A 2.8-to-5.8 GHz harmonic VCO based on an 8-shaped inductor in a 28 nm UTBB FD-SOI CMOS process

A 2.8-to-5.8 GHz harmonic VCO designed in a 28 nm UTBB FD-SOI CMOS process adopts a reconfigurable active core to save power at the lower oscillation frequencies, and to enable a trade-off between power consumption and phase noise at all frequencies. Interference caused by the magnetic coupling to and from the VCO inductor is greatly attenuated by resorting to an inductor in the shape of an 8. Simulations of the magnetic coupling between an 8-shaped inductor and a reference inductor show a reduction in magnetic coupling as high as 44 dB, depending also on size, orientation, and shape of the reference inductor. The UTBB FD-SOI CMOS process is instrumental to achieve a tuning range in excess of one octave at low power consumption. The VCO operates from 0.9 V and has a figure-of-merit of 186–189 dBc/Hz, depending on the oscillation frequency and the configuration of the oscillator core. The active area of the VCO is 380 × 700 µm.