CN102288942A - Method for designing millimeter wave radar signal waveform - Google Patents

Abstract

The invention relates to a design method of a millimeter-wave radar signal waveform, in particular to a design method of a radar signal waveform under the condition of multi-target identification in complex roads or military environments, and belongs to the technical field of radar communication. The combination of linear frequency modulation continuous wave radar system and pseudo-random code continuous wave radar system is adopted, and the variable period method is adopted in the design process of the transmission signal waveform of the automobile anti-collision radar. The invention utilizes the good correlation characteristics of pseudo-random coding to realize the effective detection of long-distance targets; the combination of linear frequency modulation and pseudo-random coding can effectively suppress the distance side lobe; The periodic mode is helpful for the detection of multiple targets in complex environments; the pseudo-random code phase modulation can realize different codes for different vehicle radars, so as to eliminate the interference caused by oncoming vehicle radars.

Description

A Design Method of Millimeter Wave Radar Signal Waveform

technical field

The invention relates to a design method of a millimeter-wave radar signal waveform, in particular to a design method of a radar signal waveform under the condition of multi-target identification in complex roads or military environments, and belongs to the technical field of radar communication.

Background technique

In the environment where automobile active anti-collision systems and military multi-targets exist, radars face multi-target situations in most cases. In addition to relying on antenna beams to distinguish targets in different directions, multi-targets in the same direction can only rely on Therefore, the selection of the ranging signal system of the millimeter wave radar must be able to meet the basic requirements of multi-target detection.

At present, the ranging signal schemes researched and applied in anti-collision radar mainly include pulse scheme, FSK scheme, SFCW scheme, LFMCW scheme and pseudo-random coding scheme. Because the linear frequency modulation system is relatively simple, in recent years, there are many researches and applications of this anti-collision radar in foreign countries, while the pulse system is less used due to the influence of many factors.

The LFMCW system can achieve better ranging resolution, but for the linear frequency modulation system, its ambiguity function presents the coupling of distance and speed, so the simple sawtooth wave frequency sweep cannot correctly measure the distance of moving vehicle targets, in order to solve this problem The problem is that a triangular wave linear sweep is used to separate the distance and speed of the target by sweeping in two directions. In the case of multiple targets, it is necessary to find out the relationship between the targets obtained by the two sweeps in order to pair and calculate the distance and speed. Speed, in order to enhance the accuracy of target pairing in the case of multiple targets, a combination of different linear frequency sweep slopes is used. Some anti-collision radars use a combination of linear frequency sweep and simple continuous wave to measure speed with a single frequency and use To eliminate the coupling of the distance and speed of the sweep signal. However, these methods are not yet suitable for applications in complex road environments.

In essence, the problems faced by the SFCW system and LFMCW are the same. Although the above-mentioned method of distinguishing multiple targets is adopted, the road conditions or military environment are very complicated, and there are certain problems in the adaptability of the SFMCW signal system when there are many targets within the radar antenna beam range.

Pseudo-noise coded continuous wave radar has received more research in other fields in recent years. The commonly used m-sequence pseudo-random coded phase-modulated continuous wave system has strong anti-interference ability, and the pin-shaped fuzzy map can achieve high-precision distance measurement and speed measurement. capability, however the existence of its non-correlated sidelobes limits the wider application of this regime.

Contents of the invention

The purpose of the present invention is in order to make the radar ranging signal applicable to the anti-collision and target recognition of automobiles under the complex road conditions of multi-vehicle radar work, and is also applicable to anti-jamming and target recognition under the existence of multiple radars in military complex battlefields. A design method of millimeter-wave radar signal waveform is proposed, which adopts the combination of linear frequency modulation continuous wave radar system and pseudo-random code continuous wave radar system, and adopts a variable period method in the design process of vehicle anti-collision radar transmission signal waveform.

The pseudo-random coding CW radar system uses the good correlation characteristics of pseudo-random coding to realize the distance detection of the target, but there is also a certain distance side lobe in the correlation characteristics of pseudo-random coding, which is theoretically related to the reciprocal of the code length, and the distance side lobe The existence of large targets at the same time conceals the detection of small targets. In order to improve the radar's suppression of range side lobes and the accurate identification of multiple targets, this patent proposes a combination of pseudo-random code phase modulation system and linear frequency modulation system. , while adopting a variable cycle method in the design of the launch waveform. The advantages of these three systems are comprehensively utilized, combined with subsequent signal processing links to effectively realize vehicle anti-collision and anti-jamming target recognition.

