Sigma-delta FM demodulator

Details Sigma-delta FM demodulator Sigma-delta FM demodulator

1994-07-06

1995-09-05

Grimm, Siegfried H.

Demodulators

Frequency modulation demodulator

Input signal combined with local oscillator or carrier...

329336, 329341, 329343, 455214, 455337, 331 49, 331 57, H03D 318

Patent

active

054482020

ABSTRACT:
Digital frequency demodulation is accomplished by monitoring similar transitions in an FM radio signal to determine frequency. Time intervals between similar transitions in the FM signal are established by selecting anticipated transition times and accumulating error values relative to actual transition times. Accumulated error values provide a basis for further selecting anticipated transition times in such manner that a reported sequence of anticipated transition times provides a basis for inferring signal frequency. In one illustrated embodiment, the chosen transition times are positive transitions in the FM signal and the anticipated times of transition are taken from a set of two time periods, an early transition and a late transition relative to a valid transition window. In one embodiment of the invention, accumulated error is stored in an integrator device while in another embodiment accumulated error is stored in the phase of a bi-frequency oscillator. By reporting the selected anticipation times by associated values in a digital bit stream, frequency may be inferred by computing a ratio of given digital values in the bit stream relative to the total number of samples in the bit stream.

REFERENCES:
patent: 4368434 (1983-01-01), Miller et al.
patent: 4707666 (1987-11-01), Pfeifer et al.
patent: 5077538 (1991-12-01), Gehrt et al.
Two articles entitled "A Use of Limit Cycle Oscillations to Obtain Robust Analog-to-Digital Converts" and Table-Based Simulation of Delta-Sigma Modulators. Both articles are located in a manual entitled Oversampling Delta-Sigma Data Converters published by The Institute of Electrical and Electronics Engineers, Inc. in 1992.

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