Patent GB-1157899-A (GB)
Title: Tactical Landing Approach Radio Systems
IPC: G05D1/06
Filed: 1967-01-17
Abstract: 1,157,899. Radio navigation. SINGERGENERAL PRECISION Inc. 17 Jan., 1967 [11 March, 1966], No. 2542/67. Heading H4D. The Specification describes a development of the aircraft radio leading system described in Specification 965,326 wherein, so that the aircraft does not home in on any of the side lobes existing on either side of the main beam, auxiliary fixed beams F 1  and F 2  are radiated on either side of the main beam having distinctive amplitude modulation whereby, in the area of said side lobes, one of said auxiliary beams is received to inform the pilot of his position outside the main beam. The main and auxiliary beams are alternately radiated in a 200 ms. sequence, Fig. 4-the auxiliary beams F 1  and F 2  being successively radiated for equal periods of 25 ms., and the main beam being radiated for the remaining 150 ms. of the sequence. The radiation frequency is controlled by generator 32 which operates switches S1 S2 and S5. The main beam is conically scanned at 100 r.p.s. by antenna 36 under the control of motor M. A synchronous 50 c/s. signal is produced by means of a 100 p/s. synchronous pulse generator 40 and 41. During the 150 ms. main beam period, with switches S1 S2 and S5, in respective positions 45, 46, and 35 the 50 c/s. signal frequency modulates the output of 100 kc/s. oscillator 44, which modulated output, amplitude modulates the output of 15.5 kMc/s. magnetron 34 to produce the main beam. During the 50 ms. auxiliary beam period, with switches S1 S2 and S5 in respective positions 51, 52, 67, the output of the 100 kc/s. oscillator 44 is no longer frequency modulated. A generator 59, during the first 25 ms. of the period, connects switch S4 to pulse generator 55 operating at frequency N 1  and connects the output of the magnetron to auxiliary horn antenna 63. The pulse output of generator 53 operates switch S3, such that the output of oscillator 44 is applied to amplitude modulate the magnetron output in pulsed bursts or repetition frequency N 1 . The auxiliary beam F 1  is thus produced. During the following 25 ms. of the period the output of pulse generator 57 at N 2  p/s. is used to cause pulsed amplitude modulation of the magnetron at repetition frequency N 2  to produce auxiliary beam F 2  from horn 62. Values for N 1  and N 2   are 900 p/s. and 540 p/s. respectively. At the receiver on the aircraft, the main beam is received to produce on crossed pointer indicator 95 an indication of the aircraft's position with respect to the centre of the conical scan 13, in the manner described in Specification 965,326. The 100 kc/s. subcarrier is also detected by rectifier 119 to actuate a glide slope acquisition flag 94 via a driver 93. When the aircraft is positioned out of the main beam in either of beams F 1  or F 2 , the pulse amplitude modulation of the 15.5 kMc/s. carrier is detected at 75. When in beam F 1 , filter 82 tuned to frequency N 1  passes the detected modulation which is then converted into a negative voltage by diode 86. Similarly when in beam F 2  filter 83 and diode 87 produce a positive voltage. The negative or positive voltage is applied to deflect pointer 97 of the indicator, to show the pilot his position relative to the main beam. The outputs of the filters are also rectified at 90, to produce a signal which actuates auxiliary beam acquired flag 92 and inhibiting the actuation of flag 94.