Fast frequency hopping communication method and system based on four-phase soft expansion

Abstract

The invention provides a fast frequency hopping communication method and system based on four-phase soft spread, and the method comprises the steps: carrying out the three-time phase shifting of a PN code with a preset spread spectrum ratio in a signal transmission process, and obtaining four PN codes with different phases; the modulated transmitting signals are grouped in pairs according to the number of bits, and each group of data is combined with the PN codes of the corresponding phases in sequence to obtain spread spectrum signals; processing the spread spectrum signal to obtain an amplified signal, and sending the amplified signal to an antenna to complete signal emission; in the signal receiving process, the antenna receives a second radio frequency signal; processing the second radio frequency signal to obtain a baseband signal; respectively correlating the baseband signal with four PN codes with different phases to obtain correlation sums respectively corresponding to the four PN codes; obtaining the correlation sum with the maximum energy, and obtaining the signal after soft spread removal based on the PN code corresponding to the correlation sum with the maximum energy; and decoding and demodulating the signal subjected to soft spread de-spreading to obtain a transmitting signal, and completing signal receiving.

Description

Technical Field

[0001] The present invention relates to the field of radio communication technology, and in particular to a fast frequency hopping communication method and system based on four-phase soft expansion. Background Art

[0002] The anti-interference capability under high-speed communication is an important basis for improving the stability, reliability and security of multi-node communication systems, and plays an important role in modern electronic communication systems. However, the communication system is subject to interference from various aspects in a complex electromagnetic environment, which affects the reliable communication of the system. The data link system realizes communication between nodes in the wireless channel by designing a communication frame structure, source coding, channel coding, modulation and demodulation technology that suits the needs. The data link system usually uses frequency hopping technology, direct sequence spread spectrum technology, channel selection and switching technology to improve the signal quality of the communication system, thereby improving the reliability and stability of the system communication.

[0003] At present, some data link communication systems only achieve some basic anti-interference capabilities through antennas and hardware circuit filtering, but the anti-interference ability is poor and the system is easily affected by the environment; the data link using spread spectrum technology has improved the system's anti-interference ability to a certain extent, and its anti-interference ability is positively correlated with the spread spectrum multiple, and the larger the spread spectrum multiple, the lower the user's communication rate under the same code rate, affecting the system communication rate; the data link system using frequency hopping technology can prevent all signals from being interfered with by avoiding interference frequencies, and use non-interfered signals to capture and demodulate signals, thereby completing communication. The anti-interference performance of the frequency hopping system is positively correlated with the frequency hopping spectrum and the frequency hopping rate. The faster the hopping speed and the more difficult it is to predict the frequency hopping spectrum, the higher the anti-interference performance. However, the current data link hopping speed is slow and the frequency hopping spectrum is single, which affects the system's anti-suppressive interference performance. Summary of the invention

[0004] The present invention provides a fast frequency hopping communication method and system based on four-phase soft expansion, which can solve the technical problem that the existing communication system has poor anti-interference ability.

[0005] According to one aspect of the present invention, a fast frequency hopping communication method based on four-phase soft spreading is provided, the method comprising:

[0006] During the signal transmission process, the FPGA encodes the transmission signal to be transmitted to obtain an encoded transmission signal; modulates the encoded transmission signal to obtain a modulated transmission signal;

[0007] The four-phase soft spread spectrum module in the FPGA performs three phase shifts on a PN code with a preset spread spectrum ratio to obtain four PN codes with different phases; the modulated transmission signal is grouped in pairs according to the number of bits, and each group of data is combined with the PN code of the corresponding phase in sequence to obtain a spread spectrum signal;

[0008] The FPGA sends the spread spectrum signal to the RF transceiver module;

[0009] The radio frequency transceiver module processes the spread spectrum signal to obtain a first radio frequency signal;

[0010] The digital frequency generation module generates a frequency hopping local oscillator at a preset frequency point;

[0011] The up-conversion module performs up-conversion processing on the first radio frequency signal and the frequency-hopping local oscillator to obtain an up-converted signal;

[0012] The power amplifier amplifies the up-converted signal to obtain an amplified signal, and sends the amplified signal to the antenna to complete signal transmission;

