A phase coded signal recognition method and system based on instantaneous frequency

Abstract

The present invention discloses a phase-coded signal recognition method and system based on instantaneous frequency. The present invention extracts the instantaneous frequency of the radar signal based on the instantaneous autocorrelation method, and then accumulates the instantaneous phase to improve the anti-noise capability and enhance the instantaneous frequency characteristics of the phase-coded signal. The present invention is simple and easy to implement in engineering, can improve the accuracy of phase-coded signal recognition and has strong anti-noise capability, and is of great significance for complex electronic warfare sorting and target signal recognition.

Description

Technical Field

[0001] The present invention belongs to the field of radar detection technology, and more specifically, relates to a phase coded signal recognition method and system based on instantaneous frequency. Background Art

[0002] Phase coded signals are also called phase shift keying (PSK) signals. Two-phase coded (BPSK) and four-phase coded (QPSK) phase coded signals are more common in radar modulation. At present, the time-frequency analysis method and wavelet transform method for identifying radar modulation signals are complex, have poor system delay performance, and require large amounts of calculation, which is not conducive to engineering implementation. Pulse word description, spectrum analysis, instantaneous frequency recognition and other methods cannot distinguish phase coded waveforms when the signal-to-noise ratio deteriorates, and the recognition probability is low. Summary of the invention

[0003] In response to at least one defect or improvement need in the prior art, the present invention provides a phase-coded signal recognition method and system based on instantaneous frequency, which can improve the accuracy of phase-coded signal recognition and has strong anti-noise ability, and is of great significance for complex electronic warfare sorting and target signal recognition.

[0004] To achieve the above object, according to a first aspect of the present invention, a method for identifying a phase coded signal based on instantaneous frequency is provided, comprising the steps of:

[0005] The phase-coded signal is digitally channelized and discretely sampled to obtain instantaneous phase information of the sampling point of each sub-channel signal;

[0006] Obtaining instantaneous frequency information of a sampling point of each subchannel signal according to instantaneous phase information of adjacent sampling points;

[0007] The modulation type of the phase-coded signal is determined according to the distribution characteristics of the instantaneous frequency information of the sampling points, and the phase-coded signal is identified.

[0008] Furthermore, the instantaneous frequency information of the sampling point is corrected according to the instantaneous frequency information of the adjacent sampling points, and the modulation type of the phase coded signal is determined according to the distribution characteristics of the instantaneous frequency information of the corrected sampling points, and the phase coded signal is identified.

[0009] Furthermore, the average value of the instantaneous frequency information of the sampling point and its adjacent sampling points is used as the corrected instantaneous frequency information of the sampling point.

[0010] Further, the determining the modulation type of the phase coded signal comprises the steps of:

[0011] Identify all frequency hopping points contained in each sub-channel signal according to the instantaneous frequency information of the sampling point;

[0012] Obtain the time domain amplitudes of all frequency hopping points, and accumulate the time domain amplitudes of all frequency hopping points;

[0013] The modulation type of the phase coded signal is determined according to the distribution characteristics of the frequency hopping points.

[0014] Furthermore, the identifying frequency jump point comprises the steps of:

[0015] A frequency difference jump threshold is set. If the instantaneous frequency information difference between two adjacent sampling points is greater than the frequency difference jump threshold, the later sampling point of the two sampling points is recorded as a frequency jump point.

[0016] Further, the step of obtaining the instantaneous frequency information of the sampling points of each subchannel signal according to the instantaneous phase information of adjacent sampling points comprises the following steps:

[0017] First, the instantaneous phase information of adjacent sampling points of each subchannel signal is defuzzified, and then the instantaneous autocorrelation is calculated using the first-order difference algorithm to obtain the instantaneous deviation value of each subchannel signal from its center frequency. The instantaneous deviation value is added to the center frequency value of the corresponding channel signal to obtain the instantaneous frequency information of the sampling point of each subchannel signal.

[0018] Further, the determining the modulation type of the phase coded signal comprises the steps of:

[0019] The instantaneous frequency information of the sampling point is a constant with a phase mutation; if the instantaneous frequency information of the sampling point has only one phase mutation value, the phase-coded signal is a two-phase coded signal; if the instantaneous frequency information of the sampling point has two mutation values ​​whose peak values ​​are multiples of each other, the phase-coded signal is a four-phase coded signal.

