Fringing Aperture Modulation of Transverse Electric Mode Excited Microstrip Antenna for Wireless Underground Sensor Networks

In the present era, the key challenge for a low-frequency planar antenna applied to a wireless underground sensor network (WUSN) and other underground wireless communication is to achieve positive gain with good efficiency. Besides that, a relatively wider bandwidth with more than one operating frequency is desirable for operational versatility. In this work, a simple artificial magnetic conductor (AMC)-integrated rectangular microstrip antenna (RMA) of size <inline-formula> <tex-math notation="LaTeX">$0.28\lambda _{0} \times 0.28\lambda _{0} \times 0.07\lambda _{0}$ </tex-math></inline-formula> is employed. By meticulously exploiting a dual-periodic AMC along with dielectric strips (AMC radiating patch and AMC ground plane) and proper utilization of an L-probe feed, two resonances at 572 MHz (low band) and 768 MHz (high band) can be yielded with a wide bandwidth of around 12%. Unlike the classical RMA design, a transverse electric (TE) mode excited RMA is proposed. The proposed antenna can also achieve good positive gains of 4.3 dBi (572 MHz) and 6.1 dBi (768 MHz) across both bands with an efficiency of 71% and 75%, respectively.