Patent ID: 6862001

Claim:
A communication device for receiving and transmitting signals, comprising: a box formed from a metallic base plate, sidewalls and a metallic lid separated from the base plate by the sidewalls; semiconductors mounted on a surface of the metallic base plate, which forms high frequency circuit including a first amplifier inputting signals received from an antenna, a first mixer mixing an output signal of the first amplifier with an output signal from an high frequency signal source, a second mixer mixing an input signal to be transmitted with an output signal from said high frequency signal source, and a second amplifier inputting an output signal of the second mixer and outputting to the antenna; wherein at least a part of a ceiling part of the lid facing the inside of the box has a periodic structure to prevent propagation of undesired signal between said high frequency signal source, input side of the first amplifier and output side of the second amplifier.