Echo cancellation in multi-frequency differentially encoded digital communications
AssigneeMercury Digital Communications, Inc.
InventorPaul H. Moose
Life of this patent
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Abstract
A differentially encoded digital signal waveform is generated as a discrete time representation of a desired analog signal utilizing multi-frequency modulation techniques. The computational capability of present day, industry-standard microcomputers equipped with a floating point array processor or digital signal processor chip is utilized to perform digital frequency encoding and compute both discrete Fourier transforms and inverse discrete Fourier transforms to provide a transmitter and receiver system utilizing suitably programmed microcomputers coupled by a communications channel.
Claims5
A data-driven, two-stage echo cancellation circuit for use in a full duplex communications system which encodes and decodes transmission signal data in the time domain and the frequency domain, said echo cancellation circuit comprising:
- a first stage for generating a first estimate of an echo signal utilizing transmission signal data in the time domain, said first estimate of an echo signal subtracted from a received analog signal;
- and
- a second stage for generating a second estimate of residual echo signal utilizing transmission signal data in the frequency domain, said second estimate subtracted from said received signal after said received signal has been converted to a digital signal in the frequency domain.
Dependencies are inferred from the claim text.