Design and analysis of clover leaf‐shaped fractal antenna integrated with stepped impedance resonator for wireless applications

Abstract

SummaryA novel multi‐band clover leaf‐shaped fractal antenna with integrated filtering to reduce higher order harmonics has been proposed. Existing microstrip filtering antennas endure limited gain, narrow impedance bandwidth, and undesired frequency radiations. The proposed antenna is designated to operate simultaneously in following operating bands: 3.35–3.6 GHz for WiMAX, 5.156–5.825 GHz for WLAN, 5.7–6.4 GHz for Intelligent Transport Systems (ITS), and 7.7–8.5 GHz for ITU‐R applications. The proposed patch is realized by combining two semi‐fractal ring microstrip patches like the geometry of a three‐leaf clover with dual‐layered stepped impedance resonator (SIR) integrated at bottom layer of the second substrate. The SIR bandpass filter exhibits odd and even modes suppresses higher order harmonics and undesired radiations. An aperture coupled feeding in the proposed patch offers better bandwidth and impedance matching. The number of iterations is increased to get the desired multiband characteristics. The proposed microstrip fractal antenna has the geometrical dimensions of 50 × 50 × 2 mm3. It is observed that both the simulated and measured results offers peak gain of >5 dBi and better return loss (S11), that is, 3.3–3.6‐GHz band offers S11 of −33.73 dB, 5.15–5.825‐GHz band offers S11 of −36.69 dB, and 5.795–6.4‐GHz band shows the S11 of −36.25 dB, and for 7.725–8.5 GHz, the return loss is −33.209 dB. Harmonics at 6.42 GHz (1.8f0), 7.37 GHz (1.5f0), and 9.04 GHz (1.73f0) has been suppressed and shows linear polarization in the WLAN band and circular polarization in the ITU‐R and WiMAX bands.