Impedance optimization of linearizer to suppress intermodulation distortion in 2.45GHz SiGe WLAN power amplifier

An RF power amplifier (PA) for IEEE 802.11g WLAN terminals is implemented with 33 GHz-f_T, 0.8-mum-SiGe bipolar technology. This paper demonstrates a linearizer consisting of a varactor diode and a base-emitter junction diode of a bias transistor. Intermodulation distortion (IMD) is suppressed by optimized impedance of the linearizer. The reactance of the varactor diode is minimized at low output power level to eliminate IMD3, and maximized near 1-dB compression point (P1dB). IMD3 is improved as much as 0.2~6 dB up to 20 dBm output power. The IMD3 value is less than -34 dBc at 3 dB back-off from P1dB. The power amplifier exhibits P1dB of 24 dBm, with power-added efficiency (PAE) of 31%, and power gain of 17 dB under 3.3V power supply