A 21-24 GHz Low-Phase-Noise mmWave VCO with Third-Harmonic Expansion using a Triple-Coupled Transformer based Tank

TL;DR

This paper introduces a novel sixth-order triple-coupled transformer tank for mmWave VCOs, enabling wideband third-harmonic expansion with low phase noise and reduced area in 65-nm CMOS.

Contribution

It proposes a new tank design supporting third-harmonic expansion without additional tuning elements, improving phase noise and area efficiency over conventional designs.

Findings

Achieved 21.03-23.99 GHz tuning range in simulations.

Demonstrated minimum phase noise of -116.25 dBc/Hz at 1 MHz offset.

Realized high FoM and FoMT values with low power consumption.

Abstract

This work presents the design and analysis of a sixth-order triple-coupled transformer-based tank, enabling third-harmonic expansion for mmWave VCOs. Unlike conventional fourth-order tanks, the proposed tank inherently supports three resonance modes, enabling wideband third-harmonic expansion without additional low-Q switched-capacitor tuning elements. In contrast to conventional class-F23 designs, the proposed VCO removes the head resonator and adopts a noise circulating core to maintain low phase noise with reduced area. Implemented in TSMC 65-nm CMOS, post-layout simulation results demonstrate a 21.03-23.99 GHz (13.5%) tuning range, minimum phase noise of -116.25 dBc/Hz at 1 MHz offset, and peak FoM/FoMT/FoMA of 195.86/198.24/212.31 dBc/Hz while consuming 5.4 mW and occupying 0.02268 mm2.