摘要

In this letter, a transmission line (TL) loaded with active circular substrate integrated waveguide (SIW) resonator is presented and used in microwave oscillator to reduce phase noise. By compensating the resonance loss in SIW cavity using coupling negative resistance method in active resonator, the TL loaded with active SIW resonator exhibits a sharp reflective property at the fundamental mode resonance frequency which is suitable for series feedback oscillator. The simulated loaded Q-factor of the proposed TL achieves 379. To validate this method, X-band oscillators using TL loaded with active and passive SIW resonator are designed and implemented. The measured results show that the oscillator base on active SIW resonator exhibits a low phase noise of -128.75 dBc/Hz at 1 MHz offset frequency from 11.01 GHz carrier, which is 9 dB better than the oscillator based on passive SIW resonator.