A novel 4-port lumped element circulator for high-isolation duplex architecture

A novel 4-port circulator for multi-standard and multi-band cellular handsets has been successfully developed by using the Core-Circulator technique. The circulator is realized with lumped element circuits and a weak magnetic field operation. The insertion loss of 1.3dB maximum in 777-787MHz (Band 13) and the TX-RX isolation of 20dB minimum in 35% fractional bandwidth which is including cellular whole low-band have been obtained. Its size is 2.0 mm width X 2.0 mm length X 0.5 mm height. Experimental results of the combination of conventional SAW filters and the developed 4-port circulator have exhibited an extremely high isolation performance of 79dB and robustness against variations of antenna impedance.