| 摘要 |
PROBLEM TO BE SOLVED: To obtain a radar transponder which transmits only a neighborhood of a receiving signal frequency and reduces signals which become noises to other vessels as compared with the prior art. SOLUTION: A pulse radar signal entering from a reception antenna 50 is passed through one of a plurality of filters 52 which has a center frequency closest to a frequency of the signal, and inputted to a signal detection logic circuit 53. A frequency of an intermediate frequency oscillator 54 corresponding to the filter 52 is determined and swept. A pulse with information of the radar transponder itself is inputted to a pulse width control circuit 55, thereby pulse modulating an output of the intermediate frequency oscillator 54. A power source for a microwave oscillator 57 and a microwave amplifier 58 is turned on by a transmission gate circuit 56. Outputs of the intermediate frequency oscillator 54 and microwave oscillator 57 are converted to microwave outputs of a frequency including the pulse radar signal frequency by an up converter mixer 59. After amplified, the outputs are transmitted by a transmission antenna 61.
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