2W HBT Power Amplifier Module with Dual Second Harmonic Suppression Technique

This paper presents a high-power heterojunction bipolar transistor (HBT) power amplifier (PA) module designed for GSM/EDGE applications. The proposed HBT PA employs a differential output stage that delivers high output power at a low supply voltage. A transformer-based output matching network is employed to combine the differential output signals. Through the selection of an appropriate capacitor value at the transformer's center tap, linearity is enhanced across a wide bandwidth without requiring additional second harmonic termination. When assembled with a low-pass filter and an antenna switch, the PA module achieves an output power of 36 dBm and a power-added efficiency (PAE) exceeding 40% in GSM mode. In EDGE mode, it delivers an output power of 28.5 dBm with a PAE exceeding 20%. Additionally, the designed PA module achieves an adjacent channel power ratio of -60 dBc at a 400 kHz offset with an output power of 28.5 dBm.