CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. § 119(a) of French Patent Application FR 1856202, filed Jul. 5, 2018, the entire disclosure of which is hereby incorporated herein by reference.

TECHNICAL FIELD

This disclosure generally relates to a radar device for a motor vehicle and its control method, and more particularly relates to the adjustment of the transmission power of the radar signal of the device in case of obstruction of the field of view of the radar.

BACKGROUND

The motor vehicles are increasingly equipped with drive assistance systems. A widely used technology in this context is the radar. The radar systems help the driver and can be used to detect the obstacles in the front, in the rear or on the sides of the vehicle.

Basically, the principle of the radar detection sends a fixed-frequency wave in a permitted frequency band with a given bandwidth. In addition, a certain transmission power is applied to have a detection range sufficient to detect obstacles distant from the vehicle.

When two or more vehicles equipped with radar systems are in the vicinity of each other, the field of view of a vehicle radar can be obstructed by another vehicle. This induces a useless electrical energy consumption associated with the radar.

SUMMARY

According to one embodiment, a radar device for a motor vehicle comprises a radar antenna configured to detect a reflected signal characterized as a reflection of a transmitted signal reflected by an object present in the field of view of the radar antenna; a controller configured to transmit at least one radar signal from the radar antenna, the radar signal being transmitted according to a determined object detection transmission power; the controller being configured to detect the power level of the reflected signal derived from the transmitted radar signal reflected by the detected object. The controller is configured to adjust the transmission power, according to (i.e. based on) the power level of the reflected signal detected, to a minimum power sufficient for the detection of the detected object.

The controller may also be configured to transmit a plurality of successive radar signals according to the determined transmission power, the controller being configured to adjust the transmission power according to the average of the power levels of the reflected signals detected.

The reflected signal may comprise a plurality of reflected waves distributed in the field of view of the radar antenna so that the controller can be configured to detect the power level and the angular orientation, along the main axis of the field of view, of each reflected wave. The controller is configured to determine a rate of obstruction of the field of view of the radar antenna according to the power level and angular orientation of each reflected wave detected. The controller is configured to compare the obstruction rate determined with a preset obstruction rate threshold. The controller can be configured to adjust the transmission power when the obstruction rate is higher than the preset obstruction rate threshold.

According to another embodiment, a method for controlling a radar device comprises the steps of: transmitting at least one radar signal, according to a determined object detection transmission power, from the radar antenna; detecting the power level of the reflected signal derived from the transmitted radar signal reflected by the detected object; characterized in that the method comprises the step of: adjusting the transmission power, according to the detected power level of the reflected signal, to a minimum power sufficient for the detection of the detected object.

The transmission step may comprise the successive transmission of a plurality of radar signals according to the same preset transmission power and the step of adjusting the transmission power may comprise the adjustment of the transmission power according to the average of the power levels of the reflected signals detected.

The reflected signal may comprise a plurality of reflected waves distributed in the field of view of the radar antenna so that the step of detecting the power level of the reflected signal comprises the step of detecting the power level and angular orientation, along the main axis of the field of view, of each reflected wave. The step of adjusting the transmission power may comprise a prior step of determining a rate of obstruction of the field of view of the radar antenna according to the power level and angular orientation of each reflected wave detected and a step of comparing the determined obstruction rate with a preset obstruction rate threshold. The step of adjusting the transmission power may comprise a step of adjusting the transmission power when the obstruction rate is higher than the preset obstruction rate threshold.

According to another embodiment, a method for controlling a radar device arranged in a host vehicle comprises the steps of: transmitting a radar signal of the host vehicle according to a determined object detection power; detecting a reflected signal derived from the transmitted radar signal; determining the presence of a target vehicle in the field of view of the radar device; determining a rate of obstruction of the field of view of the radar antenna; comparing the determined obstruction rate with a preset obstruction rate threshold; reducing the transmission power of the radar signal to a minimum target vehicle detection power when the obstruction rate is higher than the preset obstruction rate threshold.

According to another embodiment, a method for detecting an object by a host vehicle comprising a vehicle-to-vehicle communication system comprises the steps of: comparing the rate of obstruction of the field of view of a radar device with the preset obstruction rate threshold; allocating the function of detecting an object in the field of view of the radar device to the vehicle-to-vehicle communication system when the obstruction rate is higher than the preset obstruction rate threshold; determining the location coordinates of the obstructed field of view; detecting the data, received by the vehicle-to-vehicle communication system, relating to an object present in the field of view obstructed according to the determined location coordinates.

Further features and advantages will appear more clearly on a reading of the following detailed description of the preferred embodiment, which is given by way of non-limiting example only and with reference to the accompanying drawings.

