A dual-mode frequency hopping communication system based on module reuse

Abstract

This invention provides a dual-mode frequency-hopping communication system based on module multiplexing, relating to the field of wireless communication technology. The dual-mode frequency-hopping communication system of this invention includes a first transmitting end comprising an input control module, a second transmitting end comprising a pseudo-random sequence-based frequency-hopping communication subsystem, and a third transmitting end comprising a differential frequency-hopping communication subsystem; the first receiving end comprises a second receiving end comprising a pseudo-random sequence-based frequency-hopping communication subsystem, a third receiving end comprising a differential frequency-hopping communication subsystem, and an output control module; this invention transmits baseband data to different subsystems to generate communication signals according to control signals input by the transmitting host computer; and selects the corresponding subsystem to receive and demodulate the communication signals according to control signals input by the receiving host computer to obtain baseband data. This invention combines pseudo-random sequence-based frequency-hopping communication and differential frequency-hopping communication functions, improving the flexibility and environmental adaptability of the communication process and effectively saving hardware resources.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, and specifically relates to a dual-mode frequency hopping communication system based on module multiplexing. Background Technology

[0002] Frequency hopping communication (FQH) is a typical spread spectrum communication technique that transmits information by modulating it onto a carrier wave whose frequency varies over time, within a frequency range much larger than the signal bandwidth. Based on the principle of evasion, FQH has strong anti-interception and anti-interference capabilities. Conventional FQH systems use pseudo-random sequences to generate the FQH pattern, resulting in periodic changes in the carrier frequency, which poses a certain risk of identification under long-term reception conditions. Differential frequency hopping (DFM) is a special type of FQH that uses the information to be transmitted and the G-function rule to generate a FQH pattern to control the carrier frequency transitions. Its core principle is to transmit information using carrier frequency changes. The FQH pattern is random, providing stronger anti-interference capabilities, but the data transmission rate is lower than that of conventional FQH.

[0003] Conventional frequency-hopping communication technology and differential frequency-hopping communication technology have different characteristics due to their different information transmission mechanisms. The former has a higher data transmission rate but is subject to certain interception risks; the latter has a relatively lower data transmission rate but stronger resistance to tracking interference and interception. If the two can be combined to build a dual-mode frequency-hopping communication system, and the corresponding communication mode can be selected according to different communication needs, the communication performance in complex electromagnetic environments can be ensured, and the flexibility and adaptability of the communication process can be improved. Summary of the Invention

[0004] To address the need for improved flexibility and adaptability in frequency hopping communication technology, this invention provides a dual-mode frequency hopping communication system based on module multiplexing, involving a differential frequency hopping communication system and a frequency hopping communication system based on pseudo-random sequences, including a first transmitting end and a first receiving end;

[0005] The first transmitting end includes an input control module, a second transmitting end of a pseudo-random sequence-based frequency hopping communication subsystem, and a third transmitting end of a differential frequency hopping communication subsystem;

[0006] The first receiving end includes a second receiving end of a pseudo-random sequence-based frequency hopping communication subsystem, a third receiving end of a differential frequency hopping communication subsystem, and an output control module;

[0007] The input control module is used to send the baseband data input by the sender to the differential frequency hopping communication subsystem or the frequency hopping communication subsystem based on pseudo-random sequences according to the control signal input by the sender's host computer; the differential frequency hopping communication subsystem and the frequency hopping communication subsystem based on pseudo-random sequences are used to generate communication signals and send them to the first receiving end;

[0008] The output control module is used to select the corresponding differential frequency hopping communication subsystem or the pseudo-random sequence-based frequency hopping communication subsystem to receive communication signals according to the control signals input by the host computer of the receiver; the differential frequency hopping communication subsystem and the pseudo-random sequence-based frequency hopping communication subsystem are used to demodulate the communication signals, obtain baseband data and send it to the receiver.

[0009] Furthermore, the second transmitter of the pseudo-random sequence-based frequency hopping communication subsystem and the third transmitter of the differential frequency hopping communication subsystem include a shared instruction decoder and frequency synthesizer;

[0010] The instruction decoder is used to convert the shift register state generated by the pseudocode generator into a frequency control word or to... The frequency hopping pattern state generated by the function module is converted into a frequency control word; the frequency synthesizer is used to generate a frequency hopping carrier signal based on the frequency control word.

[0011] Furthermore, the second transmitting end of the frequency hopping communication subsystem based on pseudo-random sequences also includes a modulator, a pseudo-code generator, and a mixer;

[0012] The modulator is used to modulate the baseband data to be transmitted, obtain the intermediate frequency modulated signal, and send it to the mixer; the pseudocode generator is used to generate the shift register state and send it to the instruction decoder; the mixer is used to mix the intermediate frequency modulated signal output by the modulator and the frequency hopping carrier signal to obtain the communication signal and send it to the receiver of the frequency hopping communication subsystem based on pseudo-random sequence.

[0013] Furthermore, the third transmitter of the differential frequency hopping communication subsystem also includes a bit symbol converter and Function modules;

[0014] A bit symbol converter is used to convert serial baseband data into parallel transmission symbols; The function module is used to calculate the frequency hopping pattern state of the next hop based on the frequency hopping pattern state of the previous hop and the current transmitted symbol.

[0015] Furthermore, the second receiver of the pseudo-random sequence-based frequency hopping communication subsystem and the third receiver of the differential frequency hopping communication subsystem share a common FFT module, peak searcher, and frequency detector.

[0016] The FFT module is used to perform FFT processing on the received communication signal to obtain the spectrum distribution result; the peak searcher is used to detect the spectrum distribution result to obtain the instantaneous signal frequency peak; the frequency point detector identifies the frequency hopping carrier frequency estimate of the received signal.

[0017] Furthermore, the second receiver of the frequency hopping communication subsystem based on pseudo-random sequences also includes a frequency change detection module, a pseudo-code generator, an instruction decoder, a frequency synthesizer, a mixer, and a demodulator;

[0018] The frequency change detection module is used to perform synchronous acquisition and synchronous tracking processing based on the change of the carrier frequency estimate, and controls the pseudo-code generator, instruction decoder and frequency synthesizer to generate local frequency hopping carrier signals; the mixer is used to process the local frequency hopping carrier information to obtain a modulated signal with a fixed frequency; the demodulator demodulates the modulated signal to obtain baseband data.

[0019] Furthermore, the third receiver of the differential frequency hopping communication subsystem also includes Function modules and sign bit converters;

[0020] The function module is used to demodulate the transmission symbols based on the frequency estimation of the frequency hopping carrier; the symbol bit converter is used to convert the transmission symbols into baseband data.

[0021] Furthermore, the first receiver of the module-multiplexed dual-mode frequency hopping communication system achieves frequency hopping synchronization with the first transmitter of the module-multiplexed dual-mode frequency hopping communication system based on a fast acquisition algorithm for dual-frequency hopping point decision. The fast acquisition algorithm for dual-frequency hopping point decision includes:

[0022] The FFT module is used to perform multiple FFT processes on the received signal, converting the time-domain received signal into a frequency-domain signal.

[0023] A peak searcher is used to calculate the power spectrum of each frequency point by performing the sum of squares of the real and imaginary parts for each frequency index of the frequency domain signal; local maxima are searched in the power spectrum of each FFT output and the corresponding peak frequency index is recorded.

