Three multiband microstrip patch antennas (MPAs) to operate at (3.5/5.5 GHz) WiMAX, upper (5.2/5.8 GHz) WLAN and C frequency bands are presented in this paper. The proposed antenna structures are mainly constructed from the fork-shaped monopole antenna. These three antennas (Ant.1-3) are namely mender fork-shaped antenna (MFA), spiral fork-shaped antenna (SFA) and double SFA (DSFA). All antennas are fed by coplanar waveguide (CPW) structure and printed on the front side of FR substrate with surface area of 21×21 mm~(2). A new approach is presented for designing the proposed antennas to resonate at the specified operating frequency bands. Initially, a conventional MPA fed by microstrip-line is designed to operate at 5.8-GHz WLAN band. Then, intermediate antenna prototype structures are obtained during the design process until achieving the desired antennas. The Ant.1 and Ant.3 gives dual-band characteristic covering 5.2/5.8 GHz-WLAN band including 5.150–5.875 GHz and 3.5/5.5 GHz-WiMAX including 3.4–3.7 GHz and 5.25–5.85 GHz, respectively. The Ant.2 gives tri-band covering the aforementioned dual-band besides to C-band 7.25 GHz (6.84 – 7.50 GHz). An electromagnetic simulator CST MWS ver. 2018 was used to analyze the designed antennas. The simulated results demonstrate that a dual- and tri-band operation can be easily provided by these antennas as well they have good dipole-like and omnidirectional radiation characteristics, stable gain and high-radiation efficiency indicating that the proposed antennas are candidate for WLAN/WiMAX applications.
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