摘要 |
An IFF device comprises a beam generator for directing an unmodulated beam at a target. The target has a plurality of retro-reflectors mounted on it. These retro-reflectors have internal reflecting surfaces for reflecting the unmodulated beam penetrating the retro-reflector. A device is associated with the internal reflecting surfaces for modulating the beam at a predetermined frequency so that the reflected beam emerging from the retro-reflector is modulated at the same frequency. A tuner is positioned in the path of the reflected modulated beam and tuned to predetermined frequency, so that if the tuner receives a signal, it indicates the target is friendly.
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