阅读说明：本技术 一种毫米波多天线距离测量系统 (Millimeter wave multi-antenna distance measuring system ) 是由 赛景波 申朝维 张昕 于 2020-12-10 设计创作，主要内容包括：本发明公开了一种毫米波多天线距离测量系统,包括多天线收发结构,和与其对应窗口处理及距离角度结合扩展算法。多天线收发结构含四个发射天线、八个接收天线及电子切换开关。系统利用天线采集数据,并进行距离维度FFT,依次实现一次加窗、一次截取、二次加窗、二次截取操作获取处理窗口。之后二次采集,将天线虚拟为一发三十二收,对数据进行距离维度FFT并利用窗口截取及保存数据,再依次进行第二次距离维度FFT及天线维度FFT,结合窗口得角度范围角度仓,对其进行调整和扩展扫描得内部角度值。之后选取角度对应天线的数据处理,扩展1024点扫描获取距离值,最后进行距离在角度仓内角度方向投影,得高精度距离值。(The invention discloses a millimeter wave multi-antenna distance measuring system which comprises a multi-antenna transceiving structure and a window processing and distance angle combination expansion algorithm corresponding to the multi-antenna transceiving structure. The multi-antenna transceiving structure comprises four transmitting antennas, eight receiving antennas and an electronic change-over switch. The system acquires data by using an antenna, performs distance dimension FFT, and sequentially realizes primary windowing, primary interception, secondary windowing and secondary interception to acquire a processing window. And secondly, performing secondary acquisition, namely virtualizing the antenna into one-sending-thirty-two-receiving, performing distance dimension FFT on the data, intercepting and storing the data by using a window, sequentially performing secondary distance dimension FFT and antenna dimension FFT, obtaining an angle range angle bin by combining the window, and adjusting and expanding the angle range angle bin to obtain an internal angle value. And then selecting data processing of the antenna corresponding to the angle, expanding 1024-point scanning to obtain a distance value, and finally projecting the distance in the angle direction in the angle bin to obtain a high-precision distance value.)

1. A millimeter wave multi-antenna distance measuring system is characterized in that the invention designs a multi-antenna receiving and transmitting structure, which is composed of a transmitting antenna array, a receiving antenna array and an electronic change-over switch; and designing a window processing and distance angle combination expansion algorithm corresponding to the structure to realize high-precision distance measurement.

2. The millimeter wave multi-antenna distance measuring system according to claim 1, wherein the multi-antenna transceiving structure comprises four transmitting antennas and eight receiving antennas, and the system uses an electronic switch to switch the transmitting antennas and the receiving antennas respectively. All the antennas are connected with an AWR1243, the system is cascaded by using two AWR1243 chips, and each AWR1243 is connected with two transmitting antennas and four receiving antennas.

3. The millimeter wave multi-antenna distance measurement system according to claim 1, characterized in that four transmitting antennas are used for switching, data acquisition and distance dimension Fast Fourier Transform (FFT) processing are sequentially performed on eight receiving antennas, and primary windowing, primary interception, secondary windowing and secondary interception are sequentially realized in cooperation with window processing to obtain a window required for final processing.

4. The millimeter wave multi-antenna distance measurement system according to claim 1, characterized in that the system performs secondary scanning after acquiring the window, the antennas are virtualized as one-transmission thirty-two-reception, distance dimension FFT is performed first and window interception is performed to retain data, then window data secondary distance dimension FFT is performed and antenna dimension FFT of multiple receiving antennas is performed to obtain an angle range, i.e. an angle bin, and the angle bin is scaled to a horizontal position and expanded for 128-point scanning to obtain a high-precision angle in the angle bin. And then selecting antenna reserved data corresponding to the high-precision angle for processing, carrying out window data expansion 1024 point scanning to obtain a distance value, and finally carrying out high-precision angle direction projection of the distance in an angle bin to obtain a high-precision distance value.

Technical Field

The invention relates to the field of antenna technology and distance measurement, in particular to a millimeter wave multi-antenna distance measurement system working in a frequency band of 77 GHz-81 GHz.

