CN112924949B - System and method for generating chaotic radar transmitting signals in real time based on FPGA - Google Patents
System and method for generating chaotic radar transmitting signals in real time based on FPGA Download PDFInfo
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Abstract
The invention discloses a system and a method for generating a chaotic radar emission signal in real time based on an FPGA, wherein the system comprises the following components: the system comprises a baseband IQ path waveform generation module, a DAC module, an IQ modulator, a transmitting up-conversion module and a frequency source; the baseband IQ waveform generation module is realized by an FPGA and is used for respectively generating baseband I-path and Q-path waveform data of the chaotic radar; the DAC module is used for respectively performing digital-to-analog conversion on the baseband I-path and Q-path waveform data to obtain baseband I-path and Q-path analog waveforms; the IQ modulator is used for carrying out IQ modulation on the baseband I-path and Q-path analog waveforms combined with the intermediate frequency local oscillation signals to generate intermediate frequency chaotic signals; the transmitting up-conversion module is used for mixing the medium-frequency chaotic signal and the radio-frequency local oscillation signal to generate a radio-frequency chaotic signal; the frequency source is used for providing an FPGA working clock, an intermediate frequency local oscillator signal and a radio frequency local oscillator signal.
Description
Technical Field
The invention relates to the technical field of chaotic radar signal processing, in particular to a system and a method for generating chaotic radar transmitting signals in real time based on an FPGA.
Background
The noise radar adopts random or pseudo-random signals as transmitting waveforms, and is currently applied to a plurality of fields such as military and civil use (reference [1]: patent CN104777461A, a method and a system for generating broadband chaotic radar signals with random carrier frequency hopping; reference [2]: krzysztof Kulpa, signal Processing in Noise Waveform Radar, ISBN: 9781608076611).
In noise radars, the generation of random or pseudo-random transmitted signals is a critical technique. Compared with a common thermal noise signal, the chaotic signal is easier to generate and control. The chaotic signal is a pseudo random signal generated by a deterministic system. The chaotic signal is very sensitive to an initial value, and the subsequent signal has huge difference due to the small change of the initial value; and the chaotic signal has the characteristics of non-periodicity and unpredictability. The chaos signal is adopted as a transmitting signal of the radar, so that the advantages of low interception probability characteristic, effective spectrum utilization and the like are achieved.
The field programmable gate array (Field Programmable Gate Array, FPGA) has a series of advantages of large capacity, high speed, high integration, and the like, and is increasingly applied to radar control, digital signal processing, and the like. Therefore, the real-time generation of chaotic signals required for radar emission based on the FPGA brings new technological innovation.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a system and a method for generating chaotic radar transmitting signals in real time based on an FPGA.
In order to achieve the above object, the present invention provides a system for generating a chaotic radar emission signal in real time based on an FPGA, the system comprising: the system comprises a baseband IQ path waveform generation module, a DAC module, an IQ modulator, a transmitting up-conversion module and a frequency source; wherein,,
the baseband IQ waveform generation module is realized by an FPGA, is used for respectively generating baseband I waveform data and baseband Q waveform data of the chaotic radar, and is input into the DAC module;
the DAC module is used for respectively performing digital-to-analog conversion on the baseband I-path waveform data and the baseband Q-path waveform data to obtain a baseband I-path analog waveform and a baseband Q-path analog waveform, and inputting the baseband I-path analog waveform and the baseband Q-path analog waveform into the IQ modulator;
the IQ modulator is used for carrying out IQ modulation on the baseband I-path analog waveform and the baseband Q-path analog waveform by combining the intermediate frequency local oscillation signals, generating intermediate frequency chaotic signals and inputting the intermediate frequency chaotic signals into the transmitting up-conversion module;
the transmitting up-conversion module is used for mixing the medium-frequency chaotic signal and the radio-frequency local oscillation signal to generate a required radio-frequency chaotic signal;
the frequency source is used for providing an operating clock of the FPGA, providing an intermediate frequency local oscillator signal to the IQ modulator, and providing a radio frequency local oscillator signal to the transmitting up-conversion module.
