TW202009515A - A target detection method by stepped-frequency modulation signals - Google Patents

Abstract

In a target detection method by stepped-frequency modulation signals, continuous wave signals are transmitted through electromagnetic waves by increasing a fixed frequency step by step; two groups of signals are obtained from all fixed time differences of each step corresponding to the electromagnetic wave reflected by a target during the signal transmission process; a third group of signals are obtained from one of the aforementioned two groups of signals in the time delayed by one step in order to obtain two phase difference values; and the two phase difference values are used to analyze and calculate a relative distance and a relative speed of the target.

Description

Target detection method of stepped frequency modulation signal

A target detection method of stepped frequency modulation signal, which detects the relative distance and relative speed of the target by transmitting a specific frequency modulation signal and a sample analysis signal, and its analysis method can avoid the possibility of false targets and reduce errors in the frequency modulation process And reduce the time it takes to sample the overall signal.

According to press, current cars are equipped with reversing radar or distance radar. The aforementioned radar is an active sensing device, which receives the reflection signal actively sent by the radar, and calculates the relative distance of the target object by analyzing the difference between the sent and received signals. Relative speed, different ways of transmitting signals will need to cooperate with the corresponding receiving mode.

In the existing technology, Linear Frequency Modulated Continuous Wave (Linear Frequency Modulated Continuous Wave) is a transmission method for basic measurement of relative distance and relative speed. But the measured signal is a fuzzy signal, which can be expressed by a relationship.

；

;

為測量到的頻差、

為目標物的距離、

為光速、

為單位時間頻率變化率、

為目標物速度、

為載波波長。Among them,

For the measured frequency difference,

Is the distance of the target,

For the speed of light,

Is the frequency change rate per unit time,

For the target speed,

It is the carrier wavelength.

In order to parse out the relative distance and relative speed, it is necessary to transmit the chirped continuous wave with different parameters to obtain the second relational expression, and parse out the relative distance and relative speed using these two relational expressions. However, this method will require additional sampling time. In addition, in the case of multiple targets, the relationship between the two measurements cannot be effectively matched, which will cause false targets.

For the two groups of signals with the same sampling number and the same sampling time interval, after Fast Fourier Transform (Fast Fourier Transform), because the time difference between the starting sampling point is small and the frequency change in the interval is the same, the target will be in the spectrum. A frequency distribution showing almost the same intensity. And the phase of the frequency obtained from the spectrum will also confirm the corresponding relationship. The phase difference between the two groups of frequencies can be expressed by the following relationship.

；

;

為兩個頻率的相位差；

為第一組信號相對於每個鋸齒波起始的時間，

為第二組信號相對於每個鋸齒波起始的時間，

與

是接收與發射頻率對時間參數的函數；可理解到習用的作法同樣花費額外的取樣時間，另外，在多目標物的情況下前後兩次測量的關係式無法有效的配對將會造成虛假目標。

Is the phase difference between the two frequencies;

Is the time of the first set of signals relative to the start of each sawtooth wave,

Is the time of the second set of signals relative to the start of each sawtooth wave,

versus

It is a function of the receiving and transmitting frequency as a function of time parameters; it can be understood that the conventional method also takes extra sampling time. In addition, in the case of multiple targets, the relationship between the two measurements cannot be effectively matched will cause false targets.

Therefore, how to solve the above-mentioned conventional technical problems and deficiencies is the subject of urgent research and development of related industries.

The main object of the present invention is to provide a target detection method of a stepped frequency modulation signal, which is combined with a signal sampling and analysis method to form a target distance and relative speed detection method.

The main technology of the present invention is to use electromagnetic waves to emit continuous wave signals in a step-by-step manner to increase the fixed frequency. During the transmission process, the electromagnetic waves reflected on the target all correspond to each set of fixed time differences to obtain two sets of signals and one set of signals The third set of signals is delayed by the first-order time to obtain two phase differences. The relative distance and relative speed can be resolved through the two phase differences.

According to this, the technology of the present invention can reduce the possibility of false targets, reduce the error in the frequency modulation process, and reduce the time taken for the overall signal sampling compared to the conventional technology.

