Abstract: A voltage controlled oscillator (VCO) for connection and operation in a phase locked loop arrangement has two or more operational states in each of which the VCO circuit is operable to provide activation of a selected one of two or more different phase locked loops when connected to the VCO circuit, the VCO circuit including switching means for switching the state of the VCO circuit to allow the operational state of the VCO to be selected. A frequency synthesizer circuit for use in radio communications to generate a stable frequency signal, the circuit includes the VCO circuit. The synthesizer circuit includes two or more different phase locked loops each having a first state in which the loop is activated and a second state in which the loop is deactivated. At least part of the VCO circuit is connected in and shared by the loops, so that the loop to be activated can be selected by selecting the operational state of the VCO.

Abstract: A voltage controlled oscillator (VCO) for connection and operation in a phase locked loop arrangement has two or more operational states in each of which the VCO circuit is operable to provide activation of a selected one of two or more different phase locked loops when connected to the VCO circuit, the VCO circuit including switching means for switching the state of the VCO circuit to allow the operational state of the VCO to be selected.