A Synaesthesia Integrated Signal Waveform Design Method Based on Continuous Frequency Modulation Signal

Abstract

The present invention belongs to the field of radar signal processing technology, and specifically relates to a method for designing a synaesthesia integrated signal waveform based on a continuous frequency modulation signal. The synaesthesia integrated signal waveform of the present invention has the following characteristics: a pulse duration period of the integrated signal is T, and according to the number of bit symbols modulated in each pulse duration period, it is divided into N equal parts in the time domain, and the duration of the sub-pulses of each segment is equal. The frequency modulation slope of each segmented signal is determined by the modulated bit information. The end frequency of each segmented signal is the initial frequency of the next segmented signal, and the frequency of the entire integrated signal changes nonlinearly, but within each segmented signal, the signal frequency changes linearly. The integrated signal has a constant envelope and is phase continuous. In addition, through the designed integrated signal structure characteristics, the matched filter demodulation method is improved, and by limiting the frequency range, the influence of the system background noise on the demodulation is reduced, thereby improving the signal-to-noise ratio.

Description

Technical Field

[0001] The present invention belongs to the technical field of radar signal processing, and is a synaesthesia integrated signal waveform design method based on continuous frequency modulation (FM) signals. Background Art

[0002] In modern radio systems, radar and communications systems have distinct functions and roles, yet each plays an indispensable role in its own field. Radar systems can transmit electromagnetic waves in various frequency bands, with the frequency band selected based on the detection environment. For example, ground-penetrating radar considers the detection environment, which is typically soil containing water. The soil absorbs high-frequency electromagnetic waves much more than low-frequency waves, limiting the frequency range to less than 1 GHz. However, air-to-air radars are different, requiring consideration of the different measurement targets, measurement objectives, measurement accuracy, and the size limitations of the radar's transceiver equipment.

[0003] In the field of communication systems, since the introduction of radio equipment into communications, from wired to wireless, and then through the technological evolution of 2G, 3G, 4G, and finally 5G, the frequency bands of communication systems have been increasingly expanded to higher frequency bands. The higher the frequency band, the more severe the attenuation of electromagnetic waves in the atmosphere, reducing the reliability and range of communication. However, this allows for more compact wireless communication equipment and higher transmission rates.

[0004] With technological advancements, radar and communication systems have begun to overlap in frequency bands, previously independent of each other. This has led to overcrowding of spectrum resources in the overlapping areas, creating conflicts between radar and communication functions. The transceiver equipment in radar and communication systems shares many structural similarities. On the transmitting end, both systems modulate the transmit waveform and then transmit the electromagnetic wave through a transmitter. On the receiving end, the radar system receives the electromagnetic wave reflected from the target, performs pulse compression or frequency mixing on the reflected wave and the transmitted wave, and extracts radar parameters such as the target's range, speed, and azimuth from the processed signal. The receiving end of a communication system directly receives the electromagnetic wave signal from the transmitter and, after down-conversion, filtering, low-noise amplification, sampling, and demodulation, obtains the information transmitted by the transmitter. However, the difference is that the receiver of a radar system is typically located near the transmitter or is integrated with the transmitter and receiver, whereas the receiver and transmitter in a communication system are generally not physically connected.

[0005] Since radar systems and communication systems began to overlap in spectrum resources and their transceiver equipment and structures were similar, the concept of radar communication sharing was proposed, and dual-functional radar and communication (DFRC) has since become a hot research field.

[0006] Radar systems were first used in the military, and the earliest radar-communication integration projects also began there. In 1996, research on advanced multifunctional radio frequency systems was launched, followed by the "Jewel Pillar" project to improve avionics system integration. Over time, research on radar-communication integration has also made significant advances in civilian applications, with vehicle-to-vehicle (V2I) radar integration being a key area. Millimeter-wave radar systems are already widely used in V2I, and the design of communication-perception fusion is a critical area of ​​development. It holds significant research significance and application prospects, and is a crucial component of future intelligent transportation systems.

[0007] In summary, the research on radar communication integration has important practical significance and research value in many aspects in solving problems such as frequency band overlap and spectrum congestion between the two. Summary of the Invention

[0008] This paper proposes a synaesthesia-integrated signal waveform design based on a continuous frequency modulation signal. The specific goal is to design a radar-communication integrated signal waveform capable of transmitting a certain amount of information while meeting certain radar performance requirements. The synaesthesia-integrated signal waveform designed by this method can, based on its structural characteristics, achieve error detection for the transmitted bits of information.

