A base control Doherty power amplifier design for improved efficiency in GSM handsets

Graduation date: 2004In cellular telephones, RF power amplifiers consume a significant part of the\ud total phone current. Reducing the average PA current will extend battery life. In\ud GSM systems the handset is commanded by the base station to transmit at power\ud levels lower than full power much of the time. A Doherty amplifier can be used to\ud improve efficiency at these lower power levels, providing a lower average PA current\ud when evaluated over the entire power range.\ud A Doherty amplifier is presented that uses the DC base voltage to control the\ud output power. The base control amplifier is first studied separately, then two such\ud amplifiers are combined to create a Doherty amplifier. An analysis of battery life\ud while the phone is on a call, or talk time, is then performed. Talk time for the base\ud control Doherty amplifier is compared to an ideal class B amplifier and to a Doherty\ud amplifier composed of two class B amplifiers. Finally a base control Doherty\ud amplifier is implemented at 30 MHz, both in simulation and hardware