Abstract :
A circulating test loop setup for simulating an N-hop 2-PSK direct regenerative system in the laboratory, is described. A 2-PSK direct regenerator at carrier frequency fc = 2 GHz and bit-ratefb = 50 Mbit/s is designed and included in the test loop. The N-hop transmission is simulated by allowing a 2-PSK sequence of 16 bit to enter the test circuit and to circulate N times through the regenerator and a mini-coax loop of 500-ns delay. In direct regenerative systems the "pulses" are only partially regenerated. Therefore, the influence of one regenerator on the noise and the error-rate of the entire system cannot be exactly calculated, even if the characteristics of that regenerator are completely known. It is necessary to treat the system as a connected whole. This is rather comprehensive and requires many assumptions and approximations. The actual laboratory simulation setup will therefore be of great practical importance, and a valuable tool for investigating the influence of different parameters from a system point of view. The influence on for instance the error rate of the entire system caused by heavy rain attenuation on one or two repeater sections, cochannel and intersymbol interference, additive noise, time varying channels, etc., can be studied. The mode of operation of the test setup is illustrated by experiments.
