

Last Updated: 20050401, mei Monday, May 30, 14:00 — 17:00Chair: Ronald Aarts M1 The Effect of Noise Transfer Function Shape on Idle Tones in SigmaDelta Modulators—James Angus, University of Salford  Salford, UK Work is presented that shows that the behavior of idle tones in sigmadelta modulators depends on whether the noise transfer function has zeros at dc or not. Simulation results for a variety of transfer functions of the same order but a different shape are presented. In particular, no zeros at dc, equiripple zeros, and all zeros at dc. It shows that, without dither, the effects of different filter transfer function shapes on idle tones is minimal for a given order. However, when dither is applied noise transfer functions with all the zeros at dc are better. Convention Paper 6450 (Purchase now) M2 Fuzzy Impulsive Control of High Order Interpolative Lowpass SigmaDelta Modulators—Charlotte Yuk Fan Ho, Queen Mary University of London  London, UK; Bingo WingKuen Ling, King’s College London  Strand, London, UK; Joshua D. Reiss, Queen Mary University of London  London, UK In this paper high order interpolative sigma delta modulators (SDMs) in audio applications are considered. For these SDMs, limit cycle and divergent behaviors may be observed, especially when the inputs are overloaded. A novel fuzzy impulsive control strategy is proposed. The control law is to minimize the difference between the uncontrolled trajectory and the control trajectory, suppress the occurrence of limit cycles, and maintain the local stability of the SDMs. Examples of high order lowpass interpolative SDMs are given to illustrate the effectiveness of the proposed control strategy. Convention Paper 6451 (Purchase now) M3 Integrated Stereo SigmaDelta Class D Amplifier—Eric Gaalaas, Analog Devices Inc.  Wilmington, MA, USA; Bill Yang Liu, Naoaki Nishimura, Japan Analog Devices Inc.  Tokyo, Japan; Robert Adams, Karl Sweetland, Rajeev Morajkar, Analog Devices Inc.  Wilmington, MA, USA A 2 x 40W class D amplifier chip is realized in 0.6um BCDMOS technology, integrating two sigmadelta modulators and two Hbridge power stages. Analog feedback from Hbridge outputs helps achieve 67dB PSRR, 0.001 percent THD and 104dB dynamic range. The modulator clock rate is 6 MHz, but dynamically adjusted quantizer hysteresis reduces output data rate to 450kHz, helping achieve 88 percent power efficiency. At AM radio frequencies, the modulator output spectrum contains a single peak, but is otherwise tonefree, unlike conventional PWM modulators, which contain energetic tones at harmonics of the PWM clock frequency. Convention Paper 6452 (Purchase now) M4 Simple SelfOscillating Class D Amplifier with Full Output Filter Control—Bruno Putzeys, Philips Applied Technologies  Leuven, Belgium A stable and loadinvariant selfoscillation condition is developed for a class D amplifier employing only one single voltage feedback loop taking off after the output filter. The resulting control method is shown to effectively remove the output filter from the closed loop response. Practical discrete implementations of a comparator and gatedrive circuit are presented. A highperformance class D amplifier employing only 16 discrete transistors is constructed. Higherorder extensions of the control circuit are demonstrated which produce extremely low levels of distortion. Convention Paper 6453 (Purchase now) M5 Low Order IIR Parametric Loudspeaker Equalization: A Psychoacoustic Approach—Germán Ramos, José López, Technical University of Valencia  Valencia, Spain This paper presents an efficient loudspeaker equalization algorithm combining a novel filter optimization method with a psychoacoustic model. The equalizer topology is based on a chain of second order sections where each one is a conventional parametric IIR audio filter. A psychoacoustic model based on the detection of peaks and holes in the frequency response has been employed to determine which ones need to be equalized. Using this psychoacoustic model the order of the filter could be reduced without noticeable subjective effect. The first computed filter sections are the ones that provide more correction on the response, allowing scalable solutions when hardware limitations or different degree of correction are needed. The method has been validated in the laboratory with subjective testing. Convention Paper 6454 (Purchase now) M6 Demystifying Analog Circuits in Professional Audio Applications—Fred Floru, THAT Corporation  Milford, MA, USA The past few years have seen the continuation of the shift from analog processing to digital domain processing in professional audio products. There are still several analog sections of the box that remained purely analog. Over time the performance of mixed signal components has improved significantly to the point that, once again, the weakest link in the chain could be the analog interface. The purpose of this paper is to look at a few popular analog circuits that have a direct impact on the performance of professional audio applications. The circuits are explained with mathematical demonstrations. The impact of real life implementations on the performance specifications is explored for each circuit. Convention Paper 6455 (Purchase now) 

©2005 Audio Engineering Society, Inc. 