Design of mmWave Foldable Vertically Stacked Yagi–Uda Antenna Inspired by Origami and Kirigami Theories

This letter presents a foldable vertically stacked Yagi–Uda antenna at millimeter-wave (mmWave) frequency band. The proposed antenna is built on a FR4 substrate. The antenna consists of a balun, feed dipole element, stacked folded dipole, and inside lamina emergent torsional (LET) joint array. The LET joint array is introduced to reduce and distribute the mechanical stress generated in folding the rigid FR4 substrate. In the planar mode, the antenna results in a measured gain value of 4.9 dBi at the design frequency 24 GHz with a cross-polarization suppression level of less than 12 dB. In the folded mode, the antenna has a measured gain value of 3.9 dB at the target frequency 24 GHz with a cross-polarization suppression level of less than 10 dB. Both operation modes of the proposed antenna cover the broad bandwidth from 23 to 28 GHz (about 20
$\%$
).