Abstract: A waveguide structure composed of circular waveguide cavities resonant in the TE.sub.011 mode is capable of realizing the most general bandpass filter characteristics with significant decreases in filter loss and gain slope. In addition to the commonly used Tchebychev and Butterworth functions, the structure can realize general transfer functions including the elliptic function. In its simplest form, the structure is composed of four cylindrical cavities which form a building block for more complex filters. The first and second cavities and the third and fourth cavities each have their side walls in contact and their end walls in common planes. The third and fourth cavities are superposed to the first and second cavities with their adjacent end walls in a common plane, but the second and third cavities are offset so that they overlap at one-half diameters. The first and second cavities are coupled by means of a centrally located side wall slot, as are the third and fourth cavities.

Abstract: An interference reduction circuit to provide isolation in frequency reuse systems operates on two or more non-isolated signals by cross-coupling the signals such that the interfering signals are cancelled on each channel. In a dual-polarized frequency reuse system, cancellation is effected by adding a sample of an oppositely polarized channel of equal amplitude, but of opposite phase, to the interference. Practical implementation includes closed-loop, digital feedback control to permit dynamic signal-to-interference improvement involving no a priori knowledge of the nature of the incoming signals. The circuit has applications in satellites and earth stations in a communications satellite system.

Abstract: A planar microwave integrated circuit, including features of slot lines and coplanar lines, for use as a magic tee and a power divider.

Abstract: A method of applying an anti-reflective coating, particularly a metal oxide coating to a solar cell during the manufacture of such cell.

Abstract: A pilot signal for implementing automatic frequency control in a satellite communications system is continuously transmitted by a designated ground station. Its frequency lies in the middle of the communications band so that it will undergo the same frequency shifts or distortions as the overall communications signal. A second ground station monitors the presence of the pilot signal, and if it is lost for a predetermined time, this second station then transmits the pilot signal to ensure the continuation of the AFC function throughout the system. If the pilot signal is lost at the second station, however, an uncertainty might exist as to whether the failure is in the designated ground station or the second ground station. To resolve this uncertainty a secondary pilot signal, having a frequency different from but in the same band as the primary pilot signal, is transmitted by a third ground station.

Abstract: A low noise, multistage microwave transistor amplifier constructed using microwave integrated circuit techniques is disclosed. The illustrated embodiment is a two-stage transistor amplifier which is the basic building block for broadband, high-gain cascades. This amplifier features an interstage network consisting of a very short transmission line which minimizes the size and frequency dependence of the amplifier. This is achieved in the satellite communications band of 3.7 to 4.2 GHz by constructing the amplifier on a suitably low dielectric constant substrate rather than the usual high dielectric constant substrates used in microwave amplifier applications.

Abstract: The low noise parametric amplifier disclosed is a non-cryogenic non-redundant plural stage unit with excess gain such that failure of any one stage results in only minor degradation of signal-to-noise ratio. While the amplifier is of general application, it is specifically intended for use in the receiver of an unattended earth terminal of a satellite communication system. In this environment, reliability is achieved by employing a plurality of cascaded, modular parametric amplifier stages. Each stage includes a varactor diode, a pump circuit with its oscillator, a bias circuit, and temperature stabilizing circuitry employing a Peltier junction. The stages are connected to a multi-port circulator by quick disconnect couplings which permit the modular amplifier stages to be removed and replaced without any interruption in the operation of the amplifier.

Abstract: The valve is comprised of a substantially oblong chamber having one end thereof extending transversely into a conduit having a semi-circular slot formed therein. The portion of the chamber extending into the conduit is provided with a through passage in alignment with the conduit and a valve disc is movably mounted in the chamber for transverse movement relative to the conduit between an operative position in alignment with the conduit and an inoperative position outside of said conduit. An inflatable tube is secured in a peripheral groove in the circumference of the disc and is disposed in fluid communication with the interior of a hollow valve stem secured to the disc and extending outwardly of the chamber. A piston is connected to the valve stem for reciprocating movement in a double acting fluid cylinder and the extreme end of the valve stem extends into a chamber connectable to a source of air under pressure by a suitable valve to control the inflation of the inflatable tube.