Wide-Aperture Digital VOR
The very high frequency (VHF) omnirange has undergone a number of evolutionary changes in the past 30 years. Early measurements of large errors led to the development of the Doppler VHF omnidirectional irectioal range (VOR) and its use. Further developments have been the precision multilobe VOR and the precision Doppler VOR. Interest in area navigation has led to the desire for a VOR greatly superior to any so far developed. Specifically, the objectives of the improved VOR would be a system that would significantly reduce magnitude of siting errors, provide greater accuracy and use digital techniques to simplify processing. ssing. The wide-aperture digital VOR described herein has been developed to meet these objectives. Its design is based on the crossed-pair interferometer principle where eight such pairs are energized successively by a set of pulses and phase shifts. The time multiplexed signal, detected by the aircraft receiver, is processed and simple digital computations are performedto determine the angular coordinates. The performance improvements have been achieved by the combination of using a 275-ft antenna aperture, and the use of digital techniques to generate the ground-radiated navigational signals and to process them in the airborne processor. Field tests of the feasibility model indicate it is a high performance ance system, capable of achieving an order of magnitude improvement in both site error reduction and in accuracy compared to present VOR systems. The measured accuracies were 0.11-degree standard deviation.
VOR evolutionary system improvements in the United States
This paper discusses the techniques and system performance for several classes of VHF Omnidirectional Range (VOR). Single- and double-sideband Doppler VOR are compared with the alternating-sideband VORDAC proposed to EUROCONTROL. Results of the tests conducted on all three techniques are discussed along with the reasons why the U. S. favors a “full-time” double-sideband Doppler VOR. Results of recent tests of the Precision VOR, using the two-speed multilobe pattern combined with simultaneous operation of the Doppler VOR, are presented.
Theory of the Detection of Two Modulated Waves by a Linear Rectifier
In this paper there is developed a mathematical analysis of the detection, by a linear rectifier, or two modulated waves. Solutions are obtained which are manageable over wide ranges of values of carrier ratio and degrees of modulation. These solutions are of greater applicability and are more convenient than those previously obtained, and give a full treatment of the action of an ideal linear rectifier under the action of two modulated waves. The development is first made in terms of the derivatives of zonal harmonics of an angle which is directly related to the phase difference between the carriers. As these derivatives are tabulated functions the solution is convenient. The solutions are limited by the condition that K <(1-M)/(1+m), K being the carrier ratio, M the degree of modulation of the stronger carrier, and m that of the weaker. Two methods of attack are developed one of which is applicable when K is small and M and m large, and the other when M and m are small and K large. The cases of identical and of different programs are both considered and a number of curves are given showing the magnitudes of various output frequency components under typical operating conditions. In the latter part of the paper the phase angle between the carriers is set equal to μt so that a beat note exists.