As an improvement of the above system, the baseband IQ path waveform generation module includes: the device comprises a chaotic sequence generator, a band-pass filter, two frequency converters and two low-pass filters; wherein, two frequency converters are connected in parallel, each frequency converter is connected in series with a low-pass filter;
the chaotic sequence generator is used for generating a chaotic sequence and inputting the chaotic sequence into the band-pass filter;
the band-pass filter is used for carrying out band-pass filtering treatment on the chaotic sequence to obtain a band-limited chaotic sequence and inputting the band-limited chaotic sequence into the two frequency converters at the same time;
the two frequency converters are used for carrying out digital down-conversion on the band-limited chaotic sequence to obtain two paths of orthogonal baseband chaotic signals, and respectively inputting the two paths of orthogonal baseband chaotic signals into the low-pass filters which are respectively connected in series;
and the two low-pass filters are used for respectively carrying out low-pass filtering processing on the two paths of orthogonal baseband chaotic signals to obtain baseband I-path waveform data and baseband Q-path waveform data of the chaotic radar.
As an improvement of the above system, the chaotic sequence is:
x(n+1)＝k·x(n)·(1-x(n))
wherein x (N) represents the current value of the Logistic chaotic signal mapping, x (n+1) represents the next iteration value of the Logistic chaotic signal mapping, k is a parameter of the Logistic chaotic signal mapping, N is a sequence number of the Logistic chaotic signal mapping sequence, and n=0, 1,2, …, N P -1，N P For each transmitted pulse corresponding Logistic chaotic sequence Length:
N P ＝T P ·F sr
wherein T is P To transmit pulse signal duration F sr Is the sampling rate of the DAC module.
As an improvement of the above system, the band-limited chaotic sequence x B (n) is:
wherein h is B (k) Is a bandpassFilter coefficients, k=0, 1,2, …, K-1, K is the bandpass filter order, h B (k) According to the pass band range of the band-pass filter [0.5-B ] r /F sr ,0.5+B r /F sr ]Calculated, B r Is the bandwidth of the chaotic waveform transmitted by the radar.
As an improvement of the system, the two paths of orthogonal baseband chaotic signals are as follows:
wherein f 0 Intermediate frequency local oscillator signal for mixing, f 0 ＝F sr /4。
As an improvement of the system, the baseband I-path waveform data and the baseband Q-path waveform data of the chaotic radar are as follows:
wherein the filter coefficient h L (M), m=0, 1,2, …, M-1, M is the low pass filter order, h L (m) band width of pass band according to low pass filter is [0, B r /F sr ]And (5) calculating to obtain the product.
The method for generating the chaotic radar emission signal in real time based on the FPGA is realized based on the system, and comprises the following steps:
the baseband IQ waveform generation module respectively generates baseband I waveform data and baseband Q waveform data of the chaotic radar and inputs the baseband I waveform data and the baseband Q waveform data into the DAC module;
the DAC module respectively carries out digital-to-analog conversion on the baseband I-path waveform data and the baseband Q-path waveform data to obtain a baseband I-path analog waveform and a baseband Q-path analog waveform, and inputs the baseband I-path analog waveform and the baseband Q-path analog waveform into the IQ modulator;
the IQ modulator carries out IQ modulation on the baseband I-path analog waveform and the baseband Q-path analog waveform by combining with the intermediate frequency local oscillator signal, generates an intermediate frequency chaotic signal and inputs the intermediate frequency chaotic signal into the transmitting up-conversion module;
the transmitting up-conversion module mixes the intermediate frequency chaotic signal and the radio frequency local oscillation signal to generate a required radio frequency chaotic signal;
the working clock of the baseband IQ waveform generation module, the intermediate frequency local oscillation signal and the radio frequency local oscillation signal are all provided by a frequency source.
