Abstract: The present invention relates to an analog signal level monitor designed according to the distribution function of an analog input signal, where it is known that the percentage of time an analog input voltage spends within a desired level of operation of, for example, an A/D converter is directly related to its distribution function. Positioned at the output of an exemplary A/D converter, the present invention comprises a logic circuit (24) designed to output a first signal when the conversion is within this desired level and a second signal otherwise. The logic circuit output is passed through a normalized meter (22, 25), which provides an indication that directly corresponds to the above-described percentage, thereby indicating the optimality of the input signal level with respect to the level of operation. Alternatively, the present invention may be used to determine the maximum clock rate of a device, as for example, an A/D converter.

Abstract: The present invention relates to a technique for increasing the rain margin of a satellite communication system which includes a satellite capable of transmitting multiple concurrent beams comprising time slot bursts in a TDMA mode. The present technique creates a small pool of TDMA time slots which are dedicated or formed at some instant of time by the rearrangement of traffic to permit the power normally transmitted in any portion of the multiple concurrent beams to be applied to one beam in a multiple fixed beam or limited scanning beam system or any portion of the beams which are directed at one ground station in a multiple unlimited scanning beam system for accessing a ground station experiencing, for example, a fade condition.

Abstract: The present invention relates to a wideband digital spectrometer capable of obtaining the Fourier power spectrum of a combination of an input signal, using the Walsh functions. The input signal is low-pass filtered (10) at a cutoff frequency f.sub.c, then sampled at a rate of 2f.sub.c (12) to provide N sequences representative of the digitized input signal. Each one of the N sequences is combined with a separate one of the N Walsh functions (14), and the Walsh power spectrum of each one of these N combinations is then computed (16). These N Walsh power spectrum components are applied to an N.times.N Walsh-Fourier power transformer (18) which generates the desired N Fourier power spectrum components.

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 quasi-optical frequency diplexer capable of operating over a wide angle of scan and separating microwave signals possessing proximate center frequencies. The present invention, which in one aspect may be employed with a phased array antenna arrangement functioning so as to separate the transmit and receive frequencies associated therewith, consists of an array of waveguide sections (22) where the input and output ports (30, 32) of the array are tilted with respect to the array's longitudinal axis. The angles of tilt and the dimensions of the waveguide sections may be adjusted so as to achieve frequency diplexing with a minimal amount of interference between the diplexed signals.

Abstract: The present invention relates to an adaptive cross-polarization cancellation arrangement where a first desired polarized signal and a second interfering orthogonally polarized signal, including cross-polarization components, are concurrently received at an antenna. In the present arrangement, the orthogonally polarized components of the received signal are separated and transmitted along separate paths and recombined after the phase and amplitude of the separated polarized interfering signal sample has been appropriately adjusted for maximally cancelling cross-polarization components thereof in the other path.

Abstract: The present invention relates to a method for reducing the weather cover-induced reflection sidelobes associated with horn reflector antenna arrangements. More particularly, the present invention consists of attaching the weather cover (26) to curved forms (21,23) placed in the antenna aperture, where the forms are shaped to contour the weather cover into a cylindrical paraboloid form, this form being capable of focusing the reflections from the weather cover onto a line inside the antenna arrangement. By covering this line inside the antenna with microwave absorbing material, (36) the focused weather cover reflections may be absorbed, thereby significantly reducing the sidelobes caused by the presence of the weather cover.

Abstract: The present invention relates to a majority logic spread spectrum, FH-MFSK radio receiver capable of demodulating and decoding one or more concurrently received L-length frequency-hopping, 2.sup.K -ary frequency shift keyed signals to determine the correct signal of a particular user. In operation, the receiver spectrum-analyzes the received signal to determine which frequency components are present during each of the L chip intervals and then modulates a particular user's L-length FH address signal with the derived frequency components to arrive at a 2.sup.K by L-length detection matrix. A majority logic decision circuit determines the level having the maximum number of derived frequency components along the L-length axis of the matrix, or which is the most likely level of multiple equal levels, and decodes the chosen 2.sup.K level into the indicated message signal.

Abstract: The present invention relates to a class of adjustable microstrip and stripline tuners. An exemplary tuner comprises a pair of tuning elements, where each tuning element further comprises a pair of parallel spaced-apart conductive strips of equal length and at least one movable bridging wire connecting the two strips. The movement of the bridging wire will vary the output impedance of the tuning element, and a complementary arrangement of a pair of tuning elements will form a tuner capable of matching any impedance falling within the Smith chart.

Abstract: The present invention relates to a method for reducing the grating lobes associated with phased array antenna arrangements. The present invention, which may be employed with any phased array antenna arrangement, consists of disposing a filtering means capable of blocking the grating lobes at any real focal point in the focal plane of the antenna arrangement. The size of the central region of the filter is determined by the desired field of view at the far-field, and may be adjusted so as to reduce the grating lobes to an admissible level with minimal gain degradation of the main beam.