[0024] In a frequency hopping communication subsystem based on pseudo-random sequences, a frequency change detection module is used to obtain continuous... The peak frequency index obtained from the first FFT process is used to calculate the difference between adjacent indices. If the difference between adjacent indices meets the stability condition, the current frequency hopping point is successfully identified. The information of the current frequency hopping point is recorded, and the local m-sequence is preset as the next state of the identified current frequency hopping point. After the current frequency hopping point is identified, the monitoring of subsequent identified frequency hopping points continues. When the difference between adjacent indices is detected to be within the hopping detection range, it is determined that the carrier frequency of the first transmitter has hopped. The local m-sequence is synchronously hopping with the first transmitter according to the predetermined frequency hopping pattern to complete the acquisition process.

[0025] The beneficial effects of adopting the above technical solution are as follows: The dual-mode frequency hopping communication system based on module reuse provided by the present invention is based on the structured and modular concept of FPGA platform. By reusing instruction decoder, frequency synthesizer, FFT module, peak searcher and frequency detector, it realizes signal generation function and frequency detection function. It has both pseudo-random sequence-based frequency hopping communication function and differential frequency hopping communication function, improves the flexibility and environmental adaptability of the communication process, and effectively saves hardware resources. Attached Figure Description

[0026] Figure 1 Flowchart of the fast acquisition algorithm for dual-hop frequency point decision provided in Embodiment 1 of the present invention;

[0027] Figure 2 A schematic diagram of time-domain and FFT analysis of frequency hopping signals provided in Embodiment 1 of the present invention;

[0028] Figure 3 A schematic diagram of the overall architecture of a dual-mode frequency hopping communication system based on module reuse provided in Embodiment 1 of the present invention;

[0029] Figure 4 The RTL-level circuit structure diagram of the input control module provided in Embodiment 1 of the present invention;

[0030] Figure 5 The RTL-level circuit structure diagram of the output control module provided in Embodiment 1 of the present invention;

[0031] Figure 6 The MSK modulation principle structure block diagram provided in Embodiment 1 of the present invention;

[0032] Figure 7 The RTL stage circuit structure diagram of the MSK modulator provided in Embodiment 1 of the present invention;

[0033] Figure 8 The pseudocode generator RTL stage circuit structure diagram provided in Embodiment 1 of the present invention;

[0034] Figure 9 The RTL stage circuit structure diagram of the instruction decoder provided in Embodiment 1 of the present invention;

[0035] Figure 10 The frequency synthesizer DDS IP core configuration interface provided in Embodiment 1 of this invention;

[0036] Figure 11 The mixer FIR IP core configuration interface provided in Embodiment 1 of this invention;

[0037] Figure 12 The RTL stage circuit structure diagram of the bit symbol converter provided in Embodiment 1 of the present invention;

[0038] Figure 13 The RTL-level circuit structure diagram of the G-function module provided in Embodiment 1 of the present invention;

[0039] Figure 14 The FFT IP core configuration interface of the FFT module in the first receiver of the dual-mode frequency hopping communication system based on module multiplexing provided in Embodiment 1 of the present invention;

[0040] Figure 15 The RTL stage circuit structure of the peak seeker provided in Embodiment 1 of the present invention;

[0041] Figure 16 The RTL-level circuit structure of the frequency detector provided in Embodiment 1 of the present invention;

[0042] Figure 17 The RTL-level circuit structure diagram of the frequency change detection module provided in Embodiment 1 of the present invention;

[0043] Figure 18 The RTL stage structure diagram of the demodulator provided in Embodiment 1 of the present invention;

[0044] Figure 19 The present invention provided in Embodiment 1 RTL structure diagram of a function module;

[0045] Figure 20 The modulator output waveform diagram provided in Embodiment 1 of the present invention;

[0046] Figure 21 The pseudo-random sequence generated by the pseudo-code generator provided in Embodiment 1 of the present invention;

[0047] Figure 22 The frequency hopping carrier signal switching waveform provided in Embodiment 1 of the present invention;

[0048] Figure 23 The instantaneous frequency hopping communication signal waveform based on pseudo-random sequence provided in Embodiment 1 of the present invention;

[0049] Figure 24 The FFT module output results provided in Embodiment 1 of this invention;

[0050] Figure 25 The peak searcher output result provided in Embodiment 1 of the present invention;

[0051] Figure 26 The frequency point detector processing result provided in Embodiment 1 of the present invention;

[0052] Figure 27 The frequency change detection module provided in Embodiment 1 of this invention outputs the results.

[0053] Figure 28 The demodulator processing result provided in Embodiment 1 of the present invention;

[0054] Figure 29 The bit symbol converter output result provided in Embodiment 1 of the present invention;

[0055] Figure 30 The output result of the G function module provided in Embodiment 1 of this invention;

[0056] Figure 31 Waveform diagram of differential frequency hopping communication signal provided in Embodiment 1 of the present invention;

[0057] Figure 32 The FFT module output results provided in Embodiment 1 of this invention;

[0058] Figure 33 The frequency sequence recognition module provided in Embodiment 1 of the present invention detects frequency control words;

[0059] Figure 34 The present invention provided in Embodiment 1 The function module outputs the results;

[0060] Figure 35 The parallel-to-serial conversion module provided in Embodiment 1 of this invention outputs the waveform.

[0061] Figure 36 The comparison results of FPGA resource consumption provided in Embodiment 1 of this invention;

[0062] Figure 37 Simulation results of frequency hopping patterns provided in Embodiment 1 of the present invention;

[0063] Figure 38 Time-domain waveform diagram of frequency hopping communication signal provided in Embodiment 1 of the present invention;

[0064] Figure 39 The frequency domain amplitude spectrum simulation results of a single FFT provided in Embodiment 1 of this invention;

[0065] Figure 40 The frequency hopping carrier frequency detection trajectory provided in Embodiment 1 of the present invention;

[0066] Figure 41 The comparison chart of signal detection accuracy under different signal-to-noise ratios provided in Embodiment 1 of the present invention. Detailed Implementation

[0067] The specific implementation methods of this application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0068] Example 1:

[0069] In a frequency-hopping communication system based on pseudo-random sequences, both the transmitter and receiver generate the same frequency-hopping pattern using a pre-defined pseudo-random sequence. The receiver utilizes the periodicity of the pseudo-random sequence to lock the phase of the pseudo-random sequence and the carrier frequency and phase through a synchronous acquisition and tracking process, thereby achieving signal demodulation.

[0070] In a frequency-hopping communication system, the pseudo-random sequence generated by the transmitter's pseudo-code generator changes over time. Within each hop cycle, the shift register output state of the pseudo-code generator is converted by the instruction decoder to generate the corresponding frequency control word, driving the frequency synthesizer to output a time-varying frequency-hopping carrier signal. The baseband data, after modulation by the modulator, is mixed with the frequency-hopping carrier signal and finally amplified before being transmitted by the transmitting antenna. The receiver uses an antenna to receive the frequency-hopping communication signal. After frequency-hopping synchronization acquisition and tracking processing, it controls the pseudo-code generator to generate a pseudo-random sequence in phase with the received frequency-hopping communication signal. The frequency synthesizer then generates a local synchronization carrier, which, after processing by a mixer and an intermediate frequency filter, yields a modulated signal with a fixed frequency. Finally, a demodulator demodulates the transmitted baseband data.

[0071] Frequency hopping synchronization is the core processing step in a frequency hopping communication system. It involves capturing and tracking the pseudo-random sequence controlling the carrier frequency hopping in the received frequency hopping communication signal to align the frequency hopping pattern. This is followed by generating a local carrier for mixing and intermediate frequency (IF) filtering to obtain a fixed-frequency IF modulated signal, which is then demodulated to acquire the baseband information for transmission.