Compared with the prior art, the invention has the advantages that:
1. the method is characterized in that a chaotic radar transmitting signal is generated based on FPGA real-time calculation, the waveform of each pulse is a pseudo-random signal similar to noise, the transmitting waveform of each pulse is different, the transmitting waveform is a noise signal for an adversary, interception and decoding are difficult, and the low detection probability characteristic, the low interception probability characteristic and the electronic anti-interference capability of the radar can be effectively improved;
2. the method has the advantages that the chaotic radar transmitting signals are generated based on FPGA real-time calculation, the transmitted waveforms are pseudo-random signals generated by a deterministic system, for the own side is deterministic waveforms, the transmitted pseudo-random chaotic signals can be reconstructed by using a chaotic model in an own side radar signal processor, pulse compression processing is very convenient to be carried out on radar echo signals, the transmitting signals of each pulse do not need to be acquired back to be calibrated through a delay line in a random noise simulation generation mode, and one path of data acquisition can be reduced;
3. the system uses a general FPGA, a general DAC and an IQ modulator, has high portability, and is convenient to transplant into other radar systems.
Drawings
FIG. 1 is a block diagram of a system for generating chaotic radar transmitting signals in real time based on an FPGA of embodiment 1 of the present invention;
fig. 2 is a flowchart of the baseband IQ path waveform generation module of embodiment 1 of the present invention for generating a chaotic radar transmitting signal in real time;
FIG. 3 is a state machine block diagram of a baseband IQ path waveform generation module for generating a Logistic chaotic sequence according to embodiment 1 of the present invention;
fig. 4 (a) is a waveform diagram of a chaotic radar baseband I path generated by the baseband IQ path waveform generation module of embodiment 1 of the present invention;
fig. 4 (b) is a waveform diagram of a baseband Q path of the chaotic radar generated by the baseband IQ path waveform generation module in embodiment 1 of the present invention;
FIG. 5 (a) is a diagram of a chaotic radar baseband I-path waveform sampled by the DAC module of embodiment 1 of the present invention;
FIG. 5 (b) is a waveform diagram of the Q path of the chaos radar sampled by the DAC module of embodiment 1 of the present invention;
fig. 6 is a diagram showing the result of pulse compression of the baseband echo waveform sampled by the DAC module by the signal processor of embodiment 1 of the present invention.
Detailed Description
The invention aims to generate a chaotic radar transmitting signal in real time based on an FPGA, wherein the waveform of each transmitting pulse is a pseudo-random chaotic signal similar to noise, and the transmitting waveform of each pulse is different. The emitted waveform is a noise signal for the enemy, is difficult to intercept and decipher, and can effectively improve the low interception probability characteristic and the electronic anti-interference capability of the radar. Meanwhile, the transmitted waveform is a pseudo-random signal generated by a deterministic chaotic model, for the own waveform, the own signal processor can reconstruct the transmitted pseudo-random chaotic signal by using the chaotic model, so that pulse compression processing is very convenient for radar echo signals, and the transmitted signal of each pulse is not required to be collected back through a delay line to perform calibration like a random noise simulation generation mode (reference [2]: krzysztof Kulpa, signal Processing in Noise Waveform Radar, ISBN: 9781608076611), and one path of data collection of a radar system can be reduced.
The technical scheme of the invention is described in detail below with reference to the accompanying drawings and examples.
