Millimeter-wave radar sensors in automotive applications

Automotive millimeter wave radar sensor is currently categorized mainly by operating frequency, mainly focused on 24G, 60G, 77G, 79GHz. these operating frequency bands are not simply controlled by the OEM or equipment parts suppliers, but there is a special counterpart of the national regulations, the radar's frequency in any one country is subject to strict control.
 
In addition, millimeter wave radars are also categorized according to their operating modes, with pulsed and continuous wave types. The former sends out waves intermittently, and the latter sends out waves continuously outward to detect the position of objects, and the former has basically been eliminated due to its general functional effect.
 
The latter is roughly divided into CW (constant frequency continuous wave, only speed can not measure distance), FSK (frequency shift keying continuous wave, can detect the specific and speed of a single target), FMCW (frequency modulated continuous wave, can be realized on multiple targets to measure the distance and speed) several kinds of function with the order of progress, of course, the cost is also progressive.

ⅠWhere is millimeter wave radar generally arranged on a car?
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Considering that millimeter wave radar is mainly used to detect the distance between the front and rear of the car as well as the angle, it is installed on the front side on most products.
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A part of the car models are integrated behind the logo. Considering that the signal quality has to be guaranteed, the surface of the logo in this part of the car models is mostly very smooth and does not have the three-dimensional effect of the traditional logo design.

Another part of the model is installed in the center of the front bumper, which is relatively simple and direct, and the signal quality is also guaranteed.
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However, considering its installation position is too far down, most of the application models are SUVs and other products with slightly higher ground clearance.

Ⅱ The working principle of millimeter wave radar sensor
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Like all radars, millimeter wave radar works by sending out waves through a vibrator, bouncing back after touching an object, being received by the receiving antenna, and calculating the distance to the front vehicle based on the time difference after sampling, filtering, and converting.

Of course, most of the current vehicle millimeter wave radar can be calculated together with the speed of the car, the principle is to send out the millimeter wave is not a fixed frequency, but the frequency of the emitted waveform according to the time change, that is, variable frequency.
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This can be based on the returned waveform time difference and cycle length according to the Doppler effect to calculate the speed of the car.

Ⅲ How millimeter wave radar sensors are used in smart connected vehicles

Millimeter wave radar is only related to two functions in most scenarios on vehicles, one is ACC cruise and the other is AEB active braking.

One of the ACC cruise needs millimeter wave radar will be the distance between the front car and the speed difference between the two cars to determine whether the speed judgment is in a reasonable range, occurring too close or the front car speed is too slow to slow down in time to keep a fixed distance from the front car, i.e., to follow the car driving.
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If there is no vehicle detected in front of the vehicle is quite simple, according to the set speed can be driven.

AEB active braking is relatively simple, if the vehicle in front of you is too slow or there is a foreign object in front of you, after the distance determination, you can brake directly with the maximum force, on the one hand, to avoid accidents, and on the other hand, if you can't avoid it, you can also reduce the consequences of accidents, in order to improve the safety of driving.