Background

The millimeter wave is an electromagnetic wave with the wavelength of 1-10 mm, and the working frequency is 30-300 GHz. Millimeter waves have many advantages over electromagnetic waves in other bands such as: the beam is narrow, the directivity is good, the space resolution is extremely high, and the tracking precision is high; the Doppler effect is obvious, and the Doppler resolution is good; extremely wide bandwidth, etc. In addition, the distance measurement of the plane can be realized by combining the algorithm processing with the use of multiple antennas, and the high-precision measurement can be realized under the use of the multiple antennas. The invention uses the millimeter wave antenna working at the frequency band of 77 GHz-81 GHz, combines the multi-antenna receiving and transmitting structure with data processing, realizes the multi-antenna distance measurement, overcomes the defect of insufficient received signals, and also improves the accuracy of the distance measurement.

Disclosure of Invention

The technical problem to be solved by the invention is to realize a system for realizing multi-antenna distance measurement by using millimeter waves, select millimeter wave bands to transmit and receive, use a multi-antenna transceiving structure, and realize high-precision distance measurement by matching with window processing and distance angle combination extension algorithms corresponding to the structure.

The technical scheme adopted by the invention for solving the technical problems is as follows: designing a multi-antenna transceiving structure, and designing an expansion algorithm combining window processing and distance angles corresponding to the structure.

The multi-antenna transceiving structure consists of a transmitting antenna array, a receiving antenna array and an electronic change-over switch, millimeter waves are transmitted through the transmitting antenna, the receiving antenna receives echoes and realizes antenna transceiving by combining the electronic change-over switch, the transmitting antenna array comprises four transmitting antennas, and the receiving antenna array comprises eight receiving antennas. The system uses electronic switches to switch the transmitting antenna and the receiving antenna respectively, the transmitting antenna array uses three electronic switches to switch, and the receiving antenna array uses seven electronic switches to switch. All the antennas are connected with an AWR1243 chip, the system uses two AWR1243 chips for cascade connection, and each AWR1243 chip is connected with two transmitting antennas and four receiving antennas.

The transmitting antenna and the receiving antenna of the multi-antenna transceiving structure are microstrip linear array antennas and are composed of rectangular patches with the length of 1.5mm and the width of 0.97mm, wherein the length of a feeder line is 1.18mm, the width of the feeder line is 0.1mm, a medium adopts RO43 4350B, the thickness of the medium is 0.1016mm, and the multi-antenna transceiving structure is formed by adopting a mode of adding a medium substrate and a reference ground to the antenna.

The multi-antenna transceiving structure consists of four transmitting antennas and eight receiving antennas. Eight receiving antennas of the receiving antenna array are adjacent, the distance between every two receiving antennas is half of the waveguide wavelength, four transmitting antennas of the transmitting antenna array are adjacent, the distance between every two transmitting antennas is two waveguide wavelengths, and the distance between the transmitting antenna array and the receiving antenna array is 7 mm. The distance relationship between the transmitting antenna and the receiving antenna can make the four-transmitting eight-receiving antenna into one-transmitting thirty-two-receiving antenna.

The window processing and distance angle combined expansion algorithm comprises the following steps:

(1) the system uses a TX1 and an RX1 antenna to carry out millimeter wave transceiving, samples 512 points each time, carries out Fast Fourier Transform (FFT) on a sampling signal in a distance dimension to obtain a distance-pulse diagram, scans the distance-pulse diagram, and obtains an index t111 of the maximum pulse amplitude and indexes t110 and TX112 of left and right second-largest-value pulse amplitudes to obtain a window win11[ t110, t112 ];

(2) the system utilizes an electronic switch to switch receiving antennas according to the sequence of RX1, RX2, RX3, RX4, RX5, RX6, RX7 and RX8, each receiving antenna is processed according to (1), and the OR operation is carried out on the intervals win 11-win 18 obtained by each receiving antenna, namely the obtained intervals are merged, the adjacent intervals are merged into one interval, the original interval range is reserved for the non-adjacent intervals, a window win1[ t10, t12] containing all the interval ranges of win 11-win 18 is obtained, namely primary windowing is realized;

