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Basics of Electrical Communication Systems
Published in P. S. Neelakanta, ATM Telecommunications, 2018
The nonlinear transformation (namely, vout = g(vin)) across the transmission path renders the output waveform envelope visibly changed as illustrated. (Thus, the amplitude distortion and envelope distortion are synonymous.) A Fourier analysis would indicate the presence of harmonic frequency components in this distorted output signal, which are not present in the input signal. Thus, the amplitude distortion can be identified by the presence of harmonic components not originally present in the signal. As a result, the amplitude distortion is also known as nonlinear or harmonic distortion. The causative mechanism of amplitude distortion is the presence of nonlinear device or components in the transmission system across which the signal may pass through.
Basic Signal Processing Operations
Published in Nassir H. Sabah, Electric Circuits and Signals, 2017
Distortion also occurs in an LTI circuit because the presence of storage elements makes the response frequency dependent, as explained in Chapter 10. The relative magnitudes and phases of frequency components in the response differ from those in the input, which alters the shape of the waveform and distorts the signal, although no new frequency components are introduced. Consider, for example, an input sinω 0t+0.3sin3ω 0t (Figure 17.1.1a). If the third harmonic is attenuated with respect to the fundamental so that output becomes sinω 0t+0.2sin3ω 0t (Figure 17.1.1b), the waveform changes. This distortion, due to the variation of the relative amplitudes of the components of different frequencies, is amplitude distortion.
IMP Systems
Published in Brecht De Man, Ryan Stables, Joshua D. Reiss, IntelligentMusic Production, 2019
Brecht De Man, Ryan Stables, Joshua D. Reiss
Like other nonlinear effects, amplitude distortion introduces harmonics at frequencies that potentially were not present in the original signal. This means it may be necessary to upsample before applying distortion in order to avoid audible aliasing artifacts [317]. The extra frequency components introduced by aliasing are almost always inharmonic, and therefore deteriorate the perceived sound quality [113]. For this reason, an interpolation filter is applied to the signal before applying any kind of processing that introduces new harmonics. Afterwards, if an audio output at the original sampling frequency is desired, a decimation filter should be applied. Naturally, a higher upsampling ratio is more computationally expensive.
A Multi-Box Behavioural Nonlinear Mixer Model
Published in International Journal of Electronics, 2023
Ali Ozgun, Tayfun Nesimoglu, Simsek Demir
Mixer linearisation techniques are proposed to reduce the effects of nonlinearity, such as feed-forward (Li & Saavedra, 2018), frequency retranslation (Nesimoglu et al., 2001,2012), predistortion (Kim et al., 2002) and IM3 cancellation (Liang et al., 2008; Lv et al., 2019). Among these techniques, Nesimoglu et al. (2001) and Liang et al. (2008) did not incorporate a mixer modelling. In Li and Saavedra (2018), Kim et al. (2002) and Lv et al. (2019), mixer models are used for amplitude nonlinearity alone without phase nonlinearity. For accurate system-level analysis and linearisation, a reliable mixer model that simulates both amplitude and phase responses and memory effect is needed. Most linearisation techniques and nonlinear mixer models in the literature focus only on AM/AM response for modelling nonlinearity. In their study, Callet et al. (2010) use a large-signal FET structure to model the I/V characteristics of the mixer for amplitude distortion. Similarly, Xie et al. (2021) use IMD lookup tables to simulate the amplitude response of the IMD components.
MRI and CT image indexing and retrieval using steerable pyramid transform and local neighborhood difference pattern
Published in International Journal of Computers and Applications, 2022
Ranjit Biswas, Sudipta Roy, Abhijit Biswas
The output of the system in frequency domain is given in Equation (2). This equation also prevents amplitude distortion In terms of frequency, two successive low pass filters share a relation which is given in Equation (3): For SPT, a trade off must be maintained as the number of pyramid levels and orientations increases, the image acquires a robust representation, but the time required for computation increases. In this experiment, a 3 scale and 4 orientation SPT is applied to decompose two different types (CT and MRI) of medical image into 12 sub-bands along with lowest frequency sub-band and highest frequency residual sub-band. Figures 3 and 4 represent the SPT system considered for this experiment and Output of the same SPT respectively.
Design and Development of FM and PM Receivers Using Autocorrelation Technique
Published in IETE Journal of Research, 2022
Tosicul Wara, Karri V. R. Dinesh Kumar Reddy, Usha Bhandiwad
It is clear that the operating point of such a nonlinear detector depends on the fixed component or quiescent value, , of the input phase difference, , between the signals at the RF and LO ports of the mixer. Hence, the demodulated signal amplitude, (which also depends on the detector gain, ), will also depend on the carrier frequency, . In other words, we can say that the detector gain, , being a nonlinear function of the baseband voltage amplitude, , at the receiver output will also be the nonlinear function of carrier frequency and group delay . When the mixer/phase detector operates in the nonlinear region of its input/output characteristic, it will give rise to amplitude distortion or harmonic distortion [12–14], and consequently, the demodulated signal (i.e. the recovered baseband signal) at the FM/PM receiver output will be distorted in amplitude.