Showing papers on "Conformal antenna published in 1969"

Large-aperture expandable truss microwave antenna

Abstract: A space erectable truss antenna concept capable of deploying a rigid, lightweight (0.1 lb/ft2of aperture), parabolic reflector from 5 to 300 feet in diameter is discussed. A three-dimensional spring-loaded truss retracts into three optional packaging configurations, such that, a 100-foot diameter antenna can be packaged into a 10-foot payload envelope. Depth of the deployed antenna truss reduces thermal distortion enabling surface tolerance-to-diameter ratios less than 2 \times 10^{-4} to be achieved over the orbit. While the deployment is completely automatic, all functions can be supported by an astronaut. RF tests have been conducted on a 6-foot working model at 15 GHz with a peak gain frequency projected at 30 GHz.

The design of the mechanically despun antenna for the Intelsat III communications satellite

Abstract: The use of a spin-stabilized communications satellite of large channel capacity requires a high-gain antenna which may be despun, mechanically or electronically, with respect to the satellite. The design of a mechanically despun antenna system for the Intelsat-III communications satellite is discussed. The communications signals utilize a high-gain directive antenna which is mechanically despun while an omnidirectional antenna is used for the telemetry information. Positional control of the directional antenna is provided by the control electronics subsystem such that the antenna is always pointed directly at the earth. Satellite-borne infrared earth sensors provide earth reference pulses to the control electronic subsystem for antenna despin stabilization and pointing. Also discussed is the bearing and lubrication system for the antenna drive assembly. In-orbit performance of the two systems launched is also given.

A method of controlling current distributions on long antennas

Abstract: It is shown that a long cylindrical antenna with multiple excitations can be made to have desirable current distributions along its structure when the driving voltages and the positions of the generators are properly chosen. Applications of this technique to practical problems are discussed.

Phase principle for measuring antenna temperature

Abstract: A phase principle for measuring the temperature of a radio or radar antenna is described. The phase principle makes use of phase information exclusively and is therefore insensitive to receiver gain fluctuations. Under certain conditions the potential accuracy of the measurement is somewhat better than the potential accuracy of the corresponding measurement resulting from a balanced Dicke radiometer.

Polarization discrimination for satellite communications

Abstract: It appears feasible for satellite relay systems to provide polarization discrimination of 20 to 30 dB (or more with adaptive antennas) in the antenna main beam Thus if the systems are designed to operate with smaller wanted to unwanted signal ratios than those provided by polarization discrimination, it should be possible to double the effective spectrum available by using it independently on two orthogonal polarizations

On the receiving properties of a small horizontal bare circular loop antenna buried in the ground

Abstract: It is shown that when a small bare circular loop antenna is buried in the ground it will respond to a vertically ( E field) polarized ground-wave or sky-wave source with a directional azimuthal pattern. The response to a horizontally polarized skywave source is greatly enhanced by burying the antenna and is also shown to be far from omnidirectional in azimuth. These results depend upon the presence of a relatively small departure from a constant current distribution on the loop when it is regarded as a driven element. The current distribution formulas of Chen and King permit easy analytical estimates of these effects.