[0013] During the signal reception process, the antenna receives a second radio frequency signal;

[0014] The low noise amplifier amplifies the second radio frequency signal to obtain an amplified radio frequency signal;

[0015] The digital frequency generation module generates a frequency hopping local oscillator at a preset frequency point;

[0016] The down-conversion module performs down-conversion processing on the amplified RF signal and the frequency-hopping local oscillator to obtain a down-converted signal;

[0017] The bandpass filter performs filtering processing on the down-converted signal to obtain a filtered signal;

[0018] The RF transceiver module processes the filtered signal to obtain the baseband signal and sends it to the FPGA;

[0019] The four-phase de-softening module in the FPGA correlates the baseband signal with four PN codes of different phases respectively to obtain the correlation sums corresponding to the four PN codes; obtains the correlation sum with the largest energy, and obtains the de-softening signal based on the PN code corresponding to the correlation sum with the largest energy; decodes and demodulates the de-softening signal to obtain the transmitted signal, thereby completing signal reception.

[0020] Preferably, the ratio of the correlation peak value of the PN code with the preset spreading ratio and the corresponding phase received signal to the correlation peak value of the PN code with the non-corresponding phase received signal is greater than the preset ratio.

[0021] Preferably, the preset spreading ratio is 32, 64, 128 or 256.

[0022] According to another aspect of the present invention, there is provided a fast frequency hopping communication system based on four-phase soft expansion, the system comprising an FPGA, a radio frequency transceiver module, a digital frequency generation module, an up-conversion module, a power amplifier, an antenna, a low noise amplifier, a down-conversion module and a bandpass filter;

[0023] During the signal transmission process:

[0024] The FPGA is used to encode the transmission signal to be transmitted to obtain the encoded transmission signal; and is also used to modulate the encoded transmission signal to obtain the modulated transmission signal;

[0025] The four-phase soft spread spectrum module in the FPGA is used to perform three-time phase shift on a PN code with a preset spread spectrum ratio to obtain four PN codes with different phases; it is also used to group the modulated transmission signal in pairs according to the number of bits, and combine each group of data with the PN code of the corresponding phase in sequence to obtain a spread spectrum signal;

[0026] The FPGA is used to send the spread spectrum signal to the RF transceiver module;

[0027] The radio frequency transceiver module is used to process the spread spectrum signal to obtain a first radio frequency signal;

[0028] The digital frequency generation module is used to generate a frequency hopping local oscillator of a preset frequency point;

[0029] The up-conversion module is used to perform up-conversion processing on the first radio frequency signal and the frequency hopping local oscillator to obtain an up-converted signal;

[0030] The power amplifier is used to amplify the up-converted signal to obtain an amplified signal, and send the amplified signal to the antenna to complete signal transmission;

[0031] During signal reception:

[0032] The antenna is used to receive a second radio frequency signal;

[0033] The low noise amplifier is used to amplify the second radio frequency signal to obtain an amplified radio frequency signal;

[0034] The digital frequency generation module is used to generate a frequency hopping local oscillator of a preset frequency point;

[0035] The down-conversion module is used to perform down-conversion processing on the amplified RF signal and the frequency-hopping local oscillator to obtain a down-converted signal;

[0036] The bandpass filter is used to filter the down-converted signal to obtain a filtered signal;

[0037] The RF transceiver module is used to process the filtered signal, obtain the baseband signal, and send it to the FPGA;

[0038] The four-phase de-softening module in the FPGA is used to correlate the baseband signal with four PN codes of different phases respectively to obtain the correlation sum corresponding to each of the four PN codes; to obtain the correlation sum with the maximum energy, and to obtain the de-softening signal based on the PN code corresponding to the correlation sum with the maximum energy; and to decode and demodulate the de-softening signal to obtain the transmission signal and complete signal reception.

[0039] Preferably, the ratio of the correlation peak value of the PN code with the preset spreading ratio and the corresponding phase received signal to the correlation peak value of the PN code with the non-corresponding phase received signal is greater than the preset ratio.

[0040] Preferably, the preset spreading ratio is 32, 64, 128 or 256.

