Penta-band circularly polarised antenna using a lumped capacitor

What is it about?

This article demonstrates a very simple printed monopole antenna with penta-band circularly polarized (CP) radiation characteristics for wireless local area network (WLAN), worldwide interoperability for microwave access (WiMAX) and downlink of the X-band satellite communication applications is proposed for the first time. The antenna comprises a notched rectangular ground plane and a radiating patch consisting of inverted-U-shaped, I-shaped, and inverted-L-shaped radiators that creates four CP modes operating at the 2.4/3.5/5.8/7.5 GHz. By placing a lumped capacitor of 0.5 pF in the gap between the I-shaped radiator and the inverted-L-shaped radiator, an extra CP mode at the 5.2 GHz WLAN band is generated, thus completing the penta-band CP antenna. The measured −10-dB impedance bandwidth of the demonstrated antenna is 340 MHz (2.37–2.71 GHz) and 4.8 GHz (3.2–8 GHz), and the measured 3-dB axial-ratio bandwidth is 16.6%, 13.5%, 2.9%, 2.4%, and 4% in five distinct bands of 2.1−2.48 GHz, 3.1−3.55 GHz, 5.1−5.25 GHz, 5.76−5.9 GHz, and 7.45−7.75 GHz. To the best of the authors’ knowledge, no antenna has ever achieved penta-band CP characteristics for these applications so far.

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