AbstractThis article explores the possibilities of incorporating a defected ground structure (DGS) for widening the 3 dB axial ratio beamwidth (ARBW) of a simple low-profile planar circularly polarized (CP) antenna. Two pairs of DGSs are etched symmetrically along the diagonals of the ground plane to overcome the limited 3 dB ARBW performance of a crossed-slotted circular-shaped planar CP antenna. Here, one pair of DGSs is orthogonal to another pair of DGSs. The distance between the pairs of DGSs plays a key role in enhancing the 3 dB ARBW by 40.62%. A gap of 0.18λ0 is considered between the DGSs to maintain the symmetrical electric field distribution in the substrate. It also helps to reduce orthogonal current components and provides uniformly distributed patch surface currents. These phenomena collectively help the proposed CP antenna to exhibit right-handed circular polarization radiation with the 3 dB ARBW of 186° and 188° in the E-plane and H-plane, respectively. The measured results yield impedance bandwidth (S11 ≤ −10 dB) of 2.6% (2.283–2.342 GHz), CP bandwidth of 0.9% (2.294–2.315 GHz), gain higher than 4.8 dBic, and total antenna efficiency more than 64% across the entire CP band.

In this article, a low profile circularly polarized (CP) antenna with wide 3-dB axial ratio beamwidth (ARBW) is presented. Two-pair of parallel slots are etched on a circular patch and manifested as magnetic dipoles (MDs). These narrow slots are arranged symmetrically about the axes, and one pair is orthogonal to another pair of slots. The philosophy of CP radiation across a wide angular range strongly depends on the spacing between the paired-dipoles, for example spacing of $0.22\lambda _{0}$ , two-orthogonal far-field radiated components become equal across a wide-angle. Moreover, this particular spacing between the paired-dipoles provides a symmetrical electric field distribution along the periphery of the patch, which ensures the broadside LHCP radiation with wide 3-dB ARBW of 228° and 214° at the plane of $\varphi = 0^{\circ }$ and $\varphi = 90^{\circ }$ , respectively. The measured results from the fabricated prototype exhibit good agreement with the simulated results. The antenna has impedance bandwidth (IBW) and CP bandwidth (CPBW) of 2.6% (64 MHz), and 0.9% (22 MHz), respectively. The broadside radiation holds antenna gain higher than 5 dBic across the entire CPBW.

In this letter, a low-profile circularly polarized (CP) narrow-slots slotted-patch antenna for wide 3 dB axial-ratio beamwidth (ARBW) performance is presented. It consists of two pairs of narrow slots along the diagonal lines of a square patch with a single feed. These pairs of narrow slots are conceived and placed to serve as magnetic dipoles with quarter-wavelength separation, forcing the amplitude of the orthogonal electric field components to be equal across a wide angle. The 3 dB ARBW of the CP antenna is a strong function of the mutual magnetic field, which is feasible to alter with different parameters of the slot. The location, dimensions, and gap between the slots are tuned to achieve wide 3 dB ARBW. Measured results of the fabricated prototype exhibit 3 dB ARBW of 226° with ARmin of 0.52 dB and 198° with ARmin of 1.61 dB in two principal planes at $\boldsymbol{\varphi } = \text{0}^\circ $ and $\boldsymbol{\varphi } = \text{90}^\circ $, respectively. The antenna offers impedance bandwidth of 85 MHz (2.448–2.533 GHz) and CP bandwidth (CPBW) of 23 MHz (2.474–2.497 GHz). The minimum peak gain is 3.87 dBic in the broadside direction.

A low-profile circularly polarised (CP) antenna with wide 3 dB axial ratio beamwidth (ARBW) is proposed in this study. The possibilities of widening the 3 dB ARBW of single diagonal slot-loaded conventional CP antenna have been explored successfully by incorporating a pair of rectangular slots along the diagonal line of a square patch antenna. The design parameters and the symmetrical arrangement of this pair of slots across the centre of the patch are crucial to adjust and achieve the wide 3 dB ARBW with high CP purity. Coupling between the two diagonal slots provides nearly equal E-theta and E-phi radiation patterns over a large angular range, and hence the 3 dB ARBW has been enhanced by 85.71 and 55.4% for phi = 0 degrees and phi = 90 degrees planes, respectively, in comparison to the conventional slot-loaded CP antenna. The minimum 3 dB ARBW of 208 degrees and a maximum of 230 degrees have been achieved across different planes of radiation phi = 0 degrees, 45 degrees, 90 degrees, and 135 degrees with a minimum axial ratio of 0.20 dB only. The absolute planar antenna of size (0.29 x 0.29 x 0.013)lambda(3)(0), where lambda(0) is the free-space wavelength corresponding to the CP frequency, has been fabricated and tested. The measured and simulated results show fair consistency to each other.

The coupled fields between the slots are physically analyzed for wide 3-dB axial ratio beamwidth (ARBW) of a circularly polarized (CP) antenna. The square shaped CP antenna is decorated with a rectangular slot along one diagonal line of the patch and a pair of cross slots along another diagonal line. Dimensions of cross slots play a crucial role in adjusting the 3-dB ARBW of this CP antenna. This antenna offers the impedance bandwidth (IBW) of 83 MHz (2.443-2.526 GHz), CP bandwidth (CPBW) of 17 MHz (2.4462.463 GHz), and a maximum realizable gain of 4.28 dBic. The proposed left handed CP (LHCP) antenna exhibits wide 3-dB ARBW of 224° and 212o at φ = 0° and φ = 90° planes, respectively.

A simple dual-band antenna for MICS (402-405 MHz) and GPS (1570-1580 MHz) bands is developed and discussed in this paper. The effective shunt inductance property of shorting pin and effective electrical length property of slot is used on a conventional circular patch antenna (CPA) to reduce the resonant frequency of the modes (TM11 and TM21). A single shorting pin is placed at the periphery to drop down the resonance frequencies. After that 12 equal rectangular slots are incorporated along the circumference of a 24 mm radius circular patch for further reduction hence, the size of the antenna is reduced by 94.73% in compared to the conventional CPA. The measured impedance bandwidth for MICS and GPS band is about 8.9% (384-420 MHz) and 3.17% (1.55-1.6 GHz) respectively. The simulated 3-dB axial ratio bandwidth is about 6.21% (390-415 MHz) for MICS band and 1.9% (1.56-1.59 GHz) for GPS band. This antenna can be very useful for real-time data transmission and tracking the dynamic location of human body, especially for elderly persons. The 50 mm x 50 mm x 1.6 mm proposed antenna is fabricated and measured to validate the simulated results and it shows good agreement.

A GSM1800 band antenna using inverted suspended circular patch is presented in this work. The proposed antenna is suitable for some specific used such as energy harvesting systems. The main objective of simulation is to increase the gain of patch antenna. A circular patch antenna of 32 mm radius has been optimized using Ansotf HFSS.v.15. The simulation results of antenna shows the return loss is -21 dB at 1.8 GHz for VSWR≤ 2. The maximum gain of antenna is obtained at 7.5 dB. The gain of antenna is increased by inverted suspended circular patch with same dimension of radiating patch from 7.5 dB to 8.5 dB. The gain of the antenna is increased with increasing the gap between top and bottom patch because of coupling between them. The gain of antenna is increased from 8.2 dB to 8.5 dB when gap is increased from 1 mm to 4 mm.