The purpose of the present invention is achieved through the following technical solutions.

A method for designing a millimeter-wave radar signal waveform of the present invention is used in an automobile anti-collision radar system, and its implementation process specifically includes the following steps:

1) The automotive anti-collision radar system uses a pseudo-random code signal to phase-modulate the variable-period linear frequency modulation signal to generate a radar transmission waveform;

2) The vehicle anti-collision radar system receives target echo signals;

3) The signal processing module of the automobile anti-collision radar system mixes the target echo signal received in step 2) with the local oscillator with the frequency sweep signal to obtain a signal after filtering out the high-frequency component;

4) The automotive anti-collision radar system uses the same pseudo-random code sequence as in step 1) to perform time-delay search, and correlates the pseudo-random code sequence with the signal output in step 3) to suppress other radar emission signals and The interference signal generated by the mixing of the local oscillator signal of the radar;

5) The vehicle anti-collision radar system performs local multi-target recognition on the signal after the correlation processing in step 4).

Beneficial effect

The invention utilizes the good correlation characteristics of pseudo-random coding to realize the effective detection of long-distance targets; the combination of linear frequency modulation and pseudo-random coding can effectively suppress the distance side lobe; The periodic mode is helpful for the detection of multiple targets in complex environments; the pseudo-random code phase modulation can realize different codes for different vehicle radars, so as to eliminate the interference caused by oncoming vehicle radars.

Description of drawings

Fig. 1 is the waveform diagram of the transmitted signal frequency of the variable-period chirp radar in Embodiment 1 of the present invention;

Fig. 2 is the variable-period FMCW radar time-domain signal transmission waveform of the pseudo-random code modulation in Embodiment 1 of the present invention;

Fig. 3 is the frequency spectrum of the variable-period FMCW radar time-domain signal transmission waveform of pseudo-random code modulation in Embodiment 1 of the present invention, wherein the ordinate is the amplitude of the frequency spectrum after doing FFT to the time-domain waveform, and the abscissa is the signal frequency;

Fig. 4 is the cross-correlation output after false target recognition in embodiment 1 of the present invention, wherein the ordinate is the amplitude of the cross-correlation output, and the abscissa is time;

Fig. 5 is the autocorrelation output during effective target recognition in embodiment 1 of the present invention, wherein the ordinate is the amplitude of the autocorrelation output, and the abscissa is time;

Figure 6 is a schematic diagram of all possible results of four groups of targets in Example 2 of the present invention;

FIG. 7 is a schematic diagram of output results after sorting overlapping data among four sets of target calculation results in Embodiment 2 of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Example 1

A method for designing a millimeter-wave radar signal waveform, the specific process of which is:

1) The signal processing module of the automotive anti-collision radar system generates a pseudo-random code sequence PN(t), and uses this pseudo-random code to modulate the variable-period FM signal as shown in Figure 1, thereby obtaining the pseudo-random code sequence within one bit The radar emission waveform can be expressed as:

$\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; PN</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; rect</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; jy\&pi;</span>}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ]</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="j"\; filenames="HSA00000524301300021.png,HSA00000524301300022.png"\; state="\{\{state\}\}">j</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

其中B是调频带宽；f₀为发射信号在t＝nT时的瞬时频率；Among them, t is the duration of a certain bit, the bit width period is T, and T=T ₁ +T ₂ +T ₃ +T ₄ , as shown in Figure 1, where T ₁ , T ₂ , T ₃ and T ₄ are For each small period in the variable-cycle FM signal, n represents the subscript from 1 to 4, that is, T _n represents T ₁ , T ₂ , T ₃ and T ₄ ;

Wherein B is the FM bandwidth; f ₀ is the instantaneous frequency of the transmitted signal at t=nT;

Figure 2 and Figure 3 are obtained by simulating the radar emission waveform and its spectrum;

则式(1)公式可简单表达为：Let the chirp signal be

The formula (1) can be simply expressed as:

S(t)＝PN(t)FM(t)

