Hewlett-Packard Company

David E Shoup

James L Adcock

A digital mixer is supplied with two digitized input signals in complex form. The product of the complex input signals is converted to analog form and provides the desired output signal without any alias terms. The first input signal is desirably stored in a first memory as a sequence of data points corresponding to a complex exponential sinusoid. The second input signal is a baseband excitation waveform that is also stored in complex form in a memory. Operands from these two sources are provided periodically to the mixer for complex multiplication. The sequence of sinusoid operands provided from the first memory is determined by a phase counter that indexes through the memory by a .DELTA..theta. term. .DELTA..theta. is selected so that the data indexed thereby corresponds to samples of a sine wave of the desired frequency. If .DELTA..theta. indexes a signal phase intermediate two complex data in the memory, an interpolated value is provided.

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Seattle, WA, United States of America

David E Shoup