| 摘要 |
PURPOSE:To make it possible to easily change the response time of the change in receiving gain, to change gain even if a S/N ratio is inferior and to keep a receiving level constant, by calculating the square average value of error voltage through the level comparison of a detection receiving signal and a reference signal to control an analogue attenuator. CONSTITUTION:In the synthetic aperture radar mounted to an artificial satellite, the part good in a S/N ratio of a receiving signal is cut off in a time window controlled by a gate signal from a controller 16 corresponding to the altitude and posture of a platform to a detector 13 and the output of this detector 13 is compared with the reference signal from the controller 16 corresponding to reference signal command in a comparator 14 while error voltage subjected to A/D conversion is supplied to the controller 16. Subsequently, the square average value voltage of time constant of error voltage is calculated and corrected corresponding to time constant command to control an analogue attenuator 11 through a gain setting circuit 17 and a D/A converter 18. By this method, a variable condenser is dispensed with and the change in a receiving gain response time is easily performed and, even if S/N is inferior, desired gain setting can be performed and a receiving level can be made constant. |
