A Quad-Band 8PSK/GMSK

Abstract

The addition of 8PSK modulation to the GSM stan- dard creates the need for architectural modifications to achieve necessary performance while maintaining a cost-effective solution. A large-signal polar modulation transmitter allows the use of an ef- ficient nonlinear power amplifier (PA) for both GMSK and 8PSK. Digital interfaces are used for both receiver and transmitter, with analog options available for compatibility with older technology baseband systems. The receiver section of the transceiver is pro- grammable to operate in direct conversion mode or multiple VLIF modes. All analog and digital filtering necessary to define the final channel is included. The transmit section of the transceiver uses an all digital system with a fractional-N digital modulator for the phase path. The amplitude path uses a Powerstar PA with both the ramp and the amplitude modulation applied to the collector. The transceiver meets or exceeds all specifications for both GMSK and 8PSK in all four cellular bands (850/900/1800/1900).