Please refer to figures 1 to 3, a method for detecting a target of a stepped frequency modulation signal of the present invention is divided into five steps, the first step is signal generation, the second step is to receive reflected signals, and the third step is Signal processing, the fourth step is target detection, and the fifth step is distance and speed analysis.

,時間為

的分階連續調頻波共N個，N為每組信號的取樣數，而每一階起始會相對前一階增加固定頻率

；可以理解到該信號偵測單元在一定時間內會發送出電磁波，並且如第二圖所示電磁波會逐漸調升固定的頻率。Please refer to the first and second figures. The present invention at least includes a signal detection unit that uses electromagnetic waves to step-up a fixed frequency to emit a continuous wave signal. As shown in the second figure, the frequency generated by the signal generation method is the bandwidth for

And the time is

There are a total of N fractional continuous frequency modulation waves, N is the number of samples of each group of signals, and the beginning of each step will increase the fixed frequency relative to the previous step

; It can be understood that the signal detection unit will send out electromagnetic waves within a certain period of time, and as shown in the second figure, the electromagnetic waves will gradually increase the fixed frequency.

，每間隔固定時間

內發射連續波之後增加固定頻率

共N次。使用頻寬共為

，使用時間為

。The following formula can be derived through the technique in the second figure: Controlling FM transmission starts at the carrier frequency

, At regular intervals

Increase the fixed frequency after the continuous wave is transmitted internally

A total of N times. Use bandwidth is

, Used for

.

的時間，由兩個通道I(in-phase)與Q(quadrature)組成的複數值。第一組取樣起始時間相對調頻起始時間為a0，第二組取樣起始時間相對調頻起始時間為b0。第三組取樣起始時間相對調頻起始時間為a1，其中前N-1個取樣點會與第一組後N-1個取樣點重疊。Please refer to the first and third figures. The second step is to collect the reflected electromagnetic waves. When the electromagnetic waves in the first figure are sent and touch an object or an obstacle, a reflected electromagnetic wave is generated. All the aforementioned reflected electromagnetic waves correspond to the first step. With a fixed time difference, you can obtain two sets of signals and a set of signals delayed by a first-order time to obtain the third set of signals. The specific technology is as follows: the signal detection unit receives the reflected wave and immediately samples the signal. The signal sampling method is three. Group signal, each group has N sampling points, each sampling point interval

The time is a complex value composed of two channels I (in-phase) and Q (quadrature). The first group sampling start time is a0 relative to the FM start time, and the second group sampling start time is b0 relative to the FM start time. The start time of the third group of samples is a1 relative to the start time of the frequency modulation, in which the first N-1 sampling points will overlap with the first N-1 sampling points after the first group.

，之後每個取樣點與前一點取樣時間為

，時間相關式為

，i=0~N-1。第二組信號接收時間點為

，之後每個取樣點與前一點取樣時間為

，時間相關式為

，i=0~N-1。第三組信號接收時間點為

，因為前N-1個信號重疊，所以是第一組信號的後N-1個外加最後一階取樣

，時間相關式為

，i=1~N。Therefore, the technique described in the previous paragraph combined with the second diagram can derive the following formula: The first set of signal reception time points is

, The sampling time of each sampling point and the previous point is

, The time correlation is

, I=0~N-1. The second signal reception time is

, The sampling time of each sampling point and the previous point is

, The time correlation is

, I=0~N-1. The third set of signal reception time is

, Because the first N-1 signals overlap, it is the last N-1 signals of the first group of signals plus the last sampling

, The time correlation is

, I=1~N.

As shown in the first figure, after the third step follows the second step, the reflected electromagnetic wave is sampled and the signal is analyzed to obtain the two phase differences to resolve the relative distance and relative speed. The method of signal analysis: three sets of signals The sampling points do fast Fourier transform and obtain three spectrum distributions, and the three spectrums will have similar distributions.

As shown in the first figure, the fourth step is continued after the third step, and the target detection is performed according to the constant False Alarm Rate of the unit. The detected target at the same frequency in each spectrum will be considered as The same target.

