Patent ID: 6484038
Filing Date: 2002-11-19
Classification: H03D,H04B

Abstract:
A dual-mode cellular radiotelephone apparatus for receiving and transmitting coded and modulated information symbols at a first symbol rate alternately at a second symbol rate comprising:a dual reference frequency oscillator responsive to a select signal to oscillate at a first accurate frequency or a second accurate frequency according to the select signal level and to provide an output signal of the selected frequency; a digital signal processing using said selected reference oscillator frequency signal to generate said coded and modulated information symbols for transmission at said first rate or said second rate in dependence on the selected reference frequency; a second local oscillator frequency synthesizer producing an accurate second local oscillator frequency signal phase-locked to said selected reference frequency signal; a first local oscillator frequency synthesizer producing an accurate first local oscillator frequency signal; a transmit oscillator producing a signal at a desired frequency of transmission in dependence on a control signal; a transmit oscillator frequency control comprising transmit mixer mixing said transmit frequency signal with said first local oscillator signal to produce a transmit offset frequency signal and transmit phase lock loop for comparing said transmit offset frequency signal with said second local oscillator frequency signal to generate said control signal.