A passive transformer voltage-controlled oscillator with active inductor frequency tuning for ultra wideband applications

This paper proposes a compromised design of LC tank VCOs that utilizes the superior phase noise of passive LC tank VCOs and the large frequency tuning range of active LC tank VCOs. The proposed VCO is a passive transformer LC VCO with active inductor frequency tuning. The large variation of the inductance of the active inductor connected to the secondary winding of the transformer results in a large frequency tuning range while the contribution of the noise of the active inductor is manipulated by varying the coupling of the transformer such that the phase noise and frequency tuning range of the proposed VCO can be made to fall between those of spiral LC VCOs and active VCOs. The VCO has been designed in IBM 130 nm 1.2V CMOS technology. The oscillator occupies 400µm×190µm and the total chip area including pads is 1 mm × 1 mm. The frequency tuning range of the oscillator is 6.5–10 GHz. The phase noise of the oscillator at 1 MHz frequency offset from its oscillation frequency 7.9 GHz is −100.5 dBc/Hz.