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 driver for a diode switch comprising a complementary arrangement of a first and a second type of transistor across a voltage source. The first type of transistor is coupled to receive only a-c fluctuations in the input signal and is arranged to be not saturated but at cut off at the beginning of each switching subframe and be turned on for a very short time in response to a predetermined a-c input transition. The second type of transistor is coupled to receive a-c and d-c input signal fluctuations and has a resistive element for limiting the forward-biased current through the diode switch when turned on. A resistive element across the emitter collector terminals of the first type of transistor maintains the appropriate back-biasing potential on the diode switch when both transistors are cut off.

Abstract: The present invention relates to an antenna arrangement capable of generating one or more linearly scanning spot beams which are scanned over separate strip portions of the entire field of view of the antenna. The antenna arrangement comprises an optical system comprising an aperture and a focal plane, and a novel feed arrangement. The feed arrangement comprises a separate linear phased array disposed within a separate rectangular waveguide section for each linear scanning beam desired. An offset curved reflector, disposed in each waveguide section, converts a linearly scanning planar wavefront generated by an array into a converging beam forming a linearly moving point source on the antenna's focal plane with the principle ray of each instantaneous wavefront being directed at the center of an image of the aperture of the optical system as seen by the feed arrangement.

Abstract: The present invention relates to a hybrid mode waveguide or feedhorn antenna for transforming the TE.sub.11 mode into the HE.sub.11 mode. The waveguide or antenna comprises a first waveguide section of uniform cross-section at the TE.sub.11 mode entrance port which in the antenna arrangement changes to a second section which flares outward toward the antenna mouth, and a spiro-helical projection bonded with a dielectric layer to the inner surface of the waveguide or antenna. The spiro-helical projection comprises a closely spaced helically wound wire structure formed of dielectrically coated wires which in the first section decrease in gauge size in small adjacent portions thereof as the helix progresses away from the TE.sub.11 mode entrance port and in the remainder of the helical projection, the same or decreasing gauge wire in adjacent portions can be used.

Abstract: An offset antenna and feed combination for use in a satellite communication system is disclosed wherein an array of adjacent microwave energy feed elements is disposed within a predetermined shape on the focal surface of the antenna for delivering electromagnetic energy to a remote, correspondingly shaped zone. Electromagnetic energy beams are selectively radiated towards predetermined areas of the overall remote zone by associated cluster groups of feed elements typically arranged as a minimum of one central and six surrounding feed elements. Additionally, each surrounding type of feed element of a cluster may be shared by two or more overlapping clusters, the overlapping clusters generating contiguous beams of electromagnetic energy in different frequency subbands.

Abstract: The present invention relates to a technique for displacing spurious resonances which are excited in strip transmission line circuits outside the frequency band of interest. Such displacement is accomplished by adding apertures in the capacitive elements of the strip transmission line circuit which have dimensions to move the transverse resonances out of frequency band of interest while causing, for example, no significant change in the passband ripple or the stopband attenuation of a filter. The slots effectively cause the inductance across the capacitive element to increase and, therefore, lower the frequency of the transverse modes or resonances.

Abstract: Microwave energy feed elements for launching essentially linearly polarized beams in a satellite communications system are oriented in the satellite's antenna so that the polarization directions of the feed elements form a rim and spoke configuration. The vertical polarizations are arranged to extend radially from a point on the antenna's focal surface which images the point on the surface of the celestial body directly below the satellite. Horizontal polarizations are arranged concentrically about the subsatellite image point. Electromagnetic energy launched from the feed elements will reach the surface of the earth at planes of incidence which are locally vertical and horizontal, thereby minimizing cross-polarization coupling between the orthogonally polarized signals due to such energy passing through precipitation.

Abstract: The present invention provides a processor for interfacing a TDMA burst modem (40), which transmits and receives bursts of information at high data rates in assigned time slots, and slow speed terminal processing equipment. The present processor comprises circuitry (50) capable of detecting frame or superframe markers in a received sequence and regenerating such markers, after initiation, at the normal interval for such markers despite false alarms or missed marker signals. Other circuitry (53, 57 and 52, 62) causes a memory (48, 56) to directly output a burst of information during an assigned time slot to the modem (40) and directly store received information from modem (40) during a predetermined interval which is designed to start before and end after the expected arrival of an assigned burst. Slower processing equipment is then used to find and process the burst in the stored information.

Abstract: A technique is disclosed for sharing a fixed number of identical transponders among a same or greater number of input and output signaling directions by rapidly scanning each transponder over appropriately defined group pairs of the input and output directions. The apparatus comprises n transponders having input and output terminals which are selectively and separately scanned over a plurality of m input and output signaling directions, respectively, by scanning means under the control of a controller. The scanning means can comprise separate m .times. n input and output matrix switches or a separate selectively changeable phase shifter at each antenna element which is connected to a summing and dividing means at the input and output terminal, respectively, of the associated transponder. An efficient TDMA slot assignment technique is also disclosed which covers nonuniform traffic requirements.

Abstract: A traveling wave tube arrangement for use in satellite communications systems is disclosed wherein a plurality of traveling wave tube delay structures and an electron gun are contained in a single envelope with beam deflection apparatus. The electron beam deflection apparatus is disposed between the electron gun and the plural traveling wave tube delay structures to selectively deflect the electron beam to the individual delay structures on a time division basis. In one embodiment, electron beam deflection apparatus is simplified by arranging the individual delay structures radially from a point in the path of the electron stream where the stream is deflected by the beam deflection apparatus.