阅读说明：本技术 一种mimo体制下发射波形参数设计的方法 (method for designing transmission waveform parameters under MIMO system ) 是由 胡文 王启霞 于 2019-09-04 设计创作，主要内容包括：本发明公开了一种MIMO体制下发射波形参数设计的方法,目的是能在一定距离范围内分辨车辆,达到良好的测量效果,需要通过设置发射波形的参数来提高方位、距离、速度分辨率。其中方位分辨率与接收天线数量有关,另外为了提高距离和方位分辨率,限定了带宽(B)、脉冲重复周期(PRI)及采样率(fs)等值。本发明增大等效阵列孔径,从而达到提高方位分辨率的效果；高方位分辨率,可以更好地分辨车道,这样在后续点目标检测时,可以更好地区分开目标。(The invention discloses a method for designing transmitting waveform parameters under an MIMO system, aiming at identifying vehicles within a certain distance range to achieve good measurement effect and improving the resolution of direction, distance and speed by setting the parameters of transmitting waveforms. Wherein the azimuth resolution is related to the number of receiving antennas, and in addition, in order to improve the distance and azimuth resolution, the values of bandwidth (B), pulse repetition Period (PRI) and sampling rate (fs) are defined. The invention increases the equivalent array aperture, thereby achieving the effect of improving the azimuth resolution; the high azimuth resolution can better distinguish lanes, so that targets can be better distinguished during subsequent point target detection.)

1. a method for designing transmission waveform parameters under an MIMO system is characterized by comprising the following steps:

The method comprises the following steps: designing the number of receiving and transmitting antennas influencing the measurement azimuth resolution of the MIMO radar;

Step two: designing a bandwidth influencing the measurement range resolution of the MIMO radar;

Step three: designing a pulse repetition period influencing the measurement speed resolution of the MIMO radar;

Step four: designing a pulse number;

step five: and determining the array layout mode of the transmitting and receiving antenna in the first step.

2. the method for designing transmit waveform parameters under the MIMO system according to claim 1, wherein in the first step, the method for designing the number of the transmit/receive antennas specifically comprises:

Designing an equivalent array aperture according to the azimuth resolution:

Where R is the distance over which the radar acts, ρ_aFor azimuthal resolution, λ is the wavelength,c is the speed of light, f₀Is a base carrier frequency;

Setting azimuth resolution requirement rho of system on detection scene_aa is not more than a, and a is a constant, the value range of the equivalent array aperture is as follows:

Designing the number of transmitting and receiving antennas according to the equivalent array aperture:

wherein the content of the first and second substances,n is the number of transmitting and receiving antennas, D is the equivalent arrayThe aperture of the column, r, is the cell pitch of the equivalent array.

3. the method for designing transmit waveform parameters under the MIMO system according to claim 1, wherein in the second step, the method for designing the bandwidth (B) specifically comprises:

According to distance resolution

setting distance resolution requirement R of system to detection scene_resE is less than or equal to e, and e is a constant, then:

4. The method for designing transmit waveform parameters under the MIMO system according to claim 1, wherein in step three, the pulse repetition period designing method specifically comprises:

Designing a PRF range according to the measurement distance range:

Wherein the PRF pulse repetition frequency,/_maxFor the maximum distance measured,/_minIs the minimum distance measured;

The pulse repetition period range PRI is designed according to the PRF range:

5. the method according to claim 1, wherein the number of pulses is an integer multiple of the number of transmitting antennas in the fourth step.

6. The method according to claim 1, wherein in the fifth step, the array layout of the transmit/receive antennas is equivalent antennas, that is, single-transmit single-receive equivalent antennas with the number of transmit antennas multiplied by the number of receive antennas are obtained by a geometric arrangement.

7. The method according to claim 1, wherein in the step one, the MIMO radar transmit/receive antennas are p-transmit and q-receive, that is, the MIMO radar transmit/receive antennas are p-transmit and q-receive

Technical Field

The invention discloses a method for designing a transmission waveform parameter under an MIMO system, and relates to the technical field of traffic radar antennas.

background

Angular resolution characterizes the ability of the radar system to distinguish tangential targets, which directly affects the angular accuracy of the radar. The angular resolution of a radar system depends on the beam width of the radar antenna, which in turn depends on the aperture of the antenna, and thus the larger the antenna aperture of a radar system, the higher the angular resolution and the angular measurement accuracy. The existing AWR1642 chip is a 2-transmitting 4-receiving antenna, the angle measurement resolution is low, and the requirement for distinguishing lanes is difficult to meet.

