Impact of a new TWTA linearizer upon QPSK/TDMA transmission performance
Abstract
In transmitting a band-limited PSK/TDMA signal via satellite, the signal is distorted due to the nonlinearities of an earth station HPA and a satellite TWTA. To reduce the impairments due to these nonlinearities, a new TWTA linearizer, called a soft-limiter type linearizer (SL-LRZ), has been developed. The overall amplitude characteristic of a TWTA associated with an SL-LRZ is linear up to saturation and has a constant envelope beyond saturation. As to the AM/PM conversion characteristic, it has almost zero phase shift, irrespective of the operating point. The TWTA with SL-LRZ gives better bit error rate (BER) performance and less out-of-band emission (OBE) compared to cases where TWTA is operated by itself or with a conventional linearizer. In this paper, the impact of the new TWTA linearizer upon the transmission performance of a QPSK/TDMA signal is described. The transmission performance over a nonlinear satellite channel has been evaluated experimentally using a 120 mbit/s QPSK modem and an Intelsat V channel simulator.
- Publication:
-
IEEE Journal on Selected Areas in Communications
- Pub Date:
- January 1983
- Bibcode:
- 1983IJSAC...1...39S
- Keywords:
-
- Communication Satellites;
- Phase Shift Keying;
- Pulse Communication;
- Time Division Multiple Access;
- Transmission Efficiency;
- Traveling Wave Amplifiers;
- Bit Error Rate;
- Nonlinearity;
- Signal Distortion;
- Communications and Radar