Inkjet Printing of Wideband Stacked Microstrip Patch Array Antenna on Ultrathin Flexible Substrates

Abstract

This paper presents a bandwidth-enhanced, low-cost, compact, inkjet-printed multilayer microstrip fractal patch antenna for integration into flexible and conformal devices. The antenna consists of two layers of patches, with the first layer inkjet-printed directly on a 0.125-mm (only 0.005 of the operating wavelength) Kapton polyimide substrate. On top of it, a 0.12-mm-thick SU-8 polymer is covered. To achieve the desired miniaturization and good impedance match, a Minkowski fractal geometry patch is employed as the second layer inkjet-printed on top of the SU-8 polymer. The proposed antenna has compact dimensions of only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$22\times 31$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and covers 4.79–5.04-GHz frequency spectrum with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11} &lt; -10$ </tex-math></inline-formula> dB. Moreover, a 2-bit <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times 4$ </tex-math></inline-formula> phased array antenna (PAA) is constructed, and its scan ability is estimated to demonstrate its potential application in the true-time-delay flexible PAA systems. The prototype is fabricated and tested for impedance and radiation characteristics. The measured and the simulation results show the superiority of the proposed antenna.