Patent ID: 7209494

Claim:
A method to operate a communication device, comprising: during a receive period, receiving a first carrier and deriving a receiver tracking signal that is indicative of a frequency shift between the received first carrier and a reference signal; and shifting a receiver baseband signal by an amount and in a direction indicated by the receiver tracking signal; and during a next transmission period, shifting a transmitter baseband signal by an amount indicated by the receiver tracking signal during the receive period, and in a direction opposite to the direction indicated by the receiver tracking signal during the receive period; and transmitting a second carrier signal that is modulated in accordance with the shifted transmitter baseband signal, wherein shifting comprises time multiplexing a digital phase shifter circuit between a receiver baseband subsystem and a transmitter baseband subsystem; wherein the receiver tracking signal comprises: f 0 =( CF*SH value)/ L; wherein f 0 is the receiver tracking signal; CF is a clock frequency of a local clock; SH value is a value output from the carrier loop tracking circuit; and L is a length of an accumulator that stores a plurality of SH values, one from each of a plurality of sequential clock periods.