A Broadband Stepped Monopole Antenna with Loop Ground

In this paper, a broadband monopole antenna for next generation wireless communications is proposed. The proposed antenna consists of rectangular loop ground and a stepped monopole radiator. By employing a simple two-step monopole radiator, a third resonance is introduced, thereby achieving broadband characteristics. The antenna is printed on FR4 substrate and has a compact overall dimension of (50 mm × 63 mm × 1.6 mm). At |S11| < −10 dB, the simulated and measured impedance bandwidth of the proposed antenna is 93.2% (1.61–4.425 GHz) and 95.2% (1.69–4.762 GHz), respectively. The proposed antenna covers most of the LTE bands in the frequency range from 1.7 to 2.7 GHz and newer LTE bands in the range from 3.4 to 3.8 GHz. Also, the antenna exhibits stable omnidirectional radiation pattern and has gain varying from 3.2 to 4.8 dBi. Furthermore, the lumped element equivalent circuit model is presented and it validates three resonant modes of the proposed antenna.