Example 1
The embodiment 1 of the invention provides a chaotic radar emission signal real-time generation system based on an FPGA, which comprises: the system comprises a baseband IQ path waveform generation module, a DAC module, an IQ modulator, a transmitting up-conversion module and a frequency source; wherein,,
the baseband IQ waveform generation module is realized by an FPGA, is used for respectively generating baseband I waveform data and baseband Q waveform data of the chaotic radar, and inputs the baseband I waveform data and the baseband Q waveform data into the DAC module;
the baseband IQ path waveform generation module comprises: the device comprises a chaotic sequence generator, a band-pass filter, two frequency converters and two low-pass filters; wherein, two frequency converters are connected in parallel, each frequency converter is connected in series with a low-pass filter;
the chaotic sequence generator is used for generating a chaotic sequence and inputting the chaotic sequence into the band-pass filter;
the band-pass filter is used for carrying out band-pass filtering treatment on the chaotic sequence to obtain a band-limited chaotic sequence and inputting the band-limited chaotic sequence into the two frequency converters at the same time;
the two frequency converters are used for carrying out digital down-conversion on the band-limited chaotic sequence to obtain two paths of orthogonal baseband chaotic signals, and respectively inputting the two paths of orthogonal baseband chaotic signals into the low-pass filters which are respectively connected in series;
and the two low-pass filters are used for respectively carrying out low-pass filtering processing on the two paths of orthogonal baseband chaotic signals to obtain baseband I-path waveform data and baseband Q-path waveform data of the chaotic radar.
The DAC module is used for respectively performing digital-to-analog conversion on the baseband I-path waveform data and the baseband Q-path waveform data to obtain a baseband I-path analog waveform and a baseband Q-path analog waveform, and inputting the baseband I-path analog waveform and the baseband Q-path analog waveform into the IQ modulator;
the IQ modulator is used for carrying out IQ modulation on the baseband I-path analog waveform and the baseband Q-path analog waveform by combining the intermediate frequency local oscillator signal, generating an intermediate frequency chaotic signal and inputting the intermediate frequency chaotic signal into the transmitting up-conversion module;
the transmitting up-conversion module is used for mixing the medium-frequency chaotic signal and the radio-frequency local oscillation signal to generate a required radio-frequency chaotic signal;
the frequency source is used for providing an operating clock of the FPGA, providing an intermediate frequency local oscillator signal to the IQ modulator and providing a radio frequency local oscillator signal to the transmitting up-conversion module.
It should be noted that the drawings are in a very simplified form and are all to a non-precise scale, merely for convenience and clarity in aiding in the description of embodiments of the invention.
In this embodiment, the duration T of the radar system transmitting signals P =10us, bandwidth B r =100 mhz, sampling rate of dac chip is F sr =2500 Msps. A flow chart of a method for generating chaotic radar transmitting signals in real time in the FPGA by the baseband IQ waveform generation module is shown in fig. 2.
Optionally, the method for generating the chaotic radar transmitting signal based on the FPGA in real time in the technical scheme further comprises the following steps:
step 101) generating a chaotic sequence in the FPGA by using a state machine.
In this embodiment, taking a Logistic chaotic signal as an example, the generated chaotic sequence expression is:
x(n+1)＝k·x(n)·(1-x(n)) (1)
wherein x (n) represents the current value of the Logistic map, x (n+1) represents the next iteration value of the Logistic map, k is a parameter of the Logistic map, and n is a Logistic map sequence number.
Typically, both the input and output of the Logistic map are distributed between (0, 1), and the implementation in an FPGA is first to write the decimal fraction on (0, 1) into binary, expressed as follows:
wherein c i Either 0 or 1 in binary.
Taking the first L bits to represent, then there are:
wherein,,
is an integer represented by an L-bit binary system, and corresponds to a decimal x (n) one by one. Writing x (n+1) and x (n) as the above forms can result in:
X(n+1)＝k·X(n)·(2 L-1 -X(n))·2 -(L-1) (4)
wherein X (0) =round (2) L-1 X (0)), round represents rounding the variables. X (0) is the beginning of Logistic chaotic sequenceThe value can be injected into the FPGA from the outside through interfaces such as a serial port or a network port. In the present embodiment, setting k=0.875 can be regarded as: k=1-0.125. In FPGA, the shift can be realized, and 0.125 is 3 bits shift right.
The above formula (4) is implemented in an FPGA with a state machine, and requires 4 states for each generation of a logic chaotic sequence value, as shown in fig. 3.
