GB736329A - Improvements relating to radio navigation systems - Google Patents

Abstract

736,329. Radio - navigation. SPERRY CORPORATION. Dec. 2, 1952, No. 30598/52. Class 40 (7). A radio-navigation system, e.g. a precision Loran system, comprising two transmitting stations and receiving equipment provided with means for obtaining fine indications of the distance difference from the two stations from measurements of the relative phases of radio frequency components of signals from the two stations, and for obtaining coarse indications of the distance difference from measurements of the relative phase of the modulation frequency components, is characterized in that means are provided at each station for transmitting further radio frequency signals to enable further radiations of the distance difference to be obtained by the receivers, the further indications serving to resolve ambiguities in the fine indications not resolved by the coarse indications. The transmitters may transmit pulses simultaneously on two carrier frequencies f1, f2, for example 180 and 200 Kcs./sec. respectively. Fig. 10 shows a block schematic diagram of a slave transmitter wherein the timer 11<SP>1</SP> determines the pulse repetition rate of the two transmitters 12<SP>1</SP>, 14<SP>1</SP> which feed a common aerial. Received signals are fed through an alternator 23 to R.F. amplifiers 19, 21 for frequencies f1, f2 respectively to a switch 22 so that the master and stave R.F. signals of each frequency may be compared on a cathode-ray tube 17; by switching in a detector 25 the pulse envelopes may be compared. The navigator's receiving equipment comprises two R.F. amplifiers, one for f and the other for f2 frequency, and a receiver, and a cathode-ray tube and time indicator circuits so that the signals of frequency f1 from each transmitter may be compared, and the time interval between them measured, as well on the signals of frequency f2 and the pulse modulation. Fig. 13 shows the display if the signals of frequency f1 are mis-matched by one whole cycle; the signals of frequency f1, Fig. 13 (A), appear to be matched, as do the pulse envelopes, Fig. 13 (C). but the signals of frequency f2 are clearly mis-aligned, Fig. 13 (B). Fig. 14 shows the display if the signals of frequency f1 are mis-matched by ten cycles; the signals of frequency 12, Fig. 14 (B), appears to be matched but the pulse envelopes shown in Fig. 14 (C) are not aligned.