| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a pulse Doppler radar which prevents the degradation of the noise figure of a reception system and which enhances the performance of a detection distance, by a method wherein a difference is formed between the frequency of a transmission signal and the frequency of a local oscillation signal. SOLUTION: An oscillator 6 outputs a first high-frequency signal and a second high-frequency signal whose frequency is different from that of the first high-frequency signal while both signals are being changed over at a set timing. A switch 7a outputs the first high-frequency signal to a transmission system as a transmission signal, and it outputs the second high-frequency signal to a reception system as a local oscillation signal. The transmission signal which is pulse-modulated is amplified by an amplifier 8a so as to irradiate a target from an antenna 9 by using a switch 7b. Its reflected signal is used by the switch 7b which is changed over to the reception system. A fundamental-wave mixer 10 frequency-converts the reception signal and the local oscillation signal which are amplified by an amplifier 8b, and it outputs a video signal at a frequency at which the difference FIF between the frequency of the transmission signal and the frequency of the local oscillation signal is offset to a Doppler frequency component Fd. Consequently, the video signal has the spectrum of a Doppler signal from a target in the point of a frequency FIF+d, and it can be detected by avoiding a region in which a noise component is large.</p> |