[0041] By applying the technical solution of the present invention, a PN code with good autocorrelation characteristics realizes four-phase soft spread spectrum of communication data. Compared with the use of two independent orthogonal PN codes, the communication rate of the system is improved without reducing the anti-interference performance of the spread spectrum. The method of high frequency hopping rate and random frequency hopping spectrum is adopted to improve the anti-detection ability of the system frequency hopping spectrum, and improve the anti-interference ability and stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0043] Figure 1 A flowchart of a fast frequency hopping communication anti-interference method based on four-phase soft spreading provided according to an embodiment of the present invention is shown;

[0044] Figure 2 A schematic structural diagram of a fast frequency hopping communication anti-interference system based on four-phase soft expansion according to an embodiment of the present invention is shown;

[0045] Figure 3 A schematic structural diagram of a fast frequency hopping communication anti-interference system based on four-phase soft expansion according to another embodiment of the present invention is shown;

[0046] Figure 4 A schematic diagram of a frame structure time slot provided according to an embodiment of the present invention is shown;

[0047] Figure 5 A schematic diagram of the overall design of a frame structure provided according to an embodiment of the present invention is shown;

[0048] Figure 6A schematic diagram of four-phase soft spread spectrum provided according to an embodiment of the present invention is shown;

[0049] Figure 7 A schematic diagram of PN code related characteristics provided according to an embodiment of the present invention is shown;

[0050] Figure 8 A schematic diagram of the structure of an incoherent physical data payload frame provided according to an embodiment of the present invention is shown;

[0051] Fig. 9 A relationship diagram between a non-coherent demodulation threshold and a bit error rate provided according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0052] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0054] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0055] like Figure 1 As shown, the present invention provides a fast frequency hopping communication method based on four-phase soft expansion, the method comprising:

[0056] During the signal transmission process, the FPGA encodes the transmission signal to be transmitted to obtain an encoded transmission signal; modulates the encoded transmission signal to obtain a modulated transmission signal;

[0057] The four-phase soft spread spectrum module in the FPGA performs three phase shifts on a PN code with a preset spread spectrum ratio to obtain four PN codes with different phases; the modulated transmission signal is grouped in pairs according to the number of bits, and each group of data is combined with the PN code of the corresponding phase in sequence to obtain a spread spectrum signal;

[0058] FPGA sends the spread spectrum signal to the RF transceiver module;

[0059] The radio frequency transceiver module processes the spread spectrum signal to obtain a first radio frequency signal;

[0060] The digital frequency generation module generates a frequency hopping local oscillator at a preset frequency point;

[0061] The up-conversion module performs up-conversion processing on the first radio frequency signal and the frequency-hopping local oscillator to obtain an up-converted signal;

[0062] The power amplifier amplifies the up-converted signal to obtain an amplified signal, and sends the amplified signal to the antenna to complete signal transmission;

[0063] During the signal reception process, the antenna receives a second radio frequency signal;

[0064] The low noise amplifier amplifies the second radio frequency signal to obtain an amplified radio frequency signal;

[0065] The digital frequency generation module generates a frequency hopping local oscillator at a preset frequency point;

[0066] The down-conversion module performs down-conversion processing on the amplified RF signal and the frequency-hopping local oscillator to obtain a down-converted signal;

[0067] The bandpass filter performs filtering processing on the down-converted signal to obtain a filtered signal;

[0068] The RF transceiver module processes the filtered signal to obtain the baseband signal and sends it to the FPGA;

[0069] The four-phase de-softening module in the FPGA correlates the baseband signal with four PN codes of different phases respectively to obtain the correlation sums corresponding to the four PN codes; obtains the correlation sum with the largest energy, and obtains the de-softening signal based on the PN code corresponding to the correlation sum with the largest energy; decodes and demodulates the de-softening signal to obtain the transmitted signal, thereby completing signal reception.

[0070] In the present invention, a PN code with good autocorrelation characteristics realizes four-phase soft spread spectrum of communication data. Compared with the use of two independent orthogonal PN codes, the system communication rate is improved without reducing the anti-interference performance of the spread spectrum. The method of high frequency hopping rate and random frequency hopping spectrum is adopted to improve the anti-detection ability of the system frequency hopping spectrum, and improve the anti-interference ability and stability of the system.