[0009] In order to achieve the above object, the present invention provides the following technical solutions:

[0010] A method for designing a synaesthesia integrated signal waveform based on a continuous frequency modulation signal, the method comprising:

[0011] The mathematical model of the synaesthesia integrated signal waveform is established based on the mathematical model of the linear continuous frequency modulation signal:

[0012]

[0013] Where A represents the amplitude weighting of the signal; N means that the signal is divided into N segments with equal time; Indicates the signal bandwidth occupied by the first n segment signals; f c Indicates the carrier frequency; T p Indicates the duration of each segment signal; μ n Indicates the frequency modulation slope of the nth segment signal; θ n Represents the phase compensation term of each segment signal; represents the rectangular window function;

[0014] Based on the established model, the specific modulation method for the synaesthesia integrated signal is as follows: the integrated signal is divided into multiple pulse duration periods of T with reference to the sawtooth wave linear continuous frequency modulation signal in the time domain. At the beginning of each period, the frequency of the signal changes continuously from the preset minimum frequency until the end of a period. At the beginning of the next period, the initial frequency of the signal returns to the minimum frequency. Within a pulse duration period, the integrated signal is divided into N equal parts according to the number of modulated symbols N. The duration of each segmented signal is T. p , in each segment signal, pre-set the maximum frequency modulation slope μ max and the minimum FM slope μ min ; Then, according to the modulation order M, the value interval of the frequency modulation slope (μ min ,μ max ) is divided into M equal parts; different frequency modulation slopes are selected according to the different bit information modulated by each segmented signal; starting from the second segmented signal, the initial frequency of each segmented signal of the integrated signal is equal to the ending frequency of the previous segmented signal, thereby realizing continuous frequency change.

[0015] Furthermore, starting from the second segmented signal, each segmented signal needs to be phase compensated so that the phase of the integrated signal is continuous as a whole.

[0016] Furthermore, the demodulation method is further included, specifically: at the receiving end, the signal is defined to be completely synchronized, and the receiving end determines the pulse duration T, the number of modulation symbols N, and the modulation order M according to the pre-set communication protocol; the received signal is divided into N equal parts, and then according to the modulation order M, M linear continuous frequency modulation signals with different frequency modulation slopes are pre-set, with a duration of T p , the FM slope corresponds to the modulated bit symbol, which is defined as the matching signal; each segmented signal is conjugate-multiplied by M matching signals, low-pass filtered, and a decision signal is obtained; if the FM slopes of the two are equal, the decision signal is a single-tone signal with a frequency of is the total bandwidth occupied by all the previous segmented signals; if the FM slopes of the two are not equal, the decision signal is a linear continuous FM signal; then the spectrum peaks of the decision signals are compared and judged, and the matching signal corresponding to the decision signal with the largest spectrum peak is screened out. The modulation symbol corresponding to the FM slope of the matching signal is the demodulated bit information.

[0017] Furthermore, according to the modulation order M, the number of frequency points of the nth segment signal is (n-1)(M-1)+1, thereby limiting the spectrum range of the search peak to the possible frequency point range to improve the demodulation signal-to-noise ratio.

[0018] The present invention has the following beneficial effects: through the designed integrated signal structure, the matched filter demodulation method is improved. By limiting the frequency range, the influence of the system noise floor on demodulation is reduced, and the signal-to-noise ratio is improved. At the same time, an error detection method is designed to detect whether the demodulated bit information is incorrect by verifying whether the starting frequency of the segmented signal is equal to the total bandwidth occupied by the demodulated bit information. After discarding the erroneous bit information, the demodulation signal-to-noise ratio of the communication system is further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the synaesthesia integrated signal structure based on continuous frequency modulation signal proposed by the present invention.

[0020] Figure 2 This is a time-frequency structure diagram of the integrated signal designed by the present invention when the modulation order M is 2 and the number of modulation symbols N is 4.

[0021] Figure 3 This is a time-frequency structure diagram when the integrated signal is demodulated and the frequency modulation slopes of the segmented signal and the matching signal are the same and different.

[0022] Figure 4 This is a communication bit error rate diagram of the integrated signal designed by the present invention after demodulation using a traditional matched filtering method.

[0023] Figure 5 It is a frequency range tree diagram of the integrated signal designed by the present invention.

[0024] Figure 6 This is a communication bit error rate diagram of the integrated signal after the demodulation method is improved.

[0025] Figure 7 It is a communication bit error rate diagram of the remaining data after the error detection method discards the erroneous data. DETAILED DESCRIPTION

[0026] The present invention is described clearly and completely below with reference to the accompanying drawings and MATLAB simulation examples.

