Unit-Cell for Wideband Circularly Polarized Microstrip Patch Arrays

A compact unit-cell configuration for a circularly polarized microstrip patch array is proposed. This unit-cell is composed of four sequentially rotated microstrip patch elements with chamfered corners and a cross-slot on a single substrate. Incorporated features lead to a more compact size <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(0.22\lambda_{26\text{GHz}}\times 0.22\lambda_{26\text{GHz}})$</tex> and wider axial ratio (AR) and impedance bandwidths. Designed elements are placed close to each other with an inter-element spacing of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.22\lambda_{26\text{GHz}}$</tex> thus leading to stronger mutual coupling. An 8×8 finite array example achieves <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&gt; 56\%$</tex> bandwidth with radiation and aperture efficiencies of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&gt; 95\%$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&gt; 97\%$</tex>, respectively. Moreover, the array can scan within an elevation cone of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 60^{\circ}$</tex> while maintaining <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&lt; 3.8\text{dB}$</tex> scan loss and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&lt; 3.5\text{dB}$</tex> AR from 20 to 32 GHz. The design methodology and its feasibility are validated with a proof-of-concept prototype, consisting of a simplified 2×2 finite array with integrated series power dividers. Measured results showcase symmetric radiation patterns over <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&gt; 56\%$</tex> wide VSWR <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&lt; 2:1$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1\text{dB}$</tex> AR bandwidth. Good agreement between theory and experiments validates the proposed unit-cell, its design concept, and candidacy for many RF applications.