Ultra-high sensitivity signal generation and reception method based on Ku-band wide beam antenna

Abstract

The present invention provides an ultra-high sensitivity signal generation and receiving method based on a Ku-band wide beam antenna, and relates to the field of satellite communication technology. The signal generation method includes using a three-dimensional TPC encoder to encode the data information to be sent; using an ultra-long spread spectrum code to spread spectrum modulate the encoded information; processing the spread spectrum modulated code chips, outputting a Ku-band signal, and sending it to the satellite. The signal receiving method includes: receiving satellite signals, performing spread spectrum code capture; completing optimal sampling recovery and carrier phase recovery; iteratively decoding the signal after carrier phase recovery through a decoder to obtain decoded data and complete signal reception. The present invention can effectively reduce the duration of burst signals and realize low-complexity reception of weak power and extremely low signal-to-noise ratio signals. It is particularly suitable for burst satellite communication systems with low communication rates, extremely low signal power, large system frequency deviation, and one-way communication requirements.

Description

Technical Field

[0001] The invention relates to the technical field of satellite communications, and in particular to an ultra-high sensitivity signal generation and receiving method based on a Ku-band wide beam antenna. Background Art

[0002] In the Ku-band burst satellite communication system where satellite power is strictly limited, the downlink signal attenuation is about 206dB, and the gain of the wide beam antenna is very small, about -4dBi. Therefore, the signal power received by the receiver is very small, less than -130dBW, which requires a very high sensitivity of the receiver. In the Tiantong satellite communication system, the satellite downlink attenuation is about 200dB, and the mobile phone antenna gain is greater than 0dBi. Compared with the downlink of the Tiantong satellite communication system, the downlink gain of the wide beam antenna of the Ku satellite communication system is reduced by 10dB, and the downlink beam of the Tiantong satellite is a spot beam with a large beam gain. Therefore, the power of the signal received by the Ku-band wide beam antenna receiver is much smaller than the power of the signal received by the Tiantong mobile phone. The engineering requires that the sensitivity of the Ku-band wide beam antenna receiver is higher than that of the Tiantong mobile phone receiver, and the reception performance of weak signals needs to be improved through the spread spectrum gain with a super large spread spectrum ratio. In addition, the uplink frequency of the Ku-band satellite communication system is 14GHz, and the downlink frequency is 12GHz. The uplink frequency of the Tiantong satellite communication system is 6GHz, and the downlink frequency is 4GHz. The frequency deviation of the Ku-band satellite communication system is larger, and it is more difficult to receive low-speed signals.

[0003] Direct sequence spread spectrum communication is to expand the transmission signal in the frequency domain, that is, to use high-speed pseudo-random codes to spread spectrum modulate the low-rate information code stream to be transmitted, so that the signal bandwidth used for transmission is much larger than the bandwidth of the information itself. Traditional spread spectrum signals use pseudo-random sequences such as large M sequences, small m sequences, and chaotic sequences as spread spectrum codes. In the ultra-large spread spectrum ratio spread spectrum communication system, these sequences have too many spread spectrum code phases, and the spread spectrum code synchronization requires a lot of digital signal processing resources of the FPGA chip, which is very complex to implement in engineering. Traditional timing recovery methods and carrier recovery methods based on phase-locked loops have the characteristics of long convergence time and high overhead, and are not suitable for burst communication systems. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the above-mentioned background technology and provide an ultra-high sensitivity signal generation and reception method based on a Ku-band wide beam antenna. The present invention reduces the complexity of engineering implementation, the duration of burst signals and the loss of demodulation performance.

[0005] The technical solution adopted by the present invention is:

[0006] The method for generating ultra-high sensitivity signals based on Ku-band wide beam antenna comprises the following steps:

[0007] Step 101, using a three-dimensional TPC encoder to encode the data information to be sent;

[0008] Step 102, performing spread spectrum modulation on the encoded information using an ultra-long spread spectrum code;

[0009] Step 103, the code chips after spread spectrum modulation are subjected to BPSK mapping, shaping filtering, digital-to-analog conversion, and then intermediate frequency modulation, up-conversion, power amplification, and output Ku-band signals to be sent to the satellite.

[0010] Furthermore, the three-dimensional TPC encoder encodes in the order of x-axis, y-axis, and z-axis, and outputs the encoded check bits and information bits in sequence, wherein the subcodes used in the x-axis and y-axis are extended Hamming codes, and the subcode used in the z-axis is a parity check code. The input length of the three-dimensional TPC encoder is 114 bits, and the output length is 342 bits.

