Feed horn

About: Feed horn is a research topic. Over the lifetime, 2395 publications have been published within this topic receiving 26548 citations. The topic is also known as: feedhorn.

On-orbit reconfigurability of a shaped reflector with feed/reflector defocusing and reflector gimballing

Abstract: A system and method for changing the radiation pattern of an antenna assembly of a satellite in orbit is provided. The antenna assembly includes a reflector antenna fed by a feed assembly. The reflector antenna transmits and receives signals within a radiation pattern. The reflector antenna and the feed assembly are movably mounted to a sliding mechanism so that they can be displaced with respect to one another. The displacement causes defocusing as the reflector antenna is displaced from the focus point. The defocusing causes the radiation pattern to become more compact or broadened. Thus, the radiation pattern of the satellite provided with a single reflector antenna and a single feed element may be changed while the satellite is in orbit. The system and method include gimballing the reflector antenna to steer the radiation pattern.

Development of ALMA Band 8 (385-500 GHz) Cartridge

Abstract: We have developed a cartridge-type receiver covering from 385 to 500 GHz for pre-production of ALMA Band 8. It receives two orthogonal polarizations and down-converts the sideband-separated signals to intermediate frequencies (IF) between 4 and 8 GHz. The cartridge-type receiver consists of a cold optics, a feed horn, an OMT, two sideband-separating SIS mixers, cryogenic multipliers of local oscillator (LO). These components were individually tested and then the cartridge was integrated and tested as a complete assembly. We have also developed equipment to test both components and the integrated receiver. The single sideband (SSB) noise temperature of this receiver is 130 K at the band center and 180 K at the band edges. The beam pattern and cross-polarization pattern are consistent with physical optical calculation. These results are promising for receiver production to the Atacama Large Millimeter/submillimeter Array (ALMA).

Helicopter rotorblade radar system

Abstract: A radar system for a helicopter having a mast and a plurality of blades coupled to the mast by shaft portions of the blades includes a transmitter and a receiver respectively transmitting and receiving a pulsed radar beam through a feed horn, a generator for generating the radar beam energy for transmission by the transmitter, a processor, a display, and a passive reflectarray deposited on the underside of at least one blade of the helicopter. The reflectarray is a preferably flat array of passive microstrip elements which can impart a phase to the radar beam. A typical microstrip element is a patch whose dimensions may be controlled, and the size of which determines the phase for the location within the array of that element. The reflectarray is provided with a pattern which is designed to scatter the radar beam in a desired shape and direction to produce uniform mapping of the terrain over which the helicopter travels. According to another embodiment, a passive reflectarray is provided to the underside of at least one blade, while another passive reflect is provided to the topside of at least one blade, thereby permit both terrain and sky mapping. The radar system of the invention provides a radar system utilizing a lightweight and inexpensive passive radar reflector for use on helicopters of all sizes, and achieves 360° coverage.

Facility and method for the detection and monitoring of plumes below a waste containment site with radiowave tomography scattering methods

Abstract: An embodiment of the present invention is a toxic waste containment facility subject to leaking hazardous plumes into soils beneath and adjacent to the site. The facility includes a plurality of substantially horizontal underground drillholes adjacent to and below a waste containment pit. A radio transmitter and antenna are placed in a first underground drillhole proximate to a surface waste containment site. A radio receiver and antenna are placed in a second underground drillhole opposite to the first drillhole. A position indicator is used for gauging a plurality of locations of the radio transmitter and antenna within the first underground drillhole and the radio receiver and antenna within the second underground drillhole. A data processing unit analyzes data received from radio receiver and antenna and position indicator to measure radio signal attenuation between the radio transmitter and antenna and radio receiver and antenna. The transmitted signal from the radio transmitter and antenna are synchronized by a signal from the data processing unit. Fiber optic cables are used to couple signals between the radio transmitter and antenna and radio receiver and antenna with the data processing unit. Along each path, the operating frequency is increased until all of the transmitted energy is absorbed along the path to maximize resolution. Tomographic techniques are used to translate the data collected from a variety of transmitter and receiver positions into attenuation profiles that can image a toxic plume beneath the containment pit.

Cross-Polarization Cancellation in an Offset Parabolic Reflector Antenna Using a Corrugated Matched Feed

Abstract: This letter presents the design of a dual-mode corrugated matched feed to cancel the unwanted high cross polarization and beam squinting in an offset parabolic reflector antenna. The matched feed concept has been implemented in a cylindrical corrugated structure by adding a higher order HE21 mode to the fundamental HE11 mode. The designed feed was then used to illuminate a linearly, as well as a circularly, polarized offset parabolic reflector antenna, and the secondary radiation patterns were computed. Significant improvement in the cross polarization was observed when the results were compared to that of a conventional corrugated horn illuminated offset reflector antenna.