X-band low phase noise push–push oscillator utilizing High-Q differential transmission line loaded with multiple split-ring resonator

In this study, a low phase noise X-band push–push oscillator is presented employing the differential transmission lines (TLs) loaded with multiple split-ring resonator (M-SRR). In order to enhance the coupling strength between TL and resonator cell, the single M-SRR is replaced by the coupled M-SRR cell-pair in differential TL to obtain high-frequency selectivity and deep insertion loss. The resonance properties of the differential TL have been discussed with different coupling configurations and coupling strengths of the M-SRR cell-pair, and the geometries of the proposed structure are investigated to obtain the optimum resonance properties. The loaded Q-factor of the proposed differential TL adopting 3-stages cascaded array of M-SRR cell-pairs configuration is 892 from measured results. Due to the high-Q and anti-phase current properties of the differential TL, a X-band push–push oscillator with low phase noise and superior fundamental frequency suppression performances is realized. The fabricated push–push oscillator operates at 9.52 GHz with an output power of 2.7 dBm and a fundamental frequency suppression of −54.55 dBc. It shows a measured phase noise of −115.48 dBc/Hz at 100 kHz offset frequency and a figure of merit of −201.23 dBc/Hz.