagram of the single-tone remote control signal system is given. The dashed box in the figure represents the preset frequency slot. In the time period t S0 , the frequency of the single-tone signal transmitted from the ground is in a certain frequency slot; in the time period t of the transmission symbol S1 S1 , the frequency of the ground-based single-tone signal is in another frequency slot. The signal transmitted by the ground station represents information by its specific position in the frequency slot.

[0132] In such a signal system design, the accuracy and stability of the signal frequency is a key indicator. The frequency accuracy error and stability error of the ground and satellite reference sources comprehensively determine the overall frequency accuracy and stability. The signal accuracy indicator ensures that the receiver will not misjudge the frequency slot, and the signal stability indicator ensures that the received signal will not drift in the same frequency slot within a period of time. Frequency drift will lead to incorrect frequency slot detection and cause loss of detection signal power.

[0133] Table 1 gives some specific parameters of the signals in synchronous mode and single-tone mode.

[0134] Table 1 Signal parameters in synchronous mode and single tone mode

[0135]

[0136]

[0137] Figure 3 The figure shows a functional block diagram of the transmitter of an ultra-deep space high-sensitivity remote control signal detection method, which shows the connection relationship between various functional modules.

[0138] The transmitting end of the synchronous mode includes: a ground time counter framing module, a scrambling module, a rate conversion module and a modulation module.

[0139] The ground time counter framing module completes the framing of the ground time counter. The frame format is as follows: Figure 4 As shown in the figure, EB90 (16 bits) is the frame header, the second count (32 bits) and ms count (10 bits) in the ground timing are 42 bits in total, and the CRC check method is CRC16-CCITT, that is, the whole frame length is 74 bits. The second count and ms count are the values ​​at the time of sending the current frame. The counter working clock is a 52-bit counter driven by the sampling clock 1.048576MHz. When framing, only the high 42 bits are taken, that is, the minimum unit is ms.

[0140] Since the unit of CRC check is byte, the agreed 74-bit frame length is not an integer multiple of bytes, so the frame needs to be padded with zeros before CRC check to make its frame length 80 bits (10B). After adding the CRC check bits, the zeros are removed and the 74-bit frame is finally output to the scrambling module.

[0141] The scrambling module is used to complete the scrambling of the ground time counter frame and send the scrambled data to the rate conversion module.

[0142] The rate conversion module uses FIFO to complete the data read and write rate conversion. The write clock is the transmission signal sampling clock 1.048576MHz, and the read clock is the baseband data stream clock 7.8125bps.

[0143] The modulation module is used to modulate the baseband data output by the rate conversion module according to the PCM / BPSK / PM debugging mode. Among them, the default value of the fixed frequency deviation of the remote control main carrier is 20kHz, which is shared with the fixed frequency deviation in the single-tone mode and can be adjusted through the command parameter C1.

[0144] Reasons for setting fixed frequency deviation: The receiving of AD9364 cannot adapt to true zero frequency deviation or extremely low frequency deviation, so under the premise of setting the transmitting and receiving frequencies (local oscillators) to be the same, the transmitting end needs to set a certain frequency deviation. In the case of AD9364's minimum baseband bandwidth of 100kHz (single sideband), a 20kHz frequency deviation can meet more than twice the subcarrier frequency range, which is appropriate.

[0145] The transmitting end of the single-tone mode includes: a single-tone symbol deframing module and a single-tone modulation module.

[0146] The single-tone symbol de-framing module is used to receive frames containing single-tone symbols sent by the front end (host computer or serial port). The single-tone symbol frame format is as follows: Figure 5 As shown, the frame header is EB90, the frame tail is 09D7, and the frame length is the number of single tone symbols M. When the complex signal bandwidth is 512Hz and the minimum frequency step is 1 / 128Hz, the corresponding number of frequency bins is 512*128, and 16 bits are needed to represent a single tone symbol.

[0147] The single-tone symbol de-framing module is completed by the state machine. After detecting the frame header, the frame length is detected and the single-tone symbol is extracted according to the frame length. Finally, the single-tone symbol is output to the dual-port RAM. The dual-port RAM accumulates the dual-port RAM read address according to the symbol period T, and sends the single-tone symbol to the single-tone modulation module in turn; the symbol period T is adjustable through the command parameter C2. At the same time, the single-tone symbol output by the dual-port RAM is transmitted to the PC through the serial port for storage, and is used for the subsequent bit error statistics of the receiving end.

