Spurious Mode Rejection in an Oversized Dielectric Resonator by Microstrip Metallic Pattern

In order to achieve a low phase noise oscillator, designing a high Q resonator is inevitable. Exciting higher order mode is an appropriate method to increase the quality factor. Existence of unwanted mode is a major issue that appears in higher order mode excitation. The oscillator circuit cannot oscillate in the desirable mode due to low mode separation. This paper presents a design methodology for DR which leads to improve spurious performance in higher order modes in addition to rejection of unwanted frequencies. Besides, controlling the frequency separation between resonance and unwanted frequencies is obtained to employ in low noise oscillators. An eight-GHz dielectric resonator excited by TE22δ mode perform the quality factor equals to 12450 which is higher than DR excited by TE01δ mode with quality factor of 8100. Also, unwanted frequencies at 8.05 GHz and 8.3 GHz are suppressed by proposed technique with minimum impact on the main resonance mode.