Switch-less-impedance-matching type W-CDMA power amplifier with improved efficiency and linearity under low power operation

A W-CDMA power amplifier with new impedance matching technique, Switch-Less Impedance Matching (SLIM), is fabricated to improve the efficiency and linearity of a power amplifier at medium- to low-power ranges. In a SLIM amplifier, two amplifiers with different saturation powers are connected in parallel, and operated alternately without switches in the signal path. At its full power of 25.6 dBm, fabricated SLIM amplifier module exhibited power added efficiency of 38% with ACPR of -40 dBc, which is comparable to existing PAs for W-CDMA. Furthermore, at 15 dBm, its power added efficiency is as much as 12% with ACPR of -42 dBc. Throughout its output power range up to 25.6 dBm, the SLIM PA can provide very high linearity of under -40 dBc ACPR. Furthermore, the efficiency of 12% is not possible from a single amplifier with fixed load impedance.