A novel power-amplifier module for quad-band wireless handset applications

Abstract

This paper presents a novel power-amplifier module (PAM) designed for GSM850-, GSM900 MHz, DCS1800- and PCS1900-MHz handset applications. The module combines an InGaP HBT power-amplifier integrated circuit, two integrated couplers, a dual-band logarithmic RF power detector/controller, and some additional passive components. The logarithmic RF power detector was implemented in the module to accomplish linear-in-decibel output power dependency. This allows the handset manufacturers to calibrate output power (Pout) at one or two points, with error as low as +/-0.3 dB, thus reducing test time in mass production. Due to higher accuracy, our novel design significantly reduces the power consumption during normal operation. Our design is the first to include two integrated directional couplers in a handset RF PAM. It significantly improves power control accuracy over load variations. In this paper, we show that the directivity of the integrated couplers is critical for establishing accurate power control over phase variations at high values of load mismatch. In addition, the presented module features fully integrated impedance matching at input and output ports with DC blocks. The entire module is plastic encapsulated on a 10 mm /spl times/ 10 mm laminate substrate. The module offers higher accuracy of Pout control, smaller size, lower bill-of-materials, and a shorter Pout calibration time to handset manufacturers. It is a very desirable RF PAM to handset designers because of its unique features. Under a low single supply voltage of 3.2 V, the PAM provides 35-dBm output power, 55% power-added efficiency (PAE) in the GSM900 band, and 33 dBm and 50% PAE in the DCS1800 band.