Spectrum analyzer

About: Spectrum analyzer is a research topic. Over the lifetime, 12217 publications have been published within this topic receiving 101851 citations.

Photoelectric Analysis of Polarized Light

Abstract: The light traverses a rotating polarizer and the relative intensity behind this analyzer is measured photoelectrically as a function of the analyzer azimuth. A Fourier analysis is applied to the values obtained. The Fourier constants are practically equivalent to the Stokes parameters and their relations to other polarization parameters such as the phase difference, the azimuth, and the degree of polarization are given. The method may be applied to light of any wavelength. The theory is demonstrated by some measurements which were made with an especially constructed analyzer drive. For most practical cases a very satisfactory precision in the measurement of the polarization parameters is obtained.

Measurements of acoustic impedance in a free field with two microphones and a spectrum analyzer

Abstract: A technique is presented for evaluating the normal acoustic impedance at the surface of a panel of absorbing material in a free field. The evaluation is achieved by measuring the pressure and the acoustic velocity with two microphones set very close to the panel. This technique allows measurements of impedance for panels of area about 1 m2, the two microphones being located very close to the panel so that, contrary to other methods, the effect of the finite dimension of the panel is negligible. Because of the very small spacing between both microphones, this technique allows precise measurements only for frequencies higher than 500 Hz.

Apparatus for waveform disturbance monitoring for an electric power system

Abstract: A monitor/analyzer for an alternating current (AC) electrical system responds to power line disturbances by generating a trigger signal when a change in voltage with respect to time electrical parameter is greater than a programmed threshold. The monitor/analyzer includes a sensor for sensing an AC waveform in the electrical system, an analog-to-digital converter for sampling the AC waveform, and a microcomputer. Firmware of the microcomputer cooperates with the A/D converter and provides a plurality of digital samples of the AC waveform for each of some of its AC cycles. The firmware generates each of plural dV/dt parameters of the AC waveform from a corresponding adjacent pair of the digital samples within one of the waveform's AC cycles. A trigger signal is generated when one of the dV/dt parameters is greater than the programmed threshold. The digital samples of the AC waveform before and after the power line disturbance are captured and output to a display in response to the trigger signal.

Broad-band Mach-Zehnder interferometers as high performance refractive index sensors: Theory and monolithic implementation

Abstract: Broad-band Mach-Zehnder interferometry is analytically described and experimentally demonstrated as an analytical tool capable of high accuracy refractive index measurements over a wide spectral range. Suitable photonic engineering of the interferometer sensing and reference waveguides result in sinusoidal TE and TM spectra with substantially different eigen-frequencies. This allows for the instantaneous deconvolution of multiplexed polarizations and enables large spectral shifts and noise reduction through filtering in the Fourier Transform domain. Due to enhanced sensitivity, optical systems can be designed that employ portable spectrum analyzers with nm range resolution without compromising the sensor analytical capability. Practical detection limits in the 10−6-10−7 RIU range are achievable, including temperature effects. Finally, a proof of concept device is realized on a silicon microphotonic chip that monolithically integrates broad-band light sources and single mode silicon nitride waveguides. Refractive index detection limits rivaling that of ring resonators with externally coupled laser sources are demonstrated. Sensitivities of 20 μm/RIU and spectral shifts in the tens of a pm are obtained.