CN113325372B - A random coding waveform modulation method for vehicle-grade MIMO radar - Google Patents

Abstract

The invention discloses a vehicle-mounted MIMO radar random code waveform modulation method, and belongs to the field of millimeter wave radars. The method comprises the following steps: firstly, setting a radar into a random coding mode; resetting the random signal generator and generating a set of random codes when transmitting radar signals by arranging the random signal generator; after generating random codes, writing the random codes into a register, and modulating radar signals by calling codes in the register each time the radar transmits radar signals; the demodulated data in the radio frequency chip is input into a decoder to generate a decoded receiving signal, so that the receiving end can receive an echo signal reflected by the transmitted radar signal after encountering an obstacle. According to the invention, each transmitting pulse initial phase is randomly encoded in the processor, transmitting signals of different encodings cannot interfere with each other, so that a plurality of millimeter wave radars can be used in the same environment, the robustness of the system is improved, and the anti-interference capability of the rail traffic radars can be greatly improved.

Description

A random coding waveform modulation method for vehicle-grade MIMO radar

technical field

The present invention relates to the technical field of millimeter wave radar, in particular to a random coded waveform modulation method for vehicle-level MIMO radar.

Background technique

With the rapid development of millimeter-wave chip technology, millimeter-wave radar has been widely used in civilian markets such as autonomous driving, smart security, smart transportation, and smart home. Compared with sensors such as lasers, ultrasonic waves, and cameras, millimeter-wave radar has the advantages of long detection distance, all-weather, and high reliability.

Existing vehicle-mounted millimeter-wave radars are mainly designed and developed for highway scenarios. For rail transit scenarios, there are problems such as short detection distance, low azimuth resolution, and poor anti-interference ability, which are difficult to meet the application needs. However, MIMO (multiple transmission and multiple reception) millimeter-wave radar effectively increases the antenna aperture of the radar through the multi-radio frequency chip cascade technology. It has the characteristics of high resolution and long detection distance, and can increase the diversity of target information and improve the radar anti-interference ability. The current MIMO radars mostly use time-sharing MIMO waveforms. Under the high-speed moving platform of the train, there are shortcomings such as short detection distance, low angle measurement accuracy, and poor anti-interference ability. In the rail transit industry, train-mounted millimeter-wave radars need to achieve high-precision detection of long-distance obstacles. At the same time, due to the high noise interference in rail transit scenarios, millimeter-wave radars using traditional time-sharing MIMO waveforms may not be able to meet actual needs.

Contents of the invention

The purpose of the present invention is to provide a vehicle-level MIMO radar random coding waveform modulation method. According to a vehicle-level MIMO radar random code waveform modulation method of the present invention, random code modulation is performed on the transmitted signal of each frame, and its azimuth resolution is high, the detection distance is long, and the anti-interference ability is strong. The technical scheme adopted by the present invention is as follows:

According to one aspect of the present invention, a method for modulating a vehicle-level MIMO radar random coded waveform is provided, comprising the following steps:

(1) Set the transmission mode and reception mode of the radar to random coding mode;

(2) Random signal generator is set in the processor of radar, when transmitting radar signal, resets the random signal generator in the processor according to certain time interval, under this time interval, produces one group of random codes, code length is the accumulation number of radar transmission pulse, and code number is the transmission channel number;

(3) After generating the random code, write the random code into the initial phase modulation control register corresponding to the transmission channel of the radio frequency chip in the radar, and modulate the radar signal by calling the code in the initial phase modulation control register every time the radar transmits a radar signal;

(4) Modulate the transmission mode of the radio frequency chip into a mode capable of transmitting the modulated radar signal;

(5) Input the demodulated data in the radio frequency chip into the decoder to generate the encoded and decoded receiving signal in the corresponding transmission channel, so that the receiving end of the radar can receive the echo signal reflected by the transmitted radar signal after encountering an obstacle.

Preferably, the radio frequency front-end of the radar is cascaded with 4 AWR2243 transmitting chips, and each transmitting chip is 3 transmissions and 4 receptions. There are 12 transmission channels and 16 reception channels in total. Each transmission signal encodes the initial phase with 6 bytes, a total of 64 codewords, and the code sequence length of each transmission channel is 256.

Preferably, the maximum speed measurement range of the radar is: -400km/h～50km/h.

Preferably, the radar has a detection range of more than 120 meters for targets with a radar cross-sectional area greater than 1 square meter, and a detection range for trains with a radar cross-sectional area greater than 30 square meters of greater than 500 meters.

Preferably, the radar transmission pulse repetition period is: 41.667us.

The technical scheme adopted in the present invention has the following remarkable effects:

(1) The present invention randomly encodes the initial phase of each transmission pulse in the processor, and the transmission signals of different codes will not interfere with each other, so that multiple millimeter-wave radars can be used in the same environment, increasing the robustness of the system and greatly improving the anti-interference ability of the rail transit radar;

(2) The present invention simultaneously controls multiple transmission signal channels in real time, which can avoid the Doppler phase difference introduced by time-sharing transmission;

(3) The present invention enables the millimeter-wave radar to have the ability to simultaneously transmit 12 channels and receive 16 channels. The more transmitting and receiving channels, the better the performance of the radar, and the azimuth resolution is increased to more than 0.5°, and the maximum detection distance for objects with a radar cross-sectional area (RCS) greater than 30 square meters can reach more than 500 meters.

