Abstract: The present invention relates to a switching technique for packet Frequency Division Multiplexed (FDM) communication systems. In the present system, each of N system users is assigned (a) either a separate fixed one of N transmit frequency channels or a selected free one of L transmit frequency channel for communications to a head-end FDM channel switching arrangement (IO), and (b) a fixed assigned separate one of N receive channels for communications from the head-end FDM channels switching arrangement. At the FDM channel switching means, all FDM channel signals received from the system users are directed into separate paths (21) through the switching arrangement. The signals in each path are demodulated (23) to baseband, and a destination address in each packet is detected (28) to determine where each packet is to be sent.

Abstract: The present invention relates to an antenna comprising a plurality of feeds, and either a single reflector or a single lens wherein the reflector or lens includes a predetermined curved major surface that produces a maximum field of view in a first one of two principal planes of the antenna. The major curved surface is designed to produce a first and a second "stigmatic" focal point, which are spaced apart by a predetermined amount on either side of an axis normal to the center of the reflector or lens in the first principal plane, such that the coefficient of astigmatism is at a maximum predetermined tolerable amount at the center and at the opposite edges of the maximum field of view to produce a peanut-shaped area where the coefficient of astigmatism is within tolerable limits.

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 a digital-to-digital code converter, or decimator, which implements sinc.sup.3 processing. The input signal (X) to the code converter comprises a series of groups, each group including a series of N digital sample values occurring at high rate (1/.tau.) which are converted within the converter, using sinc.sup.3 processing, into a single digital value occurring at, for example, a (1/N).tau. rate for delivery to the converter output (Y). The code converter comprises three processing stages in cascade, where each stage includes separate accumulation means, each accumulation means arranged to add, during each series of N input sample values, the signal value received by that stage from the next preceding stage.

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 multiple-user communication system wherein one carrier source is shared by a cascade of users of the system. More particularly, the present communication system uses a single carrier propagating along the system's transmissin medium onto which each user directly impresses the associated data or communication signal destined for another user preferably using either subcarrier angle modulation (phase or frequency) or TDM techniques for intensity or angle modulation. In the present system using subcarrier angle modulation, each user can either transmit or receive at a fixedly assigned or selectively assigned subcarrier channel, which is different from the subcarrier channel assigned to each of the other users. Where TDM techniques are used, the communication signal from a user can be directly impressed on the single carrier using intensity or phase modulation.

Abstract: An optical fiber is disclosed which comprises (a) a central core section of constant thickness which terminates in an outwardly gradually expanded end section, and (b) a cladding layer enveloping the core. Both the core and the cladding layer are of constant compositions throughout the fiber's length and width. Additionally, the difference between the refractive indices of the core and the cladding layer remains constant throughout the length of the fiber. Where the core gradually increases in width in the outwardly expanded end section of the fiber, the V number increases in like manner. In such optical fiber, propagation of a predetermined mode or modes is maintained throughout the entire length of the fiber, so long as the expansion of the end section occurs gradually over the order of many wavelengths.

Abstract: The present invention relates to an optimized guided wave microwave or lightwave communication system or network wherein a plurality of directional couplers (14, 17) (a) are disposed along a bus-like wave guiding means (13, 16), and (b) include separate coupling coefficients which are optimized. More particularly, the present invention relates to a guided wave communication system or network including, for example, a head-end unit (15) which is coupled to one end of a bus-like wave guiding means. Separate directional couplers are disposed along the wave guiding means to couple lightwave or microwave signals either (a) into the bus-like wave guiding means (13) from separate transmitters (11), or (b) from a bus-like wave guiding means (16) to separate receivers (12).

Abstract: The present invention relates to a fast packet assignment technique, and a TDMA or FDMA multi-port switching arrangement for implementing such technique. In the present technique, the total traffic in a two-dimensional traffic matrix (T) from and to each of N remote service areas, regardless of destination or origination, is totaled to form separate input (R) and output (S) traffic vectors, respectively. Non-conflicting assignments are then made from these vectors for each packet or channel available during a predetermined time period while also providing the capability of substantially reducing multi-path or antenna sidelobe interference. An M.times.M switch (16) is designed to implement such technique which directs C input packets from M inputs (20.sub.1-M) into separate memory locations (Z.sub.ij). During the time period of the next C input packets, the M.times.M switch directs the presently stored packets to the proper ones of M outputs (27.sub.

Abstract: The present invention relates to a burst demodulator for use, for example, in a TDMA communication system, which comprises a first section that downconverts a received r-f burst sequence signal to an approximate baseband signal with a local oscillator, samples the baseband signal at a predetermined rate, and converts the analog samples into an equivalent digital signal. A second section comprises a memory for storing the digital signals associated with a particular burst in a predetermined time period, and a slow-speed processor for reconstructing the received burst signal from the stored information and processing the reconstructed signal to provide for carrier and clock recovery, start-of-message identification, data detection, etc.

Abstract: The present invention relates to coherent optical heterodyning receivers which mix a received optical signal, including an arbitrary polarization state, and a local oscillator signal, including a fixed polarization state, while providing a performance which is independent of the polarization direction of a received signal. In one receiver version, the received signal is heterodyned using only a portion of the local oscillator signal, while in a second receiver version, the entire local oscillator signal is used. The combined polarized signals are split in a polarizing beam splitter between the two orthogonal polarization axes for propagation in separate branches. Each branch includes a photodetector and means for processing the resulting photodetector output signal to retrieve the modulation information from the processed signal. The sum of the two demodulated signals from the two branches provides a baseband signal independent of the polarization state of the received optical signal.

