GB1031012A - A system for the accurate determination of the transmission times of electro-magnetic waves - Google Patents

Abstract

1,031,012. Radio position finding. TELEFUNKEN PATENTVEBWERTUNGSGESELLSHAFT m.b.H. Feb. 1, 1963 [Feb. 7, 1962], No. 4208/63. Heading H4D. In a position finding system of the type wherein the position of an object F 1 is found from the propagation times of radio signals between the object and at least three known positions, and timing standards are used at the object and at the known positions, a transmitting station S 1 and a timing standard ZN 1 , of insufficient accuracy for the required accuracy of measurement, is provided at the object, a receiving station E 1 /E 3 and a timing standard ZN 3 /ZN 5 of sufficient accuracy, is provided at each of the known positions, and the propagation time error. #t, produced in the measured propagation times I I /I III , by the inaccuracy of the transmitter timing standard ZN 1 , is calculated in a co-ordinate computor system (not shown), taking into account the measured propagation times the known positions of the receiving stations and the length of the object, and deducted from the measured propagation times. The system is described as incorporated in a system displaying the positions of aircraft (which are the above mentioned " objects " as luminous spots f 1 , f 2 on a C.R.T. display L, the C.R.T. having a television type raster and being fed with digital information from a computer R giving the line on which a position spot is to be displayed and the distance along that line, of the position spot f 1 . The computer R is fed with the corrected propagation times or the equivalent distances. For n aircraft the signals are transmitted from each aircraft in succession at 10 m/sec. intervals. The whole procedure is repeated every 10 seconds. The position of each aircraft may be shown at successive times, to give an indication of its speed and course. The timing standards ZN 3 /ZN 5 may be in the form of atomic clocks or may be in the form of less accurate quartz clocks which are periodically synchronized with a more accurate clock at a control station. However, as long as the errors in the quartz clocks relative to each other are not too great the clock at the control station need not be highly accurate. Radio links may be used between the control station and the receiver stations. The aircraft may transmit information coded signals, for example the aircraft's height, and the decoded information may be stored. If more than 1000 aircraft are to be detected within the period of 10 seconds, then some of the aircraft may be allocated to a different frequency. The system may be reversed, the receiving stations now transmitting and the aircraft receiving the signals and computing its position. The less accurate clock is still kept in the aircraft. More than three receiving stations, or transmitting stations in the reversed system, may be used, the computer selecting the three with the shortest propagation times.