Abstract: The present invention provides a wireless communication system which employs Butler matrix combiners and circuit switching at transmitter and receiver antenna arrays to provide directive beamwidth capabilities. Such narrow beamwidths permit the communication system to determine and select the transmission path having an optimum signal quality. The antenna arrays are integrated in a multilayer construction which reduces power consumption, increases the coverage range, improves the efficiency of the antenna array, and which has lower fabrication costs.

Abstract: An intermodulation distortion (IMD) detection system improves IMD reduction capability of power shared linear amplifier networks. In one embodiment, first and second power sharing networks, preferably Butler Matrices, are provided with a plurality of linear amplifier circuits coupled therebetween. A plurality of input signals are applied to respective input ports of the first power sharing network, with a portion of each input signal amplified by each amplifier circuit and then recombined in the second power sharing network so that each amplified input signal appears at only one output port of the second power sharing network. An antenna coupled to each of these output ports then radiates the amplified signal energy associated with one of the input signals. A test signal, which may be a dual tone signal, is applied to another input port of the first power sharing network, where it is split and amplified by each amplifier circuit.

Abstract: Disclosed is a low distortion amplifier circuit of the predistortion type that employs a cuber circuit in the predistortion path to provide optimized signal energy at third order intermodulation frequencies, which cancels IMD products generated by the main power amplifier. The cuber circuit employs a pair of anti-parallel diodes that are biased with at least one D.C. source to produce a D.C. current flow through each diode. The input signal applied to the cuber circuit produces signal current flow in each diode to enable a third order output current to be extracted. A desired amount of third order power is thereby provided to realize minimal IMD power in the main amplifier output over a wide dynamic range of the input signal.

Abstract: This invention is an inventive N input by L output interconnect fabric. In operation, packets comprising an information field and an address are received at the N inputs to the interconnect fabric, and the address in each packet is mapped to a group of outputs, rather than to any particular output. Each packet is then routed to any available one of the interconnect fabric outputs associated with the group to which the packet is mapped. If a number of packets destined for the same group simultaneously arrive at the interconnect fabric inputs and the group to which they are all destined does not comprise enough outputs to accept them, then all packets in excess of the number that the destined group can accept are simply discarded. The probability of lost jackets due to such discarded packets is acceptably small. In one exemplary embodiment, the invention can be utilized to build arbitrarily large packet switches.

Abstract: This invention is large N.times.N packet switch, formed using a plurality of smaller packet switches. The invention comprises an N input, L output interconnect fabric (L>N), and a plurality of J.times.K smaller packet switches (J>K). Each of the J inputs to each packet switch is connected to a separate one of the L outputs of the interconnect fabric, and each of the K outputs from each packet switch is connected to a destination equipment. In operation, packets are received at the N inputs to the interconnect fabric, and each packet is routed to one of the inputs of the packet switch associated with the destination user equipment for the packet. Simultaneous packets, up to J in number, are routed to separate inputs of a particular packet switch for distribution to their respective destinations, while all other simultaneous packets destined for user equipments associated with the same packet switch are lost, the probability of such a loss being acceptably small.

Abstract: The present invention relates to an N-input, N-output "Knockout" packet switch (11) which uses decentralized control and distributed routing. More particularly, within the switch, the N input signals comprising fixed-length packets propagate along separate broadcast buses (14) to each of N bus interface units (15) which include N packet filters (20), a concentrator (21) and a shared buffer (22). Each bus interface unit is associated with a separate one of the N outputs (12) of the switch, and the N packet filters therein are each associated with a separate one of the N broadcast buses for detecting if a packet on the associated bus is destined for the associated switch output. The concentrator is used to reduce the number of separate buffers needed to receive packets which may arrive simultaneously and are destined for the associated output. Contending packets at the output of the concentrator are stored in the shared buffer before placement on the output line on a first-in, first-out basis.

