국내 최대 기계 및 로봇 연구정보

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타이틀	Peak Satellite-to-Earth Data Rates Derived From Measurements of a 20 Gbps Bread-Board Modem
저자	Landon, David G.;; Simons, Rainee N.;; Wintucky, Edwin G.;; Sun, Jun Y.;; Winn, James S.;; Laraway, Stephen A.;; McIntire, William K.;; Metz, John L.;; Smith, Francis J.
Keyword	COMMUNICATION SATELLITES;; DATA LINKS;; EXTREMELY HIGH FREQUENCIES;; FIELD-PROGRAMMABLE GATE ARRAYS;; MODEMS;; PROTOTYPES;; QUADRATURE AMPLITUDE MODULATION;; RADIO FREQUENCIES;; RATES (PER TIME); TRAVELING WAVE AMPLIFIERS;; WAVEFORMS
URL	http://hdl.handle.net/2060/20110023429
보고서번호	NASA/TM-2011-217241
발행년도	2011
출처	NTRS (NASA Technical Report Server)
ABSTRACT	A prototype data link using a Ka-band space qualified, high efficiency 200 W TWT amplifier and a bread-board modem emulator were created to explore the feasibility of very high speed communications in satellite-to-earth applications. Experiments were conducted using a DVB-S2-like waveform with modifications to support up to 20 Gbps through the addition of 128-Quadrature Amplitude Modulation (QAM). Limited by the bandwidth of the amplifier, a constant peak symbol rate of 3.2 Giga-symbols/sec was selected and the modulation order was varied to explore what peak data rate might be supported by an RF link through this amplifier. Using 128-QAM, an implementation loss of 3 dB was observed at 20 Gbps, and the loss decreased as data rate or bandwidth were reduced. Building on this measured data, realistic link budget calculations were completed. Low-Earth orbit (LEO) missions based on this TWTA with reasonable hardware assumptions and antenna sizing are found to be bandwidth-limited, rather than power-limited, making the spectral efficiency of 9/10-rate encoded 128-QAM very attractive. Assuming a bandwidth allocation of 1 GHz, these computations indicate that low-Earth orbit vehicles could achieve data rates up to 5 Gbps-an order of magnitude beyond the current state-of-practice, yet still within the processing power of a current FPGA-based software-defined modem. The measured performance results and a description of the experimental setup are presented to support these conclusions.