| 摘要 |
PURPOSE:To make it possible to use the receiver on an aircraft, by using two different high temperature noise source having different noise temperatures as noise sources for calibration, in the receiver of a microwave radiometer, which receives electromagnetic waves radiating from an object to be observed. CONSTITUTION:Electromagnetic waves radiating from an object to be observed is received by a receiving antenna 1 and inputted to a measuring and calibrating switch 2. At the time of calibration mode, the switch 2 is connected to a calibration source switch 5. The signal outputted from the switch 2 passes a Dicke switch 7, which switches the signal and a Dicke load 6 at a high speed and performs rectangular modulation, and is sent to an RF/IF circuit 8. Then the signal is detected by a square detector 9. The level is adjusted to AGC operation by a step attenuator 10. The result is converted into a DC voltage by a synchronous detector 11. The converted voltage is integrated 13 and again converted to a digital value by an AD converter 14. Calibrating high temperature noise sources 15 and 16 are connected to the switch 5. The noise temperatures of the noise sources 15 and 16 are set for different values. Therefore, the calibration can be performed in a microwave radiometer mounted on an aircraft. |
