Modem having a phase corrector and a voltage controlled oscillator implemented using a multi-stage ring oscillator

摘要

A carrier generator circuit for use in a modem employed in a wireless communication system is described. The carrier generator circuit includes a voltage controlled oscillator comprising an N-stage ring oscillator to generate N balanced vectors of equal magnitude and arbitrary phase difference. The carrier generator circuit also includes a phase corrector to add two of the balanced vectors to generate a sum vector and to subtract the two balanced vectors to generate a difference vector. The sum vector and difference vector have a phase difference of 90 degrees. The sum vector represents an I (in-phase) carrier signal component and the difference vector represents a Q (quadrature-phase) carrier signal component. These I and Q carrier signal components can be used to transmit and receive data signals.