Design of high isolation duplexers and a new antenna for duplex systems

A Duplexer design technique will be described which uses nominal size cavities and a single additional lump circuit element per cavity to produce transmitter to receiver isolations far greater than that produced by the cavities themselves. The lumped circuit element produces a notch in the cavity response curve which may be moved along the curve. The original design work on these duplexers was concentrated on units having approximately 5 Mc separation between the transmit and receive frequencies. It will be shown however that this design technique is applicable to other frequency separations. An antenna designed for duplex operation will also be described.