[0148] The single tone modulation module is used to complete the mapping of the single tone symbol value to the frequency control word, and the frequency slot f bin The width can be adjusted by command parameter C3.

[0149] Output frequency f out The relationship between and the frequency control word K is as follows:

[0150]

[0151] Among them, f sis the sampling rate, and N is the phase accumulator bit width.

[0152] Assuming that the current frequency slot width is 1 / 128 Hz, the frequency represented by the single-tone symbol value 1 is 1 / 128 Hz; when the phase accumulator bit width N is 32 bits, after calculation, the frequency control word K is 32.

[0153] Assuming that the current frequency slot width is 1 / 64 Hz, the frequencies represented by the single-tone symbol values ​​2 and 3 are both 1 / 64 Hz; when the phase accumulator bit width N is 32 bits, after calculation, the frequency control word K is 64.

[0154] Command parameter C4 is used to switch between synchronous mode and single-tone mode.

[0155] Figure 6 The figure shows a functional block diagram of the receiving end of an ultra-deep space high-sensitivity remote control signal detection method, which shows the connection relationship between various functional modules.

[0156] The receiving end of the synchronous mode includes: a main carrier capture and tracking module, a remote control demodulation module, a frame synchronization module, a descrambling module, a CRC check module, and a time synchronization compensation module.

[0157] The main carrier capture and tracking module adopts a phase-locked loop structure, including an in-phase branch and an orthogonal branch; the in-phase branch provides automatic gain control (AGC) and the main carrier locking state quantity Y1, and the orthogonal branch locks the phase of the main carrier signal;

[0158] The remote control demodulation module is used to complete the tracking of the remote control subcarrier and the demodulation of the remote control signal, and output the demodulated baseband data and the subcarrier locking mark Y2;

[0159] The frame synchronization module is used to receive the baseband data stream output by the remote control demodulation module, complete the frame synchronization of the fixed-length frame (74bit) shielded frame header, and also resolve the phase ambiguity that occurs in BPSK demodulation and output it to the descrambling module, and output the current frame synchronization lock mark Y3, phase ambiguity Y4, and frame synchronization header count Y5;

[0160] The descrambling module is used to descramble the data after frame synchronization.

[0161] The CRC check module is used to perform CRC check on the descrambled data stream. After the CRC check is successful, the 42-bit time timer in the current frame, that is, the clock of the ground station transmitter, is extracted and output to the time synchronization compensation module; and the CRC check correct frame count Y6, CRC check error frame count Y7, current frame CRC check correct / error status Y8, and initial synchronization status Y9 are output.

[0162] The time synchronization compensation module is used to complete the time synchronization compensation between the sender and the receiver, and output the compensated time to the time synchronization pulse module. Specifically, when the CRC check is successfully detected for the first time, that is, when the initial synchronization state quantity Y8 is equal to 1, the local second count and ms count values ​​are set to the values ​​in the transmission frame, and the delay compensation value P1 is added. When the transmission delay is ignored, the delay mainly comes from the duration of the frame processing and the delay of the receiving signal synchronization algorithm, which can be obtained by simulation. The compensation value P1 can be written online in real time, and through fine-tuning, the purpose of synchronization between the sender and the receiver is finally achieved.

[0163] After synchronization is established, the sender sets command parameter C4 to single-tone mode.

[0164] The receiving end of the single-tone mode includes: a single-tone signal preprocessing module, a timing pulse generation module and an ARM CPU end post-processing the single-tone system signal.

[0165] The single-tone signal preprocessing module performs down-conversion, multi-stage downsampling and filtering on the received single-tone system signal, and downsamples the sampling rate from 1.048576MHz to 512Hz by 2048 times. The downsampled single-tone system signal I / Q is output to the ARM CPU end.

[0166] When the transmitting end switches to the single-tone mode, the sending end and the receiving end agree on the symbol period T currently sent, and set P2 and C2 to the same parameter.

[0167] The timing pulse generation module generates a timing pulse TimingPulse according to the received symbol period P2 and the compensated local time counter, and outputs it to the ARM CPU end.

[0168] The ARM CPU receives the pre-processed single-tone signal, performs coherent integration, non-coherent accumulation, windowing and peak detection according to the timing pulse signal TimingPulse, and demaps the detected peak back to the frequency of the single-tone signal to obtain the single-tone symbol.

[0169] The demapped single tone symbol is compared with the single tone symbol of the transmitting end, and a decision is made to obtain error statistics, detection probability and false alarm probability.

