Design of band reconfigurable Koch fractal antenna for wideband applications

In this communication, a band reconfigurable fractal antenna with modified partial ground is proposed for wireless applications. Four switches using PIN diodes supported by the antenna biasing circuit provide frequency reconfigurability, while star-shaped fractal geometry is used to achieve both miniaturisation and wideband functioning in the proposed antenna. The surface current distribution of the radiating patch is altered by the ON and OFF states of the PIN diode, which leads to the multiband resonance and reconfiguration features of the designed structure. The design has an overall electrical size of 70 × 45 × 1.6 mm³ and is made on a commonly available FR4 substrate with a thickness of 1.6 mm and a dielectric constant of 4.4. The three operational bands are as follows: case I, which covers 3.7–5 GHz (30 %); case II, which covers 1.7–3.5 GHz (71 %); and case III, which covers 1.4–4 GHz (96 %). Two distinct bands are obtained in cases I and II; and case III nearly covers the frequency band of cases I and II. Therefore, the impedance bandwidth (IBW) offers continuous wideband frequency coverage from 1.4 to 5 GHz (110 %). To sense the full band and then modify its bandwidth to choose the appropriate sub-band and prefilter out the others, the proposed antenna may switch between a wide operational band of 1.4–5 GHz with three distinct subbands. The antenna could potentially be useful for wireless communication systems in the future due to its frequency-selective feature and stable radiation patterns.