An Alternative Technique to Minimize the Phase Noise of X-band Oscillators Using Improved Group Delay SIW Filters

This letter presents a new method to realize microwave low phase noise oscillators using high selectivity SIW filters. A perturbing via-hole is located inside the dual-mode circular cavity to significantly enhance the filter selectivity. By properly adjusting this perturbing via-hole position, the oscillator phase noise can be minimized at frequency location of the improved group delay peak. Several planar X-band oscillator prototypes have been fabricated and measured. Good agreement between experiment and predicted results is shown. The designed oscillators have advantages of simple design process, planar structure, and improved phase noise. At the oscillation frequency of 10.178 GHz, the measured real phase noise is -135.4 dBc/Hz@1MHz and -1.35 dBm output power.