[0071] According to an embodiment of the present invention, the ratio of the correlation peak of the PN code with the preset spreading ratio to the corresponding phase received signal and the correlation peak of the PN code with the non-corresponding phase received signal is greater than the preset ratio. In other words, a PN code with good autocorrelation is used for phase shifting.

[0072] According to an embodiment of the present invention, the preset spreading ratio is 32, 64, 128 or 256.

[0073] like Figure 2 As shown, the present invention also provides a fast frequency hopping communication system based on four-phase soft expansion, the system includes FPGA (FMQL45T900 chip can be used), radio frequency transceiver module (B9361 radio frequency transceiver chip can be used), digital frequency generation module (DDS), up-conversion module, power amplifier (PA), antenna, low noise amplifier (LNA), down-conversion module and bandpass filter (BPF);

[0074] During the signal transmission process:

[0075] The FPGA is used to encode the transmission signal to be transmitted to obtain the encoded transmission signal; and is also used to modulate the encoded transmission signal to obtain the modulated transmission signal;

[0076] The four-phase soft spread spectrum module in the FPGA is used to perform three-time phase shift on a PN code with a preset spread spectrum ratio to obtain four PN codes with different phases; it is also used to group the modulated transmission signal in pairs according to the number of bits, and combine each group of data with the PN code of the corresponding phase in sequence to obtain a spread spectrum signal;

[0077] The FPGA is used to send the spread spectrum signal to the RF transceiver module;

[0078] The radio frequency transceiver module is used to process the spread spectrum signal to obtain a first radio frequency signal;

[0079] The digital frequency generation module is used to generate a frequency hopping local oscillator of a preset frequency point;

[0080] The up-conversion module is used to perform up-conversion processing on the first radio frequency signal and the frequency hopping local oscillator to obtain an up-converted signal;

[0081] The power amplifier is used to amplify the up-converted signal to obtain an amplified signal, and send the amplified signal to the antenna to complete signal transmission;

[0082] During signal reception:

[0083] The antenna is used to receive a second radio frequency signal;

[0084] The low noise amplifier is used to amplify the second radio frequency signal to obtain an amplified radio frequency signal;

[0085] The digital frequency generation module is used to generate a frequency hopping local oscillator of a preset frequency point;

[0086] The down-conversion module is used to perform down-conversion processing on the amplified RF signal and the frequency-hopping local oscillator to obtain a down-converted signal;

[0087] The bandpass filter is used to filter the down-converted signal to obtain a filtered signal;

[0088] The RF transceiver module is used to process the filtered signal, obtain the baseband signal, and send it to the FPGA;

[0089] The four-phase de-softening module in the FPGA is used to correlate the baseband signal with four PN codes of different phases respectively to obtain the correlation sum corresponding to each of the four PN codes; to obtain the correlation sum with the maximum energy, and to obtain the de-softening signal based on the PN code corresponding to the correlation sum with the maximum energy; and to decode and demodulate the de-softening signal to obtain the transmission signal and complete signal reception.

[0090] In order to further understand the present invention, the following Figure 3-Figure 9 The fast frequency hopping communication method and system based on four-phase soft expansion of the present invention are described in detail.

[0091] In this embodiment, the specific hardware structure of the system is as follows: Figure 3As shown, the communication link adopts time division duplex mode, and the working frequency band is 3.7-3.9GHz. In the transmitting branch, the baseband signal outputs a 2GHz RF narrowband signal through B9361, and is output to the RF power amplifier part after up-conversion. The local oscillator signal is generated by the fast hopping source DDS, and the frequency hopping frequency covers 1.7-1.9Ghz. The signal frequency after up-conversion covers 3.7-3.9GHz. In the receiving path, the communication signal is limited, amplified by LNA, and mixed to generate a 2GHz RF narrowband signal, which is output to B9361, and then output to the baseband part after frequency conversion processing and AD sampling by B9361. The local oscillator signal is generated by the fast hopping source DDS, and the frequency hopping frequency covers 1.7-1.9Ghz, thereby realizing a fixed frequency and a 2GHz narrowband signal after down-conversion. The baseband signal processing part adopts the domestically produced zynq-7000 series chip SOC processor FMQL45T900, which contains rich logic resources and 4 ARM processors to modulate, demodulate and perform time and space synchronization processing on the data link baseband signal.