[0072] Traditional acquisition techniques mainly include two schemes: sliding correlation acquisition and parallel search acquisition. Sliding correlation acquisition controls the local pseudo-random sequence and the pseudo-random sequence in the received frequency-hopping communication signal to slide relative to each other. When their phases are synchronized, the sliding process ends, and synchronous acquisition is completed. Parallel search acquisition uses a matched filter structure. By setting a bandpass filter bank with the same number of frequency-hopping carriers, the output signals of all filters are processed simultaneously and joint decision is performed, so as to detect the phase of all pseudo-random sequences at the same time, which significantly improves the acquisition speed.

[0073] Sliding correlation capture technology is simple in principle, but its capture timeliness is poor. Its average capture time increases linearly with the expansion of the pseudo-random sequence period and the range of initial phase uncertainty, which cannot meet the requirements for fast capture. Parallel search capture technology adopts a "resource-for-time" design strategy, which can theoretically reduce the average capture time to a minimum, but it consumes a lot of hardware resources and is limited in applications that are sensitive to cost and power consumption.

[0074] In summary, the two existing mainstream frequency hopping synchronization acquisition technologies cannot achieve a balance between acquisition speed and resource efficiency, and thus cannot meet the comprehensive requirements of modern high-speed frequency hopping communication systems for high efficiency, low power consumption, and high flexibility.

[0075] To address the aforementioned issues, this embodiment establishes a dual-frequency-hopping point decision-based fast acquisition algorithm. Based on FFT (Fast Fourier Transform), it performs spectral analysis on the received frequency-hopping communication signal to identify the instantaneous carrier frequency of the received signal. This allows for the reverse determination of the frequency control word, thereby obtaining the shift register state of the pseudocode generator. The core of this algorithm is to transform the synchronization acquisition process from the traditional "time-domain sequence comparison" to an efficient "frequency-domain frequency positioning".

[0076] In a frequency-hopping communication system based on pseudo-random sequences, the system clock drives a local pseudocode generator to continuously update its state, forming a frequency-hopping pattern. Each state is uniquely mapped to the transmit carrier frequency through a pre-shared frequency-hopping mapping table. The core task of the receiver is to quickly locate the current frequency hopping frequency when the starting point of time is unknown, and determine its position in the frequency-hopping sequence accordingly to complete synchronization acquisition.

[0077] This embodiment of the dual-hop frequency point decision-based fast acquisition algorithm fully utilizes the high-speed spectrum analysis capability of the digital receiver, transforming the synchronization establishment mechanism from traditional time-domain sequence comparison to more efficient frequency-domain positioning, and establishing the dual-hop frequency point decision-based fast acquisition algorithm, such as... Figure 1 As shown, it includes the following steps:

[0078] Step 1: Use the FFT module to perform multiple FFT processes on the received signal to convert the time-domain received signal into a frequency-domain signal;

[0079] Step 2: Use the peak searcher to calculate the power spectrum of each frequency point by performing the sum of squares of the real and imaginary parts for each frequency index of the frequency domain signal;

[0080] Step 3: In the power spectrum of each FFT output, search for local maxima and record the corresponding peak frequency indices. ;

[0081] Step 4: In the frequency hopping communication subsystem based on pseudo-random sequences, the frequency change detection module is used to obtain continuous... Peak frequency index obtained from the first FFT process Calculate the difference between adjacent indices ;

[0082] Step 5: If the difference between adjacent indices meets the stability condition, the current frequency hopping point is successfully identified; the information of the current frequency hopping point is recorded, and the local m-sequence is preset as the next state of the identified current frequency hopping point. The system enters the waiting to start tracking mode. Through multiple confirmations, the frequency jitter caused by noise is effectively suppressed, ensuring the reliability of the determination.

[0083] The stability condition is: , To identify the current frequency point that meets the conditions;

[0084] Step 6: After identifying the current frequency hopping point, continue to monitor the frequency hopping points identified by the subsequent adjacent FFTs; when the difference between adjacent indices is detected to be within the hopping detection range, it is determined that the carrier frequency of the transmitting end has hopped; the receiving end sends a start signal to the local m-sequence, so that it follows the transmitting end to hop synchronously according to the predetermined frequency hopping pattern, thus completing the acquisition process;

[0085] Among them, the jump detection range is , This is the lower limit of the jump detection range. This represents the upper limit of the jump detection range;

[0086] The primary purpose of frequency hopping communication subsystems based on pseudo-random sequences in detecting frequency changes is to achieve synchronous tracking of the frequency hopping pattern. Upon detecting a frequency change, the system initiates synchronous tracking to align the frequency hopping rhythms of the transmitting and receiving parties. In contrast, differential frequency hopping communication subsystems do not require a fixed pseudo-random frequency hopping pattern for synchronization. Therefore, as long as the frequency of each hop can be detected, information demodulation can be completed through the transition relationships between frequency points, making them insensitive to the instantaneous nature of frequency changes.

[0087] Specifically, this embodiment addresses the received signal. Sampling is performed to obtain discrete signals. And time-frequency conversion is achieved through multiple FFTs, as shown in the following formula (1):

[0088] (1);

[0089] in, The total number of frequency points in the FFT. For the index of the time-domain sampling points, Indicates the first Complex spectral values ​​at each frequency point;

[0090] After multiple FFT processes, the power spectral density at each frequency point is obtained by calculating the sum of squares of the real and imaginary parts, as shown in the following formula (2):

[0091] (2);

[0092] in, The number of times the FFT is performed in one hop time. For the first Frequency index of the second FFT, For the real part, The virtual part, For the first sequence Power spectral density at each frequency point;

[0093] By searching for local maxima as peak frequencies and recording the corresponding peak frequency indices, the power spectral density of the peak frequency indices satisfies the condition shown in formula (3) below:

[0094] (3);

[0095] in, The preset decision threshold;

[0096] Based on the above process, the peak frequency index set is obtained. As shown in formula (4):

[0097] (4);

[0098] in, The first Peak frequency index of the next FFT;

[0099] Compare adjacent peak frequency indices in chronological order and calculate the difference between adjacent indices. As shown in equation (5):

[0100] (5);

[0101] like Figure 2 As shown, it is set that it can be performed within one jump time. If the carrier frequencies detected after FFT within a single hop are the same, then the continuity is satisfied. Difference between adjacent indices If all conditions are met, then the current frequency hopping point is identified. Based on the frequency hopping pattern agreed upon by both communicating parties, its location can be determined. If the condition is not met, FFT processing and carrier frequency search continue.

[0102] Once the carrier frequency of the current hopping signal is identified and the position corresponding to the current hop in the frequency hopping pattern is located, it is necessary to determine when to initiate the tracking process and control the local oscillator to generate a changing local carrier. Considering that the position of the time window signal corresponding to the currently detected carrier frequency in the current hopping signal cannot be predicted, the transition times of adjacent hops are continuously compared and detected. When the next hop signal is input, a local carrier of the corresponding frequency is generated, and the tracking process begins. The dual-hop frequency point decision fast acquisition algorithm can detect the instantaneous carrier frequency of the received frequency hopping communication signal through FFT processing, quickly detect the frequency control word, and achieve fast synchronization acquisition.

