In-orbit measurement of noise figure of on-board transponder. II - Measured result of CS transponder

This paper reports the results of noise figure measurement on the transponder of Japan's communication satellite (CS). The noise figure of transponder is one of the important parameters of satellite link because it is approximately proportional to the uplink carrier-to-noise ratio. The measurement was carried out by using a new method which seems to be suitable for a transponder of an in-orbit satellite. In this measurement, the measured values are affected by the input-to-output nonlinearity of TWT amplifier. The noise figures of the first stage receiver are calculated by correcting the nonlinear effect. The measured noise figure was compared with the prelaunch data in order to estimate the degradation which might occur after launch.