Microfluidic Based Ka-Band Beam-Scanning Focal Plane Array

Abstract

An eight-element 1-D Ka-band focal plane array (FPA) capable of beam scanning based on microfluidic principles is presented. The FPA is placed at the back surface of an 8-cm-diameter extended hemispherical Rexolite (ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> =2.56, tanδ = 0.0026) lens and consists of interconnected microfluidic reservoirs and channels constructed by bonding polydimethylsiloxane (PDMS) (ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> =2.8, tanδ = 0.02) and liquid crystal polymer (LCP) (ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> =2.9, tanδ = 0.0025) substrates. The antenna element of the array is a small volume (2.5 μL) of liquid metal residing inside a low-loss Fluorinert FC-77 (ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> =1.9, tanδ = 0.0005) solution. The array beam is scanned by moving the liquid-metal antenna among the reservoirs using an external pump. The proximity-coupled feed network of the array is passive and designed strategically to accommodate the position variation of the liquid-metal antenna element. The array operates with measured 7° half-power beamwidth (HPBW), >21 dB realized gain, and 3.3% dB bandwidth and provides ±30° beam-scanning range. The presented microfluidic-based beam-scanning technique operates without resorting to RF switches. Consequently, it is promising for high-power handling and low-cost realization of millimeter-wave high-gain beam-scanning antenna arrays.