According to the time length T of the transmitted pulse signal P And sampling rate F of DAC sr Calculating to obtain the length of the Logistic chaotic sequence required by each transmitted pulse signal as follows:
N P ＝T P ·F sr (5)
i.e. n=0, 1,2, …, N P -1. In the present embodiment, N P ＝25000。
Step 102) performing band-limited filtering processing on the generated chaotic sequence x (n), and further comprising:
step 102-1) setting the passband range of the bandpass filter to [0.5-B ] r /F sr ,0.5+B r /F sr ]The filter order is K, and the filter coefficient h is obtained through calculation B (k)，k＝0,1,2,…,K-1。B r Is the bandwidth of the chaotic waveform transmitted by the radar.
102-2) carrying out band-pass filtering treatment on the pseudo-random chaotic sequence x (n) to obtain a band-limited chaotic sequence x B (n) is as follows:
in the present embodiment, the passband of the bandpass filter is [0.42,0.58 ]]. Setting the order K=31 of the band-pass filter, and calculating to obtain the band-limited filter coefficient h B (k) Then, the band-pass filtering processing of the pseudo-random chaos sequence x (n) by the equation (6) is implemented in the FPGA by using the IP block.
Step 103) for x B And (n) performing digital down-conversion processing to obtain a sequence corresponding to the two paths of I/Q, wherein the sequence is shown in the following formula.
The use of parameters in engineering applications proposes a simple design approach. Using intermediate frequency signals f 0 ＝F sr /4, the parameters being chosen such that c o (spi 2f 0 n/F sr ) The value of the signal in one period is {0, -1,0,1}, -sin (2pi.f) 0 n/F sr ) The value of the signal is {1,0, -1}. The method is realized in the FPGA, and the numerical values {1,0, -1} respectively correspond to the operations of unchanged state, zero setting and negation.
Step 104) low pass filtering the I (n) and Q (n), further comprising:
step 104-1) setting the passband bandwidth of the low pass filter to [0, B ] r /F sr ]The filter order is M, and the filter coefficient h is obtained through calculation L (m)，m＝0,1,2，…，M-1。
Step 104-2) performing low-pass filtering on the I (n) and the Q (n) to obtain a sequence I L (n) and Q L (n) is as follows:
in the present embodiment, the passband of the low pass filter is [0,0.08 ]]The order m=31, the low pass filter coefficient h is calculated L (m). The low pass filtering process of formula (8) on I (n) and Q (n) is verified in FPGA using IP blocks. The I path and Q path of the obtained baseband transmitting waveform and the frequency spectrum are shown in the figures 4 (a) and (b).
Step 105), the FPGA outputs the waveforms of the I path and the Q path of the baseband transmission to the DAC chip according to the working time sequence of the radar system.
In an actual radar system, the waveforms of the I and Q paths output by the DAC are sampled by an ADC with a sampling rate of 250Msps, and the waveforms are shown in fig. 5 (a) and (b). The signal processor uses a chaotic model to reconstruct a transmitting signal, and pulse compression processing is carried out on the waveform sampled by the ADC, so that the result is shown in figure 6, and the pulse compression effect can be seen to be good.
It should be noted that, in this embodiment, the pseudo-random waveform is generated by using the Logistic mapping as an example, and the system can be used for chaotic waveforms of different algorithms, but only the algorithms forming the waveforms are different.
Example 2
Based on the system of embodiment 1, embodiment 2 of the present application proposes a method for generating chaotic radar emission signals in real time based on FPGA, which specifically comprises the following steps:
the FPGA generates I-path and Q-path waveform data of the chaotic radar baseband and simultaneously transmits the data to a 2-path DAC chip;
the 2-path DAC chip respectively carries out digital-to-analog conversion on the two paths of waveform data of I and Q to generate analog waveforms of the baseband I path and the Q path, and the analog waveforms are transmitted to the IQ modulator;
the IQ modulator carries out IQ modulation on the input I-path and Q-path analog waveforms by combining an intermediate frequency local oscillation signal LO2, generates an intermediate frequency chaotic signal and transmits the intermediate frequency chaotic signal to the transmitting up-conversion module;
the transmitting up-conversion module mixes the intermediate frequency chaotic signal with the radio frequency local oscillator LO1 to generate a required radio frequency chaotic signal.