(3) the system utilizes an electronic switch to switch a transmitting antenna from TX1 to TX3, a receiving antenna selects RX1 to transmit and receive, re-samples and carries out distance dimension FFT, and a maximum pulse value index t311 and left and right secondary maximum value indexes t310 and t312 are selected to obtain a window win31[ t310, t312 ];

(4) the system utilizes an electronic switch to switch receiving antennas according to the sequence of RX1, RX2, RX3, RX4, RX5, RX6, RX7 and RX8, each receiving antenna is processed according to (3), the system carries out OR operation on intervals win 31-38 obtained by each receiving antenna, then uses the result of OR operation to carry out AND operation on win1[ t10, t12], and the AND operation is carried out, namely, the overlapped part of two interval ranges is reserved, and other parts are discarded, so that once window interception is realized, and an interval win3[ t30, t32] is obtained;

(5) the system utilizes an electronic switch to switch a transmitting antenna into TX2, repeats the operations (1) and (2), performs windowing again, and realizes secondary windowing on the basis of win3 to obtain a win2[ t20, t22 ];

(6) the system utilizes an electronic switch to switch a transmitting antenna into TX4, repeats the operations of (3) and (4), performs interception again, and realizes secondary interception on the basis of win2 to obtain a win4[ t40, t42 ];

(7) adjusting the point number of the window win4, sequentially expanding the window win to the left and the right to form 32 points in total, and obtaining an interval win0[ i00, i31 ];

(8) performing virtual expansion on the four-transmitting eight-receiving antenna, namely realizing the expansion of the receiving antenna by using the relative position relationship of the transmitting antenna by the system, wherein the expansion result is one-transmitting thirty-two-receiving, sequentially performing transmitting and receiving, adopting 512 points, performing distance dimension FFT (fast Fourier transform) on the system after the signal acquisition of each receiving antenna is finished, and reserving points in win0[ i00, i31] of each antenna;

(9) and (3) performing FFT of a second distance dimension in the system for 1024 points of 32 x 32 in the step (8), performing FFT again on the antenna dimension on a plurality of received second distance FFT results to obtain a distance-Doppler-azimuth diagram to obtain a small angle range, wherein the angle range comprises the direction of the real distance, and processing the angle range, namely the angle range is called an angle bin. Rotating and scaling the angle bin, and converting the central position into 0 degree;

(10) multiplying the angle bin in the step (9) by a 128-point expansion factor, and scanning the points expanded by 128 times to obtain a high-precision angle in the angle bin;

(11) according to the high-precision angle in the angle bin, selecting a first distance dimension FFT result of an antenna corresponding to the direction of the angle bin to perform distance processing, namely performing frequency domain expansion on points in the range of win0[ i00, i31] of the antenna in the direction by the system, multiplying by a 1024-point expansion factor, and scanning the number of points subjected to 1024 times of expansion to obtain the maximum amplitude;

(12) calculating a distance result according to the maximum amplitude and the corresponding FFT point number of the maximum amplitude in the step (10);

(13) and (5) projecting the distance in the step (12) to the result in the direction of high-precision angle to obtain a final high-precision distance value.

Drawings

FIG. 1 is a flow chart of the system process of the present invention.

FIG. 2 is a schematic diagram of the inventive window process.

Fig. 3 is a schematic diagram of virtual extension of the antenna of the present invention.

Fig. 4 is a diagram of a transmit/receive antenna design of the present invention.

Fig. 5 is a structural diagram of a multi-transceiver antenna of the present invention.

Fig. 6 is a schematic diagram of the AWR1243 connection of the invention.

Fig. 7 is a schematic diagram of an electronic switch for a transmitting antenna of the present invention.

Fig. 8 is a schematic diagram of an electronic switch for a receiving antenna according to the present invention.

FIG. 9 is a diagram of a fast Fourier transform simulation of the present invention.

FIG. 10 is a simulation diagram of the fast Fourier transform extended scan of the present invention.

FIG. 11 is a schematic view of the angular bin processing of the present invention.

