Abstract: The invention achieves high Multiple Input, Multiple Output (MIMO) data rates over long wireless links by employing large ground relay MIMO antenna arrays and conformal airborne MIMO antenna arrays. Antenna transceiving element layouts and polarizations are optimized for enhanced channel capacity.

Abstract: For use in a wireless network having geographically-distributed base stations that serve wireless terminals, a system for, and method of, improving an operation of the wireless network. In one embodiment, the system includes: (1) a signal quality determination circuit that determines a relative quality of signals communicated between one of the wireless terminals and a set of base stations within range of the one of the wireless terminals and (2) a base station selection circuit, coupled to the signal quality determination circuit, that selects a base station in the set to serve the one of the wireless terminals based on the relative quality of signals.

Abstract: A system for inducing rapid fading in wireless communication systems, such as digital radio and television transmission is described. Orthogonal polarization combined with time varying offsets are combined to insure rapid fading and result in improved signal reception.

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: Transmission capacity of an optical fiber is increased by transmitting two optical signals of orthogonal polarizations through the fiber and distinguishing the signals from one another at the receiver by appropriately weighting polarization components representative of the transmitted signals. The weighted polarization components are summed to provide two output electrical signals that are proportional in magnitude to the two transmitted optical signals. Appropriate weighting of the signals eliminates cross-channel interference and maximizes the signal to noise ratio. Signals of arbitrary received polarizations are detected and separated from one another.

Abstract: In an angle diversity receiving system, the primary and diversity signals are produced by a waveguide signal separator coupled to a single receiving antenna.The separator operates by converting selective higher order modes in the antenna into fundamental modes that will propagate in its two output waveguides. The result is a robust system that operates over a frequency band wide enough to cover both the 4 GHz and 6 GHz common carrier bands with both horizontally and vertically polarized signals, and that can use a wide variety of antennas.

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: A terrestrial radio system which utilizes spot beams, time division multiple access and frequency reuse to provide communications services from a base station to remote customers within a system service region. The base station advantageously is arranged with multistage switching so as to permit the respective sharing of radio transmitters and receivers over larger number of antenna transmitting and receiving ports.

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 dynamic resource allocation technique for multiple users of a channel that employs variable coding and associated redundancy to provide a maximum data rate for various demand conditions while simultaneously providing a maximal margin that is matched to the current demand condition. For such technique, each first data rate input signal is synchronized to a second higher data rate, the synchronized signals are then separately demultiplexed for propagation along separate paths and encoded in a separate variable rate coder (VRC). The output from each VRC is stored in a separate bus interface which contends for a common bus when full. A rate controller maintains the activity on the common bus at a minimum level by either monitoring (1) the activity on the bus, (2) the rate the bus interfaces are filling up, or (3) both (1) and (2) above, and in response thereto to transmit control signal to the VRCs to appropriately vary the codes and redundancy used.

Abstract: The present invention relates to a scanning beam antenna comprising a doubly-curved main reflector, a doubly-curved subreflector and at least one linear array feed. The main reflector is doubly-curved in two planes to produce a separate first focus for each feed in a first plane in front of the subreflector and a separate second focus for each feed in a second orthogonal plane behind the subreflector. The subreflector is curved to refocus each second focus of the main reflector to coincide with the image line of a first axis on the reflecting surface of the main reflector in the first plane. Each feed array is disposed at a separate secondary focus of the combination of the main reflector and subreflector. The resulting antenna provides very little phase error due to aberrations as each beam is linearly scanned.

Abstract: The present invention relates to a QPSK modulator or demodulator for modulating two different input bit streams with a subharmonic pump carrier signal to produce an appropriately encoded QPSK output signal. The subharmonic pump carrier signal used is a submultiple of a predetermined microwave or millimeter-wave carrier frequency. The QPSK modulator or demodulator is capable of being fabricated on a planar substrate using appropriate stripline filters and a mixer diode in each of an in-phase and quadrature signal path. A fin line arrangement, also capable of fabrication on the substrate, can be used to introduce an appropriately phased subharmonic pump carrier signal into each of the in-phase and quadrature signal paths before each mixer diode.

Abstract: The present invention relates to an antenna arrangement which includes a polarization diplexer capable of bidirectionally directing two orthogonally polarized signals along one path in the far field of the antenna arrangement and along two separate paths in the near field for interception along at least one of the paths by an array of feed elements. The array is arranged to provide a fixed linear phase taper along one axis across the array to produce or intercept a beam squinted at an angle 90 degrees-.alpha. to the face of the array and including a signal polarized in a first direction. Phase shifting means selectively produce a linear phase taper along a second axis across the face of the array orthogonal to the first axis to cause the beam to traverse a predetermined arc in the far field of view.

Abstract: The present invention relates to antennas with a segmented reflecting surface for providing fully or partially overlapping beams from separate feeds associated with each segment without incurring cross-coupling between feeds and power loss. More particularly, a main reflector or a subreflector reflecting surface is segmented to provide separate images of the far field area of the antenna on separate focal surfaces in the vicinity of an original focal surface of a corresponding non-segmented antenna. Feeds disposed at essentially corresponding locations on each of the far field area images produced by each of the segments provide separate beam footprints which overlap each other in the far field area by a predetermined amount.

Abstract: The present invention relates to a phased array antenna system which transmits a local oscillator signal in a scanable spotbeam from a first array of feed elements (12.sub.l -12.sub.m) via a reflector or lens (16) and a frequency diplexing means (18) to a second array of feed elements (20.sub.l -20.sub.n) disposed on the image plane of the first array of feed elements. A message signal in a second beam also impinging the frequency diplexing means from a separate direction is also received at the second array of feed elements. The message signal and the local oscillator signal concurrently received at each of the feed elements of the second array are mixed in individual mixers and the output of each mixer can be reradiated for transmission to a remote receiver or combined with the outputs of the other mixers for use by a local receiver.

Abstract: To obtain optimal operational sensitivity from an amplifier connected to a source of electrical signals, a technique utilizes multiple amplifiers connected together. The technique determines the number, N, of amplifiers (31 or 51) to be used and whether they should be connected in parallel (FIG. 3) or series (FIG. 5) in order to optimize the sensitivity of a given type of amplifier. Accordingly, multiple interconnection of amplifiers may be used in lieu of noise matching with transformers to minimize the excess-noise figure of the multiple amplifier circuit. The technique capitalizes on the advances in integrated circuit amplifier design, such as compactness and wideband performance, while providing lower loss and higher reliability through redundancy.

Abstract: The present invention relates to a low power, beam switchable, antenna comprising a focusing reflector (14), a plurality of feedhorns (10.sub.1 -10.sub.N) disposed on a surface (.SIGMA.) adjacent the focal surface of the focusing reflector, and an amplifying array (20, 24, 28) disposed in the aperture of the focusing reflector. A spherical wavefront launched by a feedhorn is reflected by the focusing reflector into a first planar wavefront which is intercepted by the amplifying array using a planar array of first feed elements (20.sub.1 -20.sub.X) disposed on a fourier transform surface (.SIGMA.') of the surface on which the feedhorns are disposed. The signal produced by each of the first feed elements associated with a first planar wavefront is separately amplified with an equal relative phase shift to the other associated intercepted signals and reradiated in a second planar wavefront by a planar array of second feed elements (28.sub.1 -28.sub.