Microfluidic Based Ka-Band Beam-Scanning Focal Plane Array

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 (<formula formulatype="inline"><tex Notation="TeX">$\varepsilon_{\rm r}=2.56$</tex></formula>, <formula formulatype="inline"><tex Notation="TeX">$\tan\delta=0.0026$</tex> </formula>) lens and consists of interconnected microfluidic reservoirs and channels constructed by bonding polydimethylsiloxane (PDMS) (<formula formulatype="inline"> <tex Notation="TeX">$\varepsilon_{\rm r}=2.8$</tex></formula>, <formula formulatype="inline"> <tex Notation="TeX">$\tan\delta=0.02$</tex></formula>) and liquid crystal polymer (LCP) (<formula formulatype="inline"><tex Notation="TeX">$\varepsilon_{\rm r}=2.9$</tex></formula>, <formula formulatype="inline"><tex Notation="TeX">$\tan\delta=0.0025$</tex> </formula>) substrates. The antenna element of the array is a small volume (2.5 <formula formulatype="inline"><tex Notation="TeX">$\mu$</tex></formula>L) of liquid metal residing inside a low-loss Fluorinert FC-77 (<formula formulatype="inline"> <tex Notation="TeX">$\varepsilon_{\rm r}=1.9$</tex></formula>, <formula formulatype="inline"> <tex Notation="TeX">$\tan\delta=0.0005$</tex></formula>) 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 <formula formulatype="inline"> <tex Notation="TeX">$7^{\circ}$</tex></formula> half-power beamwidth (HPBW), <formula formulatype="inline"><tex Notation="TeX">$>$</tex></formula>21 dB realized gain, and 3.3% <formula formulatype="inline"><tex Notation="TeX">$\vert{ S}_{11}\vert<-10~$</tex></formula>dB bandwidth and provides <formula formulatype="inline"> <tex Notation="TeX">$\pm 30^{\circ}$</tex></formula> 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.

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