Adaptive filter theory (2nd ed.)
Adaptive filter theory (2nd ed.)
Fully sigma-delta modulation encoded FIR filters
IEEE Transactions on Signal Processing
Multistage sigma-delta modulation
IEEE Transactions on Information Theory
Performance analysis of an autocorrelation based frequency tracker for LFM and QFM signals
ICICS'09 Proceedings of the 7th international conference on Information, communications and signal processing
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Over the last few decades, the use of sigma-delta (@S-@D) modulators, has moved into various signal processing and communication application areas. Usually, @S-@D modulators produce single-bit outputs and thus are well suited for VLSI circuits that could be implemented using a small number of multipliers. For improved signal-to-noise (quantization) performances, higher-order modulator schemes with multi-loop and multi-stage architecture are utilized in most of the @S-@D applications. The quantization noise behavior of these higher-order modulators is well understood. Based on the quantization noise characteristics, various demodulator filter architectures, such as optimal FIR, Sinc filter and non-linear filters are reported in the literature. In this paper, we propose efficient recursive filters that could be used as the demodulator filter. In particular, a Laguerre filter architecture and a Kalman filter architecture are described. In usual @S-@D architecture, the demodulator filter operates at a lower (down-sampled) rate. However, in certain applications a full-rate (FR) demodulator is needed to achieve a high signal-to-noise ratio. It will be demonstrated that the proposed recursive filters are ideally suitable for FR demodulator applications.