Linearization of the First-order TDTL Using a Pre-distortion Scheme
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In this paper the architecture of a first-order time delay digital tanlock loop (TDTL) with linearized phase detector (PD) using a feedforward pre-distortion technique is proposed. The technique, which has been traditionally used with power amplifiers, involves pre-distorting the input signal to the TDTL so as to compensate for the nonlinearity of the TDTL caused by its fixed time delay unit. The performance of the proposed system was evaluated in noisy and noise-free environments and compared with the original TDTL system using sudden changes in input signal frequency using MATLAB/Simulink. In both cases, results indicate that the performance of the proposed TDTL with pre-distortion outperforms that of the original TDTL system. (5 pages)Keywords:
Distortion (music)
Feed forward
Linearization
Phase distortion
SIGNAL (programming language)
The distortion performance is one of the most important factors in loudspeakers.In this paper,a general introduction about the distortion is given and some useful methods to reduce the distortion are introduced.
Distortion (music)
Amplitude distortion
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The results of experiments in which subjects rated the perceived quality of speech and music that had been subjected to various forms of both linear and nonlinear distortion are reported. Experiment 1 made use of artificial distortions (such as ripples in frequency response combined with peak clipping). Experiment 2 included both artificial distortions and real distortions introduced by transducers. The results were compared with the predictions of a new model based on a weighted sum of predictions for linear distortion alone and for nonlinear distortion alone. There was a very good correspondence between the obtained and predicted ratings. Correlations were greater than 0.85 for speech stimuli and 0.90 for music stimuli. It is concluded that the new model can predict accurately the perceived quality of speech and music subjected to combined linear and nonlinear distortion.
Distortion (music)
Clipping (morphology)
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Nonlinear distortion produced in a given circuit can be reduced by pre- or postdistorting the signal applied to or from the circuit. Such complementary distortion cannot reduce the original distortion to zero in practice because of distortion of distortion, but it can result in greatly reduced output distortion over a limited amplitude range. General results for the design of pre- or postdistortion circuits are given, and the mathematical results are illustrated by comparing the total harmonic distortions obtained with pre- and postdistortion corrections of increasing complexity applied to a simple nonlinear circuit.
Amplitude distortion
Distortion (music)
THD analyzer
Phase distortion
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Multisine signals are shown to be useful for estimating distortion of communication signals. In particular, a generalized approach for the evaluation of effective in-band distortion in a nonlinear amplifier using multisine excitation is presented. The output of the nonlinearity is represented as the sum of uncorrelated components by the transformation of a behavioral model. Simulated and measured results are presented for code-division multiple-access signals
Distortion (music)
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The application of the feedforward amplifier linearization technique to the removal of both harmonic and intermodulation distortions is well understood and has been discussed in the literature. An additional benefit of the feedforward technique, which has received relatively little attention, is that of so-called linear distortion removal. Linear distortion is a term used to describe the nonideal gain and phase response (e.g., frequency response ripple) present in all practical amplifiers, and it is possible to significantly improve these parameters, in a practical application, using the feedforward technique. This paper discusses the improvements in this area, which may be achieved by utilizing the feedforward technique, demonstrates mathematically how they arise, and presents both simulation and practical results to demonstrate the effect for various types of gain and phase response nonlinearity.
Feed forward
Distortion (music)
Phase distortion
Linearization
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Multi-sine signals are useful for approximating communication signals when analyzing distortion generated by nonlinear circuits. In this work the correlated and uncorrelated components of distortion are derived using multi-sine signals with random phases. Distortion analysis of two-tone and four-tone random phase signals demonstrates the in-band distortion characteristics of multi-tone signals. Simulated in-band distortion for a sixteen-tone random phase signal is verified against measured in-band distortion characteristics of a CDMA forward link signal.
Distortion (music)
Phase distortion
Tone (literature)
Sine
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Amplitude distortion
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Signal degradation may be due to noise or to distortion. Linear distortion may be caused by filters, dispersion or multipath effects. These effects are well understood and can often be minimized by linear equalizers. To make further improvements it is necessary to consider the correction of nonlinear distortion. Distortion correction can be performed by using pre or post distortion to compensate (Bellafemina and Benedetto 1985, Benedetto et al 1979, Falconer 1977, Saleh 1982, Saleh and Salz 1982, Schetzen 1980). It is desirable to know whether the structure chosen for a distortion compensator is capable of correcting a particular class of distortion. To this end it is necessary to have a valid model of the distortion to be corrected. The model must be able to simulate the output quite accurately. This apphcation is more demanding than some where a reasonable estimate of the magnitude of the distortion may be all that is required.
Distortion (music)
Amplitude distortion
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Though many sorts of measuring methods using digital signal processing techniques have been developed, most of them are only for measurements in a linear range. There is still no suitable digital measuring method for nonlinear distortion of acoustical devices. An accurate and convenient nonlinear distortion measurement system should be developed for evaluation of electroacoustical transducers. A new digital distortion measuring method for acoustical devices is presented briefly. This method applies a Pink-TSP signal (time stretched pulse, i.e., quickly swept sinusoidal signal), whose frequency band is partially eliminated, to an acoustical system to be measured. The detected component produced in the rejected band is picked up by a bandpass filter and measured as a distortion. First, two kinds of small size electrodynamic loudspeaker units were measured by using the dynamic distortion measurement system mentioned above. Next, distortion characteristics of mechanical single resonant system models whose component shows amplitude-dependent nature were examined. This paper describes the relationship between distortion characteristics and quality factor, input signal level, and nonlinear parameters. The difference in distortion of two kinds of loudspeakers is detected by this measurement. It is seen that the resonant phenomenon has an influence on distortion characteristics.
Distortion (music)
Amplitude distortion
Phase distortion
SIGNAL (programming language)
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On peculiarities of evaluating the quality of speech and music signals subjected to phase distortion
In this paper, subjective and objective estimators of the quality of speech and music signals subjected to phase distortion are compared, and mapping between objective and subjective quality estimates is realized. It was found that the phase distortion of speech signals is perceived stronger than ones for musical signals. Two types of phase distortion are considered: 1) low-frequency signal components lag behind high-frequency components in the 30-90 ms; 2) high-frequency signal components lag behind low frequency components in the same time. It is shown that the human auditory system is more sensitive to the latter type of phase distortion referenced previously. As far as objective quality measures, it was found they are useless for distinguishing these types of phase distortion. Maximum differences between group delay times for low (125 Hz) and high (8 kHz) frequencies, for which distortion is acceptable, were established. These threshold values are 40 ms for speech and 80 ms for music.
Distortion (music)
Phase distortion
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Amplitude distortion
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The present objective measuring methods for nonlinear distortion and the reasons why they cannot suffi-ciently reflect the characteristics of electro-acoustical system′s nonlinearity are analysed. The latest scientific researches of nonlinear distortion about subjective and objective sound quality evaluation around the world are introduced. It is pointed out that multitone will be a good choice to evaluate nonlinear distortion.
Distortion (music)
Sound Quality
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