A dual band stub-loaded AMC design for the gain enhancement of a planar monopole antenna

Abstract

A dual band stub-loaded artificial magnetic conductor (AMC) structure to enhance the gain of a dual band monopole is presented. Designed for operation in the 2.4 and 5 GHz WLAN bands, the AMC unit cell is intended to be capable of independently tuning the upper (5 GHz) band by varying the stub length of the structure. To assess the effectiveness of the AMC plane, it is integrated underneath a coplanar waveguide (CPW)-fed planar monopole antenna. Both structures are designed and fabricated on a FR4 substrate. The unit cell is first multiplied into a 5 x 5 array to form the AMC plane, which acts as a reflector to the monopole antenna. Measurements indicated values of 6.76 dBi (at 2.4 GHz) in band-I, 6.5 dBi (at 3.53 GHz) in band-II, and finally 7.26 dBi (at 4.85 GHz) in band-III. It is also observed that the measured antenna gain is improved to 7.26 dBi from 4.2 dBi at 4.85 GHz with reduced SAR values. Moreover, its overall size of 70 × 70 × 10.76 mm3 (0.45λ0 × 0.45λ0 × 0.07λ0) validated the compactness in comparison with other similar structures, with reasonable realized gain.