Accession Number:

ADA000425

Title:

A Digital Spectral Limiter for a Synchronous Multiple-Access Satellite Communication.

Descriptive Note:

Technical note,

Corporate Author:

MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB

Personal Author(s):

Report Date:

1974-08-08

Pagination or Media Count:

158.0

Abstract:

A satellite processing concept for automatically power-balancing the simultaneous accesses of non-cooperative users was investigated. Basically, the scheme consists of a forward and backward fast Fourier transformation with an intermediate clipping operation on spectral magnitudes exceeding an adaptive threshold. The clipper is suitable for applications involving many low-cost mobile terminals where the transmitting terminals need not or cannot pre-correct Doppler shifts or fine timing. As a satellite component preceding a bandpass hard-limiting transponder, the spectral clipper presents an easier alternative to complete in-satellite demodulation of the user signals. Computer simulations of ten pseudorandomly specified users indicate a significant improvement in the performance of the weaker users compared to a hard-limiting transponder. Both an orthogonal block code and a convolutional code with maximum-likelihood decoding were simulated. The spectral-clipping scheme would also be effective with PSK modems and in strong narrowband interference. Implementations composed of 100 integrated circuit packages consuming 10 watts of power are feasible. Author

Subject Categories:

  • Radio Communications

Distribution Statement:

APPROVED FOR PUBLIC RELEASE