Patent ID: 6680639
Filing Date: 2004-01-20
Classification: H03H,H03L

Abstract:
A phase shifting arrangement for generating a set of mutually orthogonal sinusoidal signals, comprising:a phase shifting unit for receiving a sinusoidal input signal and having a first phase shift circuit for generating a first sinusoidal output signal phase-shifted by a first amount with respect to the sinusoidal input signal, a second phase shift circuit for generating a second sinusoidal output signal phase-shifted by a second amount with respect to the sinusoidal input signal, and a third phase shift circuit for generating a third sinusoidal output signal phase-shifted by a third amount with respect to the sinusoidal input signal; the phase shift caused by each of the first, second and third phase shift circuits being adjustable in response to a feedback signal; and a phase shift adjustment circuit for generating the feedback signal and arranged to receive the first, second and third sinusoidal output signals and a fourth sinusoidal output signal of the same phase as the sinusoidal input signal and thereby generate an error signal dependant on the deviation of the first, second, third and fourth signals from mutual orthogonality; and a feedback circuit arranged to receive the error signal and form the feedback signal in dependence thereon in so as to cause the first, second and third phase shift circuits to, on receiving the feedback signal, generate the first, second and third signals in closer orthogonality to each other and to the sinusoidal input signal, wherein the first, second and third phase shift circuits are of the same type.