Patent ID: 7538719

Claim:
A mixer circuit comprising: a power distribution circuit including a closed loop transmission line having a first coupling end, a second coupling end, a third coupling end, and a fourth coupling end, arranged in that order, along the transmission line in a predetermined direction that is one of clockwise and counterclockwise directions, the first to fourth coupling ends being equally spaced by a first electrical path length from one another, in that order, and the fourth coupling end being spaced from the first coupling end by a second electrical path length in the predetermined direction; a first coupling circuit for receiving a local oscillator signal at a first frequency, said first coupling circuit being connected to the first coupling end; a second coupling circuit for passing a radio frequency signal at a second frequency that is an even multiple of the first frequency, said second coupling circuit being connected to the third coupling end; a first diode element and a second diode element connected in the same polarity to ground potential, said first diode element being connected between the second coupling end and the ground potential, said second diode element being connected between the fourth coupling end and the ground potential; and a filter circuit for passing an intermediate frequency signal determined by the local oscillator signal and the radio frequency signal, said filter circuit being connected to a fifth coupling end of said transmission line at a position spaced from the first coupling end by an electrical path length of double the first electrical path length along said transmission line, wherein the first electrical path length is approximately one-quarter of one wavelength of the local oscillator signal and the second electrical path length is approximately three-quarters of one wavelength of the local oscillator signal.