Bandlimits and coherent modulation filtering of non-stationary signals

Pascal Clark; Les Atlas

doi:10.1117/12.795685

3 September 2008 Bandlimits and coherent modulation filtering of non-stationary signals

Pascal Clark, Les Atlas

Proceedings Volume 7074, Advanced Signal Processing Algorithms, Architectures, and Implementations XVIII; 70740R (2008) https://doi.org/10.1117/12.795685
Event: Optical Engineering + Applications, 2008, San Diego, California, United States

Abstract

Modulation filtering is a technique for filtering slowly-varying envelopes of frequency subbands of a non-stationary signal, ideally without affecting the signal's phase and fine-structure. Coherent modulation filtering is a potentially more effective subtype of such techniques where subband envelopes are determined through demodulation of the subband signal with a coherently detected subband carrier. In this paper we propose a coherent modulation filtering technique based on detecting the instantaneous frequency of a subband from its time-frequency representation. We show that coherent modulation filtering imposes a new bandlimiting constraint on the modulation product plus the ability to recover arbitrarily chosen envelopes and carriers from their modulation product. We show that a carrier estimate based on the time-varying spectral center-of-gravity satisfies the bandlimiting condition as well as Loughlin's previously derived bandlimiting constraint on the instantaneous frequency of carrier. These bandwidth constraints lead to effective and distortion-free modulation filters, offering new approaches for potential signal modification. The spectral center-of-gravity does not satisfy the condition on arbitrary recovery, however, which somewhat limits the flexibility of coherent modulation filtering. Demonstrations are provided with speech signals.

Citation Download Citation

Pascal Clark and Les Atlas "Bandlimits and coherent modulation filtering of non-stationary signals", Proc. SPIE 7074, Advanced Signal Processing Algorithms, Architectures, and Implementations XVIII, 70740R (3 September 2008); https://doi.org/10.1117/12.795685

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KEYWORDS

Modulation

Modulators

Electronic filtering

Demodulation

Filtering (signal processing)

Convolution

Frequency modulation

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