scholarly journals Quadrature Mapping, Saleh’s Representation, and Memory Models

2016 ◽  
Vol 62 (4) ◽  
pp. 389-394
Author(s):  
Andrzej Borys
Keyword(s):  
Taylor Series ◽  
Power Amplifiers ◽  
Transfer Functions ◽  
Volterra Series ◽  
Memory Models ◽  
Memory Effects ◽  
Impulse Responses ◽  
Real Numbers ◽  
Nonlinear Transfer ◽  
Complex Valued

Abstract In the literature, Saleh’s description of the AM/AM and AM/PM conversions occurring in communication power amplifiers (PAs) is classified as a representation without memory. We show here that this view must be revised. The need for such revision follows from the fact that the Saleh’s representation is based on the quadrature mapping which, as we show here, can be expanded in a Volterra series different from an usual Taylor series. That is the resulting Volterra series possesses the nonlinear impulse responses in form of sums of ordinary functions and multidimensional Dirac impulses multiplied by coefficients being real numbers. This property can be also expressed, equivalently, by saying that the nonlinear transfer functions associated with the aforementioned Volterra series are complex-valued functions. In conclusion, the above means that the Saleh’s representation incorporates memory effects.

scholarly journals On Modelling AM/AM and AM/PM Conversions via Volterra Series

2016 ◽  
Vol 62 (3) ◽  
pp. 267-272
Author(s):  
Andrzej Borys ◽  
Wiesław Sieńko
Keyword(s):  
Power Amplifiers ◽  
Transfer Functions ◽  
Volterra Series ◽  
Polynomial Coefficient ◽  
Necessary Condition ◽  
Sufficient Condition ◽  
Necessary And Sufficient Condition ◽  
Nonlinear Transfer ◽  
Necessary And Sufficient ◽  
Nonzero Polynomial

Abstract In this paper, we present the expressions, not published up to now, that describe the AM/AM and AM/PM conversions of communication power amplifiers (PAs) via the Volterra series based nonlinear transfer functions. Furthermore, we present a necessary and sufficient condition of occurrence of the nonzero values of AM/PM conversion in PAs. Moreover, it has been shown that Saleh’s approach and related ones, which foresee nonzero level of AM/PM conversion, are not models without memory. It has been also shown that using a polynomial description of a PA does not lead to a nonzero AM/PM conversion. Moreover, a necessary condition of occurrence of an AM/AM conversion in this kind of modelling is existence of at least one nonzero polynomial coefficient associated with its odd terms of degree greater than one.

BEHAVIORAL MODELING OF RF POWER AMPLIFIERS USING MODIFIED VOLTERRA SERIES

2009 ◽  
Vol 18 (02) ◽  
pp. 351-359 ◽  
Author(s):  
ZHE JIN ◽  
YANWEI ZHOU ◽  
ZHIHUAN SONG
Keyword(s):  
Data Storage ◽  
Power Amplifiers ◽  
Communication Systems ◽  
Volterra Series ◽  
Memory Effects ◽  
Behavioral Modeling ◽  
Recursive Least Squares ◽  
Volterra Model ◽  
Rf Power Amplifiers ◽  
Identification Algorithm

There has been intensive research in memoryless nonlinear behavioral modeling of power amplifiers (PAs). But in broadband communication systems, memory effects of PAs can no longer be ignored and traditional memoryless model cannot accurately characterize the input-output relationship of PAs. In order to treat memory effects and reduce the complexity of general Volterra model, a new behavioral PA model based on modified Volterra series is proposed. Since the characteristics of power amplifiers change during transmission time, a recursive least squares algorithm with size-fixed observation matrices is developed to update the parameters of the PA model. This identification algorithm, which uses only the latest sample data to identify the parameters, can decrease computational complexity and data storage space needed for identification. Simulations are carried out to validate the performances of the proposed PA model and identification algorithm.

scholarly journals Dynamic Binaural Rendering: The Advantage of Virtual Artificial Heads over Conventional Ones for Localization with Speech Signals

2021 ◽  
Vol 11 (15) ◽  
pp. 6793
Author(s):  
Mina Fallahi ◽  
Martin Hansen ◽  
Simon Doclo ◽  
Steven van de Par ◽  
Dirk Püschel ◽  
...  
Keyword(s):  
Transfer Functions ◽  
Microphone Array ◽  
Head Tracking ◽  
Impulse Responses ◽  
Sound Fields ◽  
Listening Tests ◽  
Spatial Sound ◽  
Localization Performance ◽  
Complex Valued ◽  
Positive Effect

As an alternative to conventional artificial heads, a virtual artificial head (VAH), i.e., a microphone array-based filter-and-sum beamformer, can be used to create binaural renderings of spatial sound fields. In contrast to conventional artificial heads, a VAH enables one to individualize the binaural renderings and to incorporate head tracking. This can be achieved by applying complex-valued spectral weights—calculated using individual head related transfer functions (HRTFs) for each listener and for different head orientations—to the microphone signals of the VAH. In this study, these spectral weights were applied to measured room impulse responses in an anechoic room to synthesize individual binaural room impulse responses (BRIRs). In the first part of the paper, the results of localizing virtual sources generated with individually synthesized BRIRs and measured BRIRs using a conventional artificial head, for different head orientations, were assessed in comparison with real sources. Convincing localization performances could be achieved for virtual sources generated with both individually synthesized and measured non-individual BRIRs with respect to azimuth and externalization. In the second part of the paper, the results of localizing virtual sources were compared in two listening tests, with and without head tracking. The positive effect of head tracking on the virtual source localization performance confirmed a major advantage of the VAH over conventional artificial heads.

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