Abstract: The present invention relates to an N-input, N-output "Knockout" packet switch (11) which uses decentralized control and distributed routing for routing high-speed, time-multiplexed, variable-length packets of information from the N inputs to the N outputs. More particularly, within the switch, the N input signals are separately synchronized such that the start of each arbitrarily arriving variable-length packet is synchronized to the start of a next mini time period of a sequence of mini time periods common to all inputs. The synchronized N input signals then propagate along separate broadcast buses (14) to each of N bus interface units (15) which include N packet filters (20), a concentrator (21) and a shared buffer (22) capable of processing variable-length packets.

Abstract: The present invention relates to a space diversity combiner which includes two branches wherein separate multipath signals received from a remote source are propagated. The branch signals are combined and the combiner output signal is used for obtaining noncoherent spectrum measurements which are in turn used to account for both dispersion and noise in controlling the relative amplitudes and phases of the two branch signals to provide a maximum performance measure for the combiner.

Abstract: A digital communications satellite (12,44) receives signals from a plurality of narrow input spot-beams (14) of an uplink. It regenerates, multiplexes and routes the signals for transmission in a plurality of narrow output spot-beams (42) of a downlink. The uplink beams (14) each include a plurality of frequency re-use channels (18), while the downlink beams (42) each have only a single wide-band channel. The satellite (12,44) may multiplex the signals either before or after routing them. The spot-beams (14,42) may be fixed or scanning.

Abstract: The present invention relates to a technique for efficient spectrum utilization in mobile radio systems divided into a plurality of geometrically-shaped cells (10-21). Mobiles (24) in each cell are served by at least one base station (30-40) comprising a directional antenna having a beamwidth corresponding to the overall area of the associated cell. Each base station communicates with mobiles within the associated cell using separate primary channels (C.sub.p) within a first portion of the system frequency spectrum when a mobile is not experiencing interference above a predetermined interference level, and switches a mobile to a separate secondary channel (C.sub.p) within a selected section (f.sub.1, f.sub.2, f.sub.3) of the remaining second portion (f.sub.i) of the system frequency spectrum when the interference at a mobile exceeds the predetermined interference level. Each selected section used in adjacent portions of adjacent cells being within a different frequency subband of the second portion.

Abstract: The present invention relates to a cooperating arrangement for a pair of space diversity stations (30 and 40) interconnected by a communication link (20) wherein each station normally communicates independently with a remote point (12) of the system while handling traffic related to a separate service region (32 and 42) or separate portion of an overall service region. At the occurrence of a fade condition at one of the two stations, the fading station alerts the other station of the pair of such condition, and both stations are enabled to cause the normal two-way communications between the faded station and the distant point to be routed over the communication link for two-way transmission between the non-faded station of the pair and the distant point along with the normal associated two-way transmissions between the non-faded station and the distant point.

Abstract: The present invention relates to a technique for creating dedicated in-band, two-way, signaling channels between a master signaling ground station and each remote ground station of a satellite communication system using either an area coverage beam or a plurality of fixed and/or scanning spot beams. In the present technique, separate bursts of information within a superframe sequence are dedicated for only providing signaling information between the master signaling station and each ground station of the system. Each ground station, in turn, is dedicated a separate burst of information for transmitting only signaling information back to the master signaling station. Coarse ranging is performed by triangulation methods and then each ground station transmits a unique word within the predetermined time period of its dedicated signaling burst to the master signaling station.

Abstract: The present invention relates to a satellite communication system which uses a separate up-link and down-link fixed spot beam for communication with each of a plurality of, for example, spaced-apart high traffic demand ground areas and an up-link and a down-link scanning spot beam for communication with a plurality of, for example, spaced-apart low traffic demand ground areas on a time division multiple access (TDMA) basis. More particularly, a satellite repeater is disclosed for accomplishing the switching of signals concurrently received via the up-link fixed and scanning spot beams to the appropriate down-link fixed and scanning spot beams. Additionally, a transmission and a switching format is disclosed for the efficient multiple access of the low traffic demand ground station areas while still providing minimal buffering demands for the high traffic demand ground station areas.

Abstract: The present invention relates to method and apparatus for substantially reducing the effects of interference at a receiver between concurrently received first and second digital signals which use the same frequency spectrum. Interference between signals is effectively reduced by transmitting the first digital signal in an uncoded form while concurrently transmitting the second digital signal with both reduced capacity when compared with the first signal and in coded form using a forward error correcting code such as, for example, a block or convolutional code. At the receiver intercepting both digital signals, a suitable detection process is performed to decode the second signal and separate both signals. The present invention is applicable to the simultaneous satellite transmission of an area coverage beam and a plurality of spot coverage beams or to increase capacity on a radio channel.

