| 摘要 |
An electromagnetic detector (1, 100) is designed to locate an object (22, 12 2) behind a separator. The detector (1, 100) includes a PRF generator (10, 104) for generating 2 MHz pulses, a homodyne oscillator (102) for generating a 2 kHz square wave, and for modulating the pulses from the PFR generator (10, 104). A transmit antenna (18, 188) transmits the modulated pulses through the separator (24), and a receive antenna (20, 120) receives the signals reflected from the separator (24). The receiver path of the detector (1, 100) includes a sample and hold circuit (26), an AC coupled amplifier (129) which filters out DC bi as level shifts in the sample and hold circuit (26), and a rectifier circuit (130) connected to the homodyne oscillator and to the AC coupled amplifier (129), for synchronously rectifying the modulated pulses transmitted over the transmit antenna (18, 118). The homodyne oscillator (10 2) modulates the signal from the PFR generator (10, 104) with a continuous wave (CW) signal, and the AC coupled amplifier (129) operates with a passband centered on that CW signal.
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