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Abstract

An improved demodulation mechanism (and corresponding methods of operation) that demodulates a differentially-encoded GMSK signal in a manner that is accurate and efficient and with reduced complexity. The demodulation mechanism includes at least one buffer for storing sequences of in-phase and quadrature-phase baseband samples that carry the GMSK signal therein. A channel estimation block operates on the sequences of in-phase and quadrature-phase baseband samples to derive estimates for timing errors (preferably sample timing errors as well as carrier frequency and phase errors) in the samples. The channel estimation block uses the timing error estimates to transform the sequences of in-phase and quadrature-phase baseband samples to compensate for such timing errors. A de-rotation block operates on the transformed sequences to perform a de-rotation of .pi./2 per symbol in the GMSK signal. The result of the de-rotation is a sequence of complex values each having a real part and an imaginary part. An estimation block uses the result of the de-rotation to derive an estimate for the bits in the GMSK signal. Such estimation is generated by adding a first contribution to a second contribution, the first contribution derived from an imaginary part of a first complex value, and the second contribution derived from a real part of a second complex number. The first and second complex values are spaced apart by one symbol. Such mechanisms and methodologies are readily adaptable for the demodulation of other pre-coded partial response signals.

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