2) The vehicle anti-collision radar receives the echo signal of the target, assuming that two targets with the same echo intensity have time delay τ ₁ and τ ₂ respectively, where: τ ₁ -τ ₂ >T;

An echo signal with two targets can be expressed as:

S _r (t)=S ₁ (t)+S ₂ (t)=A·PN(t-τ ₁ )FM(t-τ ₁ )+A·PN(t-τ ₂ )FM(t-τ ₂ )(3)

Among them, A is the amplitude of the received signal;

3) The echo signal is mixed with a local oscillator with a frequency sweep signal, and the signal after filtering out the high frequency component is:

S _r (t)=S ₁ (t)+S ₂ (t)=A·PN(t-τ ₁ )SM(t-τ ₁ )+A·PN(t-τ ₂ )SM(t-τ ₂ )(4)

Where SM(t) is the LFM local oscillator and echo mixing output signal;

4) The automotive anti-collision radar system uses the same pseudo-random code sequence in formula (1) to perform delay search, and performs correlation processing with the S _r (t) signal in formula (4), and sets the delay of the local code and the One goal is the same, but not related to the other. Discuss the mechanism of the correlation property of the pseudo-random code on the linear sweep signal. Assuming that the local pseudo-random code is PN(t-τ ₁ ), the signal related to the echo signal is:

S _c (t)＝A·PN(t-τ ₁ )PN(t-τ ₁ )SM(t-τ ₁ )+A·PN(t-τ ₁ )PN(t-τ ₂ )SM(t- τ ₂ )(5)

In order to simplify the analysis without loss of generality, it is assumed that the delay of the local code and the echo delay of the target with a delay of _τ1 are exactly the same, and the ability to suppress the target with a delay of _τ2 is discussed, so that the above formula can be written as:

S _c (t) = A·SM(t-τ ₁ )+A·PN(t-τ ₃ )SM(t-τ ₂ )(6)

Among them, PN(t-τ ₃ )=PN(t-τ ₁ )PN(t-τ ₂ ), the power spectrum of the second item in the above formula is the convolution of the power spectrum of the two signals, it can be seen that the second target produces The side lobe of the second term power spectrum is effectively suppressed, and the degree of suppression is proportional to the length of the PN code.

This is simulated, Figure 4 is the cross-correlation output after false target recognition; Figure 5 is the auto-correlation output when effective target recognition. When the length of the PN code is 63 bits, the suppression of nearly 36dB can be achieved. Therefore, the combined effect of the range sidelobe of the integrated linear frequency modulation and pseudo-random code signal can be suppressed more when a longer pseudo-random code is used.

Example 2

A design method of millimeter-wave radar signal waveform, using variable-period FMCW waveform has good advantages in multi-target recognition, and can solve the problem of false targets existing in traditional linear frequency modulation continuous wave radar.

Assuming that there are 4 targets in front of the car, the echo signal is the superposition of the echo signals of these 4 points, and the beat signal can also be approximately considered as the sum of the beat signals of the echo signals of each point target and the transmitted signal.

Spectrum analysis of the beat signal in the frequency rising section can obtain 4 spectral peaks, which are represented as f _a1 , f _a2 , f _a3 , f _a4 respectively, similarly, the spectrum analysis of the beat signal in the frequency falling section can be obtained The other four spectral peaks are denoted as f _b1 , f _b2 , f _b3 , f _b4 respectively. Since the corresponding relationship between the spectral lines in the two family trees cannot be obtained, in fact, the distance and velocity information cannot be obtained at all. Consider all possibilities, that is, consider all possible pairwise combinations of the two genealogy lines, namely:

$\left[\begin{array}{cccc}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; )</span>\\ <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; )</span>\\ <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; )</span>\\ <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span>& <span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; )</span>\end{array}\right]$

The relationship between velocity v, distance R and spectral line f is shown in the following two formulas:

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; ai</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="f"\; filenames="HSA00000524301300012.png,HSA00000524301300021.png"\; state="\{\{state\}\}">f</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; B</span>}}{\mathrm{<span\; class="notranslate">\; c</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; bj</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; B</span>}}{\mathrm{<span\; class="notranslate">\; c</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

