CN115436929A - Sawtooth wave radar speed measurement extension method based on amplitude comparison angle measurement mode - Google Patents
Sawtooth wave radar speed measurement extension method based on amplitude comparison angle measurement mode Download PDFInfo
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- 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
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Abstract
The invention discloses a sawtooth wave radar speed measurement expansion method based on a amplitude comparison angle measurement mode, which belongs to the technical field of radar speed measurement and comprises the following steps: s1: a transmitting antenna of the radar transmitter alternately transmits linear frequency modulation continuous wave signals with the same sweep frequency period of T at a first scanning position and a second scanning position respectively; s2: for location in radar
Firstly, collecting data I of M scanning positions I and data II of M scanning positions II on a target with a direction, a distance of R and a speed of v; s3: eliminating constant phase difference caused by the directional change of the antenna direction on the first data phase and the second data phase; s4: performing coherent processing through two-dimensional FFT (fast Fourier transform), and fully utilizing signals to improve the signal-to-noise ratio after the data I and the data II are combined; s5: carrying out CFAR detection on the target; s6: and performing velocity deblurring according to the phase difference on the distance velocity spectrum after the two-dimensional FFT of the data I and the data II.
Description
Technical Field
The invention belongs to the technical field of radar speed measurement, and particularly relates to a sawtooth wave radar speed measurement extension method based on a amplitude comparison angle measurement mode.
Background
Existing sawtooth wave radars typically perform range-velocity decoupling through a two-dimensional FFT. According to the nyquist sampling theorem, the slow time dimension sampling rate is less than the doppler shift produced by object motion, which produces velocity ambiguity. In order to implement the velocity ambiguity resolution radar, a multi-frequency working mode is usually adopted, the selected multi-frequency is relatively prime in a certain frequency unit, the frequency is subjected to regularization processing, and the unambiguous Doppler frequency range is the least common multiple of the unambiguous Doppler frequency range. However, the current multi-frequency working mode has the problems of low time utilization rate, high hardware/calculation complexity, poor robustness and the like.
Considering the presence of a target in front of the radar with velocity v and doppler shift f v =2v/λ, and the repetition frequency of the radar sweep is f T . When the doppler shift is larger than the repetition frequency of the radar sweep, it can be known from the sampling theorem that the doppler frequency measurement has ambiguity, which can be expressed as follows:
in the formula
For sampling frequency f T The apparent doppler shift of (d), m is an integer. According to the formula v = f λ/2, the corresponding velocity blur can be expressed as:
wherein v is T ＝f T Lambda/2 is the maximum unambiguous velocity measurement range at a sampling frequency of 1/T,
is the blur speed at the sampling frequency 1/T.
For speed ambiguity resolution, radars usually use multiple frequencies
The working mode is that the selected multiple frequencies are mutually prime in a certain frequency unit, the frequency is normalized, and the unambiguous Doppler frequency range is the least common multiple of the unambiguous Doppler frequency range:
where lcm (. Cndot.) is taken to be the least common multiple. For actual Doppler shift of f v Is different fromThe apparent doppler frequencies corresponding to the repetition frequencies are:
then there should be:
according to the velocity doppler shift formula, the velocity expression can become:
the Doppler velocity which meets the formula can be conveniently found within a certain range, and the target unambiguous Doppler velocity can be obtained. According to the multiple PRF speed ambiguity resolution principle, the sawtooth wave radar can send two sawtooth wave signals with different sweep frequency periods, the time domain diagram of the sent signals is shown in figure 1, and a transmitting antenna firstly transmits N 1 A sweep period of T 1 Then transmitting N 2 Period T of frequency sweep 2 Is used to generate a chirped continuous wave. Assuming that the target speed remains unchanged, the sampling rate 1/T is estimated from data 1 and data 2 respectively 1 And 1/T at the sampling rate 2 And calculating the target fuzzy speed, and finally performing speed deblurring by using a formula, wherein the flow chart of the algorithm is shown in figure 2.