[0027] The method of the present invention is specifically:

[0028] The present invention is based on the mathematical model of linear continuous frequency modulation signal:

[0029]

[0030] A mathematical model of synaesthesia integrated signal waveform was established:

[0031]

[0032] Where A represents the amplitude weighting of the signal; N means that the signal is divided into N segments with equal time; Indicates the signal bandwidth occupied by the first n segment signals; f c Indicates the carrier frequency; T p Indicates the duration of each segment signal; μ n Indicates the frequency modulation slope of the nth segment signal, whose value is determined by the modulated bit information; θ n Represents the phase compensation term of each segmented signal to ensure the overall phase continuity of the synaesthesia integrated signal; Represents a rectangular window function, ensuring that each segmented signal only lasts T p time.

[0033] According to the established integrated signal mathematical model, the structure of synaesthesia integrated signal is as follows: Figure 1 As shown in the figure, a specific modulation method for the integrated signal is presented based on the generation of a linear continuous frequency modulation signal: In the time domain, the integrated signal is divided into multiple pulse duration cycles, each lasting T, with reference to a sawtooth linear continuous frequency modulation signal. At the beginning of each cycle, the signal frequency continuously changes from a preset minimum frequency until the end of the cycle. At the beginning of the next cycle, the signal's initial frequency returns to the minimum frequency.

[0034] In a pulse duration period, the integrated signal divides the pulse duration into N parts according to the number of modulated symbols N. The duration of each segment signal is equal, which is T p In each segment signal, the maximum frequency modulation slope μ is pre-set max and the minimum FM slope μ min Then, according to the modulation order M, the frequency modulation slope value interval (μ min ,μ max ) is divided into M equal parts. Then, different frequency modulation slopes are selected based on the different bit information modulated in each segmented signal. Starting from the second segmented signal, the initial frequency of each segmented signal of the integrated signal is equal to the ending frequency of the previous segmented signal, thereby achieving continuous frequency variation. Figure 2 The figure shows the time-frequency structure of the integrated signal designed by the present invention when the modulation order M is 2 and the number of modulation symbols N is 4.

[0035] Since the integrated signal is generated in segments, the initial phase of each segment is equal to 0, while the ending phase of each segment is not equal to 0. Therefore, starting from the second segment, each segment needs to be phase-compensated to make the overall integrated signal phase continuous and reduce spectrum leakage.

[0036] The following is an integrated signal demodulation method: At the receiving end, assuming that the signal is fully synchronized, the receiving end determines the pulse duration T, the number of modulation symbols N, and the modulation order M according to the pre-set communication protocol. The received signal is divided into N equal parts, and then according to the modulation order M, M linear continuous frequency modulation signals with different frequency modulation slopes are pre-set, and their duration is T p , the FM slope corresponds to the modulated bit symbol, which is called the matching signal. Each segmented signal is conjugate-multiplied by the M matching signals, and low-pass filtered to obtain a decision signal. If the FM slopes of the two are equal, the decision signal is a single-tone signal with a frequency of f s =∑ n m＝0 μ m T p , is the total bandwidth occupied by all the previous segmented signals. If the FM slopes of the two signals are unequal, the decision signal is a linear continuous FM signal, whose spectral energy is not concentrated. The spectral peaks of the decision signals are then compared and determined, and the matching signal corresponding to the decision signal with the largest spectral peak is selected. The modulation symbol corresponding to the FM slope of this matching signal is the demodulated bit information. Figure 3 Shown is a time-frequency structure diagram when the integrated signal is demodulated and the frequency modulation slopes of the segmented signal and the matching signal are the same and different.

[0037] On the basis of the above demodulation method, the demodulation range is limited according to the structural characteristics of the designed integrated signal, and the demodulation method is improved. Since the frequency modulation slope of each segmented signal is limited according to the preset modulation order M, and the initial frequency of the first segmented signal is the preset minimum frequency. Then, at the receiving end, the frequency range of the decision signal of each single tone is fixed and is a finite number of determined frequency points. According to the modulation order M, the number of frequency points of the nth segmented signal is (n-1)(M-1)+1, which limits the spectrum range of the search peak to the possible frequency range. This can greatly reduce the impact of the background noise on the detection result when searching for the peak in the entire spectrum range, and improve the demodulation signal-to-noise ratio.

[0038] Based on the structural characteristics of the designed integrated signal, in addition to improving the demodulation method, the present invention also proposes an error detection method to detect errors in the demodulated bit information. The specific steps of the algorithm are as follows:

[0039]

[0040] After error detection by the error detection algorithm, the erroneous bit information is discarded, and the bit error rate is further reduced in the remaining demodulated information.

[0041] The signal designed by the present invention has the following characteristics: The integrated signal has a pulse duration of T, which is divided into N equal parts in the time domain based on the number of bit symbols modulated within each pulse duration. The duration of each sub-pulse in each segment is equal. The frequency modulation slope of each segmented signal is determined by the modulated bit information. The ending frequency of each segmented signal is the starting frequency of the next segmented signal. The frequency of the entire integrated signal varies nonlinearly, but within each segmented signal, the signal frequency varies linearly. The integrated signal has a constant envelope and is phase-continuous.

