Compact Dual-band ACS-fed Monopole Omnidirectional Antenna for WLAN/WiMAX Applications

A compact dual-band asymmetric coplanar strip (ACS) fed printed monopole omnidirectional antenna for WLAN/WiMAX applications is presented. The designed antenna comprises of a simple ACS-fed (Asymmetric Coplanar Strip) monopole and three different strip radiating elements. It occupies a very compact size of 15 x 24 mm(2) including the ground plane, which is only about 0.17. x 0.27 lambda (lambda is the wavelength at the frequency of 3.48 GHz in free space). This antenna has the characteristics of miniaturization and one of its resonant modes at 3.48 GHz is created by adding a rectangular branch, and the other resonant mode at 5.64 GHz is co-produced by the horizontal strip and vertical strip including an element which is like a Chinese Tai Chi fish. The Chinese Tai Chi fish element has its own resonant characteristics, which would be described in detail. By using all these unique structures, dual desired resonant frequencies can be achieved, and each of them are achieved independently. The proposed antenna has been printed on an FR4 substrate, of which the dielectric constant is 4.3. Both the simulated and measured results show reasonable agreement, and the measured dates show that the antenna has an impedance bandwidth of 300 MHz (3.43-3.73 GHz) and 950 MHz (5.03-5.98 GHz) with a reflection coefficient of less than -10 dB. The patterns of this antenna in H-plane are omnidirectional which can be achieved over the desired operating bands. These bands are suitable for WLAN 5.2/5.8 GHz applications and 3.48 GHz WiMAX bands. The proposed antenna along with acceptable peak gain makes the best suitable candidate for the above intended applications.