The frequency source provides an operating clock of the FPGA, an intermediate frequency local oscillator LO2 used by the IQ modulator transmits a radio frequency local oscillator LO1 used by up-conversion.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and are not limiting. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the present invention, which is intended to be covered by the appended claims.
Claims (4)
1. A chaotic radar transmitting signal real-time generation system based on an FPGA, the system comprising: the system comprises a baseband IQ path waveform generation module, a DAC module, an IQ modulator, a transmitting up-conversion module and a frequency source; wherein,,
the baseband IQ waveform generation module is realized by an FPGA, is used for respectively generating baseband I waveform data and baseband Q waveform data of the chaotic radar, and is input into the DAC module;
the DAC module is used for respectively performing digital-to-analog conversion on the baseband I-path waveform data and the baseband Q-path waveform data to obtain a baseband I-path analog waveform and a baseband Q-path analog waveform, and inputting the baseband I-path analog waveform and the baseband Q-path analog waveform into the IQ modulator;
the IQ modulator is used for carrying out IQ modulation on the baseband I-path analog waveform and the baseband Q-path analog waveform by combining the intermediate frequency local oscillation signals, generating intermediate frequency chaotic signals and inputting the intermediate frequency chaotic signals into the transmitting up-conversion module;
the transmitting up-conversion module is used for mixing the medium-frequency chaotic signal and the radio-frequency local oscillation signal to generate a required radio-frequency chaotic signal;
the frequency source is used for providing an operating clock of the FPGA, providing an intermediate frequency local oscillation signal to the IQ modulator, and providing a radio frequency local oscillation signal to the transmitting up-conversion module; the baseband IQ path waveform generation module comprises: the device comprises a chaotic sequence generator, a band-pass filter, two frequency converters and two low-pass filters; wherein, two frequency converters are connected in parallel, each frequency converter is connected in series with a low-pass filter;
the chaotic sequence generator is used for generating a chaotic sequence and inputting the chaotic sequence into the band-pass filter;
the band-pass filter is used for carrying out band-pass filtering treatment on the chaotic sequence to obtain a band-limited chaotic sequence and inputting the band-limited chaotic sequence into the two frequency converters at the same time;
the two frequency converters are used for carrying out digital down-conversion on the band-limited chaotic sequence to obtain two paths of orthogonal baseband chaotic signals, and respectively inputting the two paths of orthogonal baseband chaotic signals into the low-pass filters which are respectively connected in series;
the two low-pass filters are used for respectively carrying out low-pass filtering treatment on the two paths of orthogonal baseband chaotic signals to obtain baseband I-path waveform data and baseband Q-path waveform data of the chaotic radar;
the chaos sequence is as follows:
x(n+1)＝k·x(n)·(1-x(n))
wherein x (n) represents the current value of the Logistic chaotic signal mapping, x (n+1) represents the next iteration value of the Logistic chaotic signal mapping, k is the parameter of the Logistic chaotic signal mapping, and n is the Logistic mixingSequence number of the sequence of the chaotic signal map, n=0, 1,2, …, N P -1，N P For each transmitted pulse corresponding Logistic chaotic sequence Length:
N P ＝T P ·F sr
wherein T is P To transmit pulse signal duration F sr Sampling rate for the DAC module;
the band-limited chaotic sequence x B (n) is:
wherein h is B (k) K=0, 1,2, …, K-1, K is the bandpass filter order, h B (k) According to the pass band range of the band-pass filter [0.5-B ] r /F sr ,0.5+B r /F sr ]Calculated, B r Is the bandwidth of the chaotic waveform transmitted by the radar.
