Abstract: A modular data link having a transmit processor for receiving input data and for providing different portions of the input data at each of a plurality of outputs. A plurality of transmit channels each receive an input data portion and transmit a signal corresponding to the received input data portion. An antenna collects the transmitted signals and provides an output thereof. A plurality of received channels each receive the collected signals from the antenna and extract a different input data portion from the collected signals. A receive processor having a plurality of input each coupled to a respective receive channels receives the extracted different input data portions so as to recombine the different input data portions in regenerating said original input data as output data.

Abstract: A method for the broadcasting of digital data, intended to be received notably by mobile receivers moving about in an urban environment, that is, under conditions of multiple propagation and in the presence of parasites and jamming, enabling a coherent demodulation under such conditions of reception. This method is one for the broadcasting of digital data, notably for radio broadcasting at a high bit rate towards mobile receivers, of the type providing for the distribution of the data in the form of digital elements in the frequency-time space f-t and the transmission of symbols each constituted by a multiplex of N orthogonal carrier frequencies modulated by a set of digital elements and broadcast simultaneously, certain of the digital elements being reference elements with a value and position in the frequency-time space f-t that are known to the receivers.

Abstract: A method for automatically selecting optimum frequencies for transmitting data from remote terminals upstream to a system manager is provided. The system manager initially selects a set of frequencies from a larger set of available frequencies and transmits a command downstream to each remote terminal indicating which frequencies to use. Each remote terminal transmits data messsages on each selected frequency in response to addressed commands generated by the system manager. The system manager receives and counts the data messages on each of the frequencies, and after a statistically significant number of messages are received, removes from use the frequency with the lowest number of data messages received. This frequency is replaced with either (1) a previously untried frequency, or if all frequencies have been tried, (2) a previously tried frequency with the highest number of data messages received.

Abstract: A method for the diffusion of digital data designed to be received notably by mobile receivers moving in an urban environment, that is, in the presence of stray signals and jamming, and in conditions of multiple propagation (Rayleigh process) providing an optimized mode of setting up the frame structure of the broadcast signal, so as to derive the maximum benefit from the resistance of the system to pulsed stray signals and to jamming. The header of each frame has a first empty synchronization symbol and eventually a second, unmodulated wobbled signal forming a two-stage analog synchronization system. So, the recovery of synchronization is achieved in an analog way, without prior extraction of a clock signal at the binary level. The constitution of the sequence of the useful symbols in the frame results from temporal and sequential interlacing operations, combined to obtain an implicit de-interlacing at the receiver.

Abstract: An error correction system for a multicarrier radio transmission system is provided. At the transmission end, a frame alignment bit and error correction bits are added to each of the signals from a serial/parallel converter. Positions of the frame alignment bits in the signals are controlled by a common frame counter. The signals added to frame alignment bits and error correction bits are radio transmitted on several carriers. At the receiving end, frame alignment of each demodulated signal is established based on demodulated signals transmitted on two carriers. Therefore, even if one carrier is deteriorated, frame alignment of data signals on the carrier can be established based on the frame alignment bit in the other data signal on the intact other carrier.

Abstract: Disclosed is a method of selecting a relatively high reliability signal path between a mobile communication unit and a number of possible base sites.

Abstract: A spread spectrum receiver using a correlator is disclosed, in which first and second comparing means comparing a correlation spike coming from the correlator with a first and a second reference voltage are used, the reference voltages being regulated, depending on the output of the first comparing means so that variations of the correlation spikes are followed precisely to obtain a two-valued correlation pulse.

Abstract: A spread spectrum receiver subsystem for utilization in a CDMA cellular telephone having a searcher receiver for scanning the time domain so as to use the PN processing gain and time discrimination properties of spread spectrum coding to determine the location in the time domain and the received signal strength of multiple receptions of a pilot signal traveling upon one or more physical propagation paths to reception. The searcher receiver provides a control signal indicative of the received pilot signals of greatest strength and corresponding time relationship. A data receiver receives spread spectrum communication signals accompanying each received pilot signal and is responsive to the searcher control signal for acquiring and demodulating a spread spectrum communication signal, concomitant with the pilot signal of greatest signal strength, and thus providing a corresponding information bearing encoded output signal.

Abstract: A communication signalling system containing a control unit receiving input data from one source and a reference signal from another source, a modulator receiving an input from the control unit, and a plurality of tones from a separate source, the phase of each of the tones received by the modulator being modulated in response to the input received from the control unit, an adder which receives the modulated signals from the modulator and converts the signals into a composite signal which is then sent to a latch unit which also receives a signal from a symbol interval clock, the latch unit sending a composite signal to a transmitter for transmission during a given symbol interval, an antenna and receiver detector unit for receiving the signal being transmitted, the signal being forwarded to a filter and correspondence circuit which breaks out the individual modulated signals comprising the original frequency, the modulating phase, and a random unknown interference, the individual signals being applied to and

Abstract: A digital broadcasting process, suitable for digital audiobroadcast, comprises encoding the data in the form of binary words using a redundant code to obtain a sequence of modulation symbols and transmitting the symbols in a plurality of subchannels at different frequencies. The symbols are time interlaced with such a distribution that two adjacent symbols cannot be transmitted in time succession and at the same one of the frequencies. Preferably, a Viterbi decoder is used. Particular construction of an emitter and a receiver are also described.

