Itt Manufacturing Enterprises, Inc.

Itt Corporation

Rockland Systems Corporation

Wavetek Rockland Inc.

Wavetek Rockland Scientific, Inc.

John Bertrand

Joseph H Flink

Marvin A Epstein

Joseph M Fine

Gary V Blois

Richard Alan Kwolek

Charles Francis Haight

Bryan S Majkrzak

John Batzer

Daniel M Caprioni

Rodger H Hosking

Daniel Shamah

Matthew J Noah

Mitchell Friedman

The communication system has a first modem having a digital port for communicating a first data block in a first format between a first transmission channel and the digital port and a second modem having a digital port for communicating a second data block in a second format between a second transmission channel and the digital port. The first data block has a header block and a message block. The controller/processing device comprises a first interface means, a second interface means and a conversion means. The first interface means is adapted for receiving the first data block in the first format from the first digital port. The conversion means is coupled to the first interface means. The conversion means converts the first data block in the first format to the second data block in the second format. The second interface means is coupled to the conversion means. The second interface means is adapted for sending the second data block in the second format to the second digital port. The second interface means starts sending the second data block after said the interface means has received the header block and before it has received the message block.

Modulation and signaling converter

There is disclosed an improved multi-mode, spread spectrum digital radio comprising: a radio frequency (RF) subsystem for converting spread spectrum digital signals comprising voice and data communications between baseband and RF signal frequencies in response to control signals; a digital signal processor based baseband subsystem having isolation interface means bidirectionally coupled to the RF subsystem for minimizing RF and baseband signal interference; the baseband subsystem operable to control the mode of operation, to provide interface control signals to the RF subsystem based on the mode, to format the transmitted and received digital signals, and to provide external controls and status to a user to enable selectable mode switching.

Radio architecture for an advanced digital radio in a digital

There is disclosed in a frequency hopping digital communications system having a transmitter for transmitting a data signal via a noisy transmission path, and a receiver responsive to the transmitted signal for receiving the same, a method for removing bias in the data signal at the receiver comprising the steps of: forming a sample amplitude histogram from the received data signal samples for a given hop frequency; correlating the amplitude histogram against a stored reference amplitude histogram to obtain a correlated output signal having a peak correlation position; determining the position difference between the peak correlation position and the correlation center position to provide an offset signal corresponding to the difference and indicative of an estimated bias offset value; and applying the estimated bias offset value to the received signal samples in response to the offset signal to obtain an output signal indicative of an unbiased received data signal.

Method for removing bias in a frequency hopping digital communication

A secure narrowband digital conferencing system is capable of handing multiple speakers simultaneously and in a full duplex mode. The system uses a multipulse or a code-excited linear predictive (CELP) speech processing algorithm for colding the speech signals of the respective participants. A conference director receives the multipluse or CELP encrypted voice signal streams over normal telephone links, decrypts them, then synthesizes a composite speech signal and uses an analysis-by-synthesis algorithm to compress them, and then encrypts the composite signal and transmits it back to all the participants.

Secure digital conferencing system

An analog to digital converter for a speech signal is implemented in modules to allow for changes in bit rate and changes in bit stream length according to requirements of the digital transmission system. A pre-emphasis circuit provides an array of pre-emphasized speech samples which are stored in memory. A linear predictive coder provides an array of reflection coefficients and an array of filter coefficients. A pulse processor receives the speech samples and filter coefficients and generates speech amplitude and location signals. These signals are multiplied to generate quantized speech samples. The quantized speech samples and reflection coefficients are provided to a buffer which provides an output signal of a proper bit stream length and bit rate for the digital transmission system.

Multi-rate digital voice coder apparatus

A decimator of the type having a decimation factor of K, is implemented by a finite impulse response (FIR) filter network of length N. The filter network includes N/K accumulators each of which arithmetically combines samples of an input signal as multiplied by a corresponding set of K network branches, and provides a corresponding output sample. The N/K output samples from the accumulators are provided sequentially at the filter output prior to arrival of the next set of N input signal samples at the filter input.

Decimator employing finite impulse response digital filters

A spectrum analyzer for FFT analyzing and displaying the frequency spectrum of a digital signal over a given frequency band (background), as well as over a more limited frequency band (foreground). The spectrum of the signal over each frequency band is calculated and displayed so as to appear on a screen as a simultaneous display. The position of the limited frequency band as well as the width thereof, may be varied.

Spectrum analyzer with frequency band selection

A spectrum analyzer using digital filters for providing third octave spectrum analysis comprises means for breaking up input information into a plurality of digital data blocks, each block being of a given time duration and being within respective frequency ranges, means for weighting the information contained in the data blocks and means for digitally filtering the weighted digital data blocks with digital filtering devices having at least one center frequency falling within the frequency range represented by each of the data blocks, each of the data blocks comprising N samples satisfying the following equation-

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Upper Nyack, NY, United States of America

John Bertrand