1. Introduction

The planar end fire tapered slot antenna (TSA) is a novel technique and is presently quite new [1], this has been less studied theoretically with little information or analysis results available in journals and literature today. These types of radiating structures find wide applications [2] vis-à-vis: as feed structures for reflectors or lens and in radars for imaging including phased array radars. Other applications include remote sensing, satellite communication and MMIC based communication systems. The accurate design, its precise fabrication, need for impedance matching over a wide range of frequencies (in case of multi-frequency wide band operations) is quite time consuming and laborious, often demanding high-end simulation software to optimize the structures.

Experimental investigations have reveled that the electrical and structural properties contribute to the overall performance of the radiating structure. Antenna parameters such as dielectric substrate, its thickness, associated tangential loss; the permittivity variation with frequency and the temperature significantly affect the overall performance of the planar LTSA, especially under high-frequency operations. Other parameters affecting performance include: size of the ground plane, its conductivity (material used), thickness; the dimensions of the slot, the microstrip feed line, taper / flare angle, opening width of the tapered structure at the space interface, lateral edge and feed location. Further, the LTSA is a slow surface wave structure [1, 2] with limitations like non-resonant, formation of standing waves that greatly reduce the RF bandwidth. The TSA offer many advantages [3, 4] over the MSA like unidirectional and bidirectional radiation field, wide band width, low spurious radiation and very low cross polarization.

2. Analysis and Design

Because of the limitations of the transmission line method, moment method and finite difference time domain, the LTSA structure was analyzed using SAM [3, 6]. Since the impedance of LTSA depends on the separation between the two surfaces that is a function of the linearly increasing width of the slot / opening. The tapered section is uniformly divided into a number of quarter wavelength slots as subsections with progressively increasing width. Using this quarter wavelength impedance matching method the reflection coefficient associated with each of the sub-sectioned step is calculated and shown in Table 1. The same has been optimized in the simulation. The assumption for the SAM analysis is that the lateral edges extend to infinity, while the power conservation law validates at each step discontinuity, further, no reflection or radiation occurs at the step junction and hence a full


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