Radar apparatus and radar system for a vehicle

1. A radar apparatus including a plurality of radar devices, the radar apparatus comprising:

means for transmitting and receiving an electric wave to detect a target via a radar device;

means for detecting wave interference caused by surroundings from said radar device;

means for controlling a modulation state of the transmitted wave;

communication means for acquiring modulation state information being used by other radar devices of the plurality of radar devices; and

means for selecting such a modulation state as to avoid interference with the modulation state information when the wave interference detecting means detects the wave interference,

wherein the modulation state selecting means selects the same modulation state for the radar devices having different mounting directions by an angle not less than 90 degrees.

2. A radar system for a vehicle that includes a plurality of radar devices installed on the vehicle,

each of the radar devices comprising:

means for transmitting and receiving an electric wave to a target;

means for detecting wave interference caused by surroundings; and

means for controlling a modulation state of the transmitted wave from the radar device,

the system further comprising:

communication means for acquiring modulation state information being used by other of the plurality of radar devices radar devices; and

means for selecting such a modulation state as to avoid interference with the modulation state information when the wave interference detecting means detects the wave interference,

wherein the modulation state selecting means determines whether the modulation state is to be changed or not according to a priority of the radar device, the priority being determined based on the modulation state information acquired by the communication means, and a higher priority is provided to a radar device disposed at a front side of the vehicle.

3. A radar apparatus according to claim 1 , wherein the modulation state includes one or more of a carrier frequency, a modulation type, an orientation of polarization plane of the wave, a transmission cycle, and a modulation code.

4. A radar apparatus according to claim 1 , wherein the wave interference detecting means processes a received signal of the wave for determination.

5. A radar apparatus according to claim 1 , wherein a random factor is included in the modulation state selecting means.

6. A radar apparatus according to claim 1 , wherein the wave interference detecting means determines the presence of the wave interference with use of the modulation state information of the other radar apparatuses.

7. A radar system for a vehicle including the radar system set forth in claim 2 , comprising:

means, when the usable modulation state becomes insufficient, for stopping functions of the radar devices in an increasing order of the priority.

8. A radar apparatus according to claim 1 , wherein one or more of the wave interference detecting means, the communication means, and the modulation state selecting means are provided outside the radar apparatus.

9. A radar apparatus according to claim 1 , comprising means for acquiring a usable range of the modulation state, and wherein a limitation is applied to the means for selecting the modulation state according to the acquired range.