[0011] Furthermore, the ultra-long spread spectrum code is composed of a GOLD sequence repeated N times, and the value range of N is 100 to 300; during spread spectrum modulation, the starting position of each encoded information is aligned with the first code bit of the first GOLD sequence, and the ending position of each encoded information is aligned with the last code bit of the Nth GOLD sequence.

[0012] An ultra-high sensitivity signal receiving method based on a Ku-band wide beam antenna is used to receive the signal generated by the above method, comprising the following steps:

[0013] Step 201, receiving the satellite downlink Ku-band signal through a wide beam antenna, performing analog amplification, down-conversion, analog-to-digital conversion, digital amplification in sequence, and then performing spread spectrum code capture;

[0014] Step 202, start multiple correlators to generate multiple despread symbols, select the best symbol from them, and complete the best sampling recovery;

[0015] Step 203, performing open-loop carrier phase compensation twice to complete carrier phase recovery;

[0016] Step 204, iteratively decode the signal after carrier phase recovery through a decoder to obtain decoded data, thereby completing signal reception.

[0017] Furthermore, in step 201, the specific method of capturing the spread spectrum code is:

[0018] The GOLD sequence with a length of M is correlated with the twice sampled signal after digital amplification. A correlation operation corr is performed for each input sampled signal. The GOLD sequence with a length of M has a total of 2M sampled signals, generating 2M correlation values. The value of M is 63, 127, 255 or 511.

[0019] Every 2M correlation values ​​are taken as a group, and the values ​​of the corresponding positions of the correlation values ​​of the 1st group to the Ath group are accumulated to generate the first group of coherent values, and the values ​​of the corresponding positions of the correlation values ​​of the A+1th group to the 2Ath group are accumulated to generate the second group of coherent values, and so on, a total of B groups of coherent values ​​are generated; the value range of A is 1 to 16, and the value range of B is 480 to 512;

[0020] The coherence values ​​of group B are digitally amplified again and then stored in the cache;

[0021] Combine the first number of each group of coherent values ​​in the B groups of coherent values ​​in the cache, perform P-point FFT operation, where P is 512, 1024 or 2048, and find the maximum value after the FFT operation; sequentially combine the second number, the third number to the 2Mth number of each group of coherent values, perform P-point FFT operation respectively, and find the maximum value after the FFT operation, and obtain 2M maximum values ​​in total;

[0022] The position corresponding to the maximum value among the 2M maximum values ​​in the 2M positions is aligned with the phase of the local spread spectrum code to complete the spread spectrum code capture synchronization.

[0023] Furthermore, the specific method of step 202 is:

[0024] The local spreading code starts one correlator every 1 / R pre-spreading symbols, where R is 4, 8 or 16, and a total of R correlators are started to generate R despread symbols in parallel.

[0025] The power values ​​of the R-path despread symbols are calculated, and the 1-path symbol with the largest power value is used as the best despread symbol to complete the best sampling recovery.

[0026] Furthermore, the specific method of step 203 is:

[0027] Taking the phase of the first symbol as a reference, performing the first open-loop carrier phase compensation from front to back, and storing the phase-compensated symbol in a memory;

[0028] Taking the phase of the last symbol of the first open-loop carrier phase compensation as a reference, after the phase transformation, the second open-loop carrier phase compensation is performed from back to front to complete the carrier phase recovery; wherein, the phase transformation method is as follows:

[0029] Negate the imaginary part of the sign;

[0030] Divide the negated imaginary part by the real part to get the quotient;

[0031] Taking the inverse tangent of the quotient completes the phase shift.

[0032] Further, the decoder includes an X-subdecoder, a Y-subdecoder and a Z-subdecoder that are iterated in a serial loop, and the X-subdecoder, the Y-subdecoder and the Z-subdecoder are all soft-input and soft-output subdecoders;

[0033] In the first iteration of each loop process, the data after carrier recovery is first input to the X-subdecoder, and then, after a delay, the data after carrier recovery is transmitted to the Y-subdecoder together with the soft external information output by the X-subdecoder. Then, after a delay, the data after carrier recovery is transmitted to the Z-subdecoder together with the soft external information output by the Y-subdecoder. In subsequent iterations, the data after carrier recovery is no longer input, and the soft external information output by the Z-subdecoder is transmitted to the X-subdecoder. The X-subdecoder, the Y-subdecoder and the Z-subdecoder work in series, and the soft external information output by the previous subdecoder is transmitted to the next subdecoder. When the number of iterations I is reached, the decoder outputs the decoded data, and the value range of I is 20 to 50. In the first iteration of the next loop process, the data after carrier recovery is input to the decoder again.