2. The FPGA-based chaotic radar transmission signal real-time generation system of claim 1, wherein the two paths of quadrature baseband chaotic signals are:
wherein f 0 Intermediate frequency local oscillator signal for mixing, f 0 ＝F sr /4。
3. The system for generating the chaotic radar transmitting signal in real time based on the FPGA according to claim 2, wherein the baseband I-path waveform data and the baseband Q-path waveform data of the chaotic radar are:
wherein the filter coefficient h L (m)，m＝0,1,2，…，M-1, M is the low pass filter order, h L (m) band width of pass band according to low pass filter is [0, B r /F sr ]And (5) calculating to obtain the product.
4. A method for generating chaotic radar emission signals in real time based on an FPGA, the method being implemented based on the system of one of claims 1 to 3, the method comprising:
the baseband IQ waveform generation module respectively generates baseband I waveform data and baseband Q waveform data of the chaotic radar and inputs the baseband I waveform data and the baseband Q waveform data into the DAC module;
the DAC module respectively carries out digital-to-analog conversion on the baseband I-path waveform data and the baseband Q-path waveform data to obtain a baseband I-path analog waveform and a baseband Q-path analog waveform, and inputs the baseband I-path analog waveform and the baseband Q-path analog waveform into the IQ modulator;
the IQ modulator carries out IQ modulation on the baseband I-path analog waveform and the baseband Q-path analog waveform by combining with the intermediate frequency local oscillator signal, generates an intermediate frequency chaotic signal and inputs the intermediate frequency chaotic signal into the transmitting up-conversion module;
the transmitting up-conversion module mixes the intermediate frequency chaotic signal and the radio frequency local oscillation signal to generate a required radio frequency chaotic signal;
the working clock of the baseband IQ waveform generation module, the intermediate frequency local oscillation signal and the radio frequency local oscillation signal are all provided by a frequency source;
the baseband IQ path waveform generation module comprises: the device comprises a chaotic sequence generator, a band-pass filter, two frequency converters and two low-pass filters; wherein, two frequency converters are connected in parallel, each frequency converter is connected in series with a low-pass filter;
the chaotic sequence generator is used for generating a chaotic sequence and inputting the chaotic sequence into the band-pass filter;
the band-pass filter is used for carrying out band-pass filtering treatment on the chaotic sequence to obtain a band-limited chaotic sequence and inputting the band-limited chaotic sequence into the two frequency converters at the same time;
the two frequency converters are used for carrying out digital down-conversion on the band-limited chaotic sequence to obtain two paths of orthogonal baseband chaotic signals, and respectively inputting the two paths of orthogonal baseband chaotic signals into the low-pass filters which are respectively connected in series;
the two low-pass filters are used for respectively carrying out low-pass filtering treatment on the two paths of orthogonal baseband chaotic signals to obtain baseband I-path waveform data and baseband Q-path waveform data of the chaotic radar;
the chaos sequence is as follows:
x(n+1)＝k·x(n)·(1-x(n))
wherein x (N) represents the current value of the Logistic chaotic signal mapping, x (n+1) represents the next iteration value of the Logistic chaotic signal mapping, k is a parameter of the Logistic chaotic signal mapping, N is a sequence number of the Logistic chaotic signal mapping sequence, and n=0, 1,2, …, N P -1，N P For each transmitted pulse corresponding Logistic chaotic sequence Length:
N P ＝T P ·F sr
wherein T is P To transmit pulse signal duration F sr Sampling rate for the DAC module;
the band-limited chaotic sequence x B (n) is:
wherein h is B (k) K=0, 1,2, …, K-1, K is the bandpass filter order, h B (k) According to the pass band range of the band-pass filter [0.5-B ] r /F sr ,0.5+B r /F sr ]Calculated, B r Is the bandwidth of the chaotic waveform transmitted by the radar.
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