[0020] According to a second aspect of the present invention, there is provided a phase coded signal recognition system based on instantaneous frequency, comprising:

[0021] An instantaneous phase acquisition module is used to digitally channelize and discretely sample the phase-coded signal to obtain the instantaneous phase information of the sampling point of each sub-channel signal;

[0022] An instantaneous frequency acquisition module, used to obtain instantaneous frequency information of the sampling points of each sub-channel signal according to the instantaneous phase information of adjacent sampling points;

[0023] The identification module is used to determine the modulation type of the phase-coded signal according to the distribution characteristics of the instantaneous frequency information of the sampling points and perform phase-coded signal identification.

[0024] Further, the determining the modulation type of the phase coded signal comprises the steps of:

[0025] Identify all frequency hopping points contained in each sub-channel signal according to the instantaneous frequency information of the sampling point;

[0026] Obtain the time domain amplitudes of all frequency hopping points, and accumulate the time domain amplitudes of all frequency hopping points;

[0027] The modulation type of the phase coded signal is determined according to the distribution characteristics of the frequency hopping points.

[0028] Further, the determining the modulation type of the phase coded signal comprises the steps of:

[0029] The instantaneous frequency information of the sampling point is a constant with a phase mutation; if the instantaneous frequency information of the sampling point has only one phase mutation value, the phase-coded signal is a two-phase coded signal; if the instantaneous frequency information of the sampling point has two mutation values ​​whose peak values ​​are multiples of each other, the phase-coded signal is a four-phase coded signal.

[0030] In general, compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) A new phase-coded signal recognition method and system is proposed. It is simple and easy to implement in engineering. It can recognize phase-coded signals with high accuracy and has strong anti-noise ability. It is of great significance for complex electronic warfare sorting and target signal recognition.

[0032] (2) The instantaneous autocorrelation method and the instantaneous phase accumulation algorithm are combined. The instantaneous frequency of the radar signal is extracted based on the instantaneous autocorrelation method, and then the instantaneous phase is accumulated to improve the anti-noise ability, thereby enhancing the instantaneous frequency characteristics of the phase-coded signal, which can further improve the recognition accuracy and anti-noise ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the principle of a phase coded signal recognition method based on instantaneous frequency according to an embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] A method for identifying a phase coded signal based on instantaneous frequency according to an embodiment of the present invention comprises the following steps:

[0036] S1, digitally channelize and discretely sample the phase coded signal to obtain instantaneous phase information of the sampling point of each sub-channel signal.

[0037] Specifically, for the missile-borne radar signal S(m), it is digitally channelized to obtain the I quantity (in-phase signal, i.e., the same-phase signal) and Q quantity (quadrature signal, i.e., the orthogonal signal) of each sub-channel.

[0038] Then, the CORDIC (Coordinate Rotation Digital Computer) algorithm is used to calculate the signal envelope amplitude A(m) and instantaneous phase information φ(m) of each subchannel, as shown in formula (1) and formula (2), where the instantaneous phase is used for signal frequency measurement and the envelope amplitude is used for signal energy detection.

[0039]

[0040]

[0041] Wherein, m represents the sampling point, Q(m) represents the sampling value of the m-th sampling point of the Q quantity, and I(m) represents the sampling value of the m-th sampling point of the I quantity.

[0042] S2, obtaining instantaneous frequency information of the sampling point of each sub-channel signal according to the instantaneous phase information of adjacent sampling points.

[0043] Furthermore, the instantaneous frequency information of the sampling point is corrected according to the instantaneous frequency information of the adjacent sampling points, and the modulation type of the phase coded signal is determined according to the distribution characteristics of the instantaneous frequency information of the corrected sampling points, and the phase coded signal is identified.

[0044] Furthermore, the instantaneous frequency information of the sampling point is corrected according to the instantaneous frequency information of the adjacent sampling points by taking the average value of the instantaneous frequency information of the sampling point and its adjacent sampling points as the corrected instantaneous frequency information of the sampling point.

[0045] Furthermore, the instantaneous autocorrelation algorithm is used to find the instantaneous frequency of the radar signal, and the modulation category of the phase-coded radar signal is extracted according to the instantaneous frequency characteristics. That is, the instantaneous phase information of the adjacent sampling points of each subchannel signal is first defuzzified, and then the instantaneous autocorrelation calculation is performed using the first-order difference algorithm to obtain the instantaneous deviation value of each subchannel signal from its center frequency, and the instantaneous deviation value is added to the center frequency value of the corresponding channel signal to obtain the instantaneous frequency information of the sampling point of each subchannel signal.

