Abstract: Two harmonic mixers arranged in parallel are connected to a first signal frequency gate and to a second local frequency gate by means of a single radiofrequency hybrid circuit in quadrature or by means of respective hybrid circuits of which one in quadrature and centered on the signal frequency and the other in phase, quadrature or opposition of phase and centered on the local frequency. Another intermediate frequency hybrid circuit in quadrature connects the two mixers to a third intermediate frequency gate and to a fourth gate closable on a termination. In this manner there is obtained a harmonic frequency conversion with image suppression.

Abstract: A circuit and method for the acquisition of carrier synchronism in coherent demodulators which operate with carriers modulated by Phase-Shift Keying (PSK). The invention makes use of simple, low-cost circuitry and gives the phase-lock loop of the demodulator an added frequency characteristic which prevents false locks and ensures lock between the local carrier and the reference signal even for very large frequency variations.

Abstract: An angular-diversity radiating system is described for tropospheric-scatter radio links which comprises a paraboloid and two antenna horns in which the distance between the antenna horns is adjustable in order to vary the diversity angle depending on the transmissive characteristics of the troposphere of the link involved to always have the optimal diversity angle under all link conditions.The radiating system includes four wave guides connected to the two antenna horns to permit the use of single and double polarization for both the antenna horns and the use of both the antenna horns, or alternatively only one, for receiving and transmitting signals.

Abstract: An angular-diversity radiating system is described for tropospheric-scatter radio links which accomplishes a symmetrical Cassegrain optic in transmission and is parabolic with a central focus in reception, respectively. This is accomplished by a subreflector formed of parallel metal conductors and shaped with a hyperbolic profile which is centered on the axis of the main reflector at a predetermined distance between the transmitting horn and the receiving horns. The electromagnetic waves leaving the transmitting horn and directed toward the subreflector are polarized with the electric field vector parallel to the metal conductors of the subreflector such as to be reflected toward the main reflector which reradiates them. The electromagnetic waves received are polarized orthogonally to the transmitted waves and thus pass undisturbed through the subreflector to reach the receiving horns.

Abstract: An instantaneous comparison unit with an associated sequential state logic circuit is described which functions to maintain a condition of phase locking with a reference signal which is substantially immune to disturbances which cause losses or additions of signal fronts. Continuous phase shifting conditions during the transient, which precedes phase locking, is detected and compensated for by the disclosed circuit.

Abstract: A microwave resonating cavity including a hollow cylindrical body shaped in the form of a parallelepiped and consisting of a dielectric material coated by a metallic layer, said dielectric material having a high dielectric constant having a value greater than 30, and wherein said hollow body includes an upper base, a lower base, an external surface and an internal surface, and further includes a non-metallized area defining a metallized coupling line onto the external surface of the said hollow cylinder and wherein said hollow cylinder has an inner diameter ranging between 3 and 5 mm, an outer diameter ranging between 6 and 15 mm and a height ranging between 5 and 10 mm, and further including a metallic cap welded to the upper base of said hollow body, and further including an adjusting screw for fine adjustment of the resonating frequency.

Abstract: A microwave metallic cavity, whose resonating frequency is stabilized versus operating temperature variations. Stabilization is achieved by implementing the cavity with a conical base having a thickness and a coefficient of linear expansion smaller than that of the cavity cylindrical body. In this way the volume enclosed by the conical base to in inverse ratio versus operating temperature variations, so as to compensate for the variation in volume of the cavity cylindrical body, which results in stabilization of the resonating frequency.

Abstract: A predistorter for use in transmission systems which employ power amplifiers, employing traveling wave tubes or field effect transistors. Since these active components present a nonlinear characteristic, which introduce amplitude and phase distortion in the amplified signal, the distorter circuit operates to subtract the distortion products from the output signal. In the present arrangement, the subtraction takes place before amplifying the signal by means of generation of distortion products which will present the same amplitude and opposite phase of those that will be generated by the power amplifier in order to obtain an undistorted and amplified signal.