Inventors:
Barry Herold - Barrington IL
Scott Humphreys - Greensboro NC
Assignee:
Motorola, Inc. - Schaumburg IL
International Classification:
H03D 302
US Classification:
329315, 329336, 329327, 329318, 329340, 455214, 455337, 455334
Abstract:
A circuit ( ) for generating a ratio signal indicating a ratio of frequency error to signal magnitude of an input signal includes an FM ratio detector ( ) and a sigma-delta analog-to-digital converter ( ). The FM ratio detector ( ) is responsive to the input signal and generates a magnitude signal and an error signal. The magnitude signal is representative of a magnitude of the input signal and the error signal is representative of a frequency error of the input signal relative to a preselected frequency. The sigma-delta analog-to-digital converter ( ), which is responsive to the filtered magnitude signal and the filtered error signal, generates a stream of logic â1sâ and logic â0sâ that are indicative of a ratio of the filtered error signal to the filtered magnitude signal. Thus, the sigma-delta analog-to-digital converter generates the ratio signal ( ).