[0042] The simulation parameter settings of the integrated signal are given below:

[0043] Table 1 Integrated signal simulation parameters

[0044]

[0045]

[0046] Under the simulation parameter setting, the demodulation results of the traditional matched filtering method of the integrated signal are as follows: Figure 4 shown. Figure 5 This is a frequency range tree diagram of the integrated signal designed by the present invention, including possible frequency range tree diagrams when the modulation order M is 2, the number of modulation symbols N is 8, and the modulation order M is 4, the number of modulation symbols N is 4. After the improved demodulation method, the communication bit error rate is compared with the bit error rate of the traditional demodulation method. Figure 6 As shown in Figure 2, we can see that the bit error rate has dropped by 1 to 2 orders of magnitude. After the error detection method, the communication bit error rate of the remaining data is compared with the communication bit error rate of the improved demodulation method. Figure 7 As shown, it can be seen that the communication bit error rate is reduced by about one order of magnitude at most compared with the communication without error detection method filtering bit information.

Claims

1. A method for designing a synaesthesia integrated signal waveform based on a continuous frequency modulation signal, characterized in that: The method is: The mathematical model of the synaesthesia integrated signal waveform is established based on the mathematical model of the linear continuous frequency modulation signal: Where A represents the amplitude weighting of the signal; N means that the signal is divided into N segments with equal time; Indicates the signal bandwidth occupied by the first n segment signals; f c Indicates the carrier frequency; T p Indicates the duration of each segment signal; μ n Indicates the frequency modulation slope of the nth segment signal; θ n Represents the phase compensation term of each segment signal; represents the rectangular window function; Based on the established model, the specific modulation method for the synaesthesia integrated signal is as follows: the integrated signal is divided into multiple pulse duration periods of T with reference to the sawtooth wave linear continuous frequency modulation signal in the time domain. At the beginning of each period, the frequency of the signal changes continuously from the preset minimum frequency until the end of a period. At the beginning of the next period, the initial frequency of the signal returns to the minimum frequency. Within a pulse duration period, the integrated signal is divided into N equal parts according to the number of modulated symbols N. The duration of each segmented signal is T. p , in each segment signal, pre-set the maximum frequency modulation slope μ max and the minimum FM slope μ min ; Then, according to the modulation order M, the value interval of the frequency modulation slope (μ min ,μ max ) is divided into M equal parts; different frequency modulation slopes are selected according to the different bit information modulated by each segmented signal; starting from the second segmented signal, the initial frequency of each segmented signal of the integrated signal is equal to the ending frequency of the previous segmented signal, thereby realizing continuous frequency change.

2. The method for designing a synaesthesia integrated signal waveform based on a continuous frequency modulation signal according to claim 1, characterized in that: Starting from the second segmented signal, each segmented signal needs to be phase compensated so that the overall phase of the integrated signal is continuous.

3. The method for designing a synaesthesia integrated signal waveform based on a continuous frequency modulation signal according to claim 1, characterized in that: The demodulation method is further included, specifically: at the receiving end, the signal is defined to be completely synchronized, and the receiving end determines the pulse duration T, the number of modulation symbols N, and the modulation order M according to the pre-set communication protocol; the received signal is divided into N equal parts, and then according to the modulation order M, M linear continuous frequency modulation signals with different frequency modulation slopes are pre-set, with a duration of T p , the FM slope corresponds to the modulated bit symbol, which is defined as the matching signal; each segmented signal is conjugate-multiplied by M matching signals, low-pass filtered, and a decision signal is obtained; if the FM slopes of the two are equal, the decision signal is a single-tone signal with a frequency of is the total bandwidth occupied by all the previous segmented signals; if the FM slopes of the two are not equal, the decision signal is a linear continuous FM signal; then the spectrum peaks of the decision signals are compared and judged, and the matching signal corresponding to the decision signal with the largest spectrum peak is screened out. The modulation symbol corresponding to the FM slope of the matching signal is the demodulated bit information.

4. The method for designing a synaesthesia integrated signal waveform based on a continuous frequency modulation signal according to claim 3, characterized in that: According to the modulation order M, the number of frequency points of the nth segment signal is (n-1)(M-1)+1, thereby limiting the spectrum range of the search peak to the possible frequency point range to improve the demodulation signal-to-noise ratio.

5. The method for designing a synaesthesia integrated signal waveform based on a continuous frequency modulation signal according to claim 3, characterized in that: The invention also includes an error detection method, which detects whether the demodulated bit information is wrong by verifying whether the starting frequency of the segmented signal is equal to the total bandwidth occupied by the demodulated bit information, thereby discarding the wrong bit information.

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