Dual-band inkjet printed coplanar waveguide-fed stepped-impedance slot dipole antenna for ISM application

In this work, a dual-industrial, scientific, and medical (ISM)-band flexible slot dipole antenna is investigated. It is based on quarter-guided-wavelength (lambda g/4 ${\lambda }_{g}\unicode{x02215}4$) stepped impedance resonator (SIR) slots fed by coplanar waveguide. Compared to the mostly used lambda g/2 ${\lambda }_{g}\unicode{x02215}2$ SIR, the use of the lambda g/4 ${\lambda }_{g}\unicode{x02215}4$ type SIR not only enables compact size but also leads to broadside radiation without gain decline at the first harmonic. The analysis of fundamental and spurious resonance conditions was also elaborated to reveal the theory behind compact size and harmonics suppression. Planar measurements show the impedance bandwidths are 500 MHz (20.4%) for 2.2-2.7 GHz, and 1200 MHz (21.4%) for 5-6.2 GHz, with peak gain of 3.7 and 5.8 dBi at 2.4 and 5.5 GHz, respectively. Furthermore, in curving measurement, both the reflection coefficient and radiation pattern remain stable during bending. Our proposed antenna will benefit a bunch of flexible and compact applications operating in dual-ISM-band.