Abstract: The planar transmission line attenuator and switch is formed on a flat piece of semiconductor material. Transmission line metallic conductors are deposited on a flat surface of the semiconductor material, and at least one of the metallic conductors forms a Schottky barrier contact to this flat semiconductor surface. The gap between the metallic conductors defines a shunt current path through the semiconductor material. The semiconductor material at the surface in contact with the transmission line conductor must be conductive. By applying a bias voltage to the metallic conductor forming the Schottky barrier contact, the conductivity of the shunt path can be controlled by changing the depletion layer width across the Schottky barrier. A plurality of planar transmission line switches can be combined into multi-port networks, examples of which are cross-bar switching devices and .beta. element switching devices.

Abstract: A self adaptive filter effects a distribution of the power density spectrum of two signals which are correlated in the filter adaptation process so that the filter can provide optimum adaption for a wide range of input signals. The power density distribution is provided by multiplying the operands of the correlator by a random sequence of binary numbers before applying the operands to the correlator. The multiplication effects a decorrelation of the operand input signals.

Abstract: A plurality of terrestrial interface modules (TIMs) are multiplexed and demultiplexed with common equipment through the use of mapping RAMs contained in each TIM. The common equipment provides identical addresses to each of the mapping RAMs in the TIMs. The mapping RAMs in each TIM determine whether incoming or outgoing data is to be written into or read from the associated TIM, and generate an address for the data so written into or read from the TIM. A mapping RAM is further provided in the common equipment to allow for burst-to-burst selection of data.

Abstract: Intermodulation product frequency signals in an active phased-array antenna are spacially filtered by using the beam forming and steering network as a processor to select the intermodulation beam pointing directions such that they will not interfere with the desired beams.

Abstract: In a TDMA burst preamble, the phase is varied between .+-..pi./4 radians, and carrier synchronization is achieved by averaging the phase over a given interval. Symbol timing synchronization is achieved by filtering the upper sideband of a conventional delay-and-multiply circuit and demodulating the filtered upper sideband with a coherent carrier available by the end of the preamble. After the preamble, modulation removal is used to obtain the unmodulated carrier.

Abstract: A stream of data in standard PCM format is written into sequential locations of buffer memories, and subsequently read out of the memories in a different order so as to effect a reorganization of the PCM data. The reorganization of data packs all the bits associated with a single channel into a single contiguous block of time for an entire frame of data.

Abstract: An orientation maneuver for a bias momentum stabilized spacecraft is carried out on a spacecraft initially spinning about a minimum moment of inertia axis. With the spacecraft spinning about that axis, it is precessed until the angular momentum vector points to the south along the orbit normal. The spin rate is then reduced until the angular momentum remaining in the spacecraft is substantially equal to the nominal angular momentum of the momentum wheel in an in-orbit operation. The momentum wheel is then energized and gradually spun up until it contains its nominal angular momentum. As the wheel accelerates, the angular momentum will be redistributed between the wheel and the body, with the total system angular momentum remaining constant. When the wheel has reached its final speed, the spacecraft will have re-oriented itself such that the body of the spacecraft is spinning about the positive pitch axis, coning about the angular momentum vector in a nutational motion.

Abstract: A public encryption key (c.sub.1, c.sub.2, r) in which r is the product of two relatively prime numbers, and in which c.sub.1 and r, as well as c.sub.2 and r, are relatively prime numbers, is used in an encryption algorithmx=c.sub.1 m.sub.1 +c.sub.2 m.sub.2 (mod r).The decryption algorithm will be equivalent to solving simultaneous linear equations derived from the encryption algorithm. Thus, both encrypting and decrypting are quite simplified while still maintaining a high degree of security.

Abstract: A multiplexing/demultiplexing bus structure for a TDMA communications system employs a mapping RAM in common equipment and a decoding device in a plurality of interface modules. The common equipment provides identical encoded information to each of the decoders in the interface modules, the decoders in each of the interface modules determining whether or not incoming or outgoing data is to be written into or read from the associated interface module. The decoders initiate a count to provide an address for the data written into or read out of a buffer in the associated interface module. The common equipment can thereby provide burst-to-burst selection of data. Burst and/or channel allocation may be changed in real time for any of the interface modules through a "demand assignment" process. A central network controller receives all capacity and destination requests for processing. The controller can then send capacity and destination assignments to network stations where they are received and decoded.

