The performance of newer generations of ultra high stability atomic frequency standards based on laser cooled atoms and ions appears to be limited by the local oscillator and the microwave synthesis chain. To improve this performance, the design considerations of microwave synthesizers for Cs hyperfine clock transition at 9.192 GHz that emphasize high resolution, low phase modulation (PM) and a...

[1] Earth’s background vibrations at frequencies below about 0.5 Hz have been attributed to ocean-wave energy coupling into the ground and propagating as surface waves and P-waves (compressional waves deep within the Earth). However, the origin and nature of seismic noise on land at frequencies around 1 Hz has not yet been well studied. Using array beamforming, we analyze the seismic noise fiel...

The noise levels given by spectral analysis are relevant parameters for the characterization of the time-domain stability of oscillators. The estimation of the noise levels of a sampled signal may be achieved with variances even if the sampling frequency is far lower than the high cut-off frequency. The effects of spectral aliasing for the white-phase noise are shown and a procedure for estimat...

In deep water, the dominant sources of natural ocean noise are often events occurring at the sea/air interface. In shallow water, particularly if it is warm, this is often no longer the case. Where wind-related noise is less pronounced, snapping shrimp alone can easily dominate the soundscape over two decades of bandwidth. Particularly for ambient noise imaging, the high frequency content of th...

A quantization noise reduction technique is proposed that allows fractional-N frequency synthesizers to achieve high closed loop bandwidth and low output phase noise simultaneously. Quantization induced phase noise is the bottleneck in state-ofthe-art synthesizer design, and results in a noise-bandwidth tradeoff that typically limits closed loop synthesizer bandwidths to be <100kHz for adequate...

This paper describes a CMOS transconductance element based upon two differential pairs whose outputs are summed to give a linear transfer characteristic. The circuit has been simulated using a 2pm process from MOSIS, and results show that with a single 5V supply, bandwidth in excess of 300MHz, THD below 0.7% for a lV,,k-,,k differential input signal, and dynamic range in excess of 70dB can be a...