[0046] The following is a specific implementation of the instantaneous autocorrelation algorithm in combination with the formula:

[0047] (1) Assume that the radar phase coding signal is Where f0 is the carrier frequency of the signal, f s is the sampling frequency of the signal, is the initial phase. According to formula (3), the instantaneous autocorrelation function R(m,n) of the signal S(m) is obtained:

[0048]

[0049] In formula (3) is the instantaneous phase of signal S(m) at time m, that is is the instantaneous phase of the signal S(m+n), that is, the instantaneous phase of the signal S(m) at time m+n), that is A represents the signal amplitude; n represents the time delay. If instantaneous autocorrelation is performed on two adjacent points, n is 1. The following calculations default to two adjacent points.

[0050] According to formula (3), the instantaneous phase difference of the signal is for

[0051]

[0052] First, the instantaneous phase difference Defuzzification is performed. The defuzzification process is to process all phases that are not in the range of [-180°, 180°] into phases within the range of [-180°, 180°]. Then, the instantaneous phase is calculated using the first-order difference frequency measurement method, as shown in formula (5). The instantaneous value f(m) of each channel deviating from its center frequency is obtained, and the center frequency value of the corresponding channel is added to obtain the instantaneous frequency f of the signal. CF (m). f(m) is solved as follows:

[0053]

[0054] Among them, f s is the sampling frequency.

[0055] According to the definition of phase modulation, the instantaneous phase difference of various phase modulation signals is It can be expressed as formula (6)

[0056]

[0057] Where c(m) is the encoding information of the phase-coded signal.

[0058] Therefore, the instantaneous frequency of various phase modulated signals is shown in formula (7):

[0059]

[0060] S3, determining the modulation type of the phase coded signal according to the distribution characteristics of the instantaneous frequency information of the sampling points and performing phase coded signal recognition.

[0061] When there is no code element mutation, the instantaneous frequency of the phase-coded signal remains unchanged. When there is a code element mutation, its frequency will also mutate. This frequency mutation is caused by changing its phase modulation, which is a common feature of phase-coded signals. Therefore, the modulation category of the signal can be effectively identified based on the distribution characteristics of the instantaneous frequency.

[0062] Furthermore, the modulation type of the phase-coded signal is determined specifically as follows: the instantaneous frequency information of the sampling point is a constant with a phase mutation. If the instantaneous frequency information of the sampling point has only one phase mutation value, the phase-coded signal is a two-phase coded signal (BPSK). If the instantaneous frequency information of the sampling point has two mutation values ​​whose peak values ​​are multiples of each other, the phase-coded signal is a four-phase coded signal (QPSK).

[0063] Furthermore, an instantaneous phase accumulation algorithm is used to improve the anti-noise capability of modulation signal recognition.

[0064] The specific implementation of the instantaneous phase accumulation algorithm includes the following steps:

[0065] (1) Identify all frequency hopping points contained in each sub-channel signal based on the instantaneous frequency information of the sampling point.

[0066] Identifying the frequency jump point specifically includes the steps of: setting a frequency difference jump threshold value; if the instantaneous frequency information difference between two adjacent sampling points is greater than the frequency difference jump threshold value, recording the later sampling point of the two sampling points as the frequency jump point;

[0067] (2) Obtain the time domain amplitudes of all frequency jump points and accumulate the time domain amplitudes of all frequency jump points, so that the sudden change at the jump points in the frequency domain is strengthened.

[0068] (3) Determine the modulation type of the phase-coded signal based on the distribution characteristics of the frequency jump points.

[0069] Another embodiment of the present invention is a phase coded signal recognition method based on instantaneous frequency, the principle of which is as follows: Figure 1 As shown, the steps include:

[0070] (1) The phase-coded signal is digitally channelized and discretely sampled, and the signal to be processed is subjected to a CORDIC algorithm to obtain the instantaneous phase information of the sampling point of each sub-channel signal;

[0071] (2) The instantaneous phase value is subjected to first-order difference calculation and defuzzification to obtain the instantaneous frequency information of the signal;

[0072] (3) Divide the instantaneous frequency into countless N-length segments, perform N-point sliding average processing on the instantaneous frequency, and use the mean value to replace the instantaneous frequency value of the N-point length segment;

[0073] (4) Setting the frequency difference jump threshold value and recording the positions where the frequency difference exceeds the threshold value twice;

[0074] (5) Accumulate the amplitude of the transition point in the time domain according to the threshold value to obtain the accumulation and enhancement of the mutation at the transition point in the frequency domain;

[0075] (6) Identify binary phase coded (BPSK) and quadrature phase coded (QPSK) radar modulation signals based on the distribution characteristics of the accumulated instantaneous frequency.

