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Abstract-A novel compact CPW (coplanar waveguide-fed) CPSS (Circularly polarized square slot) antenna is presented. The proposed single-layer antenna is composed of a rectangular ground plane embedded with two equal-size patches along two orthogonal directions. Equal amplitudes with 90 • phase difference values of two patches are capable of generating a resonant mode for exciting two orthogonal E vectors. Axial ratio (AR) bandwidth is significantly enhanced due to slot corner modification. The designed CPSS antenna is compact in nature with volume of 0.37λ 0 × 0.34λ 0 × 0.012λ 0 mm 3 (λ 0 = free space wavelength at centre frequency of the CP bandwidth). It has impedance bandwidth between 4.65-6.72 GHz (36.41%) and 3-dB axial-ratio bandwidth of 520 MHz (4.85-5.37 GHz), which covers 4.9 GHz (802.11j) WLAN for public safety ranging from 4.94 GHz to 4.99 GHz and WLAN (U-NII-1 and U-NII-2A) ranging from 5.150-5.350 GHz for indoor use. The gain variation for the frequencies within the CP bandwidth is also observed to be less than 0.4 dBic. The design is successfully implemented, and measured results are compared with the simulated ones, which are found good agreement.

Broadband circularly polarised square slot antenna excited by a coplanar waveguide feed with enhanced axial ratio bandwidth (ARBW) is proposed, designed and experimentally studied. Larger than 21% 3 dB ARBW can be attained by using asymmetric feed and implementing a T-shaped grounded stub from the left side of the square slot in orthogonal direction towards the slot centre. To further enhance the 3 dB ARBW of the proposed slot antenna, a pair of equal grounded L-shaped strips with different sizes is embedded at the top right corner of the square slot. Small L-shaped grounded strip plays an important role for merging two closely spaced multiresonant modes, generated by the combined effect of asymmetric feed with T-shaped grounded stub and with large L-shaped strip. Overall size of the proposed antenna is 40 × 40 × 1.6 mm 3. Measured value shows that the impedance bandwidth and 3 dB ARBW of the designed antenna are 73.39% (5.02-10.84 GHz) and 58.08% (5.07-9.22 GHz), respectively. Good agreement is achieved between simulated and measured results.

A simple and compact triple‐band dual‐sense circularly polarised (CP) microstrip line fed planar monopole antenna is presented here with ultra‐wide impedance bandwidth. The proposed antenna comprised a slit‐loaded semi‐circular radiating patch and a stub‐loaded modified ground plane. By properly embedding a slit into the patch and a stub into the modified ground plane, the proposed monopole structure radiates triple band CP in broadside direction. The overall size of the proposed antenna is 40 × 40 × 1.6 mm3. The proposed antenna is capable of generating right hand CP wave in the lower and upper CP band, while left hand CP wave is generated by the middle CP band. The measured − 10 dB impedance bandwidth is 122% (2.74–11.32 GHz) and 3‐dB axial ratio bandwidths for the triple bands are 41.55% (4.08–6.22 GHz), 17.03% (7.52–8.92 GHz) and 14.68% (9.34–10.82 GHz), respectively. The measured peak gains within three CP bands are 4.24, 4.02 and 3.78 dBic, respectively.

A broadband circularly polarized (CP) planar monopole antenna is proposed here for ultrawideband (UWB) communication. The antenna is composed of a modified annular ring patch fed by a tapered microstrip line and a rectangular semiground plane on the opposite side of the substrate. Capability of generating wide axial ratio bandwidth (ARBW) is another feature of the proposed antenna. Wide ARBW is achieved by introducing a rectangular slot and a stub in the ground plane. The CP antenna has an impressive ARBW of 5.52 GHz (81.42%, 4.02-9.54 GHz) within the UWB frequency range (3.

A compact broadband circularly polarized square-slot antenna based on an offset-fed inverted-L-shaped microstrip feed line is proposed. A rectangular slot beneath the feed line and an inverted-L-shaped grounded strip on the left bottom corner of the wide square slot produce dual-wideband circular polarization (CP) coverage in a compact size. Meander lines with a square slot loaded at the right bottom corner of the ground plane result in broadband CP through overlapping of the dual-wideband axial ratio (AR) bandwidths. The magnitude and phase differences between two field components can be controlled effectively with proper tuning of the square slot dimensions (4.5 � 4.5 mm 2 ), which is helpful for broadening AR bandwidth over the C-band by minimizing AR values (≤3 dB). The overall dimensions of the prototype are only 26 � 26 � 1.6 mm 3 . The antenna prototype has been validated experimentally. The measured results indicate an impedance bandwidth of 104% (3.56-11.22 GHz) and a 3 dB AR bandwidth of 76% . A peak gain of 3.4-4.42 dBi is achieved within the AR bandwidth. The proposed antenna is suitable for CP applications in the C-band.This 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.

A dual-band two-port MIMO antenna with very high isolation is proposed for 5G/WLAN application. The overall size of the MIMO antenna is (18 × 44 × 0.8) mm 3 . The unequal arm of the Inverted-F Antenna (IFA) is the reason for the dual bands. Bending and extending one of the arms with the staircase shape is responsible for the proposed dual-bands having resonant frequency at 3.45 GHz (3.3 GHz-3.65 GHz) and 5.1 GHz (4.8 GHz-5.5 GHz) respectively with percentage impedance bandwidth of 10% and 13.6%, respectively. The proposed antenna uses a simple decoupling structure based on a wide inverted T-shaped slot to achieve good isolation (better than 18 dB and 34 dB respectively for the dual-bands) between the ports. The envelope correlation coefficient (ECC) and channel capacity loss (CCL) are within the acceptable limits.

In this article, a geometrically simple, microstrip line‐fed planar monopole structure with slanting edge ground plane is designed to realize the dual‐band dual‐polarized operation. The proposed antenna consists of a rotated U‐shaped patch and an electromagnetically coupled L‐shaped parasitic radiating element. Owing to the combination of microstrip line‐fed radiating patch and a slanting‐edge rectangular ground plane on the opposite side of the substrate, the proposed dual‐band antenna can generate broad axial ratio bandwidth (ARBW) in the upper frequency band. The overall dimension of the prototype is only 32 × 32 × 1.6 mm3. The measured results validate that the proposed antenna has two operational frequency bands, 29.84% (1.54‐2.08 GHz) for linearly polarized radiation and 71.85% (3.96‐8.4 GHz) for circularly polarized radiation. Measured result shows that 3‐dB ARBW of the proposed antenna is 73.54% (3.80‐8.22 GHz) in the higher frequency band. It shows that the higher frequency band exhibits a left‐hand circularly polarized radiation in the boresight direction.