Abstract: A radar apparatus includes an antenna unit and a cover unit. The cover unit is arranged at a position through which an electromagnetic wave sent and received by the antenna unit passes. The cover unit has, in an order from closer to the antenna unit, a first dielectric layer formed of a dielectric and a second dielectric layer formed of a dielectric having a dielectric constant different from that of the first dielectric layer. The first dielectric layer is configured to have a thickness not more than that for a maximum external transmittance. The external transmittance indicates a transmittance of an electromagnetic wave, which is emitted in a direction of an incidence angle with respect to the first dielectric layer, which is equal to a maximum sensing angle, when the electromagnetic wave is transmitted through the cover unit.

Abstract: A radar apparatus includes an antenna unit and a cover unit. The cover unit is arranged at a position through which an electromagnetic wave sent and received by the antenna unit passes. The cover unit has, in an order from closer to the antenna unit, a first dielectric layer formed of a dielectric and a second dielectric layer formed of a dielectric having a dielectric constant different from that of the first dielectric layer. The first dielectric layer is configured to have a thickness not more than that for a maximum external transmittance. The external transmittance indicates a transmittance of an electromagnetic wave, which is emitted in a direction of an incidence angle with respect to the first dielectric layer, which is equal to a maximum sensing angle, when the electromagnetic wave is transmitted through the cover unit.