Abstract: A channel switching system without an instantaneous signal loss in a data communication system such as a digital microwave multiple radio communication system. The channel switching system includes a control unit for generating a switching control signal in response to a fault detecting circuit; a unit for receiving a phase adjustment signal from the active receiver unit of an active transmission channel and another signal from the standby receiver, for adjusting the phases between both received signals in response to the switching control signal, and for outputting a switch energizing signal; a high speed switching unit, including a unipolar high speed switching circuit, for switching signals from the phase adjustment unit in response to the switch energizing signal. The switching system further includes a compulsory switching unit, for compulsorily switching the signals supplied to the switching unit.

Abstract: Frequency diversity is employed to counter selective fadings as a result of multi-path propagation for troposcatter and short-wave connections for digital useful signals employing frequency modulation. For this purpose, the digital useful signal is supported on a frequency arrangement comprising at least three radio frequencies in that the digital useful signal, together with at least one additional oscillation, and, in fact, an additional fundamental oscillation which determines the frequency of the spacing in radio-frequency frequency arrangement, is fed to the input of a frequency modulator. At the input end, the radio-frequency carriers of the frequency arrangement, which are each modulated with the useful signal, are all converted by coherent mixing into the same frequency level, from which, by way of a combiner, a sum signal is obtained which is the optimum in respect of signal-to-noise ratio.

Abstract: An improved data transmission system has a transmitter which includes a modulator responsive to a synthesized modulating signal, which provides for transmission of data substreams on parallel subchannels, for example, by using subcarrier frequencies. At the receiver the subcarriers are received and data is selected from the received subcarriers at two diverse receivers. In addition, there are provided signals added to the transmitted data for retiming the data at the receiver.

Abstract: A single sideband communications system conveying a message through a transmitter to one or more predetermined receivers which are enabled by a coded squelch signal unique to the predetermined receivers is disclosed. The transmitter comprises means to angle modulate both the pilot signal and the information bearing single sideband signal with the coded signal at a predetermined deviation and to transmit the resulting signal.Each receiver frequency control means tracks the frequency excursions of a selected portion of the transmitted signal up to predetermined limits so that the message can be demodulated without frequency distortion being introduced. Each receiver demodulates the coded squelch without interfering with the message demodulation or tracking functions and activates the receiver squelch of those preselected receivers.

Abstract: A coherent communications link for simultaneously transmitting intelligence on a plurality of non-contiguous frequency channels by means of a plurality of coherent carrier signals which are connected to a single composite intermediate frequency signal upon reception by a fully coherent receiver. The local oscillator signals in the receiver are maintained coherent with respect to the transmitted carrier signals responsive to the composite IF signal while each of the local oscillator signals is adjusted to maintain coherence of each received carrier in the face of relatively long term drift due to thermal shifts, path effects and hardware drift.

Abstract: A single data signal is transmitted by two transmitters to two radio zones having an overlapping zone therebetween. The data signal is frequency or phase modulated and is mixed in the transmitters with RF carrier waves of equal frequency. The data signal to one of the transmitters is delayed between 5.degree. and 50.degree. with respect to the original data signal to provide a phase difference between the transmitted signals.

Abstract: A meter terminal unit, for acquiring information and transmitting the acquired information to a central reading and control unit over utility power transmission lines, includes a transmitter portion for synthesizing and modulating carrier waveforms, the frequencies of which are selectable by command data contained in frequency rotation and address fields of a command received from the central reading and control unit. The meter terminal unit receives and decodes the command and adds, in modulo form, the contents of the frequency rotation field to the contents of a portion of the address field to obtain a resultant sum which uniquely identifies the selected waveform. This sum is used to access a portion of a read only memory (ROM) having the selected waveform stored therein in digital data form. The selected waveform is reconstructed by outputting the digital data from the ROM to a digital to analog converter.

Abstract: A transmission system, for transmitting signals over an electrical power distribution circuit, comprises a transmitter arranged to produce at least two carrier signals of different frequency and to modulate each of them with the same digital signal. The respective frequencies of the carrier signals are derived by frequency division from a common master oscillator, and are thus phase-coherent. The system includes a receiver for receiving the signals, comprising a respective input circuit for each modulated carrier, the input circuits each being tuned to the frequency of their respective carrier signal. A plurality of oscillator signals of different frequencies, derived from a variable frequency oscillator, are used to beat the received carrier signals to respective signals at a common frequency, which signals are summed.

Abstract: A system for use with equipment designed for transmitting a relatively wideband signal over two or more relatively narrowband circuits so as to provide good overall system reliability even though the relability of the individual narrowband circuits is poor.

Abstract: A system for reducing noise transients in electrical carrier signals, carried simultaneously over two separate channels, that are identical in their program component but differ in transient noise content, comprising means for comparing noise transients in the respective channels and for transmitting the electrical sum of the two channels unless the noise transients of the two channels differ by more than a selectable threshold amount, in which case only the carrier signal with the lesser noise transient is transmitted.

Abstract: In a multitransmitter digital signaling system for mobile communications consisting of a plurality of base stations, different waves are superposed on the digital information signals in adjacent base stations and carrier waves of the same frequency are angularly modulated by the superposed signals at the same modulation index and simultaneously transmitted from the base stations to one service area.

Abstract: An arrangement for the remote transmission of information for the remote guidance of vehicles subject to severe acceleration. The arrangement is formed by a transmitter outside the vehicle and by a receiver on board of the vehicle. The transmitter is provided with a first source enabling a first signal of predetermined frequency to be generated and with a second source enabling a second signal of a different frequency to be generated. The receiver is provided with a mixing device consisting of a microwave diode biased in its non linear conduction zone in operation, the mixing device enabling a signal to be generated whose frequency is equal to the difference between the different frequencies of the first and second signal. A device for processing the signal whose frequency is equal to the frequency difference between the first and second signal is connected to the mixing device.