[0092] The communication system of the present invention completes the non-coherent demodulation of the data segment based on the four-phase soft spread spectrum method, and performs frequency hopping for the information bit. The communication system adopts the TDMA networking method. The frame structure includes two parts: the capture header and the data load. The length of each time slot is 50ms, supporting 10 nodes. Each node sends cyclically, and one cycle is 500ms. The time slot structure is as follows Figure 4 shown.

[0093] For a subframe with a period of 50ms, a 0.9856ms protection interval is reserved at the head and a 5ms protection interval is reserved at the tail as the communication delay protection interval for the longest communication distance of 200km. The specific time for sending the signal is 44.0144ms. In 44.0144ms, the capture header length is 5ms, the data segment length is 38.4ms, and the frequency hopping protection time slot length is 0.6144ms. Each time slot sends 3072 bits of information, which is 6144 bits after LDPC encoding and is used for user information distribution and network information distribution. Specific frame structure Figure 5 shown.

[0094] In the non-coherent system, there is no need to add a short pilot header (commonly used in the fully coherent system) before each 1ms subframe to correct the phase, so the data load is continuous in the time domain. Usually, PN codes are mutually orthogonal to each other, but it is difficult to select four mutually orthogonal PNs, and the practicality is poor. Therefore, in order to simplify the system structure, the present invention uses four pseudo-random sequences (PN codes) with a spread ratio of 128 to complete four-phase soft spread, representing bit00, bit01, bit11 and bit10 after LDPC coding respectively. The four PN codes are obtained by phase shifting a PN code, and have good autocorrelation. The correlation between different PN codes after phase shifting is poor at the corresponding positions. The data load is 39.0144ms in total, and 128 jumps are sent every 1.6256ms, for a total of 3072 jumps. In each hop, if bit00 needs to be transmitted, the system sends PN00 corresponding to bit00; if bit01 needs to be transmitted, the system sends PN01 corresponding to bit01; if bit11 needs to be transmitted, the system sends PN11 corresponding to bit11; if bit10 needs to be transmitted, the system sends PN10 corresponding to bit10. At the receiving end, PN00, PN01, PN11, and PN10 are correlated with the received signal to obtain the correlation sums S00, S01, S11, and S10. The system then determines the energy of these four results. If S00 is large, it is determined to be bit00; if S01 is large, it is determined to be bit01; if S11 is large, it is determined to be bit11; and if S10 is large, it is determined to be bit10. The schematic diagram of soft expansion is as follows: Figure 6 shown. Figure 7 To design the relevant characteristics of the PN code, it is known that its autocorrelation characteristics are good. Compared with the traditional two orthogonal PN code spread spectrum, the method based on four-phase soft spread doubles the system communication rate, and the anti-interference performance remains basically unchanged.

[0095] In the data payload length of 39.0144ms, only 38.4ms of data needs to be sent, and the remaining 0.6144ms is the frequency hopping protection time slot. The DDS frequency establishment time is 60ns (60 / 1GHz)ns. Therefore, the 200ns protection time slot between each hop ensures the signal quality of the head and tail chips between each hop. Each hop sends a symbol (four-phase soft expansion after encoding). A total of 39.0144 / 1.6256*128=3072 symbols are sent in one frame, corresponding to 3072 bits of data before encoding. Under the overall frame structure of 50ms, 2048 bits of the 3072 bits are used for user transmission and 1024 bits are used for information transmission within the network, meeting the bit rate of 2048 / 50e-3=40.96Kbps. The frequency hopping frame structure of non-coherent communication is as follows: Figure 8The instantaneous hopping speed of the system is as high as 80,000 hop / s. The frequency hopping spectrum uses the default m sequence for frequency hopping in the early stage. After the communication network reaches 10 minutes, a new m sequence is generated for frequency hopping according to the synchronization time, and the node uses the new frequency hopping spectrum for frequency hopping. The invention uses a method combining high hopping speed with random frequency hopping spectrum, which is not easy to be detected by the enemy, and the anti-interference performance is more stable.

