A plasmonic meta-rotary travelling-wave oscillator with ultrahigh phase accuracy and figure of merit.

High phase accuracy and figure of merit (FOM) of quadrature signals are essential for integrated systems, including quadrature amplitude modulation (QAM) communications and multi-input multi-output (MIMO) radar. However, the traditional quadrature oscillators often struggle to meet the stringent requirements of high FOM and high quadrature phase accuracy simultaneously. To address this challenge, we propose a spoof surface plasmon polariton (SPP) metawaveguide (Meta) to design on-chip rotary traveling-wave oscillator (RTWO). By leveraging the advanced dispersion manipulation capability of Meta, the physical and electrical lengths of transmission line (TL) are effectively decoupled, thereby overcoming the limitations associated with the unequal electrical lengths of inner and outer loops of the resonator, which is difficult to achieve in the conventional RTWOs. Based on the design methodology, we realize a Meta-RTWO using the 65 nm CMOS technology and achieve a measured FOM of 188.5 dBc/Hz and a phase error of approximately 0.21°. These metrics surpass those of the traditional oscillators fabricated even by more advanced 28 nm CMOS processes. This study demonstrates that Meta-RTWO achieves a significant improvement in both output signal quadrature accuracy and FOM under process limitations without using additional phase adjustment structures.