Comparative analysis of microstrip-line-fed gap-coupled and direct-coupled microstrip patch antennas for wideband applications

An attempt is made to improve the impedance bandwidth (S11) of a microstrip antenna by means of the gap-coupling method, yielding a bandwidth of 97.88% for the gap-coupled rectangular microstrip antenna (GC-RMSA) compared with 7.67% for the direct-coupled rectangular microstrip antenna with all dimensions the same. The maximum gain of the proposed (GC-RMSA) design is 6.725 dB with antenna efficiency of 99.86%. The proposed antenna design is analyzed using the IE3D simulator. The microstrip line feed technique is used to energize the antenna, and its performance as a function of the gap between the elements (g) and the width of the feed strip (W) is investigated. The results show that the impedance bandwidth of the gap-coupled antenna depends on the coupling gap between the elements; indeed, as the gap (g) is increased up to a certain level, the bandwidth of the proposed antenna increases, resulting in a wideband characteristic. However, after a certain value of the gap (g), the bandwidth decreases due to spurious radiation, and the antenna characteristic changes from wide to dual band with a corresponding decrease in the bandwidth. The proposed antenna design covers the frequency range from 2.093 to 6.105 GHz, including the C-band, S-band uplink and downlink frequencies, Wi-Fi, Bluetooth, WLAN, and IEEE (a/b/g) standard applications.