Patent ID: 7221922

Claim:
A switch circuit for switching the connection of receiving or transmitting circuits of first and second communication systems, having respective first and second transmitting frequencies which are closer to each other than they are to a transmitting frequency of a third communication system, to an antenna circuit, which comprises two switch means having switching elements, a first switch means comprising a first port connected to said antenna circuit, a second port connected to a transmitting circuit of said first and second communication systems, and a third port connected to a second switch means; said second switch means comprising a fourth port connected to said third port, a fifth port connected to a receiving circuit of said first communication system, and a sixth port connected to a receiving circuit of said second communication system; a first switching element being disposed between said first port and said second port; a first inductance element being disposed between said first port and said third port; a second switching element being disposed between said third port and a ground; a third switching element being disposed between said fourth port and said sixth port; a second inductance element being disposed between said fourth port and said fifth port; and a fourth switching element being disposed between said fifth port and a ground; said third port being connected to said fourth port via a capacitance element; and a transmission line constituting said first inductance element having a lower characteristic impedance than that of a transmission line constituting said second inductance element.