Signal distortion

The dynamic range of the instrument can be overwhelmed, leading to signal distortions and/or poor signal-to-noise ratios for the observed moiety ( ),... 

It has been pointed out that routine accurate mass measurements are conducted at resolutions which are too low to separate isobaric isotopic compositions in most cases. Unfortunately, coverage of multiple isotopic compositions under the same signal distort the peak shape. This effect causes a loss of mass accuracy when elemental compositions have to be determined from such multicomponent peaks, e.g., if the monoisotopic peak is too weak as the case with many transition metals. The observed decrease in mass accuracy is not dramatic and the loss of mass accuracy is counterbalanced by the information derived from the isotopic pattern. However, it can be observed that mass accuracy decreases, e.g., from 2-3 mmu on monoisotopic peaks to about 4—7 mmu on multicomponent signals. 

There are four general responses to the problem of solution resistance. First, if only qualitative information is sought in the experiment, a certain amount of iR error can be tolerated, perhaps 100 mV. Second, electronic compensation of solution resistance can be applied, and this is often quite successful and will allow accurate data to be obtained even with macroelectrodes. Nevertheless, problems of potentiostat stability and signal distortion must be addressed. 

Consider a fixed-frequency sinusoidal component (/) = sin(wojt + 00 ) from a musical signal, distorted by a pitch variation function p,v(t). The pitch-distorted component x,(t) can be written as (see [Godsill, 1993]) ... 

Mercer, 1993] Mercer, K. J. (1993). Identification of signal distortion models. PhD thesis, University of Cambridge. 

The matter of sampling and limited representation of frequencies requires a second look at the representation of data in the time and frequency domains, as well as the transformation between those domains. Specifically, we need to consider the Fourier transformation of bandwidth-limited, finite sequences of data so that the S/N enhancement and signal distortion of physically significant data can be explored. We begin with an evaluation of the effect of sampling, and the sampling theorem, on the range of frequencies at our disposal for some set of time-domain data. 

P. L. Edwards, Ultrasonic Signal Distortion and its Effects on Velocity Measurements in Dispersive Constant-Group-Velocity Media , J. Acoust. Soc. Am. 1983, 73, 1608. 

Moment analysis offers only two global parameters to characterize the peak while the exact peak shape is not taken into account, which makes this method more sensitive to signal distortions. By fitting of either analytical equations (Section 6.5.33) or simulation results to the peak shape this drawback may be overcome. It also allows an easy comparison between the calculated peak and the measured concentration profile. 

Stochastic excitation with m sequences and the use of the Hadamard transformation have been investigated in NMR spectroscopy [Kail, Zie2] as well as in NMR imaging [Chal]. Processing of the nonlinear response to m sequences by Hadamard and Fourier transformation results in signal distortions reminiscent of noise, which are caused by the nonlinear parts of the response [B1U2]. 

The dielectric constant of the substrate is the prime property because the propagation speed of the signal is inversely related to it. At these speeds the system has to be designed as a transmission line which must match the impedance of the devices used. Impedance mismatch can lead to reflected signals, and hence to signal distortion. The characteristic impedance of the line is also dependent on the dielectric constant, and for the devices now being used higher impedances are required and, therefore, low dielectric constant substrates. In addition, it is also important to have low-loss materials to prevent distortion of the pulses. 

In smoothing data with a moving polynomial, we want to remove as much noise as possible, while causing minimal signal distortion. Noise removal is... 

With the advent of acceleration detection over longer timeframes or satellite sensors near the perimeter of the vehicle, problems began to surface with signal distortion from the accelerometers. These occurred due to several specific sources. 

Delays are an important part of pulse sequences and may be characterized by their duration and the effect they cause. Short delays in the micro-second region such as the pre-scan delay de or power switching delays, are not normally illustrated explicitly in pulse sequences and NMR-SIM simulations do not take these types of delay into consideration because an ideal spectrometer is assumed. Such delays may seem superfluous but they should nevertheless be considered and included sometimes in the interpretation of experimental artefacts or signal distortions. These effects are discussed in detail in sections 2.2.1 and 5.8.2. 

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