GaAs MMIC power amplifiers for GMSK based GSM/DCS-1800 applications

The design and development of subscriber power amplifiers for GMSK based GSM (Global System Mobile) and DCS-1800 will be presented. This extremely high volume and price sensitive market dictates that state of the art electrical performance and manufacturability need to be considered as concurrent design goals. Nonlinear modeling using both harmonic balance and time domain techniques provided the optimal circuit topology and element values. These two-stage GaAs MESFET power amplifiers operate on a 6V supply which is pulsed with a 570uS burst and a 12.5% duty cycle. The GSM power amplifier provides 36dBm pulsed output power at 53% efficiency and an associated gain of 26dB over the 890-915 MHz frequency range. The DCS-1800 power amplifier provides 33dBm pulsed output power at 56% efficiency and an associated gain of 22dB over the 1710-1785 MElz frequency range. The amplifiers are packaged in a novel thermally efficient low cost plastic package and incorporate flexible high-Q off chip output matching. The inherent package size is 0.02cm3 as compared to greater than 1cm3 typical of conventional hybrid approaches and is believed to be the smallest size for an amplifier of this functionality and state of the art electrical performance.