[0034] Among them, the X-subdecoder and Y-subdecoder use the soft-in and soft-out Cyclic-2 PML algorithm, and the Z-subdecoder uses the soft-in and soft-out parity check decoding algorithm; the soft external information output by the Z-subdecoder is consistent with the correction factor After multiplication, the input is given to the X-subdecoder. The value range is 0.3 to 0.5; the soft external information output by the X-subdecoder and the correction factor After multiplication, the input is given to the Y-subdecoder. The value range is 0.7 to 0.8; the soft external information output by the Y-subdecoder and the correction factor After multiplication, the input is given to the Z-subdecoder. The value range is 0.7 to 0.8.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] 1. The signal generation and receiving method of the present invention has the characteristics of less spread spectrum code phase, less demodulation performance loss, and fast optimal sample value recovery. It can be implemented by a digital signal processing FPGA chip, and the FPGA resource overhead is small.

[0037] 2. The present invention is applicable to an extremely low-rate burst satellite communication system based on direct sequence spread spectrum, which can effectively reduce the duration of the burst signal, reduce the demodulation threshold, and reduce the complexity of signal reception.

[0038] 3. The signal receiving of the present invention adopts one-stage analog amplification, two-stage digital amplification, and ultra-large spread spectrum gain, which greatly improves the receiving sensitivity of weak signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the composition of the spreading code with an ultra-large spreading ratio and a small number of phases in an embodiment of the present invention.

[0040] Figure 2 It is a schematic diagram of ultra-high sensitivity low complexity spread spectrum code capture in an embodiment of the present invention.

[0041] Figure 3 It is a schematic diagram of the principle of optimal sample recovery in an embodiment of the present invention.

[0042] Figure 4 It is a schematic diagram of the principle of low-overhead carrier recovery in an embodiment of the present invention.

[0043] Figure 5 It is a schematic diagram of iterative decoding of a low-rate high-efficiency decoder in an embodiment of the present invention.

[0044] Figure 6 It is a schematic diagram of an application scenario of the present invention. DETAILED DESCRIPTION

[0045] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0046] like Figure 6 As shown, the ultra-high sensitivity signal generation method based on the Ku-band wide beam antenna includes the following steps:

[0047] Step 101, use a three-dimensional TPC encoder to encode the data information to be sent; the three-dimensional TPC encoder encodes in the order of x-axis, y-axis, and z-axis, and outputs the encoded check bits and information bits in sequence, wherein the subcodes used in the x-axis and y-axis are extended Hamming codes, the subcode used in the z-axis is a parity check code, the input length of the three-dimensional TPC encoder is 114 bits, and the output length is 342 bits.

[0048] Step 102, using an ultra-long spreading code to spread spectrum modulate the encoded information; Figure 1 As shown, the ultra-long spread spectrum code is composed of a GOLD sequence repeated N times, where N is in the range of 100 to 300. During spread spectrum modulation, the starting position of each encoded information is aligned with the first code chip of the first GOLD sequence, and the ending position of each encoded information is aligned with the last code chip of the Nth GOLD sequence.

[0049] Step 103, the code chips after spread spectrum modulation are subjected to BPSK mapping, shaping filtering, digital-to-analog conversion, and then intermediate frequency modulation, up-conversion, power amplification, etc., and the Ku-band signal is output and sent to the satellite.

[0050] like Figure 6As shown, the ultra-high sensitivity signal receiving method based on the Ku-band wide beam antenna is used to receive the signal generated by the above method, comprising the following steps:

[0051] Step 201, receiving the satellite downlink Ku-band signal through a wide beam antenna, performing analog amplification, down-conversion, analog-to-digital conversion, digital amplification in sequence, and then performing spread spectrum code capture; Figure 2 As shown, the specific method of spreading code capture is:

[0052] The GOLD sequence with a length of M is correlated with the twice sampled signal after digital amplification. A correlation operation corr is performed for each input sampled signal. The GOLD sequence with a length of M has a total of 2M sampled signals, generating 2M correlation values. The value of M is 63, 127, 255 or 511.

