A 3×3mm2 LTE/WCDMA dual-mode power amplifier module with integrated high directivity coupler

This paper presents a 1920-1980MHz LTE/WCDMA GaAs HBT/pHEMT-based 3×3mm² power amplifier module (PAM) with integrated directional coupler targeted for mobile handset applications. The PA operates in two power modes with a dual-path structure. Each path is optimized individually for each power mode, achieving low DC quiescent current and significant current saving compared to single-mode PAs under power backoff. Bias current and load impedance are specifically optimized for linear operation under high peak-to-average ratio LTE modulation. The PAM achieves a low quiescent current of 8mA. Under LTE modulation, the PAM exhibits 38/24% PAE at 27.5/16dBm Pout at UTRA ACLR1<;-39dBc. Under WCDMA modulation, the PAM attains 42/26% PAE at 28.5/17dBm Pout at ACLR1<;-40dBc. Further current saving is demonstrated with the use of variable power supply. The integrated 20dB coupler achieves ±0.06dB coupling variation under VSWR 2.5:1 mismatch, corresponding to a directivity of 36dB.