Cselt-centro Studi E Laboratori Telecomunicazioni S.p.a.

Paolo Bielli

Salvatore De Padova

Salvatore Contu

Giuseppe Cocito

Dario Savini

Renato Barboni

Antonio Castellani

Daniele Bresciani

Carlo Arduini

Ugo Ponzi

A method of manufacturing dichroic antenna structures, which makes use of a projector mounted on the mobile arm of a computer-controlled machine to project the shape of selective antenna elements on the surface of an insulating layer, clad with a metallic layer covered in turn with a photographic emulsion. Development and chemical etching of the excess conductive parts are then carried out.

Method of making a dichroic antenna structure

This structure for a dichroic antenna can be used in a reflector antenna capable of operating at the same time at two different frequencies or with two orthogonal polarizations, and presents mechanical characteristics allowing its use on board the satellites. The structure, suitable for a subreflector, comprises a plurality of layers with high mechanical stiffness in the external part, followed by layers with low dielectric constant and one or a plurality of metallic grids in the most internal part, separated by low-dielectric constant layers.

Structure for a dichroic antenna

To track an object such as a space probe or a satellite emitting an electromagnetic radio signal, the signal received at a ground antenna is passed through a circular waveguide section propagating modes TE.sub.11 and TE.sub.21. Polarized signal components of the higher TE.sub.21 mode are extracted from the waveguide through two pairs of lateral slots and their differences are multiplied by an r-f reference signal of the same frequency obtained from a preamplifier coupled to an output port to which the signal of mode TE.sub.11 is transmitted by way of a rotatable polarization changer. Corrective signals resulting from these multiplications are proportional to spatial coordinates of the tracked object in a predetermined Cartesian system, one of whose axes coincides with that of the waveguide section, and serve to keep the antenna trained upon the object. The polarization changer is rotated until the signal power available at the output port is a maximum, a corresponding rotation being imparted in the case of a linearly polarized radio signal to the circular waveguide section.

Method of and system for tracking an object radiating a circularly or

A parabolic reflector antenna, designed to discriminate between incoming and outgoing waves having mutually orthogonal planes of polarization, has a ratio R between focal distance f and diameter D which, for optimum efficiency and cross-polarization decoupling, lies between 0.46 and 0.5 and operation in the TE.sub.11 mode and above 0.6 for operation in the dual TE.sub.11 +TM.sub.11 mode. An associated feed, in the shape of a slightly tapering horn of circular cross-section connected to a waveguide of square cross-section, has a relative aperture .alpha., defined as the ratio between its aperture radius r and the wavelength .lambda..sub.o at the center of the operating frequency band, which in the first instance ranges between 0.52 and 0.6 and in the second instance is given by kR+h with k.apprxeq.1 and h between about 0.1 and 0.15.

Growing community of inventors

Cirie-Torino, Italy

Paolo Bielli