[0053] Every 2M correlation values ​​are taken as a group, and the values ​​of the corresponding positions of the correlation values ​​of the 1st group to the Ath group are accumulated to generate the first group of coherent values, and the values ​​of the corresponding positions of the correlation values ​​of the A+1th group to the 2Ath group are accumulated to generate the second group of coherent values, and so on, a total of B groups of coherent values ​​are generated; the value range of A is 1 to 16, and the value range of B is 480 to 512;

[0054] The coherence values ​​of group B are digitally amplified again and then stored in the cache;

[0055] Combine the first number of each group of coherent values ​​in the B groups of coherent values ​​in the cache, perform P-point FFT operation, where P is 512, 1024 or 2048, and find the maximum value after the FFT operation; sequentially combine the second number, the third number to the 2Mth number of each group of coherent values, perform P-point FFT operation respectively, and find the maximum value after the FFT operation, and obtain 2M maximum values ​​in total;

[0056] The position corresponding to the maximum value among the 2M maximum values ​​in the 2M positions is aligned with the phase of the local spread spectrum code to complete the spread spectrum code capture synchronization.

[0057] Step 202, start multiple correlators to generate multiple despread symbols, select the best symbol from them, and complete the best sampling recovery; Figure 3 As shown, the specific method is:

[0058] The local spreading code starts one correlator every 1 / R pre-spreading symbols, where R is 4, 8 or 16, and a total of R correlators are started to generate R despread symbols in parallel.

[0059] The power values ​​of the R-path despread symbols are calculated, and the 1-path symbol with the largest power value is used as the best despread symbol to complete the best sampling recovery.

[0060] Step 203, perform open-loop carrier phase compensation twice to complete carrier phase recovery; Figure 4 As shown, the specific method is:

[0061] Taking the phase of the first symbol as a reference, performing the first open-loop carrier phase compensation from front to back, and storing the phase-compensated symbol in a memory;

[0062] Taking the phase of the last symbol of the first open-loop carrier phase compensation as a reference, after the phase transformation, the second open-loop carrier phase compensation is performed from back to front to complete the carrier phase recovery; wherein, the phase transformation method is as follows:

[0063] Negate the imaginary part of the sign;

[0064] Divide the negated imaginary part by the real part to get the quotient;

[0065] Taking the inverse tangent of the quotient completes the phase shift.

[0066] Step 204, iteratively decode the signal after carrier phase recovery through a decoder to obtain decoded data, thereby completing signal reception.

[0067] like Figure 5 As shown, the decoder includes an X-sub-decoder, a Y-sub-decoder and a Z-sub-decoder that are iterated in a serial loop, and the X-sub-decoder, the Y-sub-decoder and the Z-sub-decoder are all soft-input and soft-output sub-decoders;

[0068] In the first iteration of each loop process, the data after carrier recovery is first input to the X-subdecoder, and then, after a delay, the data after carrier recovery is transmitted to the Y-subdecoder together with the soft external information output by the X-subdecoder. Then, after a delay, the data after carrier recovery is transmitted to the Z-subdecoder together with the soft external information output by the Y-subdecoder. In subsequent iterations, the data after carrier recovery is no longer input, and the soft external information output by the Z-subdecoder is transmitted to the X-subdecoder. The X-subdecoder, the Y-subdecoder and the Z-subdecoder work in series, and the soft external information output by the previous subdecoder is transmitted to the next subdecoder. When the number of iterations I is reached, the decoder outputs the decoded data, and the value range of I is 20 to 50. In the first iteration of the next loop process, the data after carrier recovery is input to the decoder again.

[0069] Among them, the X-subdecoder and Y-subdecoder use the soft-in and soft-out Cyclic-2 PML algorithm, and the Z-subdecoder uses the soft-in and soft-out parity check decoding algorithm; the soft external information output by the Z-subdecoder is consistent with the correction factor After multiplication, the input is given to the X-subdecoder. The value range is 0.3 to 0.5; the soft external information output by the X-subdecoder and the correction factor After multiplication, the input is given to the Y-subdecoder. The value range is 0.7 to 0.8; the soft external information output by the Y-subdecoder and the correction factor After multiplication, the input is given to the Z-subdecoder. The value range is 0.7 to 0.8.

