| 摘要 |
1,222,242. Pulse radar. COMPAGNIE FRANCAISE THOMSON HOUSTONHOTCHKISS BRANDT. 21 Feb., 1968 [22 Feb., 1967], No. 8512/68. Heading H4D. [Also in Divisions G1 and G2] An optical correlator system for extracting information as to range and target speed from received radar echo signals corresponding with signals originally transmitted in pseudo random code uses the received signals to control a modulatable light source 1. The modulated beam from this is directed through a movable screen 5 to a light receiver 11. The screen carries in one sector a track providing the pseudo random code, which is read by a separate source 9 and photo-detector 10 and used to control the radar transmitter. In other sectors the screen carries a series of parallel reference tracks, each track in the series representing the effects of different amounts of Doppler shift on the transmitted signals and the modulated beam from the source 1 is transmitted through these to the receiver 11, which may be a photo-diode matrix or vidicon tube &c. The screen also carries reference markers 8 which are also interrogated by a light beam, the resulting signal being used to control synchronization of the overall system. The signals received at 11 are continuously integrated, to provide for each point in the receiver matrix as the screen moves through the beam from source 1 a value of the correlation function. All the points are scanned to determine the position in time at which this function reaches a peak. This position represents the required range. Furthermore, the synchronization system operates so that the tracks representing the reference for different Doppler shifts are used successively, to determine which of these provides maximum correlation, and hence the target speed. As shown in Fig. 4, the screen is in the form of a rotating disc, with the parallel reference tracks in successively narrow arcs of sectors of the disc. The reference track corresponding to a given Doppler shift is stepped successively towards the disc centre in adjacent sectors, to enable the entire correlation for one reference track to be formed in successive bands 191 and 195 across a vidicon tube 19 situated in a position covering an area equivalent to one sector. The bands are scanned successively in accordance with synchronizing pulses to provide a read out of correlation function related to time. Fibre optics may be used to direct the light beams in the system (Fig. 9, not shown). By suitable switching and operation of the vidicon tube, the reference tracks 181-185 on the disc need only be stepped inwards twice, thereafter retuning to the outermost track (Fig. 8, not shown). The tracks may be recorded on a rotating drum rather than a disc (Fig. 10, not shown). |
