Quadrature voltage controlled oscillators with phase shift detector

摘要

In wireless application there is made use of a quadrature oscillators that generate signals that are capable of oscillating at quadrature of each other. The quadrature oscillator is comprised of two differential modified Colpitts oscillators. A capacitor bank allows for the selection of a desired frequency from a plurality of discrete possible frequencies. The quadrature oscillator is further coupled with a phase-error detector connected at the point-of-use of the generated 'I' and 'Q' channels and through the control of current sources provides corrections means to ensure that the phase shift at the point-of-use remains at the desired ninety degrees.