| 摘要 |
PURPOSE:To suppress unneeded radio waves with a better frequency selection property, by generating a response signal only when the transmission frequency and the radar frequency comes close to or equals each other. CONSTITUTION:A mixer 7 mixes the frequency fT of an output signal from a directivity coupler 2 and the frequency fR of a reception signal from an antenna to pick out the differential frequency component of fT-fR. This output is amplified with a video amplifier 8 at the next stage, the output of which is compared with a set voltage V by a voltage comparator 9 and operates a response code generator 10 at the next stage to generates a specified code and after modulated with an amplification pulse modulator 3, it is emitted from the antenna 4 as response code. In this case, it is so arranged that the response code is generated only when the radar frequency fR comes close to or equals the transmission frequency fT from a radar beacon oscillator 1 thereby enabling the suppression of unneeded radio waves with a frequency selection property.
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