Disclosure of Invention

in order to solve the problems, the invention provides a method for designing the parameters of the transmitted waveform based on an MIMO radar system, and the measurement effect is improved.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows: a method for designing transmission waveform parameters under an MIMO system comprises the following steps:

The method comprises the following steps: designing the number of receiving and transmitting antennas influencing the measurement azimuth resolution of the MIMO radar;

Step two: designing a bandwidth influencing the measurement range resolution of the MIMO radar;

Step three: designing a pulse repetition period influencing the measurement speed resolution of the MIMO radar;

step four: designing a pulse number;

step five: and determining the array layout mode of the transmitting and receiving antenna in the first step.

further, in the first step, the method for designing the number of the transmitting and receiving antennas specifically comprises:

designing an equivalent array aperture according to the azimuth resolution:

where R is the distance over which the radar acts, ρ_aFor azimuthal resolution, λ is the wavelength,c is the speed of light, f₀Is a base carrier frequency;

setting azimuth resolution requirement rho of system on detection scene_aA is not more than a, and a is a constant, the value range of the equivalent array aperture is as follows:

Designing the number of transmitting and receiving antennas according to the equivalent array aperture:

wherein the content of the first and second substances,n is the number of the transmitting and receiving antennas, D is the aperture of the equivalent array, and r is the unit spacing of the equivalent array.

Further, in the second step, the bandwidth design method specifically includes:

according to distance resolution

setting distance resolution requirement R of system to detection scene_rese is less than or equal to e, and e is a constant, then:

further, in the third step, the pulse repetition period design method specifically comprises: designing a PRF range according to the measurement distance range:

wherein the PRF pulse repetition frequency,/_maxFor the maximum distance measured,/_minIs the minimum distance measured;

The pulse repetition period range PRI is designed according to the PRF range:

And then according to a fuzzy speed formula:

Obtaining corresponding non-fuzzy speed when the target speed V is more than V_aTime, velocity blur V occurs_a：

At this time, the process of the present invention,

PRF＜4Vλ

in addition, byThe chirp rate k of the chirp signal can be obtained.

further, in the fourth step, the number of pulses is an integral multiple of the transmitting antenna.

further, in the fifth step, the transmitting and receiving antennas comprise transmitting antennas and receiving antennas, the transmitting antennas are arranged in a linear array at equal intervals, the receiving antennas are divided into two groups, and the receiving antennas in each group are arranged in a linear array at equal intervals; the array layout mode of the receiving and transmitting antennas adopts equivalent antennas, and single-transmitting single-receiving equivalent antennas with the number of transmitting antennas multiplied by the number of receiving antennas are obtained in a geometric arrangement mode.

Further, in step one, the MIMO radar transmitting and receiving antennas are p-transmitting and q-receiving, that is

Has the advantages that: 1. the invention increases the equivalent array aperture, thereby achieving the effect of improving the azimuth resolution. The high azimuth resolution can better distinguish lanes, so that targets can be better distinguished during subsequent point target detection.

2. The method meets the distance measurement range requirement for actual traffic detection and the unambiguous speed requirement for actual traffic detection.

Drawings

FIG. 1 is a simulated directional diagram;

FIG. 2 is a schematic diagram of an array layout;

FIG. 3 is a schematic diagram of an equivalent array layout;

Fig. 4 is a schematic cross-sectional view of vehicle crossing detection.