The traditional multiple PRF speed-resolving fuzzy algorithm has the following defects: the time utilization rate is low. In conventional processes, the same number of frequency modulated continuous waves, i.e. N, are transmitted 1 ＝N 2 So that the data one and the data two obtain the same signal processing gain through the two-dimensional FFT, while losing a partial utilization of the system time. The computational complexity is high. The second data and the first data are subjected to the signal processing process with the same complexity, the two-dimensional FFT and CFAR detection calculation amount is large, and hardware resources are wasted. The robustness is poor. The traditional multiple PRF speed ambiguity resolution algorithm needs to detect a target in two CFAR detections, otherwise, the speed ambiguity resolution cannot be carried out. The CFAR detection threshold is related to various factors, and cannot guarantee accurate detection of the target under the condition of low signal-to-noise ratio.
Disclosure of Invention
In view of the above, the present invention provides a signal processing method for performing velocity expansion in a case of measuring an angle from an amplitude.
In order to achieve the purpose, the invention provides the following technical scheme:
a sawtooth wave radar speed measurement expansion method based on amplitude comparison angle measurement mode comprises the following steps:
s1: a transmitting antenna of the radar transmitter alternately transmits linear frequency modulation continuous wave signals with the same sweep frequency period of T at a first scanning position and a second scanning position respectively;
s2: for location in the radar
Firstly, collecting data I of M scanning positions I and data II of M scanning positions II on a target with a direction, a distance of R and a speed of v;
s3: for each path of received echo signals, constant phase difference caused by the directional change of the antenna direction on a data one phase and a data two phase is eliminated;
s4: and performing coherent accumulation processing through the two-dimensional FFT to ensure that the signal is fully utilized to improve the signal-to-noise ratio after the data I and the data II are combined.
S5: carrying out CFAR detection on the target;
s6: and performing velocity deblurring according to the phase difference on the distance velocity frequency spectrum after the two-dimensional FFT of the data I and the data II.
Further, for location in the radar
Direction, distance R, velocity v, and far-field envelope signal received by the radar at time t from scan position one are represented as:
wherein x is k (t) is the input envelope signal of antenna element k,
is the directional pattern of the antenna element k,
is in the direction of the antenna element k
Time delay of N antenna arrays;
the far-field envelope signal from scan position two received by the radar after one sweep period, i.e. at time T + T, is represented as:
further, the constant phase difference Δ caused by the directional change of the antenna direction on the data one and the data two phases in step S3 1 Comprises the following steps:
wherein, delta (k) is the phase of the kth array element signal, and constant phase difference Delta is eliminated 1 Thereafter, the phase difference between scan position one and scan position two only includes velocity spread.
Further, the maximum non-blur speed is λ/2T.
Further, step S4 specifically includes the following steps: firstly, windowing Fourier change is carried out on received multipath callback signals for two times respectively to obtain two-dimensional images of data I and data II of range Doppler. And then combining the range-doppler of the first data and the range-doppler of the second data, wherein all phases of the first data and the second data are coherent because the constant phase difference is eliminated in the step S3, and the coherence of signals can be fully utilized after combination, so that the signal-to-noise ratio is improved. The two steps of the process are coherent accumulation process.
Further, step S5 specifically includes the following steps: under the condition of ensuring that the false alarm probability is not changed, a detection means for judging whether a target exists at the position is called Constant False Alarm Rate (CFAR) detection. Specifically, a decision threshold is adaptively adjusted through background signals such as clutter, noise and the like around a target to ensure that the false alarm probability is unchanged. The first step is to obtain the power of surrounding noise through various estimation modes, a threshold is determined according to the Newman Pearson criterion, the power exceeds the threshold, the point is considered to have a target, and otherwise, the point has no target, and the like.
