Abstract: A waveguide filter capable of operating at high power levels while retaining substantially constant filter characteristics over a wide temperature range. Two cylindrical body portions of a metal having a low temperature coefficient expansion are sandwiched between three highly thermally conducting iris members, each of which has an aperture of predetermined dimensions for determining the wave modes which propagate through the filter. Each iris member extends beyond the adjacent bodied portion to heat dissipating means which may either be cooling fins through which air is circulated or cooling coils through which a cooling fluid is circulated. Because the proportion of the total filter length occupied by the iris members is much smaller than that of the body portion, very little elongation takes place as the filter cavity is heated thus resulting in temperature-stable filter characteristics.

Abstract: A lens system is formed of spaced coaxial hyperboloidal primary and secondary lenses, each having a convex surface described by a hyperboloidal eccentricity equal to the refractive index of the lens with the lenses mounted with their convex surfaces facing each other, and with the lenses having equal beam deviation factors. A feed array is integrated with the secondary lens, with the feed array comprising array elements printed on a substrate which, in turn, is backed by a ground plane. A beam forming and control network is directly connected to the substrate at the ground plane.

Abstract: A planar microwave switch matrix is composed of three-state phase shifter switches, a planar crossover and switchable 3-dB attenuators. The three-state phase shifter switches are each composed of two planar 3-dB quadrature hybrid couplers interconnected by two switchable phase shifters. The phase shifters are both switchable between zero phase delay and a predetermined phase delay, but the predetermined phase delay is different for each phase shifter. The planar crossover is composed of two cascaded 3-dB quadrature hybrid couplers. The construction of all components of the switch matrix is readily implemented using microwave integrated circuit (MIC) technology. The switch matrix is intended for use in switched satellite time division multiple access (SS-TDMA) systems but can be remotely configured for broadcast applications.

Abstract: A method of fabrication and apparatus are disclosed for realizing a high-frequency non-transverse electromagnetic (non-TEM) mode interdigital band-pass filter. The filter has interdigital microstrip resonators R.sub.i separated a constant distance H from a ground plane by a propagation medium. The method of fabrication allows the W.sub.i /H.sub.i and S.sub.i,i+1 /H.sub.i dimensions of the filter to be obtained. The method starts by determining the self and mutual admittance values Y.sub.i,i and Y.sub.i,i+1, respectively, of each resonator R.sub.i. An estimate for W.sub.i /H.sub.i for each resonator can be made, if desired, using a single microstrip approach. The W.sub.i /H.sub.i estimates are used to obtain the S.sub.i,i+1 /H.sub.i value for each adjacent pair of resonators R.sub.i,R.sub.i+1. The S.sub.i,i+1 /H.sub.i values are used to obtain the values for Y.sub.f and/or Y.sub.fe for each resonator R.sub.i. The values for Y.sub.f and/or Y.sub.fe are used to calculate the value for Y.sub.

Abstract: A syllabic compander uses logarithmic chains in both the compressor and expander. The logarithmic chains are each constructed of a logarithmic amplifier, a scaler, and an antilogarithmic amplifier or their equivalents. The output of a logarithmic chain is equal to the input raised to a power determined by the scale factor of the scaler. A logarithmic chain is used with a multiplier and an average value circuit to implement equations of the formu.sub.o =Ku.sub.i U.sub.awhere u.sub.i is the input to the compressor or expander, u.sub.o is the output of the compressor or expander, U is the rms (or pseudo-rms) value of u.sub.i or u.sub.o averaged over the time of one syllable, K is a constant, and a is the scale factor which is a function of the compression or expansion rate. Since the scale factor a may be easily adjusted, the compander permits flexibility in changing the compression and expansion rates.

Abstract: Multiple coupled high Q cavities are used to generate odd order elliptic function band-pass filters using a minimum number of cavities connected by simple and resonant coupling elements. A specific embodiment of a 3-pole, 20 MHz band-pass wave guide cavity filter centered at 3890 MHz is disclosed. Couplings between cavities may be either on the end walls or the side walls. The simple coupling elements may be simple coupling holes, and the resonant coupling elements may be a non-shorting screw in a window between cavities.

Abstract: Frequency bands in spot beams received by a satellite transponder are selectively routed to transmitted spot beams. The total band width from each spot beam receiver is divided among a plurality of independently adjustable variable bandpass filters, and the outputs from the selected bandpass filters at each receiver are combined at the spot beam transmitters so that each downlink spectrum is made up of a frequency multiplex of selected bands from each uplink spot beam.

Abstract: Off-hook initiated demand assignment (OHIDA) has particular application in communications satellite systems and provides basic demand assignment trunk service by utilizing an off-hook and on-hook signal processing system to monitor and control terrestrial access circuits. The signal processing system operates under the control of a central processing unit to interrogate each trunk of line. The detection by a signal scanner of an off-hook condition initiates the call processing sequence. Once the trunks between the originating and terminating terrestrial circuit switches are connected via the satellite circuits, the connected trunks are under the control of the circuit switches throughout the address signalling, the message and the call terminating stages. Call complete detection is performed by a signal scanner to detect an on-hook condition so that the satellite circuit may be disconnected.

Abstract: A temperature-compensated microwave integrated circuit device such as a delay line in which the phase delay imparted to signals coupled through the delay line is substantially constant over a wide range of temperatures. A dielectric substrate is provided, with strip conductors on one surface defining a desired device configuration such as a multi-pole Butterworth filter configuration. The substrate is enclosed within a support frame with the lower side of the substrate positioned upon the bottom surface of the enclosure forming a ground plane. A conductive plate is attached to the top cover of the enclosure through a layer of compensating material. As the temperature changes, the layer of compensating material expands or contracts, thereby varying the height of the conductive plate above the substrate, which changes the electromagnetic field pattern of signals propagating along the delay line and, consequently, the propagation velocity.

