ABSTRACT
The Q factor of the LC-tank-based resonator has performance degradation at 60∼100 GHz. EM-wave-based oscillators have been studied to improve the Q factor. The commonly deployed standing-wave-based oscillator (SWO) in [79, 238, 239] increases the Q of λ/4 coplanar stripline (CPS) resonators by forming an open-circuit load when the incident and reflected EM waves perfectly move in phase with each other. The primary limitations of this approach are twofold. Firstly, the open circuit condition is hard to achieve due to loss in the λ/4 CPS line; and secondly, the dimension is still large when implementing λ/4 CPS lines on chip. Placing additional floating metal shielding to form slow-wave lines may alleviate the aforementioned problems. Alternatively, metamaterialbased designs have been explored recently within the microwave community [240, 54, 241, 78]. A number of works are proposed recently for the design of a transmission line (T-line) loaded high-Qmetamaterial resonator at the printed circuit board (PCB) scale. Split-ring resonator (SRR)-based or complementary split-ring resonator(CSRR)-based oscillator designs are explored at 5.5∼5.8 GHz [79, 80]. As the node becomes advanced, recently, a single-ended T-line loaded with SRRs (STL-SRRs) was studied in [84]. The SRR-based open-loop multiple split-ring resonator structure was studied for a 24-GHz oscillator in a 130-nm CMOS process [79, 80]. No in-depth works are, however, performed on how to design a high-Q and low-loss metamaterial resonator in advanced node. For example, it is unknown to design differential oscillators or voltagecontrolled oscillators (VCOs) with use of a metamaterial resonator at 60∼100 GHz in the 65-nm CMOS process.
