Microwave model of the glide path system

Belcher, W. R (1968). Microwave model of the glide path system Master's Thesis, School of Computer Science and Electrical Engineering, The University of Queensland.

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Author Belcher, W. R
Thesis Title Microwave model of the glide path system
School, Centre or Institute School of Computer Science and Electrical Engineering
Institution The University of Queensland
Publication date 1968
Thesis type Master's Thesis
Supervisor Bogner, R.E
Fraser, S.G
Total pages 199
Collection year 1968
Language eng
Subjects 09 Engineering
0906 Electrical and Electronic Engineering
090609 Signal Processing
090602 Control Systems, Robotics and Automation
Formatted abstract

The null reference glide path system, which forms one element of the standard Instrument Landing System (I.L.S.), relies on ground reflection to obtain the appropriate antenna radiation patterns. As the ideal system requires an infinite plane reflector, significant irregularities in the glide path are observed for actual sites with non-flat ground. At present, objectionable irregularities cannot be predicted in detail for an arbitrarily specified site. 

A satisfactory solution to this problem would require: 

(i)     an accurate method of measuring the glide path at any given installation; 

(ii)     an economical approach to the modification of existing sites to meet the glide path specifications for any desired performance category; 

(iii)    a systematic method of synthesis of a suitable ground surface, or the adoption of alternative systems which are independent of ground effects. 

The terrain problem can be investigated in accordance with (i), (ii) and (iii) above by means of geometrical modelling. A microwave model has been developed, for which the primary requirements were: 

(i)       a measuring facility to permit the calculation of Difference in Depth of Modulation (D.D.M,) to an accuracy of approximately 3% (i.e. 0.01 in elevation angle); 

(ii)      a contoured surface-modelling technique to maintain an accuracy of 3 in. (full size) in ground height. 

These tolerances were adopted to provide resolution of path bends and changes in sensitivity consistent with the performance specifications for International Civil Aviation Organization (I.C.A.O.) Category III installations. 

The utility of the model approach was tested by modelling the Avalon (Victoria) aerodrome site. Several significant differences between the flight test and model results were obtained, although the measured quality of the glide path in each case was similar. The model results established the significance of a ground region between 3700 ft. and 4200 ft. from the transmitting antennas. Several possible methods of improving the Avalon site are considered.

Keyword Glide path systems

Document type: Thesis
Collection: UQ Theses (non-RHD) - UQ staff and students only
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Created: Wed, 24 Oct 2012, 12:26:59 EST by Mr Lachlan Wong on behalf of Research Management Office