Improved radio receiving equipment for omnidirectional phase beacon navigation systems

摘要

736,281. Radio navigation. RADIO CORPORATION OF AMERICA. Dec. 4, 1953 [Jan. 2, 1953], No. 33806/53. Class 40 (7). In order to reduce random noise interference and so enable satisfactory determinations at longer ranges than previously the receiver for a phase comparison type omnidirectional beacon is provided with narrow band filters in each of the two channels feeding the phase comparison device. As a small drift in the tuning of these filters may introduce relative phase shifts in the signals passing through them checking and correcting arrangements are incorporated. In one embodiment, in which the signals which are to be phase compared are assumed to be of a frequency of 30 cycles per second the radio frequency signals from the beacon are received by antenna 1 and fed to receiver 3 which provides two outputs at 5 and 7. The output at 5 is the 30 c/s. reference phase signal and that at 7 the 30 c/s. variable phase signal. The output at 7 is fed to filter 11 which may have a pass band of 27-33 cycles per second and thence to the phase comparison device 13. The output at 5 may be coupled by switch 9 through adjustable phase shifter 15 and filter 17 (which may be identical with filter 11) to the other input of phase comparison device 13. To check if there is any relative phase shift introduced by the two channels switch 9 is moved to the position shown so that the same signal passes through both channels; any deviation from zero phase difference indication is then corrected by adjustment of phase shifter 15 and the switch 9 return to its normal position on contact 5. Either signal received may be fed through both channels to effect the phase shift check.