Radar apparatus
A radar apparatus includes a circuit board including a board surface provided with an antenna module for transmitting an electromagnetic wave, a housing accommodating the circuit board and including a facing wall facing the board surface, and a heat transfer module transferring heat generated inside the housing to the housing. The facing wall includes a transmission portion transmitting therethrough the electromagnetic wave transmitted from the antenna module and an absorption portion having a thickness different from the thickness of the transmission portion and absorbing the electromagnetic wave which is incident. The heat transfer module includes a first transfer member placed to be in contact with the absorption portion in the housing and a second transfer member transferring the heat to the first transfer member.
1. A radar apparatus, comprising:
a circuit board including a board surface provided with an antenna module for transmitting an electromagnetic wave;
a housing accommodating the circuit board and including a facing wall facing the board surface; and
a heat transfer module transferring heat generated inside the housing to the housing, wherein
the facing wall includes:
a transmission portion transmitting therethrough the electromagnetic wave transmitted from the antenna module, the transmission portion having a first thickness corresponding to a wavelength of the electromagnetic wave transmitted from the antenna module; and
an absorption portion having a second thickness different from the first a thickness of the transmission portion, the second thickness corresponding to an effective wavelength of the electromagnetic wave, and the absorption portion is configured to reabsorb a re-incident electromagnetic wave reflected from an object outside the housing which is re-incident on the housing, the absorption portion being made of a same material as the transmitting portion, and wherein
the absorption portion absorbs the electromagnetic wave by reverse-phase synthesis of:
a first electromagnetic wave resulting from reflection of the re-incident electromagnetic wave at a first surface of the absorption portion, and
a second electromagnetic wave resulting from reflection of the re-incident electromagnetic wave at a second surface different from the first surface.
2. The radar apparatus according to claim 1 , wherein the transmission portion includes a lens transmitting the electromagnetic wave to an outside of the housing.
3. The radar apparatus according to claim 1 , wherein the second thickness is λe/4×(2n+1), in case where λe represents the effective wavelength of the electromagnetic wave in the absorption portion and n is an integer greater than or equal to zero.
4. The radar apparatus according to claim 3 , wherein the second thickness determined by at least an incident angle of the electromagnetic wave onto the absorption portion.
5. The radar apparatus according to claim 1 , wherein the absorption portion includes an inclined portion inclined with respect to the transmission portion.
6. The radar apparatus according to claim 1 , wherein the absorption portion is placed around the transmission portion in the facing wall.
7. The radar apparatus according to claim 1 , wherein the heat transfer module includes:
a first transfer member placed in contact with at least the absorption portion in the housing; and
a second transfer member transferring the heat to the first transfer member.
8. The radar apparatus according to claim 7 , wherein the second transfer member is placed between the first transfer member and the circuit board.
9. The radar apparatus according to claim 7 , wherein the second transfer member is placed between the first transfer member and a heat generating component provided to the circuit board.
10. The radar apparatus according to claim 7 , wherein the first transfer member is placed on an outer side of a transmission range of an electromagnetic wave transmitted in a range of a half-power angle of the antenna module.
11. The radar apparatus according to claim 1 , wherein the first surface is a front surface of the facing wall and the second surface is a back surface of the facing wall, and the second surface is closer to the circuit board than the first surface.