A voltage controlled oscillator (300;400;700) for combining series and parallel tuned resonance modes, comprising: an active device (304;710;1120,1110) having first, second and third terminals for amplifying a signal between the second terminal and the first terminal and for providing a 180 degree phase shift to the signal; a biasing circuit coupled to the first terminal; first resonator circuitry for series resonance mode (316;714;1130), having a first and a second resonator terminal, whose second resonator terminal is coupled to the second terminal, the first resonator circuitry (316;714;;1130) having a first resonant frequency; second resonator circuitry (310;410;718;830;1140) for parallel resonance mode is coupled to a node between the second terminal and the first resonator circuitry, the second resonator circuitry having a second resonant frequency different than the first resonant frequency; a tuning network (320;740) is coupled to the first resonator terminal of the second resonator circuitry (316;714;1130); a first filter coupled to the third terminal of the active device (304;710;1120, 1110) and a second filter coupled in series to the first filter; characterised by a noise filtering network coupled between the tuning network (320;740) and the connection node between the first and the second filter (720;722) and comprising a first inductor coupled to the tuning network (320;740), a second inductor (Lnl) coupled in series to the first inductor, a first capacitor coupled between a connection node between the first and the second inductor (Ln2, Ln1) and ground, a second capacitor coupled in series to the second inductor (Lnl) and to the connection node between the first and the second filter (720;722) and at least one diode coupled between the connection node between the second inductor (Lnl) and of the second capacitor and ground. an active device (304;710;1120,1110) having first, second and third terminals for amplifying a signal between the second terminal and the first terminal and for providing a 180 degree phase shift to the signal; a biasing circuit coupled to the first terminal; first resonator circuitry for series resonance mode (316;714;1130), having a first and a second resonator terminal, whose second resonator terminal is coupled to the second terminal, the first resonator circuitry (316;714;;1130) having a first resonant frequency; second resonator circuitry (310;410;718;830;1140) for parallel resonance mode is coupled to a node between the second terminal and the first resonator circuitry, the second resonator circuitry having a second resonant frequency different than the first resonant frequency; a tuning network (320;740) is coupled to the first resonator terminal of the second resonator circuitry (316;714;1130); a first filter coupled to the third terminal of the active device (304;710;1120, 1110) and a second filter coupled in series to the first filter; characterised by a noise filtering network coupled between the tuning network (320;740) and the connection node between the first and the second filter (720;722) and comprising a first inductor coupled to the tuning network (320;740), a second inductor (Lnl) coupled in series to the first inductor, a first capacitor coupled between a connection node between the first and the second inductor (Ln2, Ln1) and ground, a second capacitor coupled in series to the second inductor (Lnl) and to the connection node between the first and the second filter (720;722) and at least one diode coupled between the connection node between the second inductor (Lnl) and of the second capacitor and ground.