A document discusses a multi-Gigabitper- second, Ka-band transceiver with a software-defined modem (SDM) capable of digitally encoding/decoding data and compensating for linear and nonlinear distortions in the end-to-end system, including the traveling-wave tube amplifier (TWTA). This innovation can increase data rates of space-to-ground communication links, and has potential application to NASA’s future spacebased Earth observation system.

The SDM incorporates an extended version of the industry-standard DVBS2, and LDPC rate 9/10 FEC codec. The SDM supports a suite of waveforms, including QPSK, 8-PSK, 16-APSK, 32- APSK, 64-APSK, and 128-QAM. The Kaband and TWTA deliver an output power on the order of 200 W with efficiency greater than 60%, and a passband of at least 3 GHz. The modem and the TWTA together enable a data rate of 20 Gbps with a low bit error rate (BER).

The payload data rates for spacecraft in NASA’s integrated space communications network can be increased by an order of magnitude (>10×) over current state-of-practice. This innovation enhances the data rate by using bandwidth- efficient modulation techniques, which transmit a higher number of bits per Hertz of bandwidth than the currently used quadrature phase shift keying (QPSK) waveforms.

This work was done by Rainee N. Simons and Edwin G. Wintucky of Glenn Research Center; and Francis J. Smith, Johnny M. Harris, David G. Landon, Osama S. Haddadin, William K. McIntire, and June Y. Sun of L-3 Communications Systems–West.

Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Innovative Partnerships Office, Attn: Steven Fedor, Mail Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. LEW-18735-1

NASA Tech Briefs Magazine

This article first appeared in the December, 2011 issue of NASA Tech Briefs Magazine.

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