Optimization of SS-TDMA communication satellite payload

The effect of rain attenuation on the design and performance of an SS-TDMA system is discussed. The relationship between multiple beam antennas (MBA) sidelobe and microwave switch matrices (MSM) isolation levels and the performance of a digital communications link operating in a SS-TDMA system is derived. The relationship between these isolation levels and the complexity of the MBA and MSM hardware is also discussed. In general, the MBA sidelobe isolation should be at least 30 dB with uncoded operation and three dB pointing loss. Use of the rate 7/8(118,122) BCH error correcting code allows reduction of the sidelobe ratio to 25 dB without significant loss in performance. However, the data rate is reduced by 12.5 percent. The difficulty in achieving 30 dB sidelobe isolation in the MBA is significant, but performance improves if a regenerative repeater with onboard demodulation and remodulation is used. A MSM switch isolation of greater than 30 dB is readily achievable.