Detailed Description

The invention relates to a millimeter wave multi-antenna distance measuring system, which mainly comprises a multi-antenna receiving and transmitting structure and an extended algorithm combining window processing and distance angles corresponding to the structure, wherein the system mainly measures a horizontal plane. The processing flow diagram of the system is shown in fig. 1. The multi-antenna receiving and transmitting structure carries out antenna design and electronic change-over switch design according to the use condition, an algorithm processing part system firstly utilizes the antenna to receive and transmit to obtain echo data, the number of sampling points of each receiving and transmitting antenna is 512 points, four transmitting antennas are sequentially switched, a receiving antenna is correspondingly switched with each transmitting antenna to carry out eight-antenna switching, window processing as shown in figure 2 is sequentially realized, the window processing comprises primary windowing, primary intercepting, secondary windowing and secondary intercepting, and the final window size is adjusted to enable the window size to be 32 points. And then, performing secondary scanning, performing antenna virtualization as shown in fig. 3 on the four-transmitting eight-receiving antenna, virtualizing the antenna into a one-transmitting thirty-two-receiving antenna, performing data acquisition and one-time distance dimension FFT (fast Fourier transform), and intercepting through a window to obtain an interested data range. On one hand, data storage is carried out on the data intercepted by the window for subsequent calculation; and on the other hand, performing distance dimension FFT again and antenna dimension FFT of a plurality of receiving antennas in sequence on the basis of the first FFT to obtain a distance-Doppler-azimuth diagram, obtaining an interested small-angle range, namely an angle bin, performing horizontal processing on the angle bin, performing extended scanning on the angle bin, wherein the number of extended points is 128 points, and obtaining a high-precision angle in the angle bin. And selecting first-time distance dimension FFT window data of the antenna corresponding to the high-precision angle from the previously stored data, and performing extended scanning, wherein the number of extended points is 1024 points, so as to obtain a distance value. And finally, projecting the distance value in the high-precision angle direction in the angle bin to obtain the high-precision distance value.

In the above embodiment, the frequency range of the antenna is 77 to 81GHz, and the center frequency f₀And (4) obtaining a preliminary antenna parameter according to theoretical calculation of the antenna, wherein the antenna parameter is 78.5 GHz.

The antenna width W is calculated as follows:

changing c to 3 × 10⁸m/s, antenna center frequency f₀Dielectric constant ε of material at 78.5GHz_rSubstituting 3.66 to calculate W1.252 mm.

Effective relative dielectric constant epsilon of antenna_eAnd a waveguide wavelength lambda_gThe calculation is as follows:

substituting the thickness h of the plate to 0.1mm to obtain epsilon_e＝3.277，λ_g＝2.116mm。

The calculation formula of the length L of the antenna patch and the calculation formula of the length Delta L of the radiation slot of the antenna is as follows:

substitution gave Δ L of 0.0487mm and L of 0.966 mm.

In the above embodiment, the antenna structure is designed as shown in fig. 4. The rectangular patch of each antenna has a length of 1.5mm and a width of 0.97mm, a feeder length of 1.18mm, and a feeder width of 0.1 mm.

In the above embodiment, the structure of the four-transmitting eight-receiving antenna is as shown in fig. 5, all the antennas perform two scans for each measurement, the first scan is performed from the TX1 transmitting antenna to the TX4 transmitting antenna for four transmitting antennas, and each transmitting antenna corresponds to eight receiving antennas, namely, the RX1 receiving antenna to the RX8 receiving antenna. The connection of the transceiver antenna to the AWR1243 is shown in fig. 6.

The electronic switch for the transmitting antenna and the electronic switch for the receiving antenna in the above-described embodiments are shown in fig. 7 and 8, respectively, and the electronic switch used is the model HMC-SDD 112. The single electronic change-over switch realizes the function of one of two, four transmitting antennas use three electronic change-over switches to realize the switching, and eight receiving antennas use seven electronic change-over switches to realize the switching.

In the above specific embodiment, the distance is calculated according to the difference frequency signal obtained by antenna processing, and the calculation formula is as follows:

R＝c*f_m*T/2B

wherein B is the effective bandwidth of 4GHz, T is a sweep period of 114.4us, and f_mIs the difference frequency, c is the speed of light 3 x 10⁸m/s。

The difference frequency signal is obtained by fast fourier transform, and the formula is as follows:

wherein N is the number of sampling points, and the number of sampling points of the system is 512.

