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Golshan, N.

Publications and source records attributed to Golshan, N..

27 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

L-Band Mobile Terminal Antennas for Helicopters

The feasibility of using a low gain antenna (LGA) as a mobile terminal antenna for helicopters is described in this paper. The objectives are 1) to select the lowest cost antenna system which can be easily mounted on a helicopter and capable of communicating with a satellite, and 2) to determine the best antenna position on the helicopter to mitigate the signal blockage due to rotor blades and the multipath effect from the helicopter's body. The omni-directional low gain antenna (LGA) is selected because it is simple, reliable, and low cost. The helix antenna is selected among the many LGAs because it is the most economical one and has the widest elevation beamwidth. Both 2-arm and 4-arm helices are studied experimentally to determine the antenna's performance and the scattering effects from the helicopter's body. It is found that the LGA should be located near the tail section and at least 8 inches above the helicopter.

helicopter↗
NASA NTRS1993

Direct Broadcast Satellite-Radio, Receiver Development

This paper reports on the status of the ongoing Direct Broadcast Satellite-Radio (DBS-R) Receiver Development Task being performed at the Jet Propulsion Laboratory, California Institute of Technology (JPL). This work is sponsored by the Voice of America/U.S Information Agency through an agreement with NASA.

Radio↗
NASA NTRS1993

Mobile terminal antennas for helicopters

In this paper, the feasibility of using an L-band low gain antenna (LGA) as a mobile terminal antenna for helicopters is described. The objective is to select the lowest cost antenna system which can be easily mounted on a helicopter and capable of communicating with a geosynchronous satellite. To ensure that all the antenna options are being considered, the steerable high gain reflector and medium gain array antennas as well as LGA are studied and compared in an exhaustive survey. The high gain reflector antenna in L-band is usually very large in size and heavy in weight. In addition, a bulky and expensive tracking system is needed to steer the antenna beam to the satellite direction. The medium gain antennas (including mechanically and electronically steered arrays) are also more expensive and less reliable than an LGA due to the addition of a beam steering system to track the satellite. The omni-directional LGA is simple, reliable, and inexpensive. It is typically ten times smaller than the medium gain antenna. This makes the position, selection, and mounting on the helicopter relatively easier. Therefore, the LGA is selected as a mobile terminal antenna for helicopters. Among the many LGA's (cross-dipole, helix, spiral, and slot antennas), the helix antenna is the most inexpensive. One can also change the size, shape, or pitch angle of the helix to optimize the gain in the desired direction. Therefore, the helix antenna is selected for further study. Both 2-arm and 4-arm helices are studied theoretically and experimentally to determine the antenna's performance and the scattering effects from the helicopter body and the blades. The multipath, Doppler, and Doppler rate issues as well as the periodic fading effects caused by the helicopter rotor blades will be briefly discussed in the paper.

Wu, Te-Kao↗
NASA NTRS1993

L-band mobile terminal antennas for helicopters

The feasibility of using a low gain antenna (LGA) as a mobile terminal antenna for a helicopter is described in this paper. The objectives are to select the lowest cost antenna system which can be easily mounted on a helicopter and capable of communicating with a satellite, and to determine the best antenna position on the helicopter to mitigate the signal blockage due to rotor blades and the multipath effect from the helicopter's body. The omnidirectional LGA is selected because it is simple, reliable, and low cost. The helix antenna is selected among the many LGA's because it is the most economical one and has the widest elevation beamwidth. Both 2-arm and 4-arm helices are studied experimentally to determine the antenna's performance and the scattering effects from the helicopter's body. It is found that the LGA should be located near the tail section and at least eight inches above the helicopter.

Wu, T. K.↗