High-Q thermoelectric-stabilized sapphire microwave resonators forlow-noise applications |
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Authors: | Tobar M.E. Giles A.J. Edwards S. Searls J.H. |
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Affiliation: | Dept. of Phys., Western Australia Univ., Nedlands, WA; |
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Abstract: | Two low-noise high-Q sapphire-loaded cavity (SLC) resonators, with unloaded Q values of 2×105 and very low densities of spurious modes, have been constructed. They were designed to operate at 0°C with a center frequency of 10.000000 GHz. The cavity was cooled with a thermoelectric (TE) Peltier element, and in practice achieved the required center frequency near 1°C. The resonator has a measured frequency-temperature coefficient of -0.7 MHz/K, and a Q factor which is measured to be proportional to T-2.5. An upper limit to the SLC residual phase noise of ℒ (100) Hz=-147 dBc/Hz, ℒ (1 kHz)=-155 dBc/Hz, and ℒ (10) kHz=-160 dBc/Hz has been measured. Also, we have created a free-running loop oscillator based on one of the SLC resonators, and measured a phase noise of ℒ(f)~-10-30log [f] dBc/Hz between f=10 /Hz and 25 kHz, using the other as a discriminator |
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