Continuous wave technique

The continuous wave technique has a definite advantage over the other techniques a very narrow band of frequencies is needed to transmit the information. The pulse techniques, on the contrary, use a large band of frequencies, and the various noises, pump noises in particular, are more difficult to eliminate. 

In principle, several channels of information could be transmitted simultaneously with the continuous wave technique. In particular, a downward channel to control the tool modes and an upward channel to bring up the information. 

Continuous wave techniques do not offer the optimum use of luminescence for sensing applications. CW methods, also known as intensity-based techniques, have many inherent limitations. These limitations will be discussed later in the chapter. Many of the limitations of intensity-based methods can be overcome by using steady-state modulated excitation of the form... 

There are two basic methods to determine the resonance condition and to record a NMR spectrum, viz. a) the continuous wave technique (CWNMR) and b) the pulsed NMR or pulsed Fourier Transform technique (FTNMR). 

The range resolution with the IBIS radar series is obtained with the Frequency Modulated Continuous Wave technique. In this case, the range resolution is related to the total swept bandwidth B as follows (Taylor, 2000) ... 

Application of continuous wave techniques and line shape analysis to wide-line n.m.r. spectra Cf D-xylose, D-mannose, D-glucose, D-fructose, and D-sorbose suggests that the lattice is effectively rigid in all except possibly D-fructose. Previously published C n.m.r. data for arabinosides and ribosides have been tabulated with correlation diagrams constructed in such a way that the data on new compounds can be used to assign the anomerlc configurations and ring size. Measurements of self-diffusion coefficients of carbo-... 

Figure 1 First-derivative spectra obtained by continuous-wave techniques for the phenalenyl radical (A) ESR, (B) ENDOR, (C) special TRIPLE resonance, (D) general TRIPLE resonance, and (E) ENDOR-induced ESR. The arrows indicate the positions of the RF pumping frequencies there are several possibilities in (D). The RF pumping frequency in (E) is set in the same position as shown in (B). (Reprinted from Kurreck H, Kirste B, and Lubitz W (1988) Electron Nuclear Double Resonance Spectroscopy of Radicals In Solution. Weinheim VCH Publishers.)...

Continuous wave techniques CW NQR spectrometers are based on the use of oscillator-detectors, which are built around the circuits of a marginal oscillator or a limited oscillator (Robinson oscillator). Such an oscillator-detector includes a tank circuit with a coil, into which the studied sample is inserted. When the frequency of the oscillator-detector coincides with the NQR frequency in the sample, the... 

CW Continuous wave or frequency sweep, the older, less sensitive, more time consuming basic technique of NMR detection... 

Why are pulse Fourier transform (PFT) NMR experiments preferred over continuous wave (CW) NMR techniques ... 

Johnson SG, Fearey BL (1993) Spectroscopic study of thorium using continuous-wave resonance ionization mass-spectrometry with rrltraviolet ionization. Spectrochim Acta Part B 48 1065-1077 Knoll GF (1989) Radiation Detection and Measurement. J. Wiley and Sons, New York Kuss HM (1992) Applications of microwave digestion technique for elemental analyses. Fresenins J Anal Chem 343 788-793... 

To meet all these system requirements specific waveform design techniques must be considered. For ACC systems both radar types of classical pulse waveform with ultra short pulse length (10 ns) or alternatively continuous wave (CW) transmit signal with a bandwidth of 150 MHz are considered. The main advantage of CW systems in comparison with classical pulse waveforms is the low measurement time and low computational complexity. 

Electron-nuclear double resonance (ENDOR) spectroscopy A magnetic resonance spectroscopic technique for the determination of hyperfine interactions between electrons and nuclear spins. There are two principal techniques. In continuous-wave ENDOR the intensity of an electron paramagnetic resonance signal, partially saturated with microwave power, is measured as radio frequency is applied. In pulsed ENDOR the radio frequency is applied as pulses and the EPR signal is detected as a spin-echo. In each case an enhancement of the EPR signal is observed when the radiofrequency is in resonance with the coupled nuclei. 

---