[0070] The main innovations of the present invention are:

[0071] 1) Design of generating spread spectrum signal with large spread ratio and small number of phases:

[0072] In a low-rate satellite communication system with an ultra-large spread ratio, the spread code is very long, the number of phases of the spread code synchronization increases exponentially, the engineering implementation is highly complex, and digital signal processing requires a lot of FPGA resources, which is difficult for general chip resources to bear. To this end, the present invention designs an ultra-long spread code based on short code repetition, which can reduce the number of spread code phases by hundreds of times while realizing ultra-large spread ratio spread of low-rate signals.

[0073] After the data information is TPC-encoded, it is spread using an ultra-long spread spectrum code. The spread spectrum code consists of a GOLD sequence repeated N times. The spread spectrum code composition diagram is shown in the figure below. Figure 1 As shown; the starting position of each encoded information is aligned with the first code chip of the first GOLD sequence, and the ending position of each encoded information is aligned with the last code chip of the Nth GOLD sequence; the code chips after spread spectrum are processed by baseband signals such as symbol mapping and shaping filtering, intermediate frequency modulation, up-conversion, power amplification, antenna and other analog processing units, and then output Ku-band signals and sent to the satellite.

[0074] 2) Design to resist large frequency deviation of the system:

[0075] In low-rate satellite communication systems, the system frequency deviation between the transmitter and the receiver is one of the main factors affecting the system reception performance and synchronization overhead. To this end, the present invention designs a system frequency deviation compensation method that combines frequency scanning with frequency estimation, which greatly improves the system's ability to resist frequency deviation.

[0076] The present invention adopts a frequency scanning method to identify large frequency deviations of the system, the system frequency deviation is ±10kHz, the frequency scanning step is ±2kHz, and the remaining frequency deviation after the frequency scanning is ±1kHz; data of 30 symbols are collected at each frequency scanning point for correlation calculation with the local spread spectrum code, and used for large frequency deviation identification; while completing the frequency scanning, two frequency verification branches are added, and when the frequency scanning branch is synchronized at the correct frequency point, the correlation values ​​output by the two verification branches are much smaller than the correlation value output by the frequency scanning branch; on the contrary, if the frequency scanning branch is synchronized at the wrong frequency point, then at least one of the verification branches outputs a correlation value greater than the correlation value of the frequency scanning branch. After completing the correction of the large frequency difference deviation, the frequency estimation is performed again to further improve the precision of the frequency deviation correction.

[0077] 3) Ultra-high sensitivity and low complexity spread spectrum code capture design:

[0078] In the traditional spread spectrum code capture method based on matched filtering or sliding correlation, the number of correlator taps is consistent with the spread spectrum code length, the implementation complexity is high, and the hardware FPGA resources are occupied, and it is impossible to realize the spread spectrum code capture of the spread spectrum signal with ultra-large spread ratio and high sensitivity. Therefore, the present invention designs a spread spectrum code capture method based on one-stage analog amplification, two-stage digital amplification, partial correlation, memory instead of logic resources and FFT processing.

[0079] like Figure 2 As shown, the wide beam antenna receives the satellite downlink Ku-band signal, which enters the digital correlator after passing through an analog amplifier, down-conversion, analog / digital conversion, and a digital amplifier; a GOLD sequence with a length of M is correlated with the received sampling signal, and every 2M correlation values ​​are a group. The first group of coherent values ​​is generated by accumulating the 1st to 16th groups of correlation values; the second group of coherent values ​​is generated by accumulating the 17th to 32nd groups of correlation values; and so on, the 480th group of coherent values ​​is generated; the coherent values ​​are stored in RAM after passing through the digital amplifier; a 512-point FFT operation is performed on the 480 groups of coherent values ​​to find the maximum value after each FFT operation; a total of 2M maximum values; the corresponding phase of the maximum value among the 2M maximum values ​​is aligned with the local code phase, and the spread spectrum code capture is completed.

[0080] 4) Best sample recovery design:

[0081] Spread spectrum code capture only achieves precise synchronization of the short code phase, and cannot directly use correlation operations and code tracking methods to complete optimal sample value recovery.

[0082] Traditional optimal sample recovery methods based on optimal sample point selection or interpolation require a large amount of symbol accumulation before extracting sample errors, which results in high overhead for optimal sample value recovery and is not suitable for optimal sample value recovery of burst signals. To this end, the present invention designs a multi-channel parallel demodulation method based on signal energy detection to shorten the optimal sample value recovery time.

