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Radio Frequency Distortion Mechanisms and Analysis
Published in Jerry C. Whitaker, Electronic Systems Maintenance Handbook, 2017
Distortion refers to the corruption encountered by a signal during transmission or processing that mutilates the signal waveform. A simple model of the atmospheric radio channel, as shown in Fig. 22.1, will help to illustrate the sources of radio frequency distortion. The channel is modeled as a linear time-variant system with additive noise and additive interference. In the figure, s(t) is the RF signal to be transmitted through the channel, h(t, τ) is the channel impulse response, n(t) is the additive noise, i(t) is the interference, and r(t) is the received signal. Sources of signal corruption, such as signal attenuation, amplitude distortion, phase distortion, multipath effects and time-varying channel characteristics, constitute the linear time-variant channel impulse response. Noise and interference are additive sources of signal corruption. Corruption by noise may result in a roughness of the output waveform, but the original signal waveform is usually discernible. This is one sense in which noise differs from the distortion mechanisms discussed in this section.
Distortion
Published in Roey Izhaki, Mixing Audio, 2017
A linear device is one that has perfect proportionality between input and output. The transfer curve of such a device is one straight line. An example of a nonlinear device is a compressor with any ratio other than 1:1. When a signal passes through a nonlinear system, different kinds of distortion are produced. The less linear the system, the more profound the distortion. One type of distortion is harmonic distortion—essentially, added harmonics. Analog components are incapable of being perfectly linear. A specification called total harmonic distortion (THD) measures the harmonic distortion content produced by an analog device under standard test conditions. There are different flavors to analog distortion. The ratio between the low-order harmonics produced by a tube is different from that produced by a transistor. This is a major contributor to the different sounds that a tube and solid-state equipment produce. Although technically speaking the lower the distortion the better, harmonic distortion is an intimate part of the analog sound in general and the charac teristics of analog gear in particular. Digital systems are capable of being perfectly linear and thus might not produce harmonic distortion. Although it is technically superior, many find the digital sound lifeless and pale.
Amplifiers and The Audio Signal
Published in Douglas Self, Audio Power Amplifier Design, 2013
Intermodulation distortion occurs when signals containing two or more different frequencies pass through a non-linear system. Harmonics that are integer multiples of the fundamental frequencies are generated as in harmonic distortion, but, in addition, intermodulation between any pair of frequency component creates new components at the sum and difference frequencies of that pair, and at multiples of those sum and difference frequencies. Thus, if the input signal is composed of two sine waves at f1 and f2, harmonics will be generated at 2fl, 3f1, 4f1, etc., and at 2f2, 3f2, 4f2, and so on. In addition, inharmonic components are generated at f1+f2, f1 -f2, 2fi+f2, and so on. The number of frequencies generated is already large, and increases significantly if three or four signals with non-commensurate frequencies are present in the input. Very soon the total power in the inharmonic sum-and-difference frequencies completely dominates the output and gives the unpleasant muddled and crunchy sound associated with the distortion of music. Orchestral music can easily be composed of a hundred or more signals from individual instruments, so the sensation of intermodulation distortion is often not unlike the addition of white noise.
Improved data hiding capacity through repeated embedding using modified weighted matrix for color image
Published in International Journal of Computers and Applications, 2019
Partha Chowdhuri, Pabitra Pal, Biswapati Jana
The proposed reversible data hiding scheme is verified and tested using standard original color image of size pixels collected from University of Southern California, ‘The USC-SIPI Image Database’ [17] shown in Figure 5 and secret image of different sizes has been considered as logo image which are shown in Figure 6. The Figure 7 shows the stego image after embedding maximum bits secret data within original image. Our developed data hiding algorithms: embedding and extraction are implemented in platform independent programming language such as Java 8. Here, the distortion is measured by means of two parameters namely, Mean Square Error (MSE) and Peak Signal to Noise Ratio (PSNR). The MSE is calculated as follows:
Evaluation of Bonding Quality in the Carbon Fiber--Reinforced Polymer (CFRP) Composite Laminates by Measurements of Local Vibration Nonlinearity
Published in Research in Nondestructive Evaluation, 2019
Igor Solodov, Damien Ségur, Marc Kreutzbruck
From (1), the ratio of the second harmonic to the fundamental frequency signal is ~. For all “classical” (flawless) materials , so that even for a high acoustic strain () the above ratio is . As the nonlinear wave propagates, the higher harmonic contribution leads to the waveform distortion which accumulates with propagation distance. This benefit is used to enhance the second harmonic response at the detector position. However, in reality even for a high acoustic strain of fundamental frequency the normalized cumulative second harmonic in majority of “classical” materials is substantially <1%.
Supraharmonics reduction in LED drivers via random pulse-position modulation
Published in International Journal of Electronics, 2018
Joaquin Garrido-Zafra, Antonio Moreno-Munoz, Aurora Gil-De-Castro, Manuel A. Ortiz-López, Tomás Morales
There is growing concern about the quality of electricity. One of the main reasons is that new generation of loads are more sensitive to variations in energy quality than in the past (Moreno-Muñoz, 2007). PQ is not a new term, however still nowadays there are attempts to deal with it. It is an umbrella concept considering many types of power system disturbances. It indistinctly refers to both current and voltage. While the current quality usually characterises the emission of equipment and installations, the voltage quality describes how equipment connected to a certain point in the distribution grid is affected by other equipment emissions. Customer equipment affects the voltage quality, and the latter also affects customers, therefore to find the responsible for a PQ concern is difficult. Both definitions have in common that they are related to the non-sinusoidal waveform of the voltage or current, leading to a distortion. Therefore, this waveform distortion is defined as a steady-state deviation from an ideal sine wave of power frequency principally characterised by the spectral content of the deviation.