Further, step S6 specifically includes the following steps: the position of a target on the range-velocity spectrum is determined through CFAR detection, and the phase difference of the positions of the first data target and the second data target is compared;
if the phase difference is less than +/-pi/2, the target speed range does not exceed the signal speed measurement range with the period of T, and the speed is calculated according to the following formula:
v＝Δ θ λ/4πT
wherein, delta θ Representing the phase difference of the positions of the first data target and the second data target;
if the phase difference is larger than +/-pi/2, the target speed exceeds the speed measurement range, the occurrence of blurring needs to be considered, and the speed is calculated according to the following formula:
v＝Δ θ λ/4πT+v max
wherein v is max Is the maximum tachometer speed of the signal with the period T.
The invention has the beneficial effects that: the invention can expand the speed measuring range of the radar, can carry out reasonable parameter design according to actual requirements and realizes speed measurement. The method processes phase change caused by scanning, realizes full utilization of signals, fully utilizes time accumulation to gain the signals, and has high time utilization rate compared with the traditional speed ambiguity resolution algorithm. According to the method, the data I and the data II are subjected to coherent processing, and the data II and the data I do not need to be subjected to CFAR detection respectively, so that hardware resources are saved. The method fully utilizes the received signals to realize maximum signal gain processing, thereby obtaining the highest signal-to-noise ratio, ensuring the accuracy of CFAR detection and ensuring the robustness of the system.
Additional advantages, objects, and features of the invention will be set forth in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims thereof.
Drawings
In order to make the object, technical scheme and beneficial effect of the invention more clear, the invention provides the following drawings for explanation:
FIG. 1 illustrates a multi-band operation;
FIG. 2 is a flow chart of a multi-frequency velocity deblurring algorithm;
FIG. 3 is a diagram of a scanning pattern of a transmitting antenna at a ratiometric angle;
FIG. 4 is a schematic diagram of speed measurement extension under amplitude comparison angle measurement;
FIG. 5 is a signal processing flow diagram;
FIG. 6 illustrates a dual constant false alarm detector principle;
fig. 7 shows (a) a scanning-position-distance-velocity spectrum diagram and (b) a scanning-position-velocity spectrum diagram.
Detailed Description
Aiming at the problems of the traditional multiple PRF speed ambiguity resolution algorithm, the invention provides a signal processing algorithm for carrying out speed extension under the condition of amplitude comparison and angle measurement.
The radar transmitter mode of operation is first described. Because the pitch angle measurement is performed using the amplitude comparison angle. The transmitting antenna firstly transmits the linear frequency modulation continuous wave with the sweep frequency period of T at the scanning position, and then transmits the linear frequency modulation continuous wave with the sweep frequency period of T at the scanning position two. The transmitted chirped continuous wave signals are alternated for the same sweep period at scan positions one and two, respectively, as shown in fig. 3.
Assumed to be located in the radar
And a target with a speed v is located at the distance R in the direction. Then the far-field envelope signal received by the radar at time t from scan position one may be expressed as:
wherein x is k (t) is the input envelope signal of antenna element k,
is the directional pattern of the antenna element k,
is in the direction of the antenna element k
Time delay of (2). N number of antenna arrays. The far-field envelope signal from scan position two received by the radar after one sweep period, i.e. at time T + T, can be represented as:
the received signals of the first scanning position and the second scanning position of the radar are known by a formula, and the difference in amplitude is mainly determined by a directional diagram
Therefore, the amplitude comparison angle measurement can be carried out, and the angle of the target can be determined. The emphasis is that the phase difference is the time delay caused by the velocity
And directional pattern differences. The scanning mode is found to be a case of continuous scanning at different angles, which causes the initial phases of different scanning angles to be inconsistent. Thus eliminating this phase prior to speed ambiguity by phase
Wherein, Δ (k) is the phase of the kth array element signal.
