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Ultra-low Noise Cavity Stabilized Microwave Reference Oscillator using an Air-dielectric Resonator



Craig Nelson, David A. Howe, A Sen Gupta


Ultra-low noise microwave oscillators are often required to serve as reference signals in precision PM noise measurement systems and in a host of other applications. We have significantly improved the spectral purity of NIST¿s traditional cavity-stabilized microwave oscillator design which uses a conventional air-dielectric cavity resonator as a frequency discriminator. We developed and tested an accurate model of the expected PM noise that indicates, among other things, that a conventional air-dielectric resonator of moderate Q will exhibit less discriminator noise than more esoteric and expensive dielectric resonators tuned to a high-order, high-Q mode and driven at the dielectric's optimum power. Additionally, we increase the discriminator's intrinsic signal-to-noise ratio by use of a high-power carrier signal to interrogate an optimally coupled cavity, while the high-level of the carrier is suppressed before the phase detector. We report exceptionally low PM noise levels from a microwave oscillator operating at 10 GHz.
Proceedings Title
Proc. PTTI
Conference Location
Washington, DC, USA
Conference Title
Precise Time and Time Interval Planning and Applications Meeting


cavity stabilized, frequency standard, microwave, oscillator, phase noise


Nelson, C. , Howe, D. and Sen Gupta, A. (2004), Ultra-low Noise Cavity Stabilized Microwave Reference Oscillator using an Air-dielectric Resonator, Proc. PTTI , Washington, DC, USA, [online], (Accessed April 22, 2024)
Created December 6, 2004, Updated October 12, 2021