DE2603317

1533426 Radio obstacle detection LIGNES TELEGRAPHIQUES ET TELEPHONIQUES 21 Jan 1976 [29 Jan 1975] 02377/76 Heading H4D With a Doppler effect obstacle detector mounted at the front of a vehicle, it is difficult, with r.f. frequencies and aerial dimensions in use, to confine detected 'obstacles' to those actually lying in the path of the vehicle. To effectively narrow the angular zone of detection, an inhibiting radar/direction finder is added, wherein microwave radiation is alternately radiated from small angularly offset printed circuit aerials 13, 14, Fig. 2, in respective beams 3 and 4, Fig. 1, which overlap in an angular region 6 lying along the axis of the vehicle. Echoes from an 'obstacle' are detected using a third small printed circuit aerial 20 with a reception lobe 5. With the line to the 'obstacle' outside the region 6, e.g. at P2, the detector (21) output is as S2, Fig. 3, i.e. no echoes due to radiation from beam 4. With the 'obstacle' at P3 however the output S3 at no time falls to zero. After removal of the D.C. component by capacitor C a threshold detector 22 produces an output from signal S3, which signal is used to enable the utilization of detection signals from the Doppler effect obstacle detector.