Efficient Wi-Fi Power Amplifier LTCC Module Using a Buck Converter With a Power Inductor Implemented in Ferrite-Filled PCB Technology

This paper presents a power amplifier module (PAM) that operates efficiently in low-power mode for IEEE 802.11g Wi-Fi applications. The PAM consists of a power amplifier (PA), a buck converter, and a power detector. Two packaging technologies were used to integrate the compact module: a low-temperature co-fired ceramic (LTCC) technology and a ferrite-filled printed circuit board (PCB) technology. The LTCC portion includes radio-frequency inductors, capacitors, transmission lines, and interconnection lines to minimize the overall size, while a power inductor for the buck converter is implemented in ferrite-filled PCB. The PA and the buck converter are designed in 2-μm InGaP/GaAs heterojunction bipolar transistor technology and 0.35-μm CMOS technology, respectively. The output power level is converted into a voltage by the power detector, and the voltage controls the buck converter, thereby optimizing the supply voltage of the PA. This adaptive supply voltage helps to improve the power-added efficiency (PAE) in the low-power regime while maintaining linearity. The PAM showed an error vector magnitude of less than 4% up to an output power of 22 dBm. The PAE is 8% and 11% at output powers of 11 and 16 dBm, respectively, representing respective improvements of 60% and 43%. The overall size of the PAM is 5×7.5×1.2 mm³.