CN111522000A - Target detection method based on OFDM-chirp waveform - Google Patents
Target detection method based on OFDM-chirp waveform Download PDFInfo
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- CN111522000A CN111522000A CN202010219048.7A CN202010219048A CN111522000A CN 111522000 A CN111522000 A CN 111522000A CN 202010219048 A CN202010219048 A CN 202010219048A CN 111522000 A CN111522000 A CN 111522000A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/06—Systems determining position data of a target
- G01S13/08—Systems for measuring distance only
- G01S13/32—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
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Abstract
The invention discloses a target detection method based on an OFDM-chirp waveform, which comprises the following steps: s1: designing an OFDM-chirp waveform; s2: carrying out target detection on the OFDM-chirp waveform by adopting an energy detection method; a plot of detection probability versus different SNR is obtained. The designed OFDM-chirp waveform has no distance-Doppler coupling problem faced by an LFM waveform and no problem that an envelope faced by OFDM can change rapidly along with time, and the detection probability of a target is obviously improved compared with the existing LFM waveform and OFDM waveform. In practical application, the method is simple and convenient to calculate and has a better effect.
Description
Technical Field
The invention relates to the technical field of radar signal processing, in particular to a target detection method based on an OFDM-chirp waveform.
Background
Linear Frequency Modulation (LFM) waveform is a common radar signal waveform, and has been widely used in the field of moving object detection. The method has the advantages of constant envelope, signal frequency spectrum approximate to a rectangular window and linear time-frequency characteristics, and can effectively improve the signal-to-noise ratio (SNR) of target detection. On the other hand, an Orthogonal Frequency Division Multiplexing (OFDM) waveform is a waveform orthogonal in frequency, which can implement multi-channel signal transmission on a single antenna and solve the range-doppler coupling problem faced by an LFM waveform, but the envelope of the waveform may change rapidly with time.
Disclosure of Invention
The purpose of the invention is: an OFDM-chirp waveform is designed, the problems of the LFM waveform and the OFDM waveform are solved by utilizing the waveform, and the moving object detection performance is improved. The method comprises the following steps:
s1: designing an OFDM-chirp waveform;
s2: carrying out target detection on the OFDM-chirp waveform by adopting an energy detection method; a plot of detection probability versus different SNR is obtained.
As a further improvement of the above scheme:
further, the method comprises the following steps of; the step S1, designing an OFDM-chirp waveform; let s [ n ]]＝exp[jπk(nTs)2]Representing the original LFM waveform; wherein k is B/TPIndicating the modulation frequency, B, TPRespectively representing the bandwidth and pulse width, T, of the original LFM waveforms＝1/fsDenotes the sampling interval, fs2B denotes the sampling rate, N1, 2P/TsAnd rounded down to represent the number of sample points.
Further, the method comprises the following steps of; wherein S [ p ]]＝FFT{s[n]Denotes s [ n ]]FFT { · } represents an N-point fourier transform; then S is obtained according to interpolation mode 1 and interpolation mode 21[q]And S2[q]：
S1[q]＝[S[0],0,S[1],0,…,S[N-1],0]；
S2[q]＝[0,S[N-1],0,S[N-2],0,…,0,S[0]]；
Wherein q is 1,2,. 2N;
the designed OFDM-chirp waveform is denoted as f (m) ═ iFFT { S1[q]+S2[q]}；
Wherein iFFT {. denotes a 2N-point inverse fourier transform, and m ═ 1, 2.., 2N; the bandwidth of the OFDM-chirp waveform at this time is 2 times that of the original LFM waveform.
Further, the method comprises the following steps of; the step S2 energy detection is detected by an energy detector, which is represented as:
that is, under different SNRs, when the ratio of the signal energy to the noise energy is greater than 1, it is determined that the target is detected.
Further, the method comprises the following steps of; different SNR are simulated by adopting a Monte Carlo simulation method, and the detection probability P under the SNR can be obtained by dividing the times of detecting the target by the total times of the Monte Carlo simulationDFinally, a curve of the detection probability versus different SNRs is obtained.
The invention has the beneficial effects that: the designed OFDM-chirp waveform has no distance-Doppler coupling problem faced by an LFM waveform and no problem that an envelope faced by OFDM can change rapidly along with time, and the detection probability of a target is obviously improved compared with the existing LFM waveform and OFDM waveform. In practical application, the method is simple and convenient to calculate and has a better effect.
Drawings
FIG. 1 is a flow chart of an implementation of the present invention.
Fig. 2 is a design scheme of an OFDM-chirp waveform.
Fig. 3 is a simulation result of a simulation experiment performed using an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, a target detection method based on OFDM-chirp waveform includes the following steps: s1: designing an OFDM-chirp waveform; let s [ n ]]＝exp[jπk(nTs)2]Representing the original LFM waveform; wherein k is B/TPIndicating the modulation frequency, B, TPRespectively representing the bandwidth and pulse width, T, of the original LFM waveforms＝1/fsDenotes the sampling interval, fs2B denotes the sampling rate, N1, 2P/TsAnd rounded down to represent the number of sample points.