[0076] Binary Phase Shift Keying (BPSK): Since the BPSK modulation signal S BPSK (m) can simultaneously transmit and receive information of two values ​​(1 bit), that is, the phase of the carrier signal is modulated by two code elements "0" and "1" in two ways, "0" and "π". After the code elements "0" and "1" are modulated, the carrier phase difference is 180°. Therefore, according to formula (6), the instantaneous phase difference of the BPSK modulated signal can be obtained: The specific form is shown in formula (8):

[0077]

[0078] Then the instantaneous frequency information f of the BPSK modulated signal BPSK (m) As shown in formula (9):

[0079]

[0080] When there is no code element mutation, that is, when the code element is always "0" or "1", the instantaneous frequency of the signal is f0 and remains unchanged; when there is a code element mutation, that is, when the code element mutates from "0→1" and "1→0", the instantaneous frequency of the signal mutates, and the absolute value of the frequency change is a value: |f0+f s / 2|.

[0081] Quaternary Phase Keying (QPSK): Since the QPSK modulated signal can transmit and receive 4 values ​​(2 bits) of information at the same time, the carrier is modulated by the code elements "00", "01", "10" and "11" in four phases: "π / 4", "3π / 4", "-π / 4" and "-3π / 4". According to the above steps, the instantaneous phase difference of the QPSK modulated signal can be specifically expressed as shown in formula (10):

[0082]

[0083] Then the instantaneous frequency information f of the QPSK modulated signal QPSK (m) As shown in formula (9):

[0084]

[0085] where fQPSK (m) When there is no code mutation, that is, when the code is always "00", "01", "10" or "11", the instantaneous frequency of the signal is f0 and remains unchanged; when there is a code mutation, that is, when the code is mutated to "00", "01", "10" or "11", the instantaneous frequency of the signal mutates, and the absolute value of the frequency change is two values: |f0±f s / 8| and |f0±3f s / 8|, that is, there are two mutation values ​​whose peak values ​​are multiples of each other in the time-frequency domain.

[0086] The embodiment of the present invention combines the instantaneous autocorrelation algorithm and the instantaneous phase accumulation algorithm. First, the instantaneous autocorrelation algorithm is used to obtain instantaneous frequency information with a certain anti-noise capability, thereby realizing effective recognition of radar modulation signals such as binary phase coded waveform (BPSK) and quadrature phase coded waveform (QPSK). Then, the instantaneous phase accumulation algorithm is added to improve the anti-noise capability of modulation signal recognition, and the characteristic of its time domain accumulation that the mutation at the instantaneous frequency jump in the frequency domain is strengthened is used, thereby improving the recognition probability of the phase coded modulation signal.

[0087] A phase coded signal recognition system based on instantaneous frequency according to an embodiment of the present invention includes:

[0088] An instantaneous phase acquisition module is used to digitally channelize and discretely sample the phase-coded signal to obtain the instantaneous phase information of the sampling point of each sub-channel signal;

[0089] An instantaneous frequency acquisition module, used to obtain instantaneous frequency information of the sampling points of each sub-channel signal according to the instantaneous phase information of adjacent sampling points;

[0090] The identification module is used to determine the modulation type of the phase-coded signal according to the distribution characteristics of the instantaneous frequency information of the sampling points and perform phase-coded signal identification.

[0091] Further, determining the modulation type of the phase coded signal comprises the steps of:

[0092] Identify all frequency hopping points contained in each sub-channel signal according to the instantaneous frequency information of the sampling point;

[0093] Obtain the time domain amplitudes of all frequency hopping points, and accumulate the time domain amplitudes of all frequency hopping points;

[0094] The modulation type of the phase coded signal is determined according to the distribution characteristics of the frequency hopping points.

[0095] Further, determining the modulation type of the phase coded signal comprises the steps of:

[0096] The instantaneous frequency information of the sampling point is a constant with a phase mutation; if the instantaneous frequency information of the sampling point has only one phase mutation value, the phase-coded signal is a two-phase coded signal; if the instantaneous frequency information of the sampling point has two mutation values ​​whose peak values ​​are multiples of each other, the phase-coded signal is a four-phase coded signal.

[0097] The implementation principle and technical effects of the system are similar to the above method and will not be repeated here.

[0098] It must be noted that in any of the above embodiments, the method is not necessarily executed in sequence according to the sequence number. As long as it cannot be inferred from the execution logic that it must be executed in a certain order, it means that it can be executed in any other possible order.

