In this paper a novel digital direct-driven speaker for reducing electromagnetic interference incorporating a spread spectrum clock generator is proposed. The driving signal of a loudspeaker, which has a large spectrum at specific frequency, interferes with nearby equipment because the driving signal emits electromagnetic waves. The proposed method changes two clock frequencies according to the clock selection signal generated by a pseudo-noise circuit. The noise performance deterioration caused by the clock frequency switching can be reduced by the proposed modified delta-sigma modulator, which changes coefficients of the DSM according to the width of the clock period. The proposed method can reduce out-of-band noise by 10 dB compared to the conventional method.

Authors: Yashiro, Masayuki; Iwaide, Mitsuhiro; Yasuda, Akira; Yoshino, Michitaka; Yokota, Kazuyki; Moriyasu, Yugo; Sakuda, Kenji; Nakashima, Fumiaki
Affiliation: Hosei University, Koganei, Tokyo, Japan
AES Convention: 133 (October 2012) Paper Number: 8726
Publication Date: October 25, 2012
Subject: Amplifiers, Transducers, and Equipment

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