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 ( $\varepsilon_{\rm r}=2.56$ , $\tan\delta=0.0026$ ) lens and consists of interconnected microfluidic reservoirs and channels constructed by bonding polydimethylsiloxane (PDMS) ( $\varepsilon_{\rm r}=2.8$ , $\tan\delta=0.02$ ) and liquid crystal polymer (LCP) ( $\varepsilon_{\rm r}=2.9$ , $\tan\delta=0.0025$ ) substrates. The antenna element of the array is a small volume (2.5 $\mu$ L) of liquid metal residing inside a low-loss Fluorinert FC-77 ( $\varepsilon_{\rm r}=1.9$ , $\tan\delta=0.0005$ ) 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 $7^{\circ}$ half-power beamwidth (HPBW), $>$ 21 dB realized gain, and 3.3% $\vert{ S}_{11}\vert dB bandwidth and provides $\pm 30^{\circ}$ 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.