Accession Number : ADD007477

Title :   A Half Duplex Integral Vocoder Modem System.

Descriptive Note : Patent Application,

Corporate Author : DEPARTMENT OF THE ARMY WASHINGTON DC

Personal Author(s) : Manley,Harold J ; deLillis,Joseph , Jr

Report Date : 23 Jan 1980

Pagination or Media Count : 69

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)

Descriptors :   *Patent applications, *Modems, *Vocoders, *Data links, *Digital to analog converters, *Speech scrambling, *Multichannel communications, Duplexers, Speech transmission, Inventions, Fast fourier transforms, Phase shift keyers, Analog signals, Coefficients, Spectra, Data transmission systems, Modulators

Subject Categories : Electrical and Electronic Equipment
      Voice Communications

Distribution Statement : APPROVED FOR PUBLIC RELEASE