[0096] In the analog non-coherent structure, the transmitter uses the DDS+B9361 analog frequency hopping solution, and the receiver uses the DDS+B9361 method to receive the current frequency. The specific process of the receiver is that the system first controls DDS+B9361 to generate the local oscillator corresponding to the current signal frequency, so that the received signal is down-converted to a fixed intermediate frequency (2GHz), and then the receiver completes sampling through B9361 and processes the fixed frequency signal, thereby realizing the reception of the current frequency signal. The analog non-coherent structure uses a low-speed ADC, and the sampling rate only needs to be 40Mhz, which is much smaller than the sampling rate required by the full digital coherent structure.

[0097] During the operation of the simulated incoherent structure, the signal of the current frequency point is selected by adjusting the local oscillator frequency. The phase randomness problem of two adjacent jumps requires the system to adopt an incoherent demodulation method. Similar to the incoherent FSK modulation method, this system uses an incoherent four-phase soft-spread PN code to represent bit00, bit01, bit10, and bit11 respectively. Compared with the coherent system, the incoherent system has a certain performance loss, but this system is designed to contain only one symbol per jump, so the system's anti-dynamic ability is greatly enhanced (relative to the 80K jump rate, it can easily resist the 10KHz dynamic).

[0098] The analog incoherent structure can only process one frequency point at a time, so the signal of the current frequency point can be filtered out through a narrowband filter. When the interference signal falls within 200MHz, but does not fall within the bandwidth of the current signal, this system will filter out the interference through an analog filter. The analog filter can achieve an interference suppression capability of more than 30dB. The spectrum diagram of this process is shown in the figure below. Figure 2 Even if the interference signal falls within the band of the current frequency point, since this system adopts LDPC coding, the information of the current hop can be discarded, and the information loss can be compensated by the LDPC coding gain to form a correction and erasure effect.

[0099] In the data segment non-coherent demodulation, the original 128-bit PN code demodulation based on two orthogonal codes was changed to 128-bit PN code demodulation based on four-phase soft spread spectrum. After testing, when the non-coherent threshold was set to 14.5, the bit error rate was less than 1*10-5 (100 simulation cycles, a total of 6144bit*100 data); Fig. 9The figure is a relationship diagram between different incoherent demodulation thresholds and bit error rates. As the set incoherent threshold increases, the signal-to-noise ratio of the communication system increases and the bit error rate gradually decreases. When the threshold setting reaches 14.5dB, the bit error rate meets the system design requirements.

[0100] Therefore, the non-coherent demodulation method based on four-phase soft spreading has a loss of 1 to 1.5 dB compared with the two-orthogonal PN code despreading method, but improves the communication rate by 3 dB.

[0101] The present invention is mostly used for data frequency hopping and spread spectrum in military data links, and is suitable for swarm-type weapon systems. The traditional spread spectrum method is replaced by a four-phase soft spread spectrum method; based on the hardware design of RF agile frequency conversion chip and high-speed DDS, the slow hopping speed and fixed frequency hopping spectrum method are replaced by a single data bit fast hopping and random update frequency hopping spectrum method.

[0102] In summary, the present invention provides a fast frequency hopping communication method and system based on four-phase soft expansion, which has the following beneficial effects:

[0103] 1. The system communication rate is doubled (3dB) at the expense of only increasing the non-coherent demodulation threshold by 1-1.5dB;

[0104] 2. Improved the anti-interference capability of the communication system and enhanced the system's ability to resist suppressive interference.

