Abstract: A system for creating multiple subchannels in a single two-way radio channel and a power control system for a mobile radio transmitter are described. Each subchannel in the system is capable of carrying voice or data. Each subchannel is split into an upper and a lower band with the upper band placed in a particular frequency range above the center of the channel and the lower band is placed in a corresponding frequency range below the center of the channel. Either one or two pilot tones placed at or adjacent to the center of the channel are used to provide a reference for all of the subchannels to allow for correction of distortions when the signal is received. The system includes base station with a transmitter and receiver and a plurality of mobile units each with a transmitter and a receiver. The base station transmits a signal which is the sum of all the subchannels. The mobile unit receives the signal, separates and processes the particular subchannel for that mobile unit.

Abstract: A signal transmitting apparatus using orthogonal frequency division multiplexing includes an inverse fast Fourier transform circuit for converting a digital information signal into a first multi-value QAM modulation signal. A guard interval setting circuit is operative for periodically generating a guard interval signal equal to a time segment of the first multi-value QAM modulation signal, and inserting the guard interval signal into the first multi-value QAM modulation signal to convert the first multi-value QAM modulation signal into a second multi-value QAM modulation signal. A clock signal generating circuit is operative for generating a first clock signal which drives the inverse fast Fourier transform circuit, and generating a second clock signal which drive the guard interval setting circuit. The inverse fast Fourier transform circuit is operative for generating a pilot signal which corresponds to a given-order carrier, and adding the pilot signal to the first multi-value QAM modulation signal.

Abstract: A bidirectional amplifier that compensates for signal attenuation in a transmission medium uses a first diplex filter for directing a first signal including a pilot signal and propagating in a first direction along a first section of the transmission medium onto a first path of the amplifier. A second diplex filter directs a second signal in a different frequency band than the first signal that is propagating in a second direction opposite to the first signal along a second section of the transmission medium onto a second path of the amplifier. The first and second paths interconnect separate sections of the first and second diplex filters. A compensating device is disposed in the first and second paths wherein a pilot detection circuit detects the pilot signal in the first signal and generates therefrom separate control signals to first and second Bode Slope Equalizers in the first and second paths, respectively.

Abstract: A base station, a subscriber equipment, and a method for synchronizing the subscriber equipment with the transmission of the base station in a digital cellular radio network utilizing the CDMA multiple access method. In each cell of the network, at least one base station communicates with the subscriber equipment within its area, in which network the base station transmits a separate pilot channel provided with a predetermined spreading code. In order to facilitate the synchronization of the subscriber equipment, the base station transmits a data-modulated signal on the pilot channel.

Abstract: A signal transmitting apparatus using orthogonal frequency division multiplexing includes an inverse fast Fourier transform circuit for converting a digital information signal into a first multi-value QAM modulation signal. A guard interval setting circuit is operative for periodically generating a guard interval signal equal to a time segment of the first multi-value QAM modulation signal, and inserting the guard interval signal into the first multi-value QAM modulation signal to convert the first multi-value QAM modulation signal into a second multi-value QAM modulation signal. A clock signal generating circuit is operative for generating a first clock signal which drives the inverse fast Fourier transform circuit, and generating a second dock signal which drives the guard interval setting circuit. The inverse fast Fourier transform circuit includes a device for generating a pilot signal which corresponds to a given-order carrier, and adding the pilot signal to the first multi-value QAM modulation signal.

Abstract: A method and apparatus for automatic gain control in a receiver. The input signal to the receiver includes both a DC component and a signal component. Filters are used to separate the two components. The DC component modulates a pilot signal and is then added to the signal component. The combined signal is then amplified to produce an output signal. The output is also filtered and subjected to a synchronous detector to produce a gain control level for the amplifier. The synchronous detector utilizes the filtered output signal to modulate the same pilot signal which is then compared to a reference voltage.

Abstract: Apparatus is disclosed which is advantageously used in local area, metropolitan-area, and wide-area networks using a dual bus architecture, and more particularly to a dual bus network design having significantly increased distance before termination or regeneration of the optical signal, and using wavelength division multiplexing (WDM) at one optical wavelength to transmit data over the bus and a second optical wavelength to transmit a clock signal and a CATV video signal.

Abstract: An optical wireless transmission system providing short-distance communication, such as for linking a personal computer to a LAN, utilizes direct baseband modulation of optical signals, but provides simultaneous bidirectional transmission of data between a pair of optical transmitting/receiving units while also enabling a data clock signal to be easily regenerated from a received optical signal. Effects of signal noise due to artificial illumination are eliminated by a suitable choice of transmission bandwidth, and bandpass filtering of a received data signal.