Description of drawings

Fig. 1 is a single frame waveform schematic diagram of the present invention;

Fig. 2 is the random code table of the initial phase of the radar transmission pulse of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below with reference to the accompanying drawings and preferred embodiments. However, it should be noted that many of the details listed in the specification are only for readers to have a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be implemented even without these specific details.

According to a vehicle-level MIMO radar random coding waveform modulation method of the present invention, at first, the transmitting mode and the receiving mode of the radar are set to the random coding mode; and a random signal generator is set in the processor of the radar, and the random signal generator in the processor is reset according to a certain time interval when the radar signal is transmitted. The RF front-end adopts four AWR2243 transmitting chips cascaded, each transmitting chip is 3 transmitting and 4 receiving, and there are 12 transmitting channels and 16 receiving channels in total. Each transmitting signal encodes the initial phase with 6 bytes, a total of 64 codewords, and the code sequence length of each transmitting channel is 256; secondly, after generating the random code, write the random code into the initial phase modulation control register of the RF chip in the radar corresponding to the transmitting channel. When the radar signal is transmitted each time, the radar signal is modulated by calling the random code in the initial phase modulation control register; Modulate the transmission mode of the radio frequency chip into a mode that can transmit the modulated radar signal; finally, input the demodulated data in the radio frequency chip into the decoder to generate the received signal encoded and decoded in the corresponding transmission channel, so that the receiving end of the radar can receive the echo signal reflected by the transmitted radar signal after encountering obstacles.

As shown in Figure 1-2, the starting frequency of the radar is 77GHz; the bandwidth is 350MHz; the number of transmitting antennas is 12; the number of receiving antennas is 16; the maximum speed measurement range is: -400km/h～50km/h; the detection range of the radar for targets with a radar cross-sectional area (RCS) greater than 1 square meter is greater than 120 meters, and the detection distance for trains with a radar cross-sectional area (RCS) greater than 30 square meters is greater than 500 meters.

Through the above modulation method, the speed accuracy of the radar is better than 0.18m/s, the azimuth resolution is better than 0.5 degrees, and the azimuth measurement accuracy is better than 0.05 degrees.

The working frequency of the radar of the present invention is 77 GHz, the detection distance is long, and it has the capabilities of distance measurement, direction measurement, speed measurement and anti-interference at the same time. The transmission signal of each frame is randomly coded and modulated, which can solve the problem of synchronous and asynchronous interference between radars when high-speed moving trains meet in opposite directions. The angular resolution is better than 0.5°, the distance resolution can reach 0.5 meters, and the maximum detection distance can reach 500 meters, which meets the application requirements of rail transit.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications should also be considered as the protection scope of the present invention.

Claims (5)

1. a vehicle-mounted MIMO radar random coding waveform modulation method, is characterized in that: comprise the following steps: (1) Set the transmission mode and reception mode of the radar to random coding mode; (2) Random signal generator is set in the processor of radar, when transmitting radar signal, resets the random signal generator in the processor according to certain time interval, under this time interval, produces one group of random codes, code length is the accumulation number of radar transmission pulse, and code number is the transmission channel number; (3) After generating the random code, write the random code into the initial phase modulation control register corresponding to the transmission channel of the radio frequency chip in the radar, and modulate the radar signal by calling the code in the initial phase modulation control register every time the radar transmits a radar signal; (4) Modulate the transmission mode of the radio frequency chip into a mode capable of transmitting the modulated radar signal; (5) Input the demodulated data in the radio frequency chip into the decoder to generate the encoded and decoded receiving signal in the corresponding transmission channel, so that the receiving end of the radar can receive the echo signal reflected by the transmitted radar signal after encountering an obstacle. 2. A kind of vehicle-level MIMO radar random coding waveform modulation method according to claim 1, characterized in that: the radio frequency front end of the radar adopts 4 slices of AWR2243 transmitting chips to be cascaded, each transmitting chip is 3 sending and 4 receiving, there are 12 road transmitting channels and 16 road receiving channels, each road transmitting signal carries out 6-byte encoding to the initial phase, totally 64 codewords, and the coded sequence length of each transmitting channel is 256. 3. A method for modulating a vehicle-level MIMO radar random code waveform according to claim 1, wherein the radar has a maximum speed measurement range of -400km/h to 50km/h. 4. a kind of vehicle-mounted MIMO radar random coding waveform modulation method according to claim 1, is characterized in that: described radar is greater than 120 meters to the detection distance of the target of radar scattering cross-section area greater than 1 square meter, and is greater than 500 meters to the detection distance of the train of radar scattering cross-sectional area greater than 30 square meters. 5. A method for modulating a vehicle-level MIMO radar random-coded waveform according to claim 1, wherein the pulse repetition period of the radar transmission is 41.667us.