Transmission-line mismatches and system noise figure

Mismatches and system noise factor play a particularly important part in high-sensitivity low-noise receivers, e.g., those used in satellite communication, since raising the threshold might significantly increase the length of communication time during the satellite orbit. Analysis shows that the difference between the actual system noise and that calculated for matched conditions can be of importance; this analysis permits accurate prediction of the noise figure when the performance of individual parts of the system is known. Power delivered by a r.f. generator to a load, through a transmission line, is determined as a function of standing wave ratios and reflection coefficients, instead of the conventional series or parallel impedances of equivalent circuits.