Detailed Description

the following describes the embodiments in further detail with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

The embodiment provided by the invention comprises the following steps: the width of the standard lane is 3m and the total width of the 6 lanes is 18 m. A lane width of 18m is covered at a distance of 30m, the required azimuth coverage width or azimuth scan coverage width is 35 °; standard traffic light towers are 5.5m to 7m in height and the beam width in elevation required to cover a distance of 30m to 80m is 6.6 ° (5.5m) or 8.5 ° (7m) but also taking into account the effect of vehicle height so that the far end beam is close to head-up. The elevation beamwidth therefore needs to be 10.5 ° (5.5m) or 13.4 ° (7 m). Therefore, in order to meet the requirements of the radar in the application scenarios, the radar is required to meet the following technical indexes:

Acting distance: the working distance to vehicles (including cars, trucks and the like) is 30-80 m;

The azimuth resolution is less than 3m within the range of action distance, and the lane resolution capability is achieved;

The azimuth beam width of the array surface or the azimuth scanning beam width is not less than 35 degrees,

The system has the capability of simultaneously covering 6 lanes within the range of action distance;

The width of the wave front elevation beam is not less than 13.4 degrees, and the function distance range covering capability is provided.

The design method of the number of the transmitting and receiving antennas comprises the following steps:

Wherein n is the number of the transmitting and receiving antennas, D is the aperture of the equivalent array, and r is the unit interval of the equivalent array.

To achieve lane resolution in the range of action, in particular at a distance of 80m, i.e. to achieve an azimuth resolution of less than 3m at 80m for an equivalent array formed by MIMO, the formula for the azimuth resolution is used(it isIn the formula, R is the distance of radar action, rho_aFor azimuthal resolution, λ is the wavelength,c is the speed of light, f₀Base carrier frequency), knowing that the aperture D length of the equivalent array needs to be more than 100 mm; not only the aperture length of the equivalent array needs to be larger than 100m, but also the unit spacing of the equivalent array meets the requirement that the DBF beam scans +/-17.5 degrees (meets the requirement of 35-degree azimuth coverage) without grating lobes.

fig. 1 shows an antenna coordinate design when the element pitch r of the equivalent array is 2.8mm, which can meet the requirement of scanning ± 17.5 °, and 36 equivalent antenna elements required by an equivalent antenna array with a length of 100mm are required, so that two AWR1243 chips are adopted for cascade connection, and six transmitting channels and eight receiving channels are provided, so that at most 48 equivalent antenna elements can be combined, and the requirement of the equivalent antenna array length greater than 100mm is met.

as shown in fig. 2 to 3, the eight receiving antennas are divided into two sub-arrays, the distance between the receiving antennas in each sub-array is 2.8mm, the distance between the two sub-arrays is 2.8mm × 20, the unit distance between the receiving antennas is 2.8mm × 4, and the unit distance between the six transmitting antennas is 2.8mm × 4.

The antenna arrangement mode forms 47 effective antenna radiation units, the unit interval is 2.8mm, the equivalent array aperture is 131.6mm, so that the azimuth resolution within the action distance range of 30-80 m is 0.97-2.59 m, the width of the lane is smaller, and the vehicle distinguishing capability is achieved to a certain extent. In addition, 1 overlapped equivalent array element position is formed and can be used for correcting the phase of the channel between chips.

formulation by azimuthal resolutionIt can be seen that the larger the equivalent array aperture D, the greater the azimuth resolution ρ of the radar_aThe higher.

As shown in fig. 4, the traffic radar is installed on an oblique opposite traffic light pole, and simultaneously realizes the presence detection of vehicles entering a detection section of 6 lanes within a distance range of 30m to 80m, and can output a trigger signal for each vehicle to enter a virtual coil, leave the signal and provide presence time.

because the length of the detection section is probably less than the length of the vehicle, if the distance low resolution is adopted, each vehicle can reflect back one point and the reflected point can come from different positions of the vehicle, thus not only the vehicle and other metal objects on the road surface can not be distinguished, but also the time of the vehicle entering the detection coil and leaving the detection coil can not be accurately reflected, therefore, the distance resolution is adopted with high distance resolution and is not more than 0.3m, and the formula of the distance resolution is adoptedThe available bandwidth B is more than or equal to 500MHz, so the bandwidth is 540 MHz.

In the engineering practice, the maximum distance measurement range is 80m, so that the pulse repetition period PRI is 24us, the corresponding unambiguous speed is +/-6.7 m/sthe chirp rate k for the chirp signal was found to be 22500G, the value of the chirp rate being used to simulate the defined abscissa in the plot of distances.

base-derived carrier frequency f₀at 77GHz, the number of sampling points of a single chirp is 900, the number of pulses is set to 192, and further, according tothe obtainable sampling frequency fs is 37.5 MHz.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.