A Planar Dipole for Multiband Antenna Systems With Self-Balanced Impedance

In this letter, we present a multiframe L-slot planar dipole loaded with a single microstripline for multiband antenna systems. The multiband is achieved by creating a multiframe L-slot on a host dipole and also by loading the host dipole antenna with a single microstripline to generate a couple of shunts and series of capacitive gaps with an inductive strip, eventually forming $LC$ -like resonators. The antenna supports several wireless communication bands including: LTE bands at $1.7 \sim 1.8$ and $2.3 \sim 2.6~\hbox{GHz}$ ; WLAN bands at $2.4 \sim 2.5$ , 5.2, and 5.8 GHz; WiBro/WiMAX bands at $3 \sim 4~\hbox{GHz}$ . In addition, to validate the multiband behaviors, we also proposed a simple equivalent circuit for the designed antenna in which biconical transmission lines were adopted to model the host dipole sections. The simulation, fabrication, and measurement of the proposed antenna were implemented. As a result, its reflection coefficients $\vert { S}_{11}\vert$ were found to be better than ${-}$ 7 dB for most operating frequencies along with a sufficiently large bandwidth and good radiation patterns.