Patent GB-1047465-A (GB)
Title: A system for radio position-finding
IPC: G01S3/14
Filed: 1963-07-03
Abstract: 1,047,465. Radio navigation. TELEFUNKEN PATENTVERWERTUNGS G.m.b.H. July 3, 1963 [July 6, 1962 (3)], No. 26373/63. Heading H4D. In a system which defines a position plane Fp, Fig. 1, on which lies a point P (which may be an aircraft seeking to find its own position or the position of which is to be found at a fixed station) by the equation where e 1 , e 2  are distances from P to respective high-frequency stations E 1 , E 2  and g is the distance of E 2  from E 1 , the wave propagation time intervals T s =(e 1 +e 2 )/c and T d =(e 1 -e 2 )/c are converted into pulse trains. The pulse trains may be of equal pulse repetition frequency (p.r.f.) f=c/#2gD where c is wave propagation velocity and D is a selectable unit of length in which g is to be scaled; or, since the difference has a larger percentage error than the sum, a higher p.r.f. f d  is used for interval T d  than that, f s , for interval T s . Subharmonics of the p.r.f.'s may be added. It may be arranged that length D is an integral power of ten. In the first embodiment, Figs. 2 . . . 6 using a common p.r.f. f, the quantities T s , Td are pulses of corresponding durations which open respective gates 3, 4 to permit the f pulses to pass to corresponding counters 8, 9 the outputs of which are multiplied; T s , T d  are btained from signal groups each being a reference signal Z 0  and two time markers Z 1 , Z 2  constituted by leading edges of pulses, sudden phase, frequency or amplitude changes, or maxima or zero-passages of sinusoids. In Fig. 5 signal Z 0  is transmitted from station E 1 , that signal is re-modulated on to a transmitter at point P, the signal from point P is received at stations E 1 , E 2  and the evaluation of the position plane on which point P lies takes place at station E 1 ; details of the evaluation apparatus are described in block diagram form with reference to Figs. 8 and 9 which utilizes a single p.r.f.: two p.r.f.'s are used in a modification, Figs. 19, 20. In another embodiment stations E 1 , E 2  transmit simultaneously, point P re-transmits the signals received therefrom and station E 1  receives the transmissions from point P, Fig. 7. In a further embodiment point P transmits the reference signal Z 0 , station E 1  transponds thereto, the signal therefrom is received at point P and station E 2 , and the latter station transponds, Fig. 16; the evaluation is effected at point P. In a further embodiment stations E 1  and Eg transmit time marking signals at the instant that point P generates reference signal Z 0 , Figs. 10. . . 13; in a modification p.r.f.'s f s , 2f s  and fd may be utilized, Figs. 21, 22. In another embodiment stations E 1 , E 2  each transmit a marker signal at the same instant which are retransmitted back to them by point P, Figs. 14 and 15; p.r.f.'s f and f/2 or f s ,f s /2, and f d /2, Fig. 23, may be employed. The Fig. 14 embodiment may be " inverted " Fig. 18. Delay lines may be replaced by corresponding delay in counting; position-fixing can be effected utilizing a second position plane afforded by further E-stations; and a transponder may alternately be a passive reflector.