Patent GB-1210861-A (GB)
Title: Proximity warning
Inventor: RIGGS RONALD FOREST
IPC: G01S13/933
Filed: 1968-01-24
Abstract: 1,210,861. Radar and like systems; radio receivirig circuits; transistor pulse and gating circuits. SPERRY RAND CORP. 24 Jan., 1968 [27 Jan., 1967], No. 3715/68. Headings H3T, H4D and H4L. In an automatic proximity warning device guard rings (Fig. 2, not shown) at least partially circumscribing a protected craft and at different ranges are generated and alarm and display means provide discrete indications of presence, range and bearing when an intruding craft intersects each successive guard ring. The sensing means particularly described is a pulse radar but may utilize sound or light waves; in the embodiment two guard rings, " inner " and " outer ", are provided, and each ring may be at a selectable range and of a selectable width. General arrangements. Fig. 1.-The radar incorporates a generator 17 coupled to scanner 16 and connected to gate generator 15 to vary guard ring ranges as a function of bearing, e.g. to afford different positions of the centres of the inner and outer guard rings (e.g. utilizing a non- linear potentiometer). Scanner 16 is also coupled to electromagnetic clutches 23, 24 to position inner and outer ring bearing pointers 25, 26 in synchronism with scanner rotation; when an intruder is detected in a guard ring the corresponding clutch is disengaged thereby stopping the associated pointer to indicate the bearing of the intruder. Video signal amplifier 14 may be gated " on " during the inner c and outer d range gate signals and a third gate e. A video circuit 30 receives gates j, k, l (in time correspondence with respective gates c, d, e) and produces video outputs from gates j, k and the A.G.C. voltage g utilizing gate l (corresponding to a target-free range) to afford constant average noise level (see below). When an intruder enters the outer guard ring, index 26 stops, lamp 39 lights red, a slit in the lamp housing illuminates bearing dial 40 and audible alarm 37 sounds. If a push-switch 42 is operated the system returns to normal and if the intruder is still within the outer guard ring during the next aerial scan the alarm process repeats; if, alternatively, switch 33 is placed in an " intermittent alarm " position and the intruder is within the outer guard ring on successive aerial scans momentary audible and visual alarms are given each time the intruder is detected, index 26 continuing to rotate and multiple targets are catered for. Similar events transpire for the inner guard ring. Test switches 43, 45 introduce simulated target video signals for the two guard rings. Transistor pulse and gating circuits and radio receiving circuits, Figs. 4, 5.-A range gate pulse, e.g. j, Fig. 4, is generated by differentiating the system negative trigger pulse a utilizing capacitor C305 to place monostable multivibrator 50 into its unstable state which is terminated at a time dependent on resistor R a , diode CR302 protecting transistor Q305 against burn-out; the positive output pulse from multivibrator 50 is differentiated and the negative " spike " at the trailing edge triggers monostable multivibrator 51 to afford the range gate pulse. Diode CR304 prevents spurious trigger pulses from reaching transistor Q306. A " selftest " switch permits the by-passing of multivibrator 50 to activate amplifier 14, Fig. 1 during radar transmission. The video circuit 30, Fig. 1, is shown in Fig. 5: the inner guard ring channel 60 is fed with gate pulse j and the receiver video train f and is normally " off ", forward bias from divider R346, R347 is applied through current-limiter R345 to the base of switch Q336 which provides a shunt to earth for the video signals, the collector voltage applied at the junction R344, R349 reverse-biasing diode CR313; when negative pulse j is applied switch Q336 is cut off, switch Q336 is held open, the signal shunt and the back-bias are removed, and positive video signals are transmitted through diodes CR313, CR314. A similar circuit is used in unit 66 which provides a video noise sample for the A.G.C., such sample being peakdetected in a circuit forming part of an integrator-amplifier 67. A synchro-transmitter/receiver arrangement may be employed for the bearing indication, Fig. 6 (not shown).