Doctoral Degrees (Electrical and Electronic Engineering)

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Browsing Doctoral Degrees (Electrical and Electronic Engineering) by Author "Baard, Charl Wynand"

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    Design of the dual-shaped triple layer pillbox antenna
    (Stellenbosch : Stellenbosch University, 2013-03) Baard, Charl Wynand; Palmer, K. D.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: The triple layer pillbox antenna is an antenna topology well suited for use as a stackable "plank" element in radar applications. Its suitability arises from the folding which makes it compact, and from the layered nature which can be exploited for low cost manufacture. Existing designs of these "cheese" antennas, whether two or three layers, suff er from two drawbacks: a) The bend or fold between layers introduces undesirable reflections and b) Due to their parabolic sector geometry virtually no pattern control is available to the designer. This work addresses both of these shortcomings. A low reflection transition is realized by introducing simple compensating elements into the design which, with minimal manufacturing complexity, off er high performance over a broad frequency and incidence angle range. To cater for pattern control the concept of "dual shaped reflectors" is borrowed from the high performance dish antenna literature and implemented in the pillbox geometry. This shaping off ers limited but useful control of the aperture distribution and thus indirectly over the radiation pattern. To test these innovations three X-band antennas have been designed, built and measured. An initial unshaped geometry is used for the fi rst design to show the fold or bend performance. This antenna has a simulated and measured 2GHz usable bandwidth, with a reflection coeffi cient below -10dB and side-lobes below -27dB over a bandwidth in excess of 20%. Shaping is then added to show how either side-lobe levels can be lowered to below -32dB, or the gain enhanced by 2dB. The enhanced designs have been built and experimentally veri fied.