[0105] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0106] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0107] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A fast frequency hopping communication method based on four-phase soft expansion, characterized in that: The method comprises: During the signal transmission process, the FPGA encodes the transmission signal to be transmitted to obtain an encoded transmission signal; modulates the encoded transmission signal to obtain a modulated transmission signal; The four-phase soft spread spectrum module in the FPGA performs three phase shifts on a PN code with a preset spread spectrum ratio to obtain four PN codes with different phases; the modulated transmission signal is grouped in pairs according to the number of bits, and each group of data is combined with the PN code of the corresponding phase in sequence to obtain a spread spectrum signal; The FPGA sends the spread spectrum signal to the RF transceiver module; The radio frequency transceiver module processes the spread spectrum signal to obtain a first radio frequency signal; The digital frequency generation module generates a frequency hopping local oscillator at a preset frequency point; The up-conversion module performs up-conversion processing on the first radio frequency signal and the frequency-hopping local oscillator to obtain an up-converted signal; The power amplifier amplifies the up-converted signal to obtain an amplified signal, and sends the amplified signal to the antenna to complete signal transmission; During the signal reception process, the antenna receives a second radio frequency signal; The low noise amplifier amplifies the second radio frequency signal to obtain an amplified radio frequency signal; The digital frequency generation module generates a frequency hopping local oscillator at a preset frequency point; The down-conversion module performs down-conversion processing on the amplified RF signal and the frequency-hopping local oscillator to obtain a down-converted signal; The bandpass filter performs filtering processing on the down-converted signal to obtain a filtered signal; The RF transceiver module processes the filtered signal to obtain the baseband signal and sends it to the FPGA; The four-phase de-softening module in the FPGA correlates the baseband signal with four PN codes of different phases respectively to obtain the correlation sums corresponding to the four PN codes; obtains the correlation sum with the largest energy, and obtains the de-softening signal based on the PN code corresponding to the correlation sum with the largest energy; decodes and demodulates the de-softening signal to obtain the transmitted signal, thereby completing signal reception.

2. The method according to claim 1, characterized in that The ratio of the correlation peak value between the PN code with the preset spreading ratio and the corresponding phase reception signal and the correlation peak value between the PN code with the non-corresponding phase reception signal is greater than the preset ratio.

3. The method according to claim 1, characterized in that The preset spreading ratio is 32, 64, 128 or 256.

4. A fast frequency hopping communication system based on four-phase soft expansion, characterized in that: The system includes an FPGA, a radio frequency transceiver module, a digital frequency generation module, an up-conversion module, a power amplifier, an antenna, a low noise amplifier, a down-conversion module and a bandpass filter; During the signal transmission process: The FPGA is used to encode the transmission signal to be transmitted to obtain the encoded transmission signal; and is also used to modulate the encoded transmission signal to obtain the modulated transmission signal; The four-phase soft spread spectrum module in the FPGA is used to perform three-time phase shift on a PN code with a preset spread spectrum ratio to obtain four PN codes with different phases; it is also used to group the modulated transmission signal in pairs according to the number of bits, and combine each group of data with the PN code of the corresponding phase in sequence to obtain a spread spectrum signal; The FPGA is used to send the spread spectrum signal to the RF transceiver module; The radio frequency transceiver module is used to process the spread spectrum signal to obtain a first radio frequency signal; The digital frequency generation module is used to generate a frequency hopping local oscillator of a preset frequency point; The up-conversion module is used to perform up-conversion processing on the first radio frequency signal and the frequency hopping local oscillator to obtain an up-converted signal; The power amplifier is used to amplify the up-converted signal to obtain an amplified signal, and send the amplified signal to the antenna to complete signal transmission; During signal reception: The antenna is used to receive a second radio frequency signal; The low noise amplifier is used to amplify the second radio frequency signal to obtain an amplified radio frequency signal; The digital frequency generation module is used to generate a frequency hopping local oscillator of a preset frequency point; The down-conversion module is used to perform down-conversion processing on the amplified RF signal and the frequency-hopping local oscillator to obtain a down-converted signal; The bandpass filter is used to filter the down-converted signal to obtain a filtered signal; The RF transceiver module is used to process the filtered signal, obtain the baseband signal, and send it to the FPGA; The four-phase de-softening module in the FPGA is used to correlate the baseband signal with four PN codes of different phases respectively to obtain the correlation sum corresponding to each of the four PN codes; to obtain the correlation sum with the maximum energy, and to obtain the de-softening signal based on the PN code corresponding to the correlation sum with the maximum energy; and to decode and demodulate the de-softening signal to obtain the transmission signal and complete signal reception.

5. The method according to claim 4, characterized in that The ratio of the correlation peak value between the PN code with the preset spreading ratio and the corresponding phase reception signal and the correlation peak value between the PN code with the non-corresponding phase reception signal is greater than the preset ratio.

6. The method according to claims 4 and 5, characterized in that The preset spreading ratio is 32, 64, 128 or 256.

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