An electrically tunable X-Band voltage-controlled oscillator using substrate integrated waveguide dual-mode bandpass filter with circular cavity

An electrically tunable X-Band voltage-controlled oscillator (VCO) based on the substrate integrated waveguide (SIW) dual-mode bandpass filter (BPF) technique is presented. In this VCO configuration, the SIW cavity acts as a frequency stabilization element in the feedback loop and a phase shifter is used to change the loop phase. Due to the transmission zero near the upper passband of the SIW BPF, the phase noise performance can be improved within the range of the group delay peak. Measured results show that, the proposed VCO resulting in a frequency tuning range of 11.4033 GHz-11.5565 GHz and a phase noise below -123 dBc/Hz at 1-MHz offset frequency over the entire tuning range.