Accession Number:

ADD007477

Title:

A Half Duplex Integral Vocoder Modem System.

Descriptive Note:

Patent Application,

Corporate Author:

DEPARTMENT OF THE ARMY WASHINGTON DC

Report Date:

1980-01-23

Pagination or Media Count:

69.0

Abstract:

Disclosed is a system whereby in a transmit mode analog speech is sampled and converted digitally to 12 bits of accuracy and then fed into a fast Fourier transform FFT processor which analyses the speech into spectral and pitch parameters. These parameters are then quantized into a data stream which acts as an input to a differential phase shift keying modulator. The modulator constructs a multi-tone modem output signal from a 25 tone stack which is converted to an analog signal which is fed into a communications channel. In the receive mode a modem input signal from the communications channel is fed through the same analog to digital converter which was used for input speech. A data stream is now provided which is coupled back into the same digital FFT processor which now operates to provide pitch spectral coefficients which are then separated and used by a synthesizer to reconstruct a speech waveform. The speech waveform is applied to a digital analog converter which is the same converter used to produce the line signal when the processor operates in the transmit mode. The FFT processor implements a single FFT algorithm which is used for both vocoder and modem processing in both the transmit and receive modes. Author

Subject Categories:

  • Electrical and Electronic Equipment
  • Voice Communications

Distribution Statement:

APPROVED FOR PUBLIC RELEASE