[0103] In differential frequency hopping communication technology, the transmitting end does not directly modulate information onto the carrier wave, but instead utilizes the transmitted information through... The function directly generates the frequency control word, making the frequency hopping of the differential frequency hopping communication signal carrier frequency related to the transmitted information. Therefore, it does not have a fixed frequency hopping pattern and possesses good pseudo-randomness. The receiver employs a wideband reception scheme, detecting all frequency hopping points and inputting the continuous-time differential frequency hopping communication signal carrier frequency. The function demodulates the transmitted information to obtain the transmitted data. In a differential frequency hopping communication system, the transmitting end transforms the baseband data using a bit symbol converter to obtain the transmitted symbols, according to... The function mapping rules generate a frequency control word, which controls the frequency synthesizer to produce a differential frequency hopping communication signal, which is then transmitted via an antenna. The receiving end receives the signal via the antenna and performs frequency detection to identify the carrier frequency of the received differential frequency hopping communication signal. The function demodulates the transmitted symbols, which are then processed by a bit-symbol converter to obtain the transmitted baseband data. Differential frequency hopping communication technology does not require synchronization processing; it transmits information only by utilizing the frequency changes of adjacent hopping signal carriers. Since it does not have a fixed frequency hopping pattern, it possesses stronger anti-tracking interference characteristics. The frequency detection function at the receiver can be implemented using FFT, which is the same as the frequency detection function of the dual-hop point decision fast acquisition algorithm, thus allowing for functional reuse.

[0104] Frequency hopping communication systems based on pseudo-random sequences and differential frequency hopping communication systems have different communication mechanisms and different anti-interference performance, making them suitable for different communication needs. For the design requirements of dual-mode frequency hopping communication systems, traditional design methods involve designing separate communication signal generation and reception functional units for the two communication modes, switching between them according to user selection.

[0105] Since both the pseudo-random sequence-based frequency hopping communication signal reception and processing process of the dual-frequency hopping point decision fast acquisition algorithm and the differential frequency hopping communication signal reception and processing process can use FFT for spectrum analysis to obtain the received signal carrier frequency, and then perform synchronization acquisition or... The function demodulates the transmitted baseband data. Meanwhile, the signal generation process of both pseudo-random sequence-based frequency hopping communication systems and differential frequency hopping communication systems involves generating a frequency hopping pattern, generating a corresponding frequency control word based on the pattern, and controlling the frequency synthesizer to generate the frequency hopping signal.

[0106] In view of this, in order to improve the utilization of hardware resources, this embodiment proposes a dual-mode frequency hopping communication system based on module reuse. Based on the FPGA platform, the instruction decoder and frequency synthesizer of the frequency hopping communication signal generation process are reused at the transmitting end. At the receiving end, the frequency point detection function of the dual frequency hopping point decision fast acquisition algorithm and the FFT module, peak searcher and frequency point detector used by the frequency detection function of the differential frequency hopping signal are reused, which effectively saves hardware resources.

[0107] This embodiment of the dual-mode frequency hopping communication system based on module reuse adopts a design method that combines hierarchical and modular approaches, such as... Figure 3 As shown, it includes a first transmitting end and a first receiving end; the first transmitting end includes an input control module, a second transmitting end of a pseudo-random sequence-based frequency hopping communication subsystem and a third transmitting end of a differential frequency hopping communication subsystem; the first receiving end includes a second receiving end of a pseudo-random sequence-based frequency hopping communication subsystem, a third receiving end of a differential frequency hopping communication subsystem and an output control module;

[0108] The input control module is used to output the baseband data input by the transmitter to the differential frequency hopping communication subsystem or the frequency hopping communication subsystem based on pseudo-random sequences, according to the control signals input by the transmitter's host computer, and to output an enable signal to drive the corresponding subsystem to work and generate communication signals; the RTL-level circuit structure of the input control module in this embodiment is as follows: Figure 4 As shown.

[0109] The output control module is used to drive the corresponding subsystem to demodulate the received communication signal according to the control signal input by the host computer of the receiver, and output the demodulated baseband data to the receiver; the RTL level circuit structure of the output control module in this embodiment is as follows: Figure 5 As shown.

[0110] The second transmitter of the pseudo-random sequence-based frequency hopping communication subsystem and the third transmitter of the differential frequency hopping communication subsystem share an instruction decoder and a frequency synthesizer; the second transmitter of the pseudo-random sequence-based frequency hopping communication subsystem also includes a modulator, a pseudo-code generator, and a mixer; the third transmitter of the differential frequency hopping communication subsystem also includes a bit symbol converter and... Function modules;

[0111] The instruction decoder is used to convert the shift register state generated by the pseudocode generator into a frequency control word or to... The frequency hopping pattern state generated by the function module is converted into a frequency control word; the frequency synthesizer is used to generate a frequency hopping carrier signal based on the frequency control word.

[0112] In the second transmitting end of the frequency hopping communication subsystem based on pseudo-random sequences, the modulator is used to modulate the baseband data to be transmitted to obtain an intermediate frequency modulated signal and send it to the mixer; the pseudo-code generator is used to generate the shift register state and send it to the instruction decoder; the mixer is used to mix the intermediate frequency modulated signal output by the modulator and the frequency hopping carrier signal to obtain a communication signal and send it to the second receiving end of the frequency hopping communication subsystem based on pseudo-random sequences.

[0113] Specifically, in the frequency hopping communication subsystem based on pseudo-random sequences, the second transmitter includes a modulator, a pseudo-code generator, an instruction decoder, a frequency synthesizer, and a mixer.

[0114] The modulator is used to modulate the baseband data. In this example, the frequency hopping communication system based on pseudo-random sequences uses MSK modulation. The block diagram of MSK modulation principle is shown below. Figure 6 As shown, the RTL stage circuit structure of the MSK modulator is as follows: Figure 7 As shown.

[0115] The pseudocode generator uses a ten-stage shift register to generate a frequency hopping pattern, and the primitive polynomial is shown in equation (6):

[0116] (6);

[0117] in, These are position symbols used to describe the different levels of registers involved in the feedback;

[0118] The 3rd, 6th, and 7th bits are selected to form a 3-bit state as the output to generate the frequency hopping pattern. The RTL stage circuit structure of the pseudocode generator implemented according to equation (6) is as follows. Figure 8 As shown.

[0119] The instruction decoder in this embodiment is a multiplexing module used in the pseudo-random sequence-based frequency hopping communication subsystem to convert the shift register states generated by the pseudo-code generator into different frequency control words. In this example, the frequency hopping bandwidth of the pseudo-random sequence-based frequency hopping communication subsystem is set to 8MHz, the frequency hopping range is 11~18MHz, and the interval between each frequency hopping point is 1MHz. The frequency control words and actual frequencies corresponding to the 3 bits and 8 different states output by the pseudo-code generator are shown in Table 1. The RTL-level circuit structure of the designed and implemented instruction decoder is as follows. Figure 9 As shown.

[0120] Table 1. Explanation of Frequency Control Word Mapping Table;

[0121]

[0122] The frequency synthesizer is implemented using the DDS IP core in the FPGA, with the specific configuration as follows: Figure 10 As shown in the figure. The system clock is set to 100 MHz, the phase width is configured to 16 bits, one output channel is enabled, the mode of operation is set to Standard, the phase increment programmability is set to programmable, and the phase offset programmability is set to none.

[0123] The mixer includes a multiplier and an FIR filter, where the FIR filter is implemented using an FPGA's FIR IP core. The IP core parameters are set as follows: Figure 11 As shown in the figure. The input sampling frequency and system clock are both set to 100 MHz, high-pass filtering is used, and integer coefficient quantization is selected for coefficient analysis. The coefficients of each order of the filter are shown in the figure. Figure 11 The Coefficient Vector is shown in the figure.