Abstract: The present invention relates to a method of cophasing the feed elements of a transmitting or a receiving phased array antenna. To cophase a transmitting antenna, the method entails transmitting a lower sideband and an upper sideband signal from a first and a second one of the feed elements, respectively, while transmitting a carrier signal used to generate the sideband signals on all other feed elements of the array. At each receiver the reference phase angle between the received sideband signals is measured and stored. The above step is sequentially repeated for the first and a third, the first and a fourth, etc., one of the feed elements, and the phase angle measured, subtracted from the reference phase angle, and stored. With the above method, the phase angle between each feed element and the second one of the feed elements is determined and stored and subsequently transmitted back to the transmitter for use in transmitting signals to each receiver.

Abstract: The present invention relates to method and apparatus for communicating with one or more receiver stations disposed within a blackout region located in the vicinity of and surrounding each spot beam coverage area, the blackout region being caused by interference between concurrently transmitted and overlapping global coverage and spot coverage antenna radiated beams using the same frequency band despite the application of global beam interference suppression techniques at the spot beam receiving areas. Access to the receiver stations within each blackout region is provided by selectively turning off the associated interfering spot beam during a predetermined interval of time while ensuring that the power level of the radiated global coverage beam is not suppressed within the accessed blackout region to permit the global coverage beam to communicate with these receiver stations.

Abstract: The present invention relates to method and apparatus for substantially cancelling interference between signals using the same frequency spectrum which are received via overlapping area coverage and spot coverage antenna beams. At the transmitter where the overlapping area and spot coverage beams are concurrently transmitted, a predetermined portion of the area coverage signal is coupled into each of the spot beam signals which will be overlapped at the associated spot beam receiver area by the area coverage beam. The predetermined portion coupled into each spot beam signal will have a magnitude and phase to substantially cancel the area coverage signal at the associated spot beam receiver area.

Abstract: A multiplex radio transmission system is provided with facilities for initiating protective switching from a working channel to an idle channel of the system when the signal to interference ratio on the working channel falls below a predetermined threshold value. A precise square-law detector derives, from the separate information and interference components of a signal on the working channel, a DC component and a difference-beat AC component which are processed to yield a quantity indicative of the desired signal to interference ratio. When such ratio falls below the predetermined threshold value, switching to an idle channel occurs in a manner similar to conventional signal-to-noise dependent protective switching arrangements.

Abstract: This invention is an inventive N input by L output interconnect fabric. In operation, packets comprising an information field and an address are received at the N inputs to the interconnect fabric, and the address in each packet is mapped to a group of outputs, rather than to any particular output. Each packet is then routed to any available one of the interconnect fabric outputs associated with the group to which the packet is mapped. If a number of packets destined for the same group simultaneously arrive at the interconnect fabric inputs and the group to which they are all destined does not comprise enough outputs to accept them, then all packets in excess of the number that the destined group can accept are simply discarded. The probability of lost .[.jackets.]. .Iadd.packets .Iaddend.due to such discarded packets is acceptably small. In one exemplary embodiment, the invention can be utilized to build arbitrarily large packet switches.

Abstract: This invention is large N.times.N packet switch, formed using a plurality of smaller packet switches. The invention comprises an N input, L output interconnect fabric (L>N), and a plurality of J.times.K smaller packet switches (J>K). Each of the J inputs to each packet switch is connected to a separate one of the L outputs of the interconnect fabric, and each of the K outputs from each packet switch is connected to a destination equipment. In operation, packets are received at the N inputs to the interconnect fabric, and each packet is routed to one of the inputs of the packet switch associated with the destination user equipment for the packet. Simultaneous packets, up to J in number, are routed to separate inputs of a particular packet switch for distribution to their respective destinations, while all other simultaneous packets destined for user equipments associated with the same packet switch are lost, the probability of such a loss being acceptably small.