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Abstract

A receiver for down-converting a modulated carrier into its in-phase (I) and quadrature (Q) components for further processing is proposed. This is accomplished using a sampling method in which the signal is sampled directly using a sampling circuit which is driven by a single sampling clock frequency substantially lower than the carrier frequency while allowing the I and Q components to be precisely obtained. Each of the signal samples comprises sub-samples taken successively which represent the in-phase, quadrature, negative in-phase and negative quadrature components of the signal. The negative components permit flexible application of the invention in several modes, including differential mode for the removal of common-mode noise. The invention is useful because it provides an integrated circuit means for precisely obtaining I and Q components of a very high frequency modulated carrier. This greatly eases the difficulty of implementing receiver architectures such as direct down-conversion or low-IF receivers, which permit on-chip integration of traditionally difficult-to-integrate components such as IF filters and VCO circuits while eliminating the need for image-rejection filters.

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First Claim