[0170] Example 2

[0171] Embodiment 2 of the present invention proposes a signal detection method, which is implemented based on the system of embodiment 1. Figure 7The figure shows the operation flow chart of the ultra-deep space high-sensitivity remote control system and signal detection method of the present invention. The equipment needs to be preheated after power-on, and the signal power is calibrated after 20 minutes to determine the linearity of the intermediate frequency signal output. Then set the synchronization mode at a strong level so that the link is synchronized. According to the task requirements, adjust the attenuation to the target power, set the single-tone mode at the target power, set the same symbol period for both the sender and the receiver, and perform bit error detection.

[0172] It should be noted that before the transponder receiving signal level reaches the target threshold level, the system undergoes a process of changing from strong to weak, which is a reasonable assumption.

[0173] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention and should be included in the scope of the claims of the present invention.

Claims

1. An ultra-deep space high-sensitivity remote control system, characterized in that: include: The ground station transmitter and the ultra-deep space transponder and satellite service terminal deployed on the satellite; among them, The ground station transmitting end is used to adopt a synchronous mode to transmit a PCM / PSK / PM modulation signal with adjustable power under a strong level; and is also used to switch to a single-tone mode to transmit a single-tone system signal with adjustable power; The ultra-deep space transponder adopts a superheterodyne and zero intermediate frequency architecture, and is used to receive PCM / PSK / PM modulated signals in synchronous mode, achieve time synchronization between the sender and the receiver through compensation, and then switch to single-tone mode; and is also used to receive single-tone system signals in single-tone mode and demodulate them; The satellite service terminal is used to receive and detect the demodulated single-tone signal sent by the ultra-deep space transponder, perform ultra-long FFT spectrum analysis, demap back the remote control command according to the detected frequency, and perform error judgment; the CPU of the satellite service terminal adopts the ARM CPU built in the ZYNQ FPGA; The single-tone signal adopts frequency shift keying modulation, and the keying time interval is 1 to 512 seconds, and the keying time is adjustable; each tone represents an uplink carrier signal, corresponding to an uplink remote control command, and its carrier frequency is adjustable within the kHz range; The ground station transmitter includes an intermediate frequency board, which is used to generate PCM / PSK / PM modulation signals in synchronous mode and single-tone system signals in single-tone mode, and is also used to interact with the radio frequency integration board; for the single-tone mode, the ground station transmitter also includes: a single-tone symbol deframing module and a single-tone modulation module deployed on the intermediate frequency board; wherein, The single tone symbol deframing module is used to receive a frame containing a single tone symbol sent by a host computer or a serial port, and cyclically send the parsed single tone symbol to the single tone modulation module; the bit width of the single tone symbol is determined by the complex signal bandwidth and the frequency slot width f bin Determine; each frame contains M single-tone symbols, the symbol period T is the time interval between the current symbol and the next symbol, and the symbol period T is online adjustable; The single tone modulation module is used to complete the mapping of the single tone symbol value to the frequency control word, and the frequency slot width f bin Online adjustable; The ultra-deep space transponder includes an intermediate frequency board for completing digital signal processing of intermediate frequency signals, including carrier synchronization, timing synchronization and demodulation of PCM / PSK / PM signals, and preprocessing of single-tone system signals; for single-tone mode, the ultra-deep space transponder also includes: a single-tone signal preprocessing module and a timing pulse generation module deployed on the intermediate frequency board; wherein, The single-tone signal preprocessing module is used to down-convert, filter and down-sample the received single-tone system signal, and send it to the satellite service terminal; The timing pulse generating module is used to determine the symbol boundary, generate a timing pulse with a period of a single-tone symbol period T, and output it to the satellite service terminal.

2. The ultra-deep space high-sensitivity remote control system according to claim 1, characterized in that: The PCM / PSK / PM modulation signal is: the remote control PCM signal performs PSK modulation on the subcarrier, and the modulated subcarrier then performs PM modulation on the main carrier.

3. The ultra-deep space high-sensitivity remote control system according to claim 1 or 2, characterized in that: The ground station transmitter includes: a radio frequency integrated board, a high-stability reference source, a local oscillator, a mixer and an attenuator; wherein, The radio frequency integrated board is used to generate a first-level radio frequency signal; The highly stable reference source is used to provide a clock reference; The local oscillator is used to provide a local oscillator signal for the mixer; The mixer is used for up-conversion; The attenuator adopts a combination of a fixed attenuator and an adjustable attenuator to achieve adjustable power of the transmission signal within a set power range.