Among them, the subscripts i, j, and k vary from 1 to 4; c is the speed of light; f ₀ is the operating frequency of the millimeter-wave radar; B is the frequency modulation bandwidth; the above formula (7) and formula (8) are calculated to obtain n ² sets of distance and speed, the general expressions are:

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R\; j"\; filenames="HSA00000524301300021.png,HSA00000524301300022.png"\; state="\{\{state\}\}">R</figure-callout></span><figure-callout\; id="2"\; label="R\; j"\; filenames="HSA00000524301300021.png,HSA00000524301300022.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}}{\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="v\; j"\; filenames="HSA00000524301300021.png,HSA00000524301300022.png"\; state="\{\{state\}\}">v</figure-callout></span><figure-callout\; id="2"\; label="v\; j"\; filenames="HSA00000524301300021.png,HSA00000524301300022.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; B</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

According to the above method, respectively target 4 targets—the speed is -40m/s at 20m from the radar, the speed is -20m/s at 10m from the radar, the speed is 60m/s at 18m from the radar, and the speed at 40m/s is at 18m Software simulation is carried out at 28m of the radar. Assuming that the initial frequency is 77GHz, the bandwidth is 40MHz, the sampling time is T ₁ =0.001s, T ₂ =0.002s, T ₃ =0.004s, T ₄ =0.008s. The sampling time of the system is T=1ms, thus the frequency resolution of the system is: Δf=1/(T/2)=2/T=2KHz. The minimum resolution distance of the system is:

$\mathrm{<span\; class="notranslate">\; \&Delta;R</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; cT</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 8</span>}\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&Delta;\; f</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 8</span>}\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 30</span>}}{\mathrm{<span\; class="notranslate">\; 32</span>}}<span\; class="notranslate">\; \&ap;</span>\mathrm{<span\; class="notranslate">\; 0.9</span>}\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; .</span>$

And only related to FM bandwidth. The minimum speed at which the system can be resolved is:

$\mathrm{<span\; class="notranslate">\; \&Delta;v</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&Delta;\; f</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 300</span>}}{\mathrm{<span\; class="notranslate">\; 77</span>}}<span\; class="notranslate">\; \&ap;</span>\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; .</span>$

Perform 1024-point FFT transformation on each segment of the signal, calculate all possible distance and speed values, and display them, as shown in Figure 6. And overlap the four groups of targets, the result is shown in Figure 7. It can be seen from Figure 7 that there are only 4 points overlap in all the data, and the calculated distance and speed are also equal to the set target points. Therefore, computer simulation proves that it is completely feasible to use variable-period FMCW for multi-target recognition.

Embodiment 2 shows that the present invention can solve the problem of false targets existing in traditional linear frequency modulation continuous wave radar in terms of multi-target recognition by using variable-period FMCW waveforms, and can further improve the velocity resolution of the radar. When determining the tolerance function, in order to avoid target separation, the worst case is considered. In actual work, the possibility of two targets having very detailed distance and speed at the same time is very small, so because the tolerance function is too large The probability of identifying two targets as one is very small.

The above description is only a preferred embodiment of the present invention, and the present invention should not be limited to the content disclosed in this embodiment and the accompanying drawings. All equivalents or modifications accomplished without departing from the disclosed spirit of the present invention fall within the protection scope of the present invention.

Claims (1)

1. the method for designing of a MMW RADAR SIGNAL USING waveform is used for the vehicle anticollision radar system, it is characterized in that its implementation procedure comprises following steps:

1) the vehicle anticollision radar system is carried out phase modulation (PM) with the pseudo-random code signal to the variable period linear FM signal, produces the radar emission waveform;

2) vehicle anticollision radar system receiving target echoed signal;

3) signal processing module of vehicle anticollision radar system is with step 2) target echo signal that receives and the local oscillator mixing that has swept-frequency signal, obtain the signal after the filtering high fdrequency component;

4) the vehicle anticollision radar system use with step 1) in identical pseudo-random code sequence carry out delay time search, and the signal of this pseudo-random code sequence and step 3) output carried out relevant treatment, to curb the undesired signal of other radar emission signals and this Radar Local-oscillator signal mixing generation;

5) vehicle anticollision radar system signal that step 4) is carried out after the relevant treatment carries out local multiple goal identification again.

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