| 摘要 |
PURPOSE:To enable the detection of a target Doppler frequency with one narrow band signal by generating a locally oscillated signal to include a Doppler frequency required through an FM modulation and mixing it with transmission and received signals. CONSTITUTION:A transmitter 21 emits a non-modulation continuous wave signal of a frequency fr from an antenna 22. A saw tooth wave generated with a saw tooth wave oscillator 23 is fed to a local oscillator 24, whose locally oscillated frequency is modulated in the frequency with the saw tooth wave whereby a locally oscillated signal fL containing a Doppler frequency is obtained. The signal fL is fed to a mixer 25 with the output of the transmitter 21 and the output thereof 25 to a BPF26 to obtain a frequency component of fT-fL. On the other hand, a radio wave emitted from the antenna 22 is reflected by a moving target and fed to a mixer 28 via an antenna 27. A signal of fL+ or -fd (where, fd is the Doppler frequency) is obtained and fed to a BPF29 of a narrow band to gain a necessary frequency fd which will be provided to a display 34 after amplified 30. |
