Herein a compact triple-band circularly polarized (CP) microstrip patch antenna, loaded with a single annular ring patch with eight symmetrical slots along its periphery and a series of octagonal closed ring resonators (CRRs) on the opposite side of the substrate, is proposed. Evolution process of the antenna geometry reveals that the eight symmetrical slots and the CRRs are responsible for increased impedance bandwidth (IBW), while simulated (high-frequency structure simulator (HFSS) and computer simulation tool) triple CP bands obtained due to the uses of crossshaped slit resonating at 7.5 GHz (152.2 MHz); asymmetric ground plane at 10.2 GHz (161 MHz); and square open-loop at 12.2 GHz (112.5 MHz). Series of parasitic strips improved CP radiation and remove ripple in the radiation pattern. The antenna presented here, is compact, fabricated with an optimized dimension of 35 × 30 × 1.6 mm 3 , on low cost FR-4 substrate with copper cladding. The measured <10-dB IBW ranges from 4.08-5.05 GHz and 5.98 GHz up to 13.6 GHz. Simulated maximum peak gain found to be 4.45 dBi at 13 GHz. The antenna proposed herein is appropriate for wireless applications. K E Y W O R D S asymmetric ground, circular polarization, closed ring resonators, CPW-fed, parasitic strip 1This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

A CPW-fed printed square slot antenna (PSSA) based on characteristic modes (CMs) theory is investigated for broadband circular polarization (CP). It consists of an I-shaped patch and CPW ground plane loaded with a rectangular stub, a pair of asymmetric inverted-L grounded strips, and a spiral slot to get CP radiation over a wide-angle range. CMs of this strip and slot loaded PSSA show that the entire structure takes participation to excite magnetic and electric modes to provide broadband performance. First six characteristic modes are excited using CPW feeding to find resonating frequencies and radiating behavior. The proposed antenna is fabricated over RO-3003 substrate material with a floor area of 20 × 20 mm 2 . Experimental results showcase the broadband CP performance with wide 3-dB ARBW of 56% (6.6-11.8 GHz) and impedance bandwidth (IBW) (|S 11 | ≤ −10 dB) about 115% (4-11 GHz) which make it suitable for C-band and X-band wireless and satellite communication applications. The antenna has a peak gain about 5.5 dBi with good LHCP radiations in the broadside direction.

This article presents a novel, compact, single feed circularly polarized (CP) microstrip antenna. Proposed design involve an inverted Y-shaped radiating patch fed by an L-shaped microstrip line feed and a rectangular open-loop placed near its right corner. A semi-rectangular ground plane is used on the opposite side of the substrate. Coupling between the rectangular open-loop and the inverted Y-shaped patch plays a vital role in attaining wideband CP, while the semi-rectangular ground plane is crucial for enhancing impedance bandwidth (IBW). The optimized design achieved measured wide IBW of 5.164 GHz (65.53%, spanning over 5.297-10.461 GHz) having its center frequency (f rc ) at 7.878 GHz. The corresponding measured axial ratio bandwidth (ARBW) obtained inside the measured IBW curve is 2.25 GHz (having its center CP resonating frequency f cp 7.52 GHz, spanning over 6.40-8.65 GHz, 29.92%). Measurement results are validated in both Ansys Electronics Desktop 2020 R1 and CST Microwave Studio 2018. Proposed antenna is fabricated on FR-4 epoxy substrate of 1.6 mm thickness and exhibits a very small footprint of just 400 mm 2 (20 × 20 mm 2 ) (size 0.58λ mgL × 0.58λ mgL × 0.046λ mgL , where λ mgL is the measured guided wavelength at lower resonating frequency f mrL = 5.297 GHz) with 51.31% reduction in size. Measured maximum peak gain for the impedance band is 2.04 dBi at 8.8 GHz and 1.96 dBi at f cp 7.52 GHz. The structure of the proposed antenna is extremely simple, quite small in size and its CP bands can be suitable for some C-band and ITU (International Telecommunication Union)-8 GHz application. K E Y W O R D Saxial ratio bandwidth, circular polarization, impedance bandwidth, ITU (8 GHz) band INTRODUCTIONIn recent times, demand for small Form Factor strategies used in wireless systems, is leading to design of many novel, compact, low-cost, broadband microstrip antennas. 1 Circular polarization has become one of the most sought after methods of polarization due to its considerable insulation to multipath interferences, sturdiness to polarization mismatchesThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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