As shown in the first figure, after the fifth step follows the fourth step, the phase difference between the first set of signal detected targets and the corresponding second set of signal detected targets will be a relationship of relative speed:

,

=

,

=

,

,

=

,

=

,

是載波頻率。

Is the carrier frequency.

The phase difference between the detected object of the second group of signals and the detected object of the corresponding third group of signals will be the relationship between relative speed and relative distance:

Relative speed resolved Relative distance resolved

Therefore, the distance and relative speed to the target or obstacle can be calculated after conversion, so as to provide the user with the correct adjustment of the vehicle speed and the distance of the scheduled arrival, and the technology of the present invention can eliminate multiple targets Under the circumstances, the relationship between the two measurements cannot be effectively matched, which will cause a false target and reduce the sampling time.

Ghz, 每秒發射

個弦波，每經過

=24e-6秒調升

=390Khz。對接收端接收到的頻差進行取樣，第一組取樣的起始時間6e-6秒，第二組的起始時間18e-6秒，第三組的起始時間30e-6秒會與第一組信號重疊，重疊的部分為兩組信號共用。三組取樣信號經過傅立葉轉換對於相對應目標測量到相同頻率

，卻有不同相位第一組為

，第二組為

，第三組為

。

=-0.241274為第一二組相位差，

=-0.21523264501為第二三組相位差，經所提供的算式解析可得目標物相對距離10公尺，相對速度-10公尺每秒，使用者能取得正確的車距。The actual example of the present invention is as follows: the signal is transmitted at the transmitter with continuous frequency modulation, the carrier frequency

Ghz, emission per second

Sine waves

=24e-6 seconds

=390Khz. Sampling the frequency difference received by the receiving end, the start time of the first group of sampling is 6e-6 seconds, the start time of the second group is 18e-6 seconds, and the start time of the third group is 30e-6 seconds. One set of signals overlaps, and the overlapping part is common to both sets of signals. Three sets of sampled signals undergo Fourier transform to measure the same frequency for the corresponding target

, But the first group with different phases is

, The second group is

, The third group is

.

=-0.241274 is the first and second groups of phase difference,

=-0.21523264501 is the second or third group of phase differences. After the analysis of the provided formula, the relative distance of the target object is 10 meters, and the relative speed is -10 meters per second. The user can obtain the correct distance.

In summary, the structure of the present invention has not been seen in various books or public use, since it meets the requirements of the invention patent application, I urge Junjun Mingjian to grant the patent as soon as possible.

no.

The first figure is a flow block diagram of the present invention; the second figure is a schematic diagram of signal generation of the present invention; and the third figure is a schematic diagram of signal analysis of the present invention.

Claims (6)

A target detection method of stepped frequency modulation signal, which is characterized by using electromagnetic waves to transmit a continuous wave signal in a step-by-step manner to increase the fixed frequency, reflecting all electromagnetic waves corresponding to the target every fixed time difference during the transmission process Obtain two sets of signals and obtain a third set of signals by delaying one set of signals by a first-order time to obtain two phase differences; through the two phase differences, the relative distance and relative speed can be resolved. The method for detecting a target of a stepped frequency modulation signal as described in claim 1, wherein each of the electromagnetic waves emits a fixed frequency continuous wave and then increases to the next fixed frequency before transmitting the fixed frequency continuous wave. A method for detecting a target of a stepped frequency modulation signal according to claim 1 or 2, wherein the frequency of each step of electromagnetic wave emission is the same. The method for detecting a target of a stepped frequency modulation signal according to claim 1, wherein the corresponding sampling time intervals between the three groups of signals are fixed. An object detection method for a stepped frequency modulation signal according to claim 1 or 4, wherein the sampling time point interval between two adjacent signals of each group of signals is the same. A target detection method of a stepped frequency modulation signal as described in claim 1 or 4 or 5, wherein the three sets of signals generate a frequency distribution through Fourier transform, and two phase difference values are obtained with the phase represented by the corresponding frequency.

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