Abstract: A non-magnetized ferrite material is provided as the propagating medium for a microwave transmission line such as a microstrip or stripline transmission line. The transmission system is adapted to provide a "high pass" filter characteristic by selecting the saturation magnetization of the ferrite as a function of the desired cut-off frequency such that frequencies below the cut-off are absorbed by the ferrite material thereby producing a low reflection coefficient, while frequencies above the cut-off are transmitted with very little attenuation. One of the conductors of the transmission system can further have microwave circuit elements located thereon which provide a second "filter" characteristic, such as a reactive filter or a tunnel diode. The filter characteristics produced by the ferrite material and the circuit elements combine to produce a desired system filter characteristic.

Abstract: A multichannel correlation receiver at an earth station is provided for determining the depolarization effects of atmospheric conditions on satellite communications. The receiver provides a first co-polarized signal and a second, relatively weak, cross-polarized signal indicative of the depolarization effects, and uses a phase locked loop demodulator to produce a noise free replica of the relatively strong co-polarized signal. This co-polarized signal is highly correlated with the second cross-polarized signal and is mixed therewith to provide a relatively noise free, narrow band signal which has a level indicative of the cross-polarization signal strength for both up-link and down-link propagation paths. The relative signal strengths are recorded on a digital storage means and provide an accurate measure of the depolarization effects of the existing atmospheric conditions. A programmable local oscillator also provides multiple channel capability.

Abstract: In a method and apparatus for convolutionally encoding a finite length digital data bit stream, the information samples arriving at the output of each encoder shift register are fed back to its input to simulate an infinite periodic data bit stream. Recirculation of the received information and parity symbols is also used for decoding.

Abstract: A common memory is used for asynchronous interleaved read and write operations. TDMA data compression and expansion is performed without ping-pong memories and elastic buffering is also possible. A buffer reset method is used to automatically slip a fixed number of bits in response to excessive phase shift between the read and write clock.

Abstract: A programmable frequency source is used to synthesize a wide range of frequencies in small increments. A master oscillator and a single programmable divider are used. Each selected frequency possesses a phase jitter, predictable and a function of the master oscillator-to-output frequency relationship. The output of the frequency source is a square wave whose transitions are edge synchronous with the master oscillator.

Abstract: A microwave integrated circuit (MIC) quadrature phase shift keying (QPSK) demodulator uses a novel arrangement of couplers to permit the IF ports to be adjacent one another so that, in mixer applications, it is unnecessary for the circuitry to leave the plane of the MIC. A symmetrical arrangement of the MIC ensures near-perfect phase orthogonality of the RF.sub.2 split and the power/phase identity of the RF.sub.1 split.

Abstract: The Frequency response of a Microstrip Interdigital Filter (MIDF) is improved by providing a specially dimensioned top cover separated from the MIDF ground plane along one or both of its edges by a dielectric layer comprised of thin dielectric sheets. While the upper frequency skirt is mainly determined by the MIDF itself, the bandwidth may be reduced and the slope of the lower frequency skirt may be enhanced by providing the cover in accordance with the invention. The thickness of the dielectric layer can be chosen to further improve the slope of the low frequency skirt by effectively moving the filter zero closer to the desired low frequency cut-off of the filter. The particular choice of the dielectric thickness will not substantially affect the filter bandwidth.

Abstract: A clock recovery network uses a voltage proportional to the incoming symbol rate as a coarse tuning signal to control the tuned center frequency of a voltage controlled oscillator. The incoming data is used to positively synchronize the oscillator to the incoming data stream.

Abstract: Periodic fins are provided on the lid of a microwave integrated circuit (MIC) package in order to reactively suppress specified bands of frequency and thereby increase the permissible dimensions of the MIC package.

Abstract: A microwave PIN diode switch is provided with circuitry to achieve impedance matching at both input and output ports and for both "on" and "off" switching states.

Abstract: A compact low loss microwave filter is disclosed which utilizes an angular section of a right circular cylindrical cavity at the resonance structure excited in the circular electric TE.sub.0mn mode. The individual sectors may be electrically or magnetically coupled through common walls to obtain various filter characteristics.