Abstract: The present invention relates to an optical heterodyne mixer providing image-frequency rejection which (a) detects a desired signal at frequency f.sub.L.O. .+-.f.sub.IF while rejecting interference from any signal at the image frequency f.sub.L.O. .-+.f.sub.IF, and (b) provides performance which is insensitive to fluctuations in the optical dimensions of the circuit. More particularly, the mixer receives both a local oscillator input signal and a received input signal comprising one or more optical signals, one of the input signals being linearly polarized and the other being circularly polarized. The two signals are merged by an optical device and transmitted to a polarizing beam splitter which has its polarization axes oriented at 45 degrees to the polarization direction of the linearly polarized signal. Each of the two beams from the polarizing beam splitter is detected by a separate photodetector and the resulting two currents from the two photodetectors are added by means of a 3 dB 90 degree IF coupler.

Abstract: The present invention relates to an Operational Life Test (OLT) or "burn-in" technique for testing microprocessors. In accordance with the present invention, an OLT chamber is provided wherein many Evaluation Boards are mounted within racks in a frame in the chamber, each Board being designed for separately exercising its associated microprocessor integrated circuit (IC). During the OLT or burn-in procedure, each Evaluation Boards runs its own internally stored diagnostics, simultaneously with other Boards, to exercise the associated microprocessor ICs while the power to the Boards and the environment within the chamber is appropriately cycled to simulate system testing, installation or normal customer use. During the OLT procedure, each Board periodically reports the status of the associated microprocessor IC to circuitry such as a computer outside the chamber in order to provide a means for determining and recording any failure of a Board.

Abstract: The present invention relates to a lightwave communication system, and associated transmitters (13) and receivers (14), which uses both spread spectrum, code-division-multiple-access (SS-CDMA), and wavelength-division-multiplexing (WDM) techniques for 2-way transmissions over a lightwave waveguide arrangement (11) to use the overall spectrum of the waveguide arrangement (11) while providing sufficient interference rejection of randomly spaced carriers, and associated signals, which may drift into the bandwidth of transmissions of other transmitter/receiver pairs due to instabilities in carrier laser sources (20). Techniques are also disclosed for a transceiver (10.sub.i) acquiring a 2-way link with another transceiver (10.sub.j), while other transmitter/receiver pairs are concurrently communicating using WDM, SS-CDMA, signal transmissions.

Abstract: The present invention relates to an optical communication system wherein the entire microwave frequency bandwidth of the optical source-to-detector system is subdivided into a plurality of non-overlapping frequency bands or channels, and each user transmits and/or receives information either (a) on a separate fixed one of the channels, (b) on a free channel selectively assigned via control signals transmitted on a separate control channel at the time of initiation of a communication, or (c) on a channel randomly selected at the receiver by an associated user to receive a particular program. The present optical communication system can be configured to simultaneously broadcast multiple programs over separate channels for random selection by each user, or to achieve local and/or external two-way communications with the associated system users.

Abstract: The present invention relates to a collision detection technique for an optical Star LAN using CSMA/CD. The present technique is implemented by preferably adding two or more fixed Hamming weight sequences, e.g., a fixed even or odd number of 1's in each unique cyclic error correcting code word, to the preamble section of each packet of information to be transmitted. These collision detection sequences have a length which is beyond the vulnerable time period of the CSMA/CD protocol (maximum round-trip propagation delay for each packet) by at least one code word length in order to prevent any misdetection, or false detection, of a collision. Each receiver in the listening period, looks for a code pattern with a fixed Hamming weight. When code patterns collide, the Hamming weight of the resulting code word in the collision period will exceed the nominal sequence weight (will include more 1's than the fixed Hamming weight) and a sequence weight violation is detected.

Abstract: The present invention relates to a high-power solid state amplifier arrangement comprising a large number of solid state amplifiers disposed in a waveguide array. The waveguide array is disposed in the aperture of an antenna feed arrangement at the image plane of an antenna feed to receive a uniform distribution over the array with substantially no spillover. Each of the large number of parallel waveguide sections of the array includes one or more solid state amplifiers in a serial, waveguide-interconnected, arrangement, and a wideband impedance matching arrangement in the waveguide configuration at the input and output of the section.

Abstract: The present invention relates to a multidirectional feed which can be used by itself or preferably incorporated within a surface wave structure to form a flush-mounted antenna on, for example, a mobile unit. The feed arrangement comprises a ground plane including an annular cavity with a smaller annular slot. The annular slot is connected by multiple, spaced-apart, leads to an associated transceiver. The annular cavity is also formed to prevent both a shorting of the radio waves therein and the radio waves from propagating away from the cavity in a direction opposite the slot. A surface wave structure is disposed preferably with the feed centrally mounted and can comprise any suitable structure including annular corrugations and/or a dielectric layer to provide a flush-mounted antenna arrangement which provides radiation in azimuth in all directions with moderate elevation gain.

Abstract: The present invention relates to a mode scrambling arrangement for a multimode or graded-index optical fiber and, more particularly, to an optical fiber mode scrambler achieved by forming a deformation as, for example, a groove or notch on one side of the multimode or graded-index optical fiber orthogonal to the longitudinal axis thereof. The groove or notch can be produced by any suitable etching or machining process to extend through the cladding layer and at least very slightly into the outer surface of the core of the multimode or graded-index optical fiber. The depth of the groove or notch into the core can be controlled by monitoring the mode pattern in the multimode fiber during the etching or machining process to provide maximum mode scrambling with minimal loss.