Y. Kersalé

Optimization of an ultra low-phase noise sapphire-SiGe HBT oscillator using nonlinear CAD

In this paper, the electrical and noise performances of a 0.8 /spl mu/m silicon germanium (SiGe) transistor optimized for the design of low phase-noise circuits are described. A nonlinear model developed for the transistor and its use for the design of a low-phase noise C band sapphire resonator oscillator are also reported. The best measured phase noise (at ambient temperature) is -138 dBc/Hz at 1 kHz offset from a 4.85 GHz carrier frequency, with a loaded Q/sub L/ factor of 75,000.

Ultra low phase noise sapphire-SiGe HBT oscillator

A state of the art C-band oscillator is presented. It is based on a high Q WGM sapphire resonator combined with a low residual phase noise SiGe HBT amplifier. A two oscillator experiment performed on this system has revealed a phase noise level of -133 dBc/Hz at 1 kHz offset from the 4.85 GHz carrier, which is the best published phase noise result for a single loop, free running microwave oscillator.

Measurement of the Fundamental Thermal Noise Limit in a Cryogenic Sapphire Frequency Standard Using Bimodal Maser Oscillations

We report observations of the Schawlow-Townes noise limit in a cryogenic sapphire secondary frequency standard. The effect causes a fundamental limit to the frequency stability, and was measured through the novel excitation of a bimodal maser oscillation of a Whispering Gallery doublet at 12.04 GHz. The beat frequency of 10 kHz between the oscillations enabled a sensitive probe for this measurement of fractional frequency instability of 10(-14) tau(-1/2) with only 0.5 pW of output power.

Unprecedented long-term frequency stability with a microwave resonator oscillator

This article reports on the long-term frequency stability characterization of a new type of cryogenic sapphire oscillator using an autonomous pulse-tube cryocooler as its cold source. This new design enables a relative frequency stability of better than 4.5 × 10-15 over one day of integration. To the best of our knowledge, this represents the best long-term frequency stability ever obtained with a signal source based on a macroscopic resonator.

Cryogenic monolithic sapphire-rutile temperature compensated resonator oscillator

We have tested a new temperature-compensated sapphire resonator as frequency determining element for high-stability microwave oscillator. Temperature compensation has been obtained by coating the sapphire resonator with a thin rutile film. A 2-/spl mu/m rutile thickness is sufficient to reach turnover temperature higher than 40 K, and a 2/spl times/10/sup -12/ short-term frequency stability has been obtained.

High power solid-state sapphire Whispering Gallery mode maser

We present new results on a cryogenic solid-state maser frequency standard, which relies on the excitation of Whispering Gallery (WG) modes within a doped monocrystalline sapphire resonator (α-Al2O3). Included substitutively within the highest purity HEMEX-grade sapphire crystal lattice are Fe2+ impurities at a concentration of parts per million, an unavoidable result of the manufacturing process. Mass conversion of Fe2+ to Fe3+ ions was achieved by thermally annealing the sapphire in air. Above-threshold maser oscillation was then excited in the resonator at zero applied DC magnetic field by pumping high-Q WG modes coincident in frequency with the Electron Spin Resonance (ESR) energy levels of the Fe3+ spin population. A two stage annealing process was undertaken, resulting in an improvement of six orders of magnitude in output power over the previous best implementation of this scheme, and giving an output seven orders of magnitude more powerful than a typical commercial hydrogen maser. We estimate the limit on the frequency stability due to the Schawlow-Townes fundamental thermal noise limit on the order of 1×10−17/√τ.

Ultra low phase noise SiGe HBT. Application to a C band sapphire resonator oscillator

In this paper, the electrical and noise performance of a 0.8 /spl mu/m Silicon Germanium (SiGe) transistor optimized for the design of low phase noise circuits are described. The nonlinear model developed for the transistor and its use for the design of low phase noise C band Sapphire resonator oscillator are reported. The best measured phase noise (at ambient temperature) is -133 dBc/Hz at 1 kHz offset from a 4.85 GHz carrier frequency for a loaded Q/sub L/ factor of 60,000.

Creating traveling waves from standing waves from the gyrotropic paramagnetic properties of Fe3+ ions in a high-Q whispering gallery mode sapphire resonator

We report observations of the gyrotropic change in magnetic susceptibility of the Fe 3+ electron paramagnetic resonance at 12.037GHz (between spin states|1/2 > and |3/2 >) in sapphire with respect to applied magnetic field. Measurements were made by observing the response of the high-Q Whispering Gallery doublet (WGH±17,0,0) in a Hemex sapphire resonator cooled to 5 K. The doublets initially existed as standing waves at zero field and were transformed to traveling waves due to the gyrotropic response.

ELISA: An ultra-stable oscillator for esa deep space antennas

The technology of the Sapphire Whispering Gallery Mode Resonator allows to surpass the frequency stability of traditional ultra-stable oscillators, and then can be exploited in number of applications requiring a high frequency stability as a frequency standard for the ESA ground station for which the requirement in term of frequency stability is σ<inf>y</inf>(τ) = 3 × 10⁻¹⁵ for integration times 1 ≤ τ ≤ 1000s.

Influence of the electron spin resonance saturation on the power sensitivity of cryogenic sapphire resonators

Here, we study the paramagnetic ions behavior in presence of a strong microwave electromagnetic field sustained inside a cryogenic sapphire whispering gallery mode resonator. The high frequency measurement resolution that can be now achieved by comparing two Cryogenic Sapphire Oscillators (CSOs) permit to observe clearly the non-linearity of the resonator power sensitivity. These observations that, in turn, allow us to optimize the CSO operation are well explained by the electron spin resonance saturation of the paramagnetic impurities contained in the sapphire crystal.