GB1083381A - Radio landing system - Google Patents

Abstract

1,083,381. Radio navigation. CSF-COMPAGNIE GENERALE DE TELEGRAPHIE SANS FIL. Feb. 22, 1965 [Feb. 27, 1964], No. 7656/65. Heading H4D. In a radio landing system employing, in the aircraft, a crossed-pointer indicator, azimuth guidance control of the vertical pointer, relative to a vertical landing plane, is produced by radiations received from a beacon similar to a standard localizer I.L.S. beacon, and elevation guidance control of the horizontal pointer relative to a chosen glide path angle is produced by radiations, received by a V.O.R. type receiver from a beacon, and having radioelectric characteristics in said vertical landing plane similar to those produced in the horizontal plane by a standard V.O.R. beacon, the selector of the V.O.R. type receiver being used to select the desired glide slope angle. One advantage of the invention is said to be that, the standard V.O.R., I.L.S. receiver system found in most large aircraft may be used in the invention with very little modification. In a preferred embodiment, the carrier frequencies f and f 1 of the V.O.R. type beacon and the I.L.S. type beacon are so chosen that f-f<SP>1</SP> = 110 Mc/s. and f 1 -f<SP>1</SP> = 330 Mc/s. Thus, after heterodyning with a frequency f<SP>1</SP> controlled to satisfy the above equations by an automatic frequency control circuit, the resulting signals can be fed directly to the V.O.R. receiver and I.L.S. receiver respectively, Figs. 7 and 8 (not shown). Normally, the I.L.S. receiver tuned to 330 Mc/s. receives the I.L.S. glide slope beam, and so controls the horizontal pointer. In the invention however the 330 Mc/s. signal is derived from an I.L.S. type localizer beam and so the receiver output must be arranged to control the vertical pointer and it must be altered to control the horizontal pointer. The V.O.R. type beacon may comprise three antennµ B, A, B<SP>1</SP>, Fig. 2 (not shown), aligned equispaced in a straight vertical line, at rightangles to the axis of the sector S 1 .A.S 2 within which it is desired to provide aircraft with elevation information. Antenna A radiates a carrier f, amplitude modulated to a depth of 30% by a subcarrier of 9960 c/s. frequency modulated at 30 c/s. Antennµ B and B<SP>1</SP> radiate sidebands at respective frequencies of f+30 c/s. and f - 30 c/s. The radiation is such that in a direction making an angle S with the axes of the antennµ the field Fp, neglecting the 9960 c/s. subcarrier, is given by: The phase difference between the reference 30 c/s. signal obtained from the frequency modulated subcarrier and the 30 c/s. signal amplitude modulation at the receiver is thus or a function of the elevation angle S. The signals feeding the three antennas may be obtained from a standard V.O.R. system by frequency translation, Fig. 4 (not shown), or by signals modulating the carrier f directly, Fig. 3 (not shown). In another embodiment, the localizer beacon may radiate a carrier of 110 Mc/s. and the V.O.R. type beacon may radiate a carrier of 330 Mc/s., in which case the controls of the indicator pointers are not altered.