Observations provide evidence that the licensed spectrum is by far not fully used neither in time nor in space. Cognitive radio, which can sense its environment and location and then alter its frequency, modulation and other parameters so as to dynamically reuse the available spectrum, could break the current spectrum availability bottleneck. The fundamental aspect to the success of such techno...

For one thing, some measurements which are very hard in the time domain are very easy in the frequency domain. Consider the measurement of harmonic distortion. It's hard to quantify the distortion of a sine wave by looking at the signal on an oscilloscope. When the same signal is displayed on a spectrum analyzer, the harmonic frequencies and amplitudes are displayed with amazing clarity. Anothe...

S U M M A R Y The power spectral density of geophysical signals provides information about the processes that generated them. We present a new approach to determine power spectra based on Thomson’s multitaper analysis method. Our method reduces the bias due to the curvature of the spectrum close to the frequency of interest. Even while maintaining the same resolution bandwidth, bias is reduced ...

Auctions have emerged as the primary means of assigning spectrum licenses to companies wishing to provide wireless communication services. Since July 1994, the Federal Communications Commission (FCC) has conducted 33 spectrum auctions, assigning thousands of licenses to hundreds of firms. Countries throughout the world are conducting similar auctions. I review the current state of spectrum auct...

An empirical model for scaling Fourier Amplitude Spectra of strong earthquake ground acceleration in terms of magnitude, M, epicentral distance, R, and recording site conditions has been presented. The analysis based on this model implies that: (a) the Fourier amplitude spectra of strong-motion accelerations are characterized by greater energy content and relatively larger amplitudes for long-p...

At present, the technology of virtual instrument has been developed very quickly in the field of electronic measurement and automatic control. The virtual instrument is a kind of functional instrument combining of software and hardware .This article is from the perspective of exploration and research, and as a reference when encounter hardware problems in the research and development of virtual...

We analyzed RXTE/PCA observations of Cyg X–1 from 1996–1998. We found a tight correlation between the characteristic noise frequencies (e.g. the break frequency ν br) and the spectral parameters in the low spectral state. The amplitude of reflection increases and the spectrum of primary radiation steepens as the noise frequency increases (ν br changes by a factor of ∼ 15 in our sample). This ca...

In this contribution, we present novel multiplexed frequency spectrum analyzer instrumentation to extract operational parameters and completely characterize the frequency response of an array of quartz crystal microbalance sensors. The effectiveness of the proposed instrumentation is proven by experimental measurements over a range of frequencies.

Cognitive radio requires real time monitoring of the spectrum to determine the frequency of transmission. Spectrum analysers tend to employ a slow frequency sweep and hence such measurements can only be used for modelling of the spectrum, which can provide vital information for frequency planning and management. Occupancy measurements every hour over a seven-day period were performed in the UK ...

A nonlinear spectral analysis technique that enables digital communication system metrics; SNR, EVM and the waveform quality factor (ρ) to be related to in-band distortion spectrum is presented. System metrics are estimated from the measured output power and in-band distortion power. The estimated metrics are verified by direct measurements of each metric using a Vector Signal Analyzer (VSA) pe...