[0124] In the third transmitter of the differential frequency hopping communication subsystem, a bit symbol converter is used to convert serial baseband data into parallel transmission symbols; The function module is used to calculate the frequency hopping pattern state of the next hop based on the frequency hopping pattern state of the previous hop and the current transmitted symbol;

[0125] Specifically, the third transmitter of the differential frequency hopping communication subsystem includes a bit symbol converter, a G-function module, an instruction decoder, and a frequency synthesizer. The bit symbol converter is responsible for converting the input serial baseband data into parallel transmission symbols. According to the G-function module configured in this example, 2 bits of symbols are transmitted each time, meaning the serial data stream is converted into parallel data every 2 bits. The RTL-level circuit structure of the bit symbol converter designed and implemented in this example is as follows: Figure 12 As shown.

[0126] The G-function module, as the core unit for generating differential frequency hopping signals, maps the baseband data to be transmitted to a frequency control word. This embodiment employs a G-function implementation scheme based on congruence theory, assuming that the three baseband data bits transmitted in each hop are... The encoded result is The encoding method is That is, when When it is 1 =-1, when When it is 0 =1; the previous hop signal frequency hopping pattern state is The current frequency hopping pattern state of the hopping signal is .

[0127] The G function is shown in the following formula (7):

[0128] (7);

[0129] Results after different encodings The frequency control word changes under the input conditions are shown in Table 2 below.

[0130] Table 2. Frequency control word variation under different input conditions;

[0131]

[0132] Based on the input baseband data information bits The value is used to calculate the current frequency hopping pattern state of the hopping signal using formula (7). Then, based on the current frequency hopping pattern status of the hopping signal... Locate the corresponding frequency control word to control the frequency synthesizer to output the carrier frequency of the differential frequency hopping communication signal. The RTL-level circuit structure of the G function module in this example is as follows: Figure 13 As shown.

[0133] The instruction decoder and frequency synthesizer in the third transmitter of the differential frequency hopping communication subsystem are the same as those in the second transmitter of the pseudo-random sequence-based frequency hopping communication subsystem, and will not be described again here.

[0134] The second receiver of the pseudo-random sequence-based frequency hopping communication subsystem and the third receiver of the differential frequency hopping communication subsystem share an FFT module, a peak searcher, and a frequency detector. The second receiver of the pseudo-random sequence-based frequency hopping communication subsystem also includes a frequency change detection module, a pseudo-code generator, an instruction decoder, a frequency synthesizer, a mixer, and a demodulator. The third receiver of the differential frequency hopping communication subsystem also includes... Function modules and sign bit converters;

[0135] The FFT module is used to perform FFT processing on the received communication signal to obtain the spectrum distribution result; the peak searcher is used to detect the instantaneous signal frequency peak value from the spectrum distribution result; the frequency point detector is used to identify the frequency hopping carrier frequency estimate of the received signal.

[0136] In the second receiver of the frequency hopping communication subsystem based on pseudo-random sequences, the frequency change detection module is used to perform synchronous acquisition and synchronous tracking processing based on the change of the carrier frequency estimate, and controls the pseudo-code generator, instruction decoder and frequency synthesizer to generate local frequency hopping carrier signals; the mixer is used to process the local frequency hopping carrier information to obtain a modulated signal with a fixed frequency; the demodulator demodulates the modulated signal to obtain baseband data.

[0137] Specifically, the second receiver of the frequency hopping communication subsystem based on pseudo-random sequences includes an FFT module, a peak searcher, a frequency detector, a frequency change detection module, a pseudo-code generator, an instruction decoder, a frequency synthesizer, a mixer, a demodulator, and an output control module.

[0138] In the second receiver of the pseudo-random sequence-based frequency hopping communication subsystem of this embodiment, the FFT module is implemented using the FFT IP core of the FPGA. The IP core parameter settings of the FFT module in the first receiver of the dual-mode frequency hopping communication system based on module multiplexing are as follows: Figure 14As shown. Here, Number of Channels is 1, Transform Length is 1024, Target Clock Frequency is 100MHz, System Clock is 100MHZ, Architecture choice is Automatically Select, Data Format is Fixed Point, Scaling Options are Block FloatingPoint, Rounding Modes are Convergent Rounding, input data bit width is 32 bits, and XK_INDEX and Non Real Time are checked.

[0139] The peak searcher is used to detect the instantaneous signal frequency peak value from the spectral distribution results processed by the FFT module. It is the core decision unit of the frequency hopping synchronization system. The FFT module processes 1024 points per FFT operation. Based on the conjugate symmetry characteristic of the FFT output results, the peak searcher in this example only searches the first 512 FFT output results. The RTL-level circuit structure of the peak searcher designed and implemented in this example is as follows. Figure 15 As shown.

[0140] The frequency detector calculates the instantaneous signal carrier frequency by receiving the peak values ​​of the spectral distribution and the index number corresponding to the maximum peak value output by the peak searcher. The RTL-level circuit structure of the frequency detector implemented in this example is as follows: Figure 16 As shown.

[0141] The frequency change detection module is the timing control core of the dual-hop frequency decision-making fast acquisition algorithm, responsible for maintaining the system's synchronization state and accurately managing frequency switching timing. Based on changes in the estimated carrier frequency, the frequency change detection module performs synchronization acquisition and tracking processing, controlling the pseudo-code generator, instruction decoder, and frequency synthesizer to generate a local frequency-hopping carrier signal.

[0142] To achieve precise timing control, the frequency change detection module employs a finite state machine. This state machine manages frequency hopping synchronization through four core states: In the IDLE state, the system initializes and waits for the signal carrier frequency output by the frequency detector, while simultaneously resetting all counters and storage units; upon entering the READY_NEXT state, a configurable timer is started, and the shift register state in the pseudocode generator corresponding to the next hop frequency hopping pattern is calculated. This shift register state is then written to the pseudocode generator via a pre-loading mechanism; the JUMPING state generates a globally synchronized pulse with precise timing, using the rising edge as a reference to synchronously drive the pseudocode transmitter to generate a new frequency control word, driving the instruction decoder and frequency synthesizer to generate a local frequency hopping carrier; the MSEQ_ACTIVE state maintains the current frequency output, continuously hopping frequencies and monitoring the signal carrier frequency state, providing a basis for subsequent state transitions. By utilizing the state machine's strict timing logic and synchronization capture mechanism, precise alignment between the transmitter and receiver in both the time and frequency domains is ensured, achieving frequency hopping synchronization. The RTL-level circuit structure of the frequency change detection module designed and implemented in this example is as follows: Figure 17 As shown.

[0143] The pseudocode generator, instruction decoder, and frequency synthesizer of the second receiver of the pseudo-random sequence-based frequency hopping communication subsystem are the same as those of the transmitter. The mixer's basic parameters are the same as those of the second transmitter of the pseudo-random sequence-based frequency hopping communication subsystem, except that the filter type is low-pass. These will not be described in detail here.

[0144] The demodulator employs a coherent demodulation scheme based on a squared-ring. The RTL-level structure of the demodulator designed and implemented in this example is as follows: Figure 18 As shown.

[0145] The third receiver of the differential frequency hopping communication subsystem includes an FFT module, a peak searcher, and a frequency detector. The module includes a function module, a sign bit converter, and an output control module. The function module is used to demodulate the transmission symbols based on the frequency estimation of the frequency hopping carrier, and the symbol bit converter is used to convert the transmission symbols into baseband data. The FFT module, peak searcher, and frequency detector have the same functions as the corresponding modules of the second receiver of the frequency hopping communication subsystem based on pseudo-random sequences, and will not be described in detail here.

