Patent GB-1183480-A (GB)
Title: Phase Comparison Radio Receiver
IPC: G01S1/30
Filed: 1967-09-28
Abstract: 1,183,480. Radio navigation. RYAN AERONAUTICAL CO. 28 Sept., 1967 [9 Aug., 1967], No. 44237/67. Heading H4D. Specification describes a hyperbolic navigation receiver of the OMEGA type. Four transmitting stations, D.E.F.G. are assumed, sequentially transmitting CW signals at 10À2 kc./s. over a transmitting cycle of 10 seconds. The signals are received at 19 and converted to I.F. signals at 300 c/s. in detector 26. The heterodyne signal at 10À5 V.c./s. is produced at 41 by dividing down the output of main voltage controlled oscillator 36. A reference signal at 300 c./s. is produced at the output of divider 46 by further frequency division. The I.F. signals are applied to phase detectors 30, 68, 82 and 94. An electronic commutator 56 sequentially energizes lines 58 in a 10 second cycle, contacts D, E, G and F of station selector switches A, B, D and C being thereby sequentially energized. The first station to be received in the cycle is to provide the signal to which oscillator 36 is to be phase locked. For this reason it must be the strongest station whereby gain control 24 may be turned down until said strongest signal is the only one to cause neon 69 to ignite. When this ignition happens, switch 50 is closed thereby energizing commutator 56 and synchronizing the commutator switching sequence to the reception of the station signals. Thus assuming station D to be nearest, this is received first in the sequence simultaneously with the energization of contact D of switch A. Relay 134 is thus energized and contact 38 closed. Contact 38 applies the output of phase detector A to integrator circuit 32 to produce an error signal representing the degree of out of phase between the received signal from station D and the reference signal. The error signal is applied to control oscillator 36 until the oscillator is phase locked to the received signal. Lamp 41 goes out when said phase looking is achieved. Contact E of switch B is next energized simultaneous with the reception of the next station (E) signal. Relay contacts 39 and 41 are thereby closed and phase detector 68 brought into operation. The incoming station signal is phase compared in 68 with the variable phase output of a resolver 78 fed with in quadrature 300 c./s. reference signals. The phase difference representative output signal from 68 is changed into a 300 c./s. chopper signal by modulator 72 and energizes motor 76 adjusting the rotor of resolver 78 until the output of the resolver is phase shifted into agreement with the received station I.F. signal. The rotation of motor 76 as registered at 114 indicates the phase difference between the signals received from the two stations and thus the isophase line position, with reference thereto, of the receiving station. A potentiometer coupled to motor 76 may transmit the phase difference to a graphic recorder. The procedure is repeated for the signals from stations G and F, using phase detectors 82 and 94, secondary voltage controlled oscillator 88, resolver 106 &c., the phase difference indication appearing at 116. Fig. 2 (not shown) illustrates a mechanical (moving brush) variation on the commutator 56.