Performance Study of open-circuited uniform and Stepped Impedance Resonator stubs with respect to their leaky wave characteristics

Abstract

Periodically loaded microstrip line based leaky wave antenna gives radiation characteristics suited for beam scanning applications. In this work, the leaky wave radiation characteristics of microstrip lines perturbed with open circuited uniform stubs and SIR (Stepped Impedance Resonator) stubs has been analysed. Over the range of frequencies from 1–16 GHz, both the antennas exhibit tri-band operation-generating single beam scanning in one band and dual beam scanning in the other two. The structure loaded with uniform stub exhibits a beam scanning range of around <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$86^{\mathrm{o}}$</tex> with gain varying between 9.73-11.1 dBi, while that loaded with SIR stub gives a scan range of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$76^{\circ}$</tex> and gain variation between 10.2-11.2 dBi, in the frequency range of around 6–11 GHz. However, in the bands exhibiting dual beam scan, the performance of the latter is better in terms of scan range as well as gain. SIR stub loaded structure provides a forward beam scanning of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$10^{\mathrm{o}}$</tex> and a backward beam scanning of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$19^{\mathrm{o}}$</tex> with a gain variation between 5.86 to 9.75 dBi in the dual-beam scanning band. On the other hand, uniform stub loaded line gives a very narrow backward and forward beam scan angle of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$5^{\mathrm{o}}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$8^{\mathrm{o}}$</tex> respectively with a gain variation of 4.77-9.34 dBi. The radiation efficiencies in both the structures is around 98%.