Once the scanning mode is fixed, the phase difference caused by the directional pointing of the antenna is a constant term, and the speed ambiguity can be eliminated. Cancellation constant Δ 1 Thereafter, the phase difference between scan position one and scan position two only includes velocity spread.
As shown in fig. 4, originally, the maximum unambiguous speed with T as the sweep frequency period is λ/4T, and the maximum unambiguous speed is λ/2T in the amplitude comparing and angle measuring mode, so that the speed measuring range is expanded, and subsequent amplitude comparing and angle measuring can be performed.
The specific signal processing flow is shown in fig. 5.
After data I and data II of M scanning positions I and M scanning positions II are collected, constant phase difference caused by antenna direction change on the data I and the data two phases is eliminated;
then, coherent processing is carried out, so that two-dimensional FFT is carried out only once after the first data and the second data are combined, time and signals are fully utilized, and maximum signal gain processing is realized; the method specifically comprises the following steps: firstly, windowing Fourier change is carried out on received multipath callback signals for two times respectively to obtain two-dimensional images of data I and data II of range Doppler. And then combining the range-doppler of the first data and the range-doppler of the second data, wherein all phases of the first data and the second data are coherent because the constant phase difference is eliminated in the step S3, and the coherence of the signals can be fully utilized after combination, so that the signal-to-noise ratio is improved. The two steps of treatment are coherent accumulation treatment;
then, CFAR detection is performed on the target, and as shown in fig. 6, under the condition that the false alarm probability is not changed, the detection means for determining whether the target exists at the position is called Constant False Alarm (CFAR) detection. Specifically, a decision threshold is adaptively adjusted through background signals such as clutter, noise and the like around a target to ensure that the false alarm probability is unchanged. The first step is that the power of surrounding noise is obtained through various estimation modes, a threshold is determined according to the Newman Pearson criterion, the power exceeds the threshold, the point is considered to have a target, otherwise, the point has no target, and the like;
according to the phase difference on the distance velocity frequency spectrum after the two-dimensional FFT of the data I and the data II, velocity deblurring is carried out, and the method specifically comprises the following steps: the position of a target on the range-velocity spectrum is determined through CFAR detection, and the phase difference of the positions of the first data target and the second data target is compared;
if the phase difference is less than +/-pi/2, the target speed range does not exceed the signal speed measurement range with the period of T, and the speed is calculated according to the following formula:
v＝Δ θ λ/4πT
wherein, delta θ Representing the phase difference of the positions of the first data target and the second data target;
if the phase difference is larger than +/-pi/2, the target speed exceeds the speed measurement range, the occurrence of blurring needs to be considered, and the speed is calculated according to the following formula:
v＝Δ θ λ/4πT+v max
wherein v is max Is the maximum tachometer speed of the signal with period T.
As shown in (a) and (b) of fig. 7, the scanning position one and the scanning position two are at the same position on the range velocity spectrum, and the target velocity is 10m/s only from the range velocity spectrum view, but the target is assumed to be 23.6m/s since the phase difference between the scanning position one and the scanning position two is 212.45 °.
Finally, it is noted that the above-mentioned preferred embodiments illustrate rather than limit the invention, and that, although the invention has been described in detail with reference to the above-mentioned preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims.
Claims (7)
1. A sawtooth wave radar speed measurement expansion method based on amplitude comparison angle measurement mode is characterized by comprising the following steps: the method comprises the following steps:
s1: transmitting linear frequency modulation continuous wave signals with the same sweep frequency period of T are alternately transmitted by a transmitting antenna of the radar transmitter at a first scanning position and a second scanning position respectively;
s2: for location in the radar
Firstly, collecting data I of M scanning positions I and data II of M scanning positions II on a target with a direction, a distance of R and a speed of v;
s3: for each path of received echo signals, constant phase difference caused by the directional change of the antenna direction on a data one phase and a data two phase is eliminated;
s4: performing coherent accumulation processing through two-dimensional FFT;
s5: carrying out constant false alarm CFAR detection on the target;
s6: and performing velocity deblurring according to the phase difference on the distance velocity spectrum after the two-dimensional FFT of the data I and the data II.
