A broadband SiGe power amplifier in an efficient polar transmitter using envelope-tracking for mobile WiMAX

This paper presents a broadband cascode SiGe power amplifier (PA) in the polar transmitter (TX) system using the envelope-tacking (ET) technique. The cascode PA achieves the power-added efficiency (PAE) of >;30% across the frequency range of 0.6~2.4 GHz in continuous wave (CW) mode. The ET-based polar TX system using this cascode PA is evaluated and compared with the conventional stand-alone cascode PA. The experimental data shows that the cascode PA is successfully linearized by the ET scheme, passing the stringent WiMAX spectral mask and the required error vector magnitude (EVM). The entire polar TX system reaches the PAE of 30%/36% at the average output power of 18/17 dBm at 2.3/0.7 GHz for WiMAX 16QAM 3.5 MHz signals. These measurement results suggest that our saturated cascode SiGe PA can be attractive for dual-mode WiMAX applications.