[0146] The function module implements the inverse transform function of the G function module, used for demodulating transmitted baseband data. Based on the G function expression, the frequency hopping pattern state... and The difference between Related, let the difference be... Considering that formula (7) includes modulo 8 processing, then when hour, ;otherwise .

[0147] The function module is based on the difference. By referring to Table 3, the transmitted baseband data can be demodulated. For example... Figure 19 As shown RTL structure diagram of the function module.

[0148] Table 3 Differences and and Corresponding results;

[0149]

[0150] This embodiment was tested and verified on the XILINX XCKU060 chip, developed and verified using Vivado 2018.3, and the generated RF signal was displayed using a Zhongkesi oscilloscope. In the second transmitter of the pseudo-random sequence-based frequency hopping communication subsystem, the modulator output waveform is as follows... Figure 20 As shown. Figure 20 The input baseband data `in_data` is differentially encoded and converted into in-phase and quadrature branch data `di` and `dq`, respectively. After MSK modulation by the modulator, the modulated signal `Msksignal` is output. The pseudo-random sequence generated by the pseudocode generator is shown below. Figure 21 As shown in Table 4, the internal shift register count_1K of the pseudocode generator performs shift feedback under clock drive to obtain a frequency hopping pattern state1 consisting of 3 bits. Based on the set frequency hopping frequency parameters, a frequency mapping table is defined, and the frequency control word corresponding to state1 is selected to control the frequency synthesizer to generate the frequency hopping carrier signal. The correspondence between state1, the frequency hopping carrier frequency, and the frequency control word is shown in Table 4.

[0151] Table 4 shows the correspondence between state, frequency hopping carrier frequency, and frequency control word;

[0152]

[0153] The switching waveforms of the state1 state of two adjacent hops, the frequency control word, and the frequency hopping carrier signal generated by the frequency synthesizer are as follows: Figure 22 As shown. From Figure 22As can be seen, when the rising edge of the frequency hopping clock clk_1K arrives, state1 switches from "111" to "011", and the frequency control word frequency_control_word switches from "11141" to "8520", causing a change in the frequency of the frequency hopping carrier signal output by the frequency synthesizer. The instantaneous frequency hopping communication signal waveform based on a pseudo-random sequence, captured using a Zhongkesi oscilloscope, is shown below. Figure 23 As shown. By Figure 23 It can be seen that the instantaneous frequency of the frequency-hopping communication signal based on the pseudo-random sequence currently captured is 11.9629MHz, which is the instantaneous frequency of the frequency-hopping communication signal corresponding to a frequency-hopping carrier frequency of 12MHz. Verification and result analysis of the core components of the second transmitter of the frequency-hopping communication subsystem based on the pseudo-random sequence show that the second transmitter of the frequency-hopping communication subsystem based on the pseudo-random sequence correctly generated the frequency-hopping communication signal based on the pseudo-random sequence.

[0154] In the second receiver of the frequency hopping communication subsystem based on pseudo-random sequences, the FFT module performs a Fourier transform on the received signal using an FFTIP core, outputting the real and imaginary parts of the data. These are then squared and summed to obtain the spectral distribution of the received signal. The output of a single FFT module is shown below. Figure 24 As shown. In Figure 24 In the process, the received signal `fft_in` is processed by the FFT IP core to obtain the real part `xk_re` and the imaginary part `xk_im` of each spectral component. `mult_reout` and `mult_imout` are the squares of the real and imaginary parts, respectively. `addout` is the signal spectrum result corresponding to each frequency component obtained by adding the real and imaginary parts, and `xk_index` is the frequency index number of each spectral component. As can be seen from the figure, a peak value of the signal spectrum `addout` exists at frequency index number 233, from which the instantaneous frequency of the received signal `fft_in` can be calculated. The peak searcher is responsible for detecting the peak values ​​of the signal spectrum output by the FFT module and extracting the corresponding frequency index numbers. Its operation result is shown in the figure. Figure 25 As shown in the figure, `index_max` represents the frequency index number corresponding to the detected signal spectrum peak. It can be seen from the figure that the detected frequency index numbers are concentrated in the range of 232-237, which corresponds to the frequency range when the frequency hopping carrier frequency is 17MHz. The frequency point detector detects the frequency hopping carrier frequency, and the processing result is as follows... Figure 26As shown, the frequency detector receives the frequency index number `index_max` output by the peak searcher. By analyzing the difference `delta` between adjacent frequency index numbers, it determines whether the frequency of the received signal remains stable, thereby determining whether the current hop has been captured. When the frequency index number input changes from 235 to 194, 193, 195..., the hop condition is met, and a hop is determined to have occurred in the received signal. At this time, the capture success signal `freq_locked` is pulled low, and the hop trigger signal `jump_trigger` is pulled high. The frequency change detection module is responsible for implementing frequency hopping synchronization timing control and state management, such as... Figure 27 The output of the frequency change detection module is as follows: the frequency change detection module determines whether the frequency detector has captured the frequency hopping signal, and uses the detected frequency index number to configure the pseudo-code transmitter. Figure 27 The intermediate frequency (IF) change detection module, based on the jump_trigger state, activates the pseudo-code generator to generate a frequency hopping pattern and drives the instruction decoder to generate a frequency control word. This word controls the frequency synthesizer to generate a local frequency-hopping carrier, which is then mixed with the received frequency-hopping communication signal based on a pseudo-random sequence to obtain the IF modulated signal. The demodulator receives the IF modulated signal and performs MSK coherent demodulation to obtain the transmitted baseband data. Figure 28 The result shown is the demodulator processing result.

[0155] The demodulator demodulates the intermediate frequency modulated signal to obtain the quadrature and in-phase branch data data_q and data_i, which are then differentially decoded to obtain the transmitted baseband data. Table 5 shows the first 20 bits of quadrature and in-phase branch data transmitted by the second transmitter of the pseudo-random sequence-based frequency hopping communication subsystem and the 20 bits of quadrature and in-phase branch data demodulated by the second receiver of the pseudo-random sequence-based frequency hopping communication subsystem.

[0156] Table 5 Results of i and q branch data transmitted by the second transmitter and received by the second receiver;

[0157]

[0158] As can be seen from Table 3, the second receiver of the frequency hopping communication subsystem based on pseudo-random sequences correctly implements the function of receiving and demodulating frequency hopping communication signals based on pseudo-random sequences.

[0159] In the third transmitter of the differential frequency hopping communication subsystem of this embodiment, the baseband data is output as follows after being converted by a bit symbol converter: Figure 29 As shown. The G function module receives the output data from the bit symbol converter, generates the frequency hopping pattern state, and the result is as follows. Figure 30 As shown. The frequency hopping pattern is processed by the instruction decoder to obtain the frequency control word, which controls the frequency synthesizer to generate a differential frequency hopping communication signal. The waveform of the differential frequency hopping communication signal captured by the oscilloscope is shown below. Figure 31As shown in the diagram. In the third receiver of the differential frequency hopping communication subsystem, the FFT module receives the differential frequency hopping communication signal, performs FFT processing, and outputs the result as shown in the diagram. Figure 32 As shown. The peak searcher detects the peak values ​​in the FFT module output, and the frequency detector analyzes these peak values ​​to obtain the signal frequency, such as... Figure 33 The frequency control word is detected by the frequency sequence recognition module. The function module demodulates the output of the frequency detector, and the result is as follows: Figure 34 As shown in the figure. Finally, it is converted into a serial data stream by the parallel-to-serial conversion module, and the output waveform of the parallel-to-serial conversion module is as follows. Figure 35 As shown.

[0160] By comparing the demodulated baseband data with the transmitted baseband data, it can be proven that the differential frequency hopping communication subsystem has achieved the functions of generating and receiving differential frequency hopping communication signals.

