| 摘要 |
PROBLEM TO BE SOLVED: To provide a radar altimeter system with closed loop modulation for generating more accurate radar altimeter values.SOLUTION: A transmitter includes a direct digital synthesizer 82 generating a reference signal based on a multiplied clock signal and a control signal; a low pass filter 78 receiving the input reference signal generated by the direct digital synthesizer; a mixer 76 receiving the reference signal input from the low pass filter 78 and offsetting the reference signal by combining the reference signal and the multiplied clock signal; and a band pass filter 72 receiving the offset reference signal input from the mixer 76. A multiplier constituent element, the low pass filter, the mixer, and the band pass filter translate the linear frequency ramp of the direct digital synthesizer up to VHF or UHF frequencies, and a phase-locked loop circuit generates a radar signal based on the offset reference signal. |
