| 摘要 |
592,571. Directive wireless systems. STANDARD TELEPHONES & CABLES, Ltd. Nov. 26, 1943, No. 19827. Convention date, Feb. 1, 1940. [Class 40 (v)] A beacon system for defining a constant intensity glide path of the form shown in Fig. 2, comprises a main radiator system and an auxiliary radiator system which is spaced from and energized at a lower level than the main system, both radiator systems being placed some distance to one side of the landing runway. A principal radiation pattern 10, Fig. 1, having a centre of radiation 11 and an auxiliary radiation pattern which may be omnidirectional or directional as shown at 13 or 16 and having a centre of radiation 12, add and subtract at a sufficiently great distance to produce a resultant pattern 15 or 17. The main and auxiliary radiating systems are spaced to one side of the landing runway 45 as shown in Fig. 3 in which 30 represents the point of contact of the aircraft with the ground. The dimensions of Fig. 3 are appropriate for a carrier frequency of about 93.9 Mc/s. The auxiliary radiator preferably comprises two elements 46, 47 which are energized at a level of between <1>/10th and <1>/50th of that supplied to the main radiator and have a maximum radiation parallel to the runway, while the maximum radiation from the main radiator which comprises a driven element 41 and parasitic elements 42, 43, is at an angle to the runway. With the systems oriented as shown, the resultant radiation diagram such as 17, Fig. 1, is such that a line of constant intensity in the plane of the runway, which does not pass through the centre of the radiating system, has the desired form of Fig. 2. The mode of energization of the main and auxiliary radiators, the elements of which may be loops of the type described in Specification 538,036, is shown in Fig. 4, the parasitic elements 42, 43 being spaced a distance of about 165 electrical degrees from the main radiator 41. Transmitter 50 feeds aerial 41 through lines 51, 52 which are joined by adjustable short-circuiting bars 53 for phase adjusting purposes, while the auxiliary radiators 46, 47 are fed at reduced power by connection of line 58 to adjustable points on the shortcircuited section 54. Short-circuiting bars 55, 56 are arranged on lines 51, 52 a quarterwavelength from the connections of bars 53 to provide a high impedance at these points so that adjustment of bars 53 does not vary the line impedance. A matching section 57 may be provided. |
