Filters and Resonance

High-temperature ceramic superconductors, which would fall into the category of advanced ceramics, are not presently a major market area. They constitute less than 1% of the advanced ceramics market. Significant growth has been predicted because of their increased use in microwave filters and resonators, with particular application in the area of cell phones. 

Pecoraro, E Andre, P.S., and Carlos, L.D. (2011) Optical filters and resonant cavities based on di-ureasil organic-inorganic hybrids./. Sol-GelSci. Technol, 59, 475-479. 

The rest of the detector signal is noise filtered and amplified by a lock-in amplifier. The output of the lock-in amplifier is monitored by an oscilloscope, and recorded as the laser scans across the gas s absorption line. The result is a spectral profile of the gas absorption, impressed on the depth of the locked resonance dip. This is then analyzed using (5.6) to find an experimental effective absorption path length. 

Little, B. E. Chu, T. Haus, H. A., Second order filtering and sensing with partially coupled traveling waves in a single resonator, Opt. Lett. 1998, 23, 1570 1572... 

Bound States and Resonances of the Hydroperoxyl Radical H02. An Accurate Quantum Mechanical Calculation Using Filter Diagonalization. 

Dawson, P.H. Whetten, N.R. Nonlinear Resonances in Quadrupole Mass Spectrometers Due to Imperfect Fields. II. Quadrupole Mass Filter and die Monopole Mass Spectrometer. Int. J. Mass Spectrom. Ion Phys. 1969, 5, 1-12. 

Because of its piezoelectric properties, synthetic CC-quartz is used for frequency control in electrical oscillators and filters and in electromechanical transducers. When mechanically stressed in the correct direction, CC-quartz develops an electric polarization. The opposite is also tme an applied electric field gives rise to a mechanical distortion in the crystal. Thin sections of quartz are cut to dimensions that produce the desired resonance frequency when subjected to an alternating electric field the vibrating crystal then reacts with the driving circuit to produce an oscillation that can be narrowly controlled. Quartz is ideal for this application because it is hard, durable, readily synthesized, and can be tuned to high accuracy, for example, quartz crystal clocks can be made that are stable to one part in 109. 

As an example, for copper with a room temperature conductivity of 5.8 x 107(O m) 1 the surface resistance at 10 GHz is 26 mil, the skin depth is 0.66 pm. Therefore, the Q of a cavity resonator with a geometric factor of several hundred is in the 104 range. However, for planar resonators like the ones shown in Figure 5.8 the G values are only a few Ohms leading to Q values of only a few hundred. This is too small for many filter and oscillator applications. 

The solution to providing stable filters and oscillators in the past lay in bulky coaxial and cavity resonators fabricated from the temperature-stable metal alloy Invar. The dielectric resonator (DR) offers a means of miniaturizing the device. 

Figure 3-20 Resonance Raman spectra of TCNQ and electrogenerated TCNQ--. [TCNQJ 1.09 mM, laser power = 20 mW, bandpass = 1.2cm-1 [TCNQ ] = 2.24 mM, laser power =74 mW, bandpass = 2.2cm 1. TCNQ - was electrogenerated by controlled potential caulome-try at -0.10 V vs. SCE in 0.1 M TBAP/CH3CN. All spectra were scanned at 50 cm 1 min-1 using a 1.00 s counting interval. Plasma lines were removed at 4579 A with an interference filter and at 6471 A with a Claassen filter. S denotes a normal Raman band of the solvent (acetonitrile). No normal Raman bands are observed for the supporting electrolyte (TBAP, tetrabutylammo-nium perchlorate). (Reproduced with permission from Ref. 75. Copyright 1976 American Chemical Society.)...

In 2D spectroscopy the Gaussian function is often preferred over exponential multiplication because little broadening at the base of the resonance is induced by this filter, and significant sensitivity improvement can still be obtained. 

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