Compact broadband frequency selective microstrip antenna and its application to indoor positioning systems for wireless networks

This study presents a low-profile broadband microstrip patch antenna with filtering response. The proposed antenna consists of a rectangular patch and four parasitic gap-coupled elements, two L- and two rectangular-shaped patches. A broadband quasi-elliptic boresight gain response is obtained without using any extra filtering circuits. The input impedance of each radiating element, i.e., driven patch and parasitic elements, is matched to its radiating quality factor and the couplings between patches are optimised for broadband impedance bandwidth with filtering response. Prototype hardware is designed and fabricated on Kappa 438 substrate with a relative permittivity of 4.4 and thickness of 3.2 mm. The antenna exhibits a total size of 25 × 23 × 3.2 mm 3 with relative impedance bandwidth (voltage standing wave ratio