The septum is extended through the opening to the radio wave receiving
portion to separate respective polarized waves received by a pair of radio
wave receiving portions, and a space between the septum and the radio wave
receiving portion is set such that an end surface of the waveguide on the
side of the substrate is surely in contact with a grounding surface
provided on one surface of the substrate, and an end surface of the radio
wave reflecting portion on the side of the substrate is surely in contact
with the grounding surface provided on the other surface of the substrate.