2. The sawtooth wave radar speed measurement expansion method based on amplitude comparison angle measurement mode according to claim 1, characterized in that: for location in the radar
For a target with direction, distance R and velocity v, the far-field envelope signal received by the radar at time t from scan position one is represented as:
wherein x is k (t) is the input envelope signal of antenna element k,
is the directional pattern of the antenna element k,
is in the direction of the antenna element k
Time delay of N antenna arrays;
the far-field envelope signal from scan position two received by the radar after one sweep period, i.e. at time T + T, is represented as:
3. the sawtooth wave radar velocity measurement expansion method based on amplitude comparison angle measurement mode as claimed in claim 2, characterized in that: step S3, constant phase difference delta caused by antenna direction pointing change on the data one phase and the data two phase 1 Comprises the following steps:
wherein, delta (k) is the phase of the kth array element signal, and the constant phase difference Delta is eliminated 1 Thereafter, the phase difference between scan position one and scan position two only includes velocity spread.
4. The sawtooth wave radar velocity measurement expansion method based on amplitude comparison angle measurement mode as claimed in claim 1, characterized in that: the maximum unambiguous speed is lambda/2T.
5. The sawtooth wave radar speed measurement expansion method based on amplitude comparison angle measurement mode according to claim 1, characterized in that: step S4 specifically includes the following steps:
s41: firstly, performing windowing Fourier transform twice on received multi-path callback signals respectively to obtain two-dimensional images of data I and data II distance Doppler;
s42: and then combining the range-doppler of the first data and the range-doppler of the second data, wherein all phases of the first data and the second data are coherent because the constant phase difference is eliminated in the step S3, and the coherence of the signals can be fully utilized after combination, so that the signal-to-noise ratio is improved. The two processes are coherent accumulation processes.
6. The sawtooth wave radar velocity measurement expansion method based on amplitude comparison angle measurement mode as claimed in claim 1, characterized in that: step S5, the constant false alarm CFAR detection is to adaptively adjust a decision threshold through a background signal around a target to ensure that a false alarm probability is unchanged, and specifically includes the following steps:
s51: firstly, obtaining the power of surrounding noise;
s52: determining a threshold according to a Newman Pearson criterion;
s53: and judging whether the noise power exceeds a threshold, if so, determining that the point has a target, otherwise, determining that the point has no target.
7. The sawtooth wave radar speed measurement expansion method based on amplitude comparison angle measurement mode according to claim 1, characterized in that: the step S6 specifically includes the following steps:
the position of a target on a distance velocity spectrum is detected and determined through the CFAR, and the phase difference of the positions of the first data target and the second data target is compared;
if the phase difference is less than +/-pi/2, the target speed range does not exceed the signal speed measurement range with the period of T, and the speed is calculated according to the following formula:
v＝Δ θ λ/4πT
wherein, delta θ Representing the phase difference of the positions of the first data target and the second data target;
if the phase difference is larger than +/-pi/2, the target speed exceeds the speed measurement range and needs to be considered to generate ambiguity, and the speed is calculated according to the following formula:
v＝Δ θ λ/4πT+v max
wherein v is max Is the maximum tachometer speed of the signal with the period T.
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| CN116299299A (en) * | 2023-05-12 | 2023-06-23 | 南京隼眼电子科技有限公司 | Speed disambiguation method, device, radar equipment and storage medium |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116299299A (en) * | 2023-05-12 | 2023-06-23 | 南京隼眼电子科技有限公司 | Speed disambiguation method, device, radar equipment and storage medium |
| CN116299299B (en) * | 2023-05-12 | 2023-08-04 | 南京隼眼电子科技有限公司 | Speed disambiguation method, device, radar equipment and storage medium |
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