[0161] Based on verifying the functional correctness of the pseudo-random sequence-based frequency hopping communication subsystem and the differential frequency hopping communication subsystem of the modular reuse-based dual-mode frequency hopping communication system, a comparison is made between the pseudo-random sequence-based frequency hopping communication system, the differential frequency hopping communication system, the total resource consumption of both, and the FPGA resources used by the modular reuse-based frequency hopping communication system proposed in this embodiment, as shown in Table 6. The comparison results of FPGA resource consumption are as follows: Figure 36 As shown.

[0162] Table 6. FPGA resource consumption of different communication systems;

[0163]

[0164] By comparing Table 6 and Figure 36 As can be seen, the dual-mode frequency hopping communication system based on module reuse proposed in this embodiment possesses both pseudo-random sequence-based frequency hopping communication and differential frequency hopping communication functions, with hardware consumption exceeding that of both. However, by reusing modules such as the FFT module, instruction decoder, and frequency synthesizer, the resource consumption is far lower than the sum of the resource consumption of the two, saving 29.83%, 19.93%, and 16.23% of LUT, SRL, and DSP resources, respectively.

[0165] The purpose of this embodiment is to improve the flexibility and adaptability of frequency hopping communication technology and reduce resource consumption. Based on an FPGA platform, a dual-mode frequency hopping communication system based on module multiplexing is proposed. This embodiment achieves dual-mode frequency hopping communication functions—based on pseudo-random sequences and differential frequency hopping—by multiplexing FFT modules, instruction decoder modules, and frequency synthesizer modules. The communication mode can be flexibly selected as needed, improving the anti-interference and flexibility of the communication process and providing a key method to ensure reliable information transmission.

[0166] This embodiment uses the MATLAB R2019b platform to simulate and verify the fast acquisition algorithm based on the dual-hop frequency point decision. The simulation parameters are shown in Table 7 below.

[0167] Table 7. Simulation Parameter Description;

[0168]

[0169] The m-sequence uses a three-stage shift register to construct a pseudo-random control of the frequency hopping pattern. Its feedback logic is taken from the XOR result of the first and third stage outputs. Each m-sequence state has a mapping relationship with a specific carrier frequency, as shown in Table 8.

[0170] Table 8. Correspondence between m-sequence and carrier frequency;

[0171]

[0172] The simulation results of the frequency hopping pattern generated by the m-sequence are as follows: Figure 37 As shown in the figure, the horizontal axis represents the hop index, indicating the nth hop in the hop sequence; the vertical axis represents the carrier frequency (MHz), indicating the transmit carrier frequency corresponding to each hop. The frequency sequence shown in the figure is 17MHz, 13MHz, 15MHz, 12MHz, 11MHz, 16MHz, and 14MHz, with a total of 7 hop points. The carrier frequency remains constant within each hop cycle, and the pattern of change is consistent with the m-sequence state and frequency mapping relationship shown in Table 2.

[0173] like Figure 38 The waveform of the generated frequency-hopping communication signal in the time domain is shown. The horizontal axis represents time (in ms), ranging from 0 to 0.07; the vertical axis represents signal amplitude, ranging from -1 to 3. The frequency hopping frequency corresponding to this waveform is 100 kHz, and the hop time is 0.01 ms, which matches the expected settings. From the magnified waveform in the upper right corner of the figure, it can be clearly observed that the carrier frequency remains constant within each frequency hopping cycle, and the signal can quickly switch between different carrier frequencies in different frequency hopping cycles.

[0174] like Figure 39 The frequency domain amplitude spectrum results of a single FFT analysis of the frequency-hopping signal are presented. The horizontal axis represents frequency (unit: MHz), ranging from 0 to 50 MHz; the vertical axis represents normalized amplitude. A significant single peak is clearly shown at 16.99 MHz, with a peak amplitude of 495.1, exceeding the set detection threshold. This is represented as 0.6 on the normalized vertical axis. The peak value corresponds to a signal frequency of 17 MHz within the current hop time, while the amplitudes of other frequency bands are close to zero, indicating that the signal energy is highly concentrated at the target frequency.

[0175] Frequency hopping carrier frequency detection trajectory based on multiple FFT analyses, as shown below Figure 40 As shown in the figure, the horizontal axis represents the number of FFT analyses, and the vertical axis represents the detected carrier frequency (unit: MHz). The figure clearly shows that the frequency changes in a step-like manner within the range of 10-17 MHz, which is completely consistent with the frequency hopping pattern at the transmitting end.

[0176] In the initial phase of the trajectory, the system continuously measures 17 MHz through the first few detection points (35 FFT iterations) to confirm the current frequency. Using this frequency information, the receiver performs a matching search operation with the locally stored frequency hopping pattern. This allows for rapid location of the current position within the frequency hopping pattern, determination of the current state of the transmitter's m-sequence, and accurate determination of its precise timing position within the complete frequency hopping sequence, thus achieving rapid signal acquisition.

[0177] As the number of FFT analyses increases, the system detects a carrier frequency jump from 17 MHz to 13 MHz at FFT number 6. This jump signal triggers the receiver to synchronously adjust its local m-sequence state, making it jump in sync with the transmitter, thus completing a smooth transition from acquisition to tracking.

[0178] like Figure 41 The diagram shows the variation of frequency detection accuracy of frequency hopping signals under different signal-to-noise ratios (SNRs). The horizontal axis represents the SNR in decibels (dB) and ranges from -20 dB to +20 dB. The vertical axis represents the detection accuracy, with a value ranging from 0 to 1.

[0179] In this embodiment, the waveform is analyzed under the simulation parameter settings. In the extremely low signal-to-noise ratio (SNR) region (below -15 dB), the detection accuracy is less than 10%, remaining at a level close to zero, indicating poor detection capability in high-noise environments. When the SNR increases from approximately -15 dB to -7 dB, the detection accuracy rises sharply in the steep transition region, reaching -7 dB and above, at which point the detection accuracy stabilizes at 100%.

[0180] The enlarged inset in the upper right corner details the transition region within the -12 dB to -4 dB signal-to-noise ratio range. The coordinates of several key data points are clearly marked, showing the precise detection accuracy at the critical signal-to-noise ratio threshold. Detection accuracy increases significantly with increasing signal-to-noise ratio (SNR): the accuracy is 90.79% at an SNR of -9.2 dB, increasing to 97.46% at -8.4 dB, and reaching 100% accuracy when the SNR drops to -6.6 dB, achieving error-free detection.

[0181] By utilizing the quasi-parallel processing capability of frequency domain FFT, the acquisition process is transformed from a "point-by-point search" in the time domain to a "global scan" in the frequency domain. Its acquisition time model is shown in Equation (8).

[0182] ;

[0183] in, It is a very small number of candidate points that need to be verified after a double-jump decision.

[0184] This makes the capture time related to the slide. The magnitude dropped sharply The scale has been increased by orders of magnitude, enabling it to meet the rapid access requirements of even the most demanding high-speed frequency hopping systems.

[0185] It requires only a single FFT processor with flexible logic control to replace the massive correlator array in parallel search. Its hardware resource consumption is sublinearly related to the number of FFT points, as shown in Equation (8).

[0186] ;

[0187] While ensuring extremely fast acquisition speed, the hardware size, chip area and system power consumption are reduced by one to two orders of magnitude, making high-performance frequency hopping synchronization possible in low-cost, low-power civilian devices.