[0099] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A phase coded signal recognition method based on instantaneous frequency, characterized in that: Includes steps: The phase-coded signal is digitally channelized and discretely sampled to obtain instantaneous phase information of the sampling point of each sub-channel signal; Obtaining instantaneous frequency information of a sampling point of each subchannel signal according to instantaneous phase information of adjacent sampling points; Determine the modulation type of the phase coded signal and perform phase coded signal recognition according to the distribution characteristics of the instantaneous frequency information of the sampling points; The method of determining the modulation type of the phase-coded signal includes the steps of: identifying all frequency hopping points contained in each sub-channel signal according to the instantaneous frequency information of the sampling point; obtaining the time domain amplitudes of all frequency hopping points, and accumulating the time domain amplitudes of all frequency hopping points; and determining the modulation type of the phase-coded signal according to the distribution characteristics of the frequency hopping points.

2. A phase coded signal recognition method based on instantaneous frequency as claimed in claim 1, characterized in that: The instantaneous frequency information of the sampling point is corrected according to the instantaneous frequency information of the adjacent sampling points, and the modulation type of the phase coded signal is determined according to the distribution characteristics of the instantaneous frequency information of the corrected sampling points, and the phase coded signal is identified.

3. A phase coded signal recognition method based on instantaneous frequency as claimed in claim 2, characterized in that: The average value of the instantaneous frequency information of the sampling point and its adjacent sampling points is used as the corrected instantaneous frequency information of the sampling point.

4. A phase coded signal recognition method based on instantaneous frequency as claimed in claim 1, characterized in that: Identifying the frequency jump point includes the following steps: A frequency difference jump threshold is set. If the instantaneous frequency information difference between two adjacent sampling points is greater than the frequency difference jump threshold, the later sampling point of the two sampling points is recorded as a frequency jump point.

5. The method for identifying a phase coded signal based on instantaneous frequency according to claim 1, characterized in that: The step of obtaining the instantaneous frequency information of the sampling points of each subchannel signal according to the instantaneous phase information of adjacent sampling points comprises the following steps: First, the instantaneous phase information of adjacent sampling points of each subchannel signal is defuzzified, and then the instantaneous autocorrelation is calculated using the first-order difference algorithm to obtain the instantaneous deviation value of each subchannel signal from its center frequency. The instantaneous deviation value is added to the center frequency value of the corresponding channel signal to obtain the instantaneous frequency information of the sampling point of each subchannel signal.

6. A phase coded signal recognition method based on instantaneous frequency as claimed in claim 1, characterized in that: Determining the modulation type of the phase coded signal comprises the steps of: The instantaneous frequency information of the sampling point is a constant with a phase mutation; if the instantaneous frequency information of the sampling point has only one phase mutation value, the phase-coded signal is a two-phase coded signal; if the instantaneous frequency information of the sampling point has two mutation values ​​whose peak values ​​are multiples of each other, the phase-coded signal is a four-phase coded signal.

7. A phase coded signal recognition system based on instantaneous frequency, characterized in that: include: An instantaneous phase acquisition module is used to digitally channelize and discretely sample the phase-coded signal to obtain the instantaneous phase information of the sampling point of each sub-channel signal; An instantaneous frequency acquisition module, used to obtain instantaneous frequency information of the sampling points of each sub-channel signal according to the instantaneous phase information of adjacent sampling points; An identification module is used to determine the modulation type of the phase coded signal and perform phase coded signal identification according to the distribution characteristics of the instantaneous frequency information of the sampling points; wherein the determination of the modulation type of the phase coded signal comprises the steps of: identifying all frequency hopping points contained in each sub-channel signal according to the instantaneous frequency information of the sampling points; obtaining the time domain amplitudes of all frequency hopping points, and accumulating the time domain amplitudes of all frequency hopping points; The modulation type of the phase coded signal is determined according to the distribution characteristics of the frequency hopping points.

8. A phase coded signal recognition system based on instantaneous frequency as claimed in claim 7, characterized in that: Determining the modulation type of the phase coded signal comprises the steps of: The instantaneous frequency information of the sampling point is a constant with a phase mutation; if the instantaneous frequency information of the sampling point has only one phase mutation value, the phase-coded signal is a two-phase coded signal; if the instantaneous frequency information of the sampling point has two mutation values ​​whose peak values ​​are multiples of each other, the phase-coded signal is a four-phase coded signal.

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