As shown in FIG. 2, where S [ p ]]＝FFT{s[n]Denotes s [ n ]]FFT {. cndot } represents an N-point fourier transform. Then S is obtained according to interpolation mode 1 and interpolation mode 21[q]And S2[q]：
S1[q]＝[S[0],0,S[1],0,…,S[N-1],0]
S2[q]＝[0,S[N-1],0,S[N-2],0,…,0,S[0]]
Wherein q is 1, 2. Then, the designed OFDM-chirp waveform may be expressed as f (m) ═ iFFT { S1[q]+S2[q]}
Where iFFT {. denotes a 2N-point inverse fourier transform, and m ═ 1, 2. The bandwidth of the OFDM-chirp waveform at this time is 2 times that of the original LFM waveform.
S2: carrying out target detection on the OFDM-chirp waveform by adopting an energy detection method; a plot of detection probability versus different SNR is obtained.
Target detection is detected by an energy detector, represented as:
that is, under different SNRs, when the ratio of the signal energy to the noise energy is greater than 1, it is determined that the target is detected. Different SNR are simulated by adopting a Monte Carlo simulation method, and the detection probability P under the SNR can be obtained by dividing the times of detecting the target by the total times of the Monte Carlo simulationDFinally, a curve of the detection probability versus different SNRs is obtained.
As shown in fig. 3, a simulation experiment was performed to obtain a simulation result, wherein the horizontal axis represents SNR in dB; the vertical axis represents the detection probability PDThe unit is 1. The imitation isThe true major parameters are as follows: center frequency fc1GHz, bandwidth B50 MHz, TPThe modulation frequency of the original LFM waveform is k, 6 mus.
To illustrate the detection performance of the OFDM-chirp waveform, another LFM waveform also having 2N points is used for comparison, and the frequency modulation rate of the LFM waveform is 2k, so that the bandwidth of the LFM waveform is the same as that of the designed OFDM-chirp waveform. According to simulation results, the OFDM-chirp waveform can obtain higher detection probability than an LFM waveform under the same bandwidth, and has better target detection performance.
The technical solutions of the embodiments of the present invention can be combined, and the technical features of the embodiments can also be combined to form a new technical solution.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (5)
1. A target detection method based on OFDM-chirp waveforms is characterized in that: the method comprises the following steps:
s1: designing an OFDM-chirp waveform;
s2: carrying out target detection on the OFDM-chirp waveform by adopting an energy detection method; a plot of detection probability versus different SNR is obtained.
2. The method of claim 1, wherein the target detection method based on the OFDM-chirp waveform comprises: the step S1; let s [ n ]]＝exp[jπk(nTs)2]Representing the original LFM waveform; wherein k is B/TPIndicating the modulation frequency, B, TPRespectively representing the bandwidth and pulse width, T, of the original LFM waveforms＝1/fsDenotes the sampling interval, fs2B denotes the sampling rate, N1, 2P/TsAnd rounded down to represent the number of sample points.
3. The method of claim 2, wherein the target detection method based on the OFDM-chirp waveform comprises: wherein S [ p ]]＝FFT{s[n]Denotes s [ n ]]FFT { · } represents an N-point fourier transform; then S is obtained according to interpolation mode 1 and interpolation mode 21[q]And S2[q]：
S1[q]＝[S[0],0,S[1],0,…,S[N-1],0]；
S2[q]＝[0,S[N-1],0,S[N-2],0,…,0,S[0]]；
Wherein q is 1,2,. 2N;
the designed OFDM-chirp waveform is denoted as f (m) ═ iFFT { S1[q]+S2[q]}；
Wherein iFFT {. denotes a 2N-point inverse fourier transform, and m ═ 1, 2.., 2N; the bandwidth of the OFDM-chirp waveform at this time is 2 times that of the original LFM waveform.
4. The method of claim 1, wherein the target detection method based on the OFDM-chirp waveform comprises: the step S2 target detection is detected by an energy detector, which is represented as:
that is, under different SNRs, when the ratio of the signal energy to the noise energy is greater than 1, it is determined that the target is detected.
5. The method of claim 4, wherein the target detection method based on the OFDM-chirp waveform comprises: different SNR are simulated by adopting a Monte Carlo simulation method, and the detection probability P under the SNR can be obtained by dividing the times of detecting the target by the total times of the Monte Carlo simulationDFinally, a curve of the detection probability versus different SNRs is obtained.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115550920A (en) * | 2021-06-30 | 2022-12-30 | 中国移动通信有限公司研究院 | Object recognition method, node and computer readable storage medium |
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| CN115550920A (en) * | 2021-06-30 | 2022-12-30 | 中国移动通信有限公司研究院 | Object recognition method, node and computer readable storage medium |
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