CN110133634B

CN110133634B - MIMO radar virtual aperture angle measurement method based on frequency division multiplexing technology

Info

Publication number: CN110133634B
Application number: CN201910378882.8A
Authority: CN
Inventors: 邹林; 黄述康; 梁飞; 钱璐; 汪学刚; 周云
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2019-05-08
Filing date: 2019-05-08
Publication date: 2022-10-14
Anticipated expiration: 2039-05-08
Also published as: CN110133634A

Abstract

The invention discloses a MIMO radar virtual aperture angle measurement method based on a frequency division multiplexing technology, belongs to a signal processing technology, and particularly relates to a radar virtual aperture direction of arrival measurement technology. The invention combines the frequency division multiplexing technology and the MIMO radar virtual aperture angle measurement technology, takes a two-transmitting four-receiving radar system as an example, a radar transmitting end simultaneously and respectively transmits linear frequency modulation continuous wave signals of different frequency bands by using two transmitting antennas, and a radar receiving end simultaneously receives signals reflected by objects by the two transmitting antennas by using four receiving antennas. In each receiving antenna, two mixers are used for carrying out beat signal processing in two paths, beat baseband signals are obtained through a low-pass filter LPF, digital signals are obtained through an AD converter, and finally the digital signals enter a digital signal processor DSP and are used for obtaining angle information of a target through an MIMO radar virtual aperture angle measuring technology, so that the aim of the invention is fulfilled. Has the following effects: both transmit antennas are active during any time period. Compared with the traditional time division multiplexing technology, the method saves half of the transmission time and improves the transmission efficiency; while increasing the average transmit power.

Description

MIMO radar virtual aperture angle measurement method based on frequency division multiplexing technology

Technical Field

The invention belongs to a signal processing technology, and particularly relates to a radar virtual aperture direction of arrival measuring technology.

Background

77G vehicle-mounted millimeter wave radar is increasingly applied to a driving assistance system due to the advantages of short wavelength, small size and high detection precision. The transmitter generates continuous high-frequency constant amplitude waves, the transmission frequency changes linearly along with time and mainly changes according to a zigzag rule, and the waveform is also called as a fast ramp mode LFMCW waveform. The echo of the target and the transmitting waveform are directly mixed, and due to the time difference between the echo and the transmitting waveform and the linear frequency modulation, the frequency of the beat signal after mixing is related to the distance, the speed and the angle of the target, and the frequency of the beat signal can be used for measuring the distance, the speed and the angle of the target.

The MIMO radar virtual aperture angle measurement technology is characterized in that a wave path difference is generated by utilizing a distance difference between receiving antennas, a phase difference can be obtained through the wave path difference, then the phase obtained by each receiving antenna is subjected to fast Fourier transform to obtain target angle information, and the more the receiving antennas are, the better the angular resolution is. In fact, due to the cost and resource limitation, an equivalent MIMO system method needs to be adopted. For example, an eight-transmit radar can be equivalent to a two-transmit four-receive radar, and a suitable distance difference is introduced between two transmitting antennas, so that the four receiving antennas can be utilized to respectively receive echo signals of the two transmitting antennas, and the eight receiving antennas can be equivalent in phase. The equivalent of double-transmitting and four-receiving requires time division multiplexing technology, that is, two transmitting channels alternately transmit signals.

The time division multiplexing technique is not high in average power of transmission because only one transmitting antenna is operated in each time period. Meanwhile, compared with the two antennas which simultaneously transmit signals with fixed total frame number, the method needs twice transmission time length, and the transmission efficiency is not high. In order to solve the problem, a MIMO radar virtual aperture angle measurement method based on the frequency division multiplexing technology is proposed.

Disclosure of Invention

The invention aims to solve the technical problems of improving the transmitting efficiency of a 77G vehicle-mounted radar and improving the average transmitting power.

The technical scheme adopted by the invention for solving the technical problems is that the MIMO radar virtual aperture angle measurement method is based on the frequency division multiplexing technology.

For a conventional 77G vehicle-mounted two-transmitter four-receiver radar, time division multiplexing and MIMO radar angle measurement are generally combined in the angle measurement technology. The two transmitting antennas alternately transmit signals, echo signals of the two transmitting antennas are respectively received through the four receiving antennas, and then eight receiving antennas are equivalently obtained through phase relation. But because the transmit average power is not high and only one transmit antenna is operating during each time period, the transmit efficiency is not high.

In order to improve the transmission efficiency of the 77G vehicle-mounted radar and improve the average transmission power. The method is characterized in that the original angle measuring system is improved on the basis of the MIMO angle measuring virtual aperture technology, and the MIMO radar virtual aperture angle measuring method based on the frequency division multiplexing technology is provided, and comprises the following steps:

step 1: a slope generator is utilized to obtain a linear frequency modulation continuous wave signal, and the linear frequency modulation continuous wave signal is divided into two paths of signals through a 77G voltage-controlled oscillator; one path of signal passes through a power amplifier and then is directly transmitted by a transmitting antenna TX1, and the other path of signal is firstly mixed with a local oscillation signal f _bios Multiplying, sequentially passing through a band-pass filter and a power amplifier, and then transmitting by a transmitting antenna TX 2; the two transmitting antennas transmit signals simultaneously, and the distance between the two transmitting antennas is 4 times 77G of signal wavelength, wherein the local oscillator signal f _bios The frequency range of (A) is 1.2GHz-3.6GHz;

and 2, step: at a receiving end, 4 receiving antennas RX1, RX2, RX3 and RX4 are adopted, and the distance between each receiving antenna is half wavelength; echo signals received by each receiving antenna pass through a Low Noise Amplifier (LNA) and are processed in two paths, wherein one path is subjected to frequency mixing with a first local oscillation signal, and the other path is subjected to frequency mixing with a second local oscillation signal to obtain a corresponding beat signal;

and step 3: obtaining beat baseband signals by passing the beat signals obtained in each path in the step 2 through a Low Pass Filter (LPF), and finally obtaining eight paths of beat baseband signals with fixed phase difference;

and 4, step 4: and (4) converting the eight paths of beat baseband signals obtained in the step (3) into digital signals after respectively passing through an analog-to-digital converter (ADC), and then entering a Digital Signal Processor (DSP) to process by utilizing a virtual aperture angle measurement method of the MIMO radar to obtain angle information of the target.

