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Modem Characterization Through a Wideband, Hard-Limited Ka-Band Satellite ChannelNASA is using a commercial customized TDMA/FDMA bandwidth on demand modem for use with the Advanced Communications Technology Satellite (ACTS) to highlight the numerous services and experiments that can be performed using small Ka-Band terminals. Characterizing the modems proved challenging due to the characteristics of the satellite transponder. The ACTS channel is hard-limited and up to 900 MHz wide. The channel has some unusual dynamic properties due to the satellite and antenna system, which make modem testing through the satellite challenging and the test requirements stringent. The satellite Multi-Beam Antenna (MBA) has a 1 hertz oscillation induced by the momentum wheel, which causes the transmit antenna pattern to move slightly. This results in a 1 hertz oscillation in the ground station receive power, with amplitude changes up to 1 dB depending on terminal location within a spot beam and associated gain slope. In addition, ACTS experiences a solar induced "thermal event" each day. This "thermal event" occurs when the sun heats the antenna support structure causing the transmit and receive reflectors to mispoint. This results in a slowly decreasing or increasing power density at the ground station receiver as the antenna pattern moves off bore-site. This paper describes the method used to fully characterize the TDMA/FDMA modem through the ACTS wideband, hard-limited transponder. In particular, techniques are discussed for conducting RF measurements on such a channel, the affect that the thermal characteristics and 1 hertz variations have on the accuracy of the results, and suggested means to minimize the error and provide useful and valuable data.
Document ID
20000004588
Acquisition Source
Glenn Research Center
Document Type
Conference Paper
Authors
Reinhart, Richard C.
(NASA Glenn Research Center Cleveland, OH United States)
Ivancic, William
(NASA Glenn Research Center Cleveland, OH United States)
Tanger, Tom
(Communications Satellite Corp. Clarksburg, MD United States)
Cronon, Chris
(Communications Satellite Corp. Clarksburg, MD United States)
Lee, Donald
(Communications Satellite Corp. Clarksburg, MD United States)
Kifer, David R.
(Cortez 3 Service Corp. Cleveland, OH United States)
Date Acquired
September 7, 2013
Publication Date
December 1, 1999
Subject Category
Space Communications, Spacecraft Communications, Command And Tracking
Report/Patent Number
NAS 1.15:209454
NASA/TM-1999-209454
E-11951
Meeting Information
Meeting: Ka-Band Utilization
Location: Taormina
Country: Italy
Start Date: October 18, 1999
End Date: October 20, 1999
Sponsors: Istituto Internazionale delle Comunicazioni
Funding Number(s)
PROJECT: RTOP 632-50-5A
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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