The measured distance accuracy expression is calculated as follows:

f_b＝f_s/N

wherein the sampling frequency f_s5MHz, 512 sampling points N, 33.71MHz/us frequency, 3 × 10 light speed c⁸m/s，f_bThe frequency accuracy was 9765.625, and the distance accuracy without extended sweep was 4.34 cm.

In the above specific embodiment, after performing fast fourier transform and distance calculation, a preliminary distance value may be obtained, and then, performing expansion processing on the original transform result, that is, multiplying the original fast fourier transform by a 1024-point expansion factor, where the expression is as follows:

wherein a is the serial number of the current interval, 1024 is the multiple of the extended scanning, the window part obtained by the selection processing is extended and re-scanned in the second scanning, the distance calculation is performed according to the scanning result, the high-precision distance can be calculated, and at the moment, the precision of the extended scanning distance is 1024 times accurate, namely the precision of 4.34cm is 42.38 um.

In the above specific embodiment, the simulation is performed for the extended scan algorithm, the simulated signal has the same form as the difference frequency signal, and the expression of the signal is as follows:

x(t)＝3cos(2πf_tt)

discretizing the signal and performing a fast Fourier transform, wherein the input signal f_t＝1MHz，f_sThe number of sampling points N is 512 at 5MHz, the unexpanded simulation result is shown in fig. 9, and the simulation result amplitude is 581.70916.

Extended scan simulation a from (-511, 512)]Taking values, wherein the frequency point of a simulation result aiming at extended scanning is 996093.75Hz according to input informationNumber f_tCalculating to obtain a point number 410 and obtain the maximum amplitude, wherein the calculation formula is as follows:

the expansion situation is simulated, the simulation result is shown in fig. 10, the amplitude is 768.2863 at this time, the expansion scanning result is brought back to calculation, the frequency can be calculated to be 1000003.813Hz, the difference between the frequency and the actual input frequency is 1MHz, 3.813Hz, the error frequency distance formula is calculated, and the error caused by the obtained frequency difference becomes 16.97 um.

In the above specific embodiment, the angle measurement is implemented by using the relative positions of different receiving antennas, and the angle estimation is implemented according to the phase of the echo signal, and the formula of the angle θ measurement is as follows:

and calculating according to an angle formula, so that the angle position of the target corresponding to the radar scanning range when the radar detects the target can be obtained.

Angular resolution theta_resThe formula is as follows:

where N is the total number of virtual antennas, N is 32, θ is 0, and the resolution is 3.58 °.

The angle expansion adopts the similar idea of distance expansion, a 128-point expansion factor is multiplied, and then the 128-point expansion scanning factor is multiplied when the antenna dimension fast Fourier transform is carried out, and the expression is as follows:

where 128 denotes an angular spread of 128 times, i.e. the scan is performed during the final angular calculation, and the final extended scan angular resolution is 0.028 °.

Maximum field angle theta of radar_maxThe formula is as follows:

further, since the relationship λ is 2d, the maximum angle of view can be [ -90 °, +90 ° ], and the finally measured angle will be within the maximum angle of view.

In the above embodiment, the angle bin processing diagram is shown in fig. 11. And calculating the number of interest points to be 32 points by the angle selected by the secondary scanning, wherein the number of the sampling points is 512 points, the angle of view is limited to be 1/8, the angle of interest is 22.5 degrees, namely the angle range bin is 22.5 degrees, the angle width is scaled, the angle bin range is limited to be +/-11.25 degrees, the left boundary is-11.25 degrees, and the right boundary is +11.25 degrees.

The extension scanning precision of angle is 0.028, combines the angle scope storehouse, will scan at 11.25, and the scanning result is the angle in the angle storehouse that the distance corresponds promptly, will be apart from carrying out the projection in the angle storehouse, will be apart from the angle combination in the angle storehouse, obtains final high accuracy distance value, realizes many antennas high accuracy distance measurement.