Abstract: An audio echo control unit for a video teleconference system is provided with a suppression attack time which is a function of the microphone-to-audio speaker distance and a suppression hangover time which is a function of the room characteristics. Echo which results from a double-talk condition is eliminated by removing the break-in capability, and receive signal level modulation is eliminated by removing any variable loss devices from the transmission path.

Abstract: The integrated data enciphering and channel encoding system consists of a message expansion function F, a convolutional encoder G.sub.e of code rate r.sub.e greater than the computational cutoff rate R.sub.comp, and an artificial noise generator emitting a noise sequence n. The expansion function F is the key to this integrated cryptosystem and can be any linear time varying or time invariant function, with or without memory. It can also be a block code or a convolutional code itself provided that the resultant concatenated convolutional code is non-catastrophic. The concatenation of the expansion function F with G.sub.e is equivalent to a new convolutional encoder G.sub.d .ident.FG.sub.e of code rate r.sub.d less than the computational cutoff rate R.sub.comp of the equivalent channel, but without knowledge of the expansion function F or the artificial noise n, the transmitted information rate appears to exceed R.sub.comp.

Abstract: A microwave guide switch having a rotor and stator each having ports spaced at 60.degree. intervals and a connecting waveguide transmission means connected to two ports spaced 120.degree. apart which forms a 3-position, 4-port switch.

Abstract: A multibeam communications satellite uses a dish-shaped reflector whose surface is a surface of revolution generated by rotating a plane parabola about an axis of revolution located in the plane of the parabola but angularly displaced from the axis of symmetry thereof. The line of revolution of the focal point of the parabola defines a focal circle, and a feed located on the focal circle will illuminate an area lying on a circle near the edge of the earth's apparent disc. Since every plane in which the axis of revolution lies is a plane of symmetry, the antenna exhibits good cross polarization cancellation, making the satellite particularly useful in frequency reuse communications systems.

Abstract: A FDM/TDM transmultiplexer uses sampling rate multiplication to increase the sampling rate for time division multiplexed (TDM) to frequency division multiplexed (FDM) conversion and decrease the sampling rate for FDM to TDM conversion. The rate multiplication filters are realized digitally in order to exploit the computational advantage of Fast Fourier Transform (FFT) algorithm, and channel filtering is implemented by a single time-shared sixth-order elliptic digital recursive filter. A novel FFT processor and recursive filter are disclosed which may be used in the system.

Abstract: A low-power voltage and low-power current driver for use with PIN diode phase shifters is disclosed. The driver uses transistors which function as emitter followers for rapid switching of the voltage applied to the PIN diode and as a voltage or current source for the diode bias. The driver provides for separate control of the reverse bias voltage and forward bias current applied to the PIN diode.

Abstract: An apparatus for blocking the transmission of echo signals in telephone communications circuits is disclosed. The apparatus employs a voice-activated switch in the transmit channel at each telephone terminal of the telephone circuit to block transmission of signals below a selectable threshold. Under all conditions where received speech signals are present at a telephone terminal, a higher threshold for the switch at that terminal is selected than would otherwise be used to block noise in the channel. This higher threshold is set above the level of the echo signals to prevent their transmission from that terminal by the switch.

Abstract: The interference components in a first composite signal are cancelled at baseband frequencies using a second composite signal. The first composite signal has a desired carrier and an interfering carrier. The desired carrier has a constant envelop and is angle modulated with baseband .phi..sub.1 (t). The interfering carrier has any type of modulation. The second composite signal has the interfering carrier. The first composite signal is angle demodulated. The first composite signal is also multiplied with the second composite signal. The product signal from the multiplier has a high and a low frequency component. The low frequency component is extracted from the product signal. The low frequency component is phase shifted by plus 90 degrees when the instantaneous frequency of the desired carrier is greater than the instantaneous frequency of the interfering carrier. When the instantaneous frequency relationship is reversed, the low frequency component is phase shifted by minus 90 degrees.

Abstract: An ion extraction system utilizing small hole accel grid (SHAG) optics is disclosed. A screen grid, an accel grid and a decel grid are positioned downstream of a neutral, highly ionized plasma source, and each of these grids have apertures in axial alignment. The accel grid has a relatively small aperture in the range of less than 50% to approximately 10% the size of the aperture of the screen grid. The electric field set up by the screen grid and the accel grid serve to extract an ion beam from the plasma source and focus the ion beam through the accel grid aperture. The small aperture in the accel grid is formed by drilling a relatively large aperture in the accel grid and then securing a thin metallic foil on at least the downstream face of the accel grid to cover the large, drilled aperture.The relatively small aperture is etched in the thin metallic foil by the ion beam.

Abstract: An SS-TDMA satellite system providing uplink and downlink interconnections through an on-board microwave switching matrix controlled by an on-board distribution control unit responsive to ground command signals. The distribution control unit is configured to permit both point-to-point and point-to-multipoint interconnections of uplinks to downlinks through the switching matrix. Point-to-point interconnections under system static mode control may be effected simultaneously with point-to-point interconnections under system dynamic mode control.

Abstract: A surface acoustic wave device is used as a unique word detector and coherent demodulator for a digital code differential phase-shift signal. The device improves code word detection by providing a coherent reference with a correlation gain of 10 log M dB. M is the additional number of fingers introduced into the surface acoustic wave device, which determine the phase of the unique word. To achieve this result with higher reliability and higher correlation coefficient, use is made also of a few bits of the clock recovery which precede the unique word in a preamble as used in Time Division Multiple Access (TDMA) systems.