Consideration of DME Beacon Improvement

Abstract

This report is written in accordance with the program conducted in the test of low-power Distance Measuring Equipment (DME) collocated with TVOR or ILS. The purpose of this study is to improve the suitability of DME ground beacon design to provide technical information for terminal use.

Some problems for the improvement of DME range accuracy are pointed out, and it emphasizes that these problems are connected with each other over an asychronous superposition navigation system, namely DME.

An object of the DME system improvement is to raise better range accuracy, and to increase the traffic loading capacity within the limited radio spectrum band. Therefore, the fundamental problem in pulse radio range fiding with responder is analyzed to over all signal transmission paths, which are in propagation media, the antenna and the receiver circuit.

From an objective point of above view, the following provides the analysis of these problems.

First, to improve range accuracy, the rise time of the pulse signal should be short, while a distortion of pulse form by the multipath reflection of radio signal propagation phenomena spreads radio spectrum of the signal. It result in DME channelizing bounds.

Next, the scope of the distorted pulse of DME signal presents the power spectrum of variation of detected signal amplitude in regard to the propagational characteristics of the signal. Radiation field distortion depends on refrections from the ground and other obstacle causes serious error of DME indication. Therefore, antenna pattern fluctuation is one of the most important problems in this system.

The final discussion is made about a total DME channel capacity, and its easy computation method. The last part of this report gives a error of due to time delay between input and output signals of the receiver circuit, and it is indicated by the probability function of time variant impulse response of the circuit.