[0083] like Figure 3 As shown in the figure, the local spreading code starts one correlator every 1 / 16 of the pre-spreading symbol, and a total of 16 correlators are started, which generate 16 despread symbols in parallel. By calculating the power values ​​of the 16 symbols, the symbol with the largest power is used as the best symbol after despreading, and the best sampling recovery is completed. After the best sampling recovery, the demodulation performance loss is less than 0.3dB.

[0084] 5) Low overhead carrier phase compensation design:

[0085] The traditional carrier phase compensation method based on loop filtering has the characteristics of long convergence time and high overhead, and is not suitable for carrier recovery of burst signals. To this end, the present invention designs a high-performance carrier phase compensation method based on data storage, initial phase estimation, first coarse carrier phase compensation, and then fine carrier phase compensation.

[0086] like Figure 4 As shown, the first open-loop carrier phase compensation is performed from front to back with the phase of the first symbol as a reference, and the symbols after phase compensation are cached in the memory; the second open-loop carrier phase compensation is performed from back to front with the phase of the last symbol of the first carrier phase compensation as a reference after the phase change. Since the initial phase of the second carrier phase compensation has been through the first carrier phase compensation, the initial phase is more accurate and the performance of carrier recovery is better.

[0087] 6) Low-rate and high-efficiency codec design:

[0088] Traditional error correction codes such as convolutional coding and RS coding have poor error correction performance; LDPC codes with longer code lengths have better performance but are not suitable for burst communication. Therefore, the present invention designs a three-dimensional efficient TPC codec with short code length and good error correction performance.

[0089] The subcodes used in the x-axis and y-axis of the three-dimensional TPC encoder are extended Hamming codes, and the subcode used in the z-axis is a parity check code; the encoding order is x-axis, y-axis, and z-axis, and the encoded check bits and information bits are output in sequence. Figure 5 As shown in the figure, the decoder is mainly composed of three serial cyclic iterative soft input / soft output (i.e. SISO) sub-decoders, and each sub-decoder iteratively sends the output soft external information of one sub-decoder to the input of another sub-decoder. The sub-decoder utilizes the characteristics of cyclic codes to greatly reduce the search space of codewords, thereby simplifying the algorithm.

[0090] The present invention reduces the number of spread spectrum code phases by using a short GOLD sequence as a long spread spectrum code after being repeated; realizes weak power signal capture by using methods based on one-stage analog amplification, two-stage digital amplification, partial correlation, etc.; improves the system's frequency deviation resistance capability by combining frequency scanning with frequency estimation; reduces demodulation performance loss by using optimal sampling recovery and secondary phase compensation methods; and designs a TPC codec with good code length performance to complete channel error correction.

[0091] In summary, the present invention can effectively reduce the duration of burst signals and realize low-complexity reception of weak-power and extremely low signal-to-noise ratio signals. It is particularly suitable for burst satellite communication systems with low communication rates, extremely low signal power, large system frequency deviations, and one-way communication requirements.

