Metamaterial Inspired Radio Frequency-Based Touchpad Sensor System

This paper proposes a metamaterial inspired radio frequency touchpad sensor system based on two split ring resonators (SRRs) realized on a Rogers/Duroid 5870 with 2.33 dielectric constant = 2.33, loss tangent = 0.0012, and thickness = 0.8 mm. The touchpad consists of two SRRs resonating at
$f_{1} = 2.74$
GHz and
$f_{2} = 3.86$
GHz. When a finger is placed on SRR 1,
$f_{1}$
changes from 2.74 to 2.57 GHz due to electromagnetic coupling between the SRR and the finger, and similarly,
$f_{2}$
changes from 3.86 to 3.76 GHz. The proposed touchpad system can detect a finger wearing a glove, in contrast to capacitive touchpads utilized in contemporary smart phones. We demonstrated 56- and 49-MHz frequency shifts for
$f_{1}$
and
$f_{2}$
, respectively, with 1.66-mm total thickness (0.69-mm-thick photo paper and 0.97-mm-thick glass slide).