We use a new technique to disseminate microwave reference signals along ordinary optical fiber. The fractional frequency resolution of a link of 86 km in length is 10-17 for a one day integration ...time, a resolution higher than the stability of the best microwave or optical clocks. We use the link to compare the microwave reference and a CO2/OsO4 frequency standard that stabilizes a femtosecond laser frequency comb. This demonstrates a resolution of 3.10-14 at 1 s. An upper value of the instability introduced by the femtosecond laser-based synthesizer is estimated as 1.10-14 at 1 s.
A simple method is presented to obtain a high-gain dual-band electromagnetic band gap (EBG) resonator antenna. The antenna is based on a one-dimensional EBG structure, made out of two low-cost ...unprinted dielectric slabs. The EBG structure is implemented as the antenna superstrate, which has been designed to provide a locally-inverted, positive reflection phase gradient with high reflectivity, in two pre-determined frequency bands. A composite dual-band antenna has been designed and tested with a stacked patch feed. Experimental results confirm the dual-band performance of the prototype antenna. Measured peak gains of 14.5 dBi and 15.1 dBi, and 3-dB gain bandwidth of 4.5% and 4.6%, are achieved at 10.6 GHz and 13.2 GHz, respectively. Measured 10-dB return-loss bandwidths are 6.4% and 3.9% in lower and upper bands, respectively. Potential enhancements of antenna radiation characteristics are studied using small 2 × 2 patch array feeds. It was found that such feeds can lead to lower side lobes, higher peak gains and larger gain bandwidths.
We present the characterisation of the most recent parametric transducers designed to enhance the Mario Schenberg gravitational wave detector sensitivity. The transducer is composed of a microwave ...re-entrant cavity that attaches to the gravitational wave antenna via a rigid spring. It functions as a three-mode mass-spring system; motion of the spherical antenna couples to a 50 μm thick membrane, which converts its mechanical motion into a frequency shift of the cavity resonance. Through the optical spring effect, the microwave transducer frequency-displacement sensitivity was measured to be 726 MHz μm−1 at 4 K. The spherical antenna detection sensitivity is determined analytically using the transducer amplification gain and equivalent displacement noise in the test setup, which are 5.5×1011 V m−1 and 1.8×10−19m Hz−1, respectively.
We use a new technique to disseminate microwave reference signals along ordinary optical fiber. The fractional frequency resolution of a link of 86 km in length is 10(-17) for a one day integration ...time, a resolution higher than the stability of the best microwave or optical clocks. We use the link to compare the microwave reference and a CO2/OsO4 frequency standard that stabilizes a femtosecond laser frequency comb. This demonstrates a resolution of 3 x 10(-14) at 1 s. An upper value of the instability introduced by the femtosecond laser-based synthesizer is estimated as 1 x 10(-14) at 1 s.
A report is presented on the residual intrinsic phase noise properties of a millimetre-wave module used to generate W-band signals from an X-band analogue signal generator. The 90 GHz outputs of two ...nominally identical millimetre-wave modules are heterodyned to measure their instantaneous frequency fluctuations and hence infer the close-to-carrier phase noise. The fractional frequency stability at 1 s integration time is 2 × 10−14, which corresponds to a total single-sideband phase noise of −50 dBc/Hz at 1 Hz Fourier frequency offset from the carrier and a residual single-sideband phase noise of −52 dBc/Hz at 1 Hz offset.
It has been proven, based on a rigorous electromagnetic analysis, that spherical TE 10p -mode Bragg-reflection resonators exhibit many times higher Q factors than corresponding cylindrical TE 01delta ...-mode dielectric resonators, dielectric whispering-gallery-mode resonators, or empty spherical TE 10p -mode cavities. Rigorous equations have been derived that allow optimally designed Q-factor and "quarter-wavelength" reflector-multilayered-spherical Bragg-reflection resonators. Experiments have been performed on three-layer spherical resonators made of single-crystal YAG and single-crystal quartz. The unloaded Q factor for the TE 012 mode in these resonators was 1.04times10 5 at 26.26 GHz for YAG and 6.4times10 4 at 27.63 GHz for quartz
This paper focuses on the development of tools aiming to solve several problems related to the microwave interrogation signal in atomic fountains. We first consider the problem related to cycle ...synchronous phase transients caused by the sequential operation of the atomic fountain. To search for such systematic phase variations deeply buried in the microwave synthesizer phase noise, we have developed a novel triggered-phase transient analyzer capable of processing the microwave signal to extract the phase in a synchronous manner even in the presence of frequency modulation. With this device we check in vivo the LNE-SYRTE fountain's interrogation signals with a resolution approaching 1 microradian. In addition, using this device, we investigate an innovative approach to solve a second problem, namely, the shift caused by microwave leakage in the fountain. Our approach consists of switching off the fountain microwave interrogation signal when atoms are outside the microwave cavity. To do that, we have developed a switch that is almost free of phase transients and is thus able to eliminate the frequency shift caused by microwave leakage without inducing significant phase transients on the interrogation signal.
The anisotropic loss tangent has been determined in monocrystalline sapphire for components parallel and perpendicular to the crystal axis, using the whispering gallery (WG) mode method. The ...Q-factors of quasi-TE and quasi-TM modes were measured precisely in four cylindrical sapphire resonators at room temperature, from which was determined a maximum attainable Q-factor of (2.1 /spl plusmn/ 0.2) /spl times/ 10/sup 5/ at 9 GHz in a quasi-TM mode. Sapphire dielectric material from three different manufacturers was compared over the 270-345 K temperature range and the 5-16 GHz frequency range.
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