Claims

1. An ultra-high sensitivity signal transmission method based on a Ku-band wide beam antenna, characterized in that: The method comprises a signal generating process and a signal receiving process, wherein the signal generating process comprises the following steps: Step 101, using a three-dimensional TPC encoder to encode the data information to be sent; the three-dimensional TPC encoder encodes in the order of x-axis, y-axis, and z-axis, and sequentially outputs the encoded check bits and information bits, wherein the subcodes used in the x-axis and the y-axis are extended Hamming codes, the subcode used in the z-axis is a parity check code, the input length of the three-dimensional TPC encoder is 114 bits, and the output length is 342 bits; Step 102, performing spread spectrum modulation on the encoded information using an ultra-long spread spectrum code; the ultra-long spread spectrum code is composed of a GOLD sequence repeated N times, where N is in the range of 100 to 300; during spread spectrum modulation, the starting position of each encoded information is aligned with the first code chip of the first GOLD sequence, and the ending position of each encoded information is aligned with the last code chip of the Nth GOLD sequence; Step 103, the code chips after spread spectrum modulation are subjected to BPSK mapping, shaping filtering, digital-to-analog conversion, and then intermediate frequency modulation, up-conversion, power amplification, etc., and the Ku-band signal is output and sent to the satellite; The signal receiving process includes the following steps: Step 201, receiving the satellite downlink Ku-band signal through a wide beam antenna, performing analog amplification, down-conversion, analog-to-digital conversion, digital amplification in sequence, and then performing spread spectrum code capture; the specific method of spread spectrum code capture is: The GOLD sequence with a length of M is correlated with the twice sampled signal after digital amplification. A correlation operation corr is performed for each input sampled signal. The GOLD sequence with a length of M has a total of 2M sampled signals, generating 2M correlation values. The value of M is 63, 127, 255 or 511. Every 2M correlation values ​​are taken as a group, and the values ​​of the corresponding positions of the correlation values ​​of the 1st group to the Ath group are accumulated to generate the first group of coherent values, and the values ​​of the corresponding positions of the correlation values ​​of the A+1th group to the 2Ath group are accumulated to generate the second group of coherent values, and so on, a total of B groups of coherent values ​​are generated; the value range of A is 1 to 16, and the value range of B is 480 to 512; The coherence values ​​of group B are digitally amplified again and then stored in the cache; Combine the first number of each group of coherent values ​​in the B groups of coherent values ​​in the cache, perform P-point FFT operation, where P is 512, 1024 or 2048, and find the maximum value after the FFT operation; sequentially combine the second number, the third number to the 2Mth number of each group of coherent values, perform P-point FFT operation respectively, and find the maximum value after the FFT operation, and obtain 2M maximum values ​​in total; Align the position corresponding to the maximum value among the 2M maximum values ​​in the 2M positions with the phase of the local spread spectrum code to complete the spread spectrum code acquisition synchronization; Step 202, start multiple correlators to generate multiple despread symbols, select the best symbol from them, and complete the best sampling recovery; the specific method is: The local spreading code starts one correlator every 1 / R pre-spreading symbols, where R is 4, 8 or 16, and a total of R correlators are started to generate R despread symbols in parallel. Calculate the power values ​​of the R-channel despread symbols, take the 1-channel symbol with the largest power value as the best despread symbol, and complete the best sampling recovery; Step 203, perform open-loop carrier phase compensation twice to complete carrier phase recovery; the specific method is: Taking the phase of the first symbol as a reference, performing the first open-loop carrier phase compensation from front to back, and storing the phase-compensated symbol in a memory; Taking the phase of the last symbol of the first open-loop carrier phase compensation as a reference, after the phase transformation, the second open-loop carrier phase compensation is performed from back to front to complete the carrier phase recovery; wherein, the phase transformation method is as follows: Negate the imaginary part of the sign; Divide the negated imaginary part by the real part to get the quotient; Take the inverse tangent of the quotient to complete the phase transformation; Step 204, iteratively decoding the signal after carrier phase recovery by a decoder to obtain decoded data, and completing signal reception; the decoder includes an X-sub-decoder, a Y-sub-decoder and a Z-sub-decoder of serial cyclic iteration, and the X-sub-decoder, the Y-sub-decoder and the Z-sub-decoder are all soft-input and soft-output sub-decoders; In the first iteration of each loop process, the data after carrier recovery is first input to the X-subdecoder, and then, after a delay, the data after carrier recovery is transmitted to the Y-subdecoder together with the soft external information output by the X-subdecoder. Then, after a delay, the data after carrier recovery is transmitted to the Z-subdecoder together with the soft external information output by the Y-subdecoder. In subsequent iterations, the data after carrier recovery is no longer input, and the soft external information output by the Z-subdecoder is transmitted to the X-subdecoder. The X-subdecoder, the Y-subdecoder and the Z-subdecoder work in series, and the soft external information output by the previous subdecoder is transmitted to the next subdecoder. When the number of iterations I is reached, the decoder outputs the decoded data, and the value range of I is 20 to 50. In the first iteration of the next loop process, the data after carrier recovery is input to the decoder again. Among them, the X-subdecoder and Y-subdecoder use the soft-in and soft-out Cyclic-2 PML algorithm, and the Z-subdecoder uses the soft-in and soft-out parity check decoding algorithm; the soft external information output by the Z-subdecoder is consistent with the correction factor After multiplication, the input is given to the X-subdecoder. The value range is 0.3 to 0.5; the soft external information output by the X-subdecoder and the correction factor After multiplication, the input is given to the Y-subdecoder. The value range is 0.7 to 0.8; the soft external information output by the Y-subdecoder and the correction factor After multiplication, the input is given to the Z-subdecoder. The value range is 0.7 to 0.8.

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