[0188] The dual-hop frequency point decision acquisition algorithm based on spectrum peak search proposed in this embodiment achieves the optimal trade-off between acquisition speed and hardware resources, realizing the performance requirements that are difficult to meet simultaneously by traditional serial acquisition and parallel acquisition techniques. Table 9 shows the complexity comparison.

[0189] Table 9 Comparison of capture algorithm complexity;

[0190]

[0191] Comparing the three capture methods from a complexity perspective, the sliding correlation method requires traversing the entire uncertain frequency band for point-by-point correlation calculations. Its synchronization establishment time is linearly related to the search range, resulting in a time complexity of O(n log n). Parallel search architecture is achieved through deployment The parallel correlator implements single-cycle decision-making, and its time complexity can be regarded as... However, its hardware complexity and power consumption increase significantly with the number of frequency points, limiting its engineering applications. The peak-searching double-hop decision mechanism used in this embodiment is first implemented through Fast Fourier Transform. The frequency domain conversion is performed, and then the decision is made on a finite set of candidate frequency points. The total system delay is close to the constant level, while avoiding the resource overhead caused by large-scale parallel structures.

[0192] In terms of space complexity, the sliding correlation method has the advantage of simple structure; the parallel search scheme requires configuration. The increased computational complexity of traditional methods leads to a significant increase in resource consumption; however, this embodiment primarily relies on an FFT IP core and simplified control logic, greatly reducing hardware complexity. Overall, this embodiment achieves a better balance across multiple dimensions, including capture timeliness, hardware scale, and system power consumption.

[0193] The specific embodiments of this invention have been described above with reference to the accompanying drawings. However, these descriptions should not be construed as limiting the scope of this invention. The scope of protection of this invention is defined by the appended claims. Any modifications based on the claims of this invention are within the scope of protection of this invention.

Claims

1. A dual-mode frequency hopping communication system based on module multiplexing, relating to a differential frequency hopping communication system and a frequency hopping communication system based on pseudo-random sequences, characterized in that, Includes a first transmitter and a first receiver; The first transmitting end includes an input control module, a second transmitting end of a pseudo-random sequence-based frequency hopping communication subsystem, and a third transmitting end of a differential frequency hopping communication subsystem; The first receiving end includes a second receiving end of a pseudo-random sequence-based frequency hopping communication subsystem, a third receiving end of a differential frequency hopping communication subsystem, and an output control module; The input control module is used to send the baseband data input by the sender to the differential frequency hopping communication subsystem or the frequency hopping communication subsystem based on pseudo-random sequences according to the control signal input by the sender's host computer; the differential frequency hopping communication subsystem and the frequency hopping communication subsystem based on pseudo-random sequences are used to generate communication signals and send them to the first receiving end; The output control module is used to select the corresponding differential frequency hopping communication subsystem or the pseudo-random sequence-based frequency hopping communication subsystem to receive communication signals according to the control signals input by the host computer of the receiver; the differential frequency hopping communication subsystem and the pseudo-random sequence-based frequency hopping communication subsystem are used to demodulate the communication signals, obtain baseband data and send it to the receiver.

2. The dual-mode frequency hopping communication system based on module multiplexing according to claim 1, characterized in that, The second transmitter of the pseudo-random sequence-based frequency hopping communication subsystem and the third transmitter of the differential frequency hopping communication subsystem include a shared instruction decoder and frequency synthesizer. The instruction decoder is used to convert the shift register state generated by the pseudocode generator into a frequency control word or to... The frequency hopping pattern state generated by the function module is converted into a frequency control word; the frequency synthesizer is used to generate a frequency hopping carrier signal based on the frequency control word.

3. A dual-mode frequency hopping communication system based on module multiplexing according to claim 2, characterized in that, The second transmitter of the frequency hopping communication subsystem based on pseudo-random sequences also includes a modulator, a pseudo-code generator, and a mixer; The modulator is used to modulate the baseband data to be transmitted, obtain the intermediate frequency modulated signal, and send it to the mixer; the pseudocode generator is used to generate the shift register state and send it to the instruction decoder. The mixer is used to mix the intermediate frequency modulation signal output by the modulator with the frequency hopping carrier signal to obtain a communication signal and send it to the receiving end of the frequency hopping communication subsystem based on pseudo-random sequence.

4. A dual-mode frequency hopping communication system based on module multiplexing according to claim 2, characterized in that, The third transmitter of the differential frequency hopping communication subsystem also includes a bit symbol converter and Function modules; A bit symbol converter is used to convert serial baseband data into parallel transmission symbols; The function module is used to calculate the frequency hopping pattern state of the next hop based on the frequency hopping pattern state of the previous hop and the current transmitted symbol.

5. A dual-mode frequency hopping communication system based on module multiplexing according to claim 4, characterized in that, The second receiver of the pseudo-random sequence-based frequency hopping communication subsystem and the third receiver of the differential frequency hopping communication subsystem share a common FFT module, peak searcher, and frequency detector. The FFT module is used to perform FFT processing on the received communication signal to obtain the spectrum distribution result; the peak searcher is used to detect the spectrum distribution result to obtain the instantaneous signal frequency peak; the frequency point detector identifies the frequency hopping carrier frequency estimate of the received signal.

6. A dual-mode frequency hopping communication system based on module multiplexing according to claim 5, characterized in that, The second receiver of the frequency hopping communication subsystem based on pseudo-random sequences also includes a frequency change detection module, a pseudo-code generator, an instruction decoder, a frequency synthesizer, a mixer, and a demodulator. The frequency change detection module is used to perform synchronous acquisition and synchronous tracking processing based on the change of the carrier frequency estimate, and controls the pseudo-code generator, instruction decoder and frequency synthesizer to generate local frequency hopping carrier signals; the mixer is used to process the local frequency hopping carrier information to obtain a fixed frequency modulation signal; The demodulator demodulates the modulated signal to obtain baseband data.

7. A dual-mode frequency hopping communication system based on module multiplexing according to claim 6, characterized in that, The third receiver of the differential frequency hopping communication subsystem also includes Function modules and sign bit converters; The function module is used to demodulate the transmission symbols based on the frequency estimation of the frequency hopping carrier; the symbol bit converter is used to convert the transmission symbols into baseband data.

8. A dual-mode frequency hopping communication system based on module multiplexing according to claim 5, characterized in that, The first receiver of the module-multiplexed dual-mode frequency hopping communication system achieves frequency hopping synchronization with the first transmitter of the same system based on a fast acquisition algorithm for dual-frequency hopping point decision. The fast acquisition algorithm for dual-frequency hopping point decision includes: The FFT module is used to perform multiple FFT processes on the received signal, converting the time-domain received signal into a frequency-domain signal. A peak searcher is used to calculate the power spectrum of each frequency point by performing the sum of squares of the real and imaginary parts for each frequency index of the frequency domain signal; local maxima are searched in the power spectrum of each FFT output and the corresponding peak frequency index is recorded. In a frequency hopping communication subsystem based on pseudo-random sequences, a frequency change detection module is used to obtain continuous... The peak frequency index obtained from the first FFT process is used to calculate the difference between adjacent indices. If the difference between adjacent indices meets the stability condition, the current frequency hopping point is successfully identified. The information of the current frequency hopping point is recorded, and the local m-sequence is preset as the next state of the identified current frequency hopping point. After the current frequency hopping point is identified, the monitoring of subsequent identified frequency hopping points continues. When the difference between adjacent indices is detected to be within the hopping detection range, it is determined that the carrier frequency of the first transmitter has hopped. The local m-sequence is synchronously hopping with the first transmitter according to the predetermined frequency hopping pattern to complete the acquisition process.

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