A 11.3–16.6-GHz VCO With Constructive Switched Magnetic Coupling in 65-nm CMOS

Abstract

Conventional transformer-based magnetic tuning has demonstrated dual-band or even multi-band operation for voltage-controlled oscillators (VCOs). However, the destructive magnetic coupling employed introduces implicit loss to the transformer thus degrading its quality factor (Q), and achieves a continuous frequency coverage resulting in inferior performance. To address this issue, this paper proposes a constructive switched magnetic coupling (CSMC) technique, realizing dual-band operation with the Q improvement into one band due to the in-phase coupling and the explicit switch. For validation, a transformer employing the CSMC technique is designed and deployed in a dual-band VCO design. Fabricated in a 65-nm CMOS process, the VCO is measured with an oscillation frequency range of 37.8%, from 11.3 to 16.6 GHz, while consuming 2.5-mW from a 0.65-V voltage supply. Within the entire frequency coverage, the measured phase noise ranges from −129.6 to −123.7 at 10-MHz offset, resulting in FoM of 186-192.1 dBc/Hz. The core area of the chip is $0.43\times 0.25$ mm2 excluding pads.