The design block diagram of the goniometric system is shown in fig. 1.

The beneficial effects of the invention are:

all transmitting antennas are ensured to be operated in each time period, and the average transmitting power is indirectly improved.

When the signal with the fixed total frame number is transmitted, compared with the time division multiplexing technology, the method can save half of the transmission time and improve the transmission efficiency.

Drawings

FIG. 1 is a block diagram of a MIMO radar virtual aperture angle measurement system based on frequency division multiplexing technology;

FIG. 2 is a time-frequency diagram of a time-division multiplexing fast ramp mode;

FIG. 3 is a time-frequency diagram of a frequency division multiplexing fast ramp mode;

FIG. 4 is a flow chart of DSP processing;

fig. 5 is a graph showing the angle measurement result.

Detailed Description

Step 1: two targets are assumed, one in the direction of 20 degrees in front of the right of the radar, with a distance of 60m; the other is 40 degrees ahead of the radar, and the distance is 80m.

And 2, step: setting the left and right cut-off frequencies of a band-pass filter (BPF) to be 77.495GHz and 78.005GHz respectively, and setting the pass band to be 502MHz; setting the left and right cut-off frequencies of 8 Low Pass Filters (LPFs) as-255 MHz and 255MHz respectively, and setting the pass band as 502MHz; the sampling rate (for a single ramp) for 8 ADCs is set to 10.1MHz.

And 3, step 3: a ramp generator is used for generating a chirp continuous wave signal, the single ramp time of the signal is 50 mus, the bandwidth is 500MHz, and the total number of the signals is 256. Voltage controlled oscillator by 77GThen dividing the signal into two paths of signals, wherein one path of signal passes through a power amplifier to obtain a radio frequency signal with the frequency band of 76.5GHz to 77GHz, and then configuring a transmitting antenna TX1 to transmit the signal; the other signal is first summed with f _bios Local oscillator signal (select appropriate f) _bios The local oscillator signals ensure that the frequency bands of the transmission signals of the last two transmission antennas are not overlapped, wherein 1G local oscillator signals are selected), then radio frequency signals with the frequency band of 77.5GHz to 78GHz are obtained through a Band Pass Filter (BPF) and a power amplifier, and finally the transmission antenna TX2 is configured to transmit signals.

And 4, step 4: configuring a receiving antenna RX1 to receive echo signals, passing through a low noise amplifier, and configuring two signal processing paths. One path of signal is multiplied by a local oscillation signal 1 through a frequency mixer to obtain a beat signal, then a low-pass filter is used for obtaining a beat baseband signal, and then a digital signal matrix is obtained through an ADC and stored in an AD buffer area; the other path of signal is multiplied by the local oscillation signal 2 through a frequency mixer, and then the other path of signal passes through a low-pass filter and an ADC (analog to digital converter) and then a digital signal matrix is stored in an AD (analog to digital) buffer area. The reception antennas RX2, RX3 and RX4 are operated in the same manner.

And 5: the data stored in the AD buffer are transmitted to the DSP for data processing by using the MIMO radar virtual aperture angle measurement method, the DSP processing flow is shown in fig. 4, and the final result is shown in fig. 5.

Experiments prove that the error of the angle measurement result is within 0.1 degree, so that the MIMO radar virtual aperture angle measurement method based on the frequency division multiplexing technology is feasible.

Claims

1. A MIMO radar virtual aperture angle measurement method based on frequency division multiplexing technology comprises the following steps:

step 1: a slope generator is utilized to obtain a linear frequency modulation continuous wave signal, and the linear frequency modulation continuous wave signal is divided into two paths of signals through a 77G voltage-controlled oscillator; one path of signal passes through a power amplifier and then is directly transmitted by a transmitting antenna TX1, and the other path of signal is firstly mixed with a local oscillator signal f _bios Multiplying, sequentially passing through a band-pass filter and a power amplifier, and then transmitting by a transmitting antenna TX 2; the two transmitting antennas transmit signals simultaneously, and the distance between the two transmitting antennas is 4 times 77G signal wavelengthMiddle local oscillator signal f _bios The frequency range of (A) is 1.2GHz-3.6GHz;

and 2, step: at a receiving end, 4 receiving antennas RX1, RX2, RX3 and RX4 are adopted, and the distance between each receiving antenna is half wavelength; echo signals received by each receiving antenna pass through a low-noise amplifier and are processed in two paths, wherein one path is subjected to frequency mixing with a first local oscillation signal, and the other path is subjected to frequency mixing with a second local oscillation signal to obtain a corresponding beat signal;

and 3, step 3: obtaining beat baseband signals by passing the beat signals obtained in each path in the step 2 through a Low Pass Filter (LPF), and finally obtaining eight paths of beat baseband signals with fixed phase difference;