4. The ultra-deep space high-sensitivity remote control system according to claim 3, characterized in that: For the synchronous mode, the ground station transmitter also includes: a ground time counter framing module, a scrambling module, a rate conversion module and a modulation module deployed on the intermediate frequency board; wherein, The ground time counter framing module is used to complete the framing of the ground counter; the frame format includes a 2-byte frame header, a 32-bit second count and a 10-bit ms count, and a 2-byte CRC check, a total of 74 bits; wherein the second count and the ms count are the values ​​of the current frame sending time; The scrambling module is used to complete the scrambling of the ground time counter frame and send the scrambled data to the rate conversion module; The rate conversion module is used to complete the read and write rate conversion of data using FIFO, the write clock is the transmission signal sampling clock, and the read clock is the baseband data stream clock; The modulation module is used to modulate the baseband data output by the rate conversion module according to the PCM / BPSK / PM modulation method, and output it to the radio frequency integration board.

5. The ultra-deep space high-sensitivity remote control system according to claim 1, characterized in that: The radio frequency signal power range generated by the transmitting end of the ground station is -100 to -180 dBm, and the adjustable step is ≤ 1 dB; the uplink signal frequency band is S or X band.

6. The ultra-deep space high-sensitivity remote control system according to claim 1, characterized in that: The ultra-deep space transponder includes: a low noise amplifier, a bandpass filter, a local oscillator, a high-stability reference source and a radio frequency integrated board; wherein, The low noise amplifier adopts a two-stage cascade connection, and an isolator is arranged between the two stages to limit the gain fluctuation caused by possible self-excitation and in-band VSWR fluctuation; The bandpass filter is used to suppress the image frequency at the receiving end; The highly stable reference source is used to provide a clock reference; The radio frequency integrated board is used to convert the received radio frequency signal into an intermediate frequency.

7. The ultra-deep space high-sensitivity remote control system according to claim 6, characterized in that: For the synchronization mode, the ultra-deep space transponder also includes: a main carrier acquisition and tracking module, a remote control demodulation module, a frame synchronization module, a descrambling module, a CRC check module and a time synchronization compensation module deployed on the intermediate frequency board; wherein, The main carrier capture and tracking module adopts a phase-locked loop structure, including an in-phase branch and an orthogonal branch; the in-phase branch is used to provide automatic gain control and main carrier locking state quantity, and the orthogonal branch is used to lock the phase of the main carrier signal; The remote control demodulation module is used to complete the tracking of the remote control subcarrier and the demodulation of the remote control signal, and output the demodulated baseband data and the subcarrier locking state quantity; The frame synchronization module is used to receive the baseband data stream output by the remote control demodulation module, complete the frame synchronization of the fixed-length frame shielding the frame header, and is also used to resolve the phase ambiguity caused by BPSK demodulation and output it to the descrambling module, and output the current frame synchronization lock, phase ambiguity and frame synchronization header count state; The descrambling module is used to perform descrambling processing on the data after frame synchronization and output it to the CRC check module; The CRC check module is used to perform CRC check on the descrambled data stream. When the CRC check succeeds, the time timer of the set bit in the current frame, that is, the clock of the ground station transmitter, is extracted and output to the time synchronization compensation module; and the CRC check correct frame count, the CRC check error frame count, the current frame CRC check correct / error state quantity and the initial synchronization state quantity are output; The time synchronization compensation module is used to complete the time synchronization compensation of the sender and the receiver. When the CRC check is successfully detected for the first time, the local second count and ms count values ​​are set to the values ​​in the transmission frame, and the compensation value is added.

8. A signal detection method, implemented based on the ultra-deep space high-sensitivity remote control system according to any one of claims 1 to 7, comprising: Under strong level, the synchronous mode is adopted, the ground station transmitter transmits PCM / BPSK / PM signal, and the ultra-deep space transponder processes the signal and completes time synchronization; When it is detected that the synchronization mode has been completed, the ground station transmitter adjusts the attenuation to reduce the signal to a weak level, switches to the single-tone mode, and transmits a single-tone system signal; The ultra-deep space transponder completes the reception and demodulation processing; The satellite service terminal performs ultra-long FFT spectrum analysis on the received demodulated single-tone signal, compares the single-tone symbol output by the detection with the single-tone symbol transmitted by the ground station, and makes error judgment.

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