In this article, a modified circular shape printed dipole structure is studied to achieve wide bandwidth and dual-band circular polarization (CP) behavior along with dual polarizations. The idea behind this structure is that asymmetric geometry can give rise to circular polarization with an optimized position of coaxial probe feed. The circular patches on both sides of the substrate are altered with elliptical slots at an optimized location in association with opening slots. With these alterations the impedance bandwidth for S 11 < −10 dB is ranging from 2.36-7.34 GHz (4.98 GHz) which is nearly 102.5% about mid-point frequency 4.85 GHz. The antenna resonates at a lower band (1.55 GHz) and shows linear polarization (LP) operation at that band whereas dual CP bands with dual senses are obtained at higher frequency ranges 4.00-4.60 GHz and 6.07-7.13 GHz respectively with 3-dB axial ratio bandwidth of 13.7% and 16.6%. The simulated and measured experimental results are in close agreement. This antenna is suitable to be used for navigation purposes, radar communication, and wireless communication (especially wireless avionics intra communications) in S and C bands, respectively.
The design of proposed antenna started with consideration of a CPW fed circular patch having patch radius 9.3 mm. This antenna is designed on glass epoxy FR4 substrate material (relative permittivity ε r = 4.4, substrate height h = 1.59 mm and loss tangent 0.025) having size 30 mm x 20 mm x 1.59 mm. Circular Patch Antenna with Defected Ground for UWB ABSTRACTThe design and performance of coplanar waveguide fed modified circular patch antenna for possible application in ultra wideband communication systems with band rejection for upper wireless local area network band (5.15 GHz -5.85 GHz) is reported. This antenna is designed on glass epoxy FR4 substrate having size 30 mm × 20 mm × 1.59 mm. The coplanar waveguide fed circular patch antenna is modified by introducing L shaped slits in ground plane and U shaped slot in patch and performance analysis of antenna is simulated by applying CST microwave studio simulation software. Different designed antennas were tested with available experimental facilities. The developed end product shows a nice matching with feed network at frequencies 2.62 GHz, 3.94 GHz and 8.50 GHz and provides 10.38 GHz (3.33 GHz -13.71 GHz) impedance bandwidth with wireless local area network 5.5 GHz (4.74 GHz -6.15 GHz) band rejection. The co and cross polar patterns in elevation and azimuth planes at two frequencies namely 2.62 GHz and 3.94 GHz are obtained which dictate that co-polar patterns are significantly better than cross polar patterns. The simulated peak gain of antenna is close to 3.86 dBi and gain variation with frequency shows a sharp gain decrease in the frequency range 4.74 GHz to 6.15 GHz. The length L g and width W g of the ground plane of considered geometry are 8.0 mm and 7.0 mm, respectively. The gap G p between patch and ground is 1.8 mm whereas the gap g between the strip line and ground plane is 0.50 mm as shown in Fig. 1(a). The length f L and width f w of feed line are 10.8 mm and 5.0 mm, respectively. The considered feed line is electrically thick and contributes in the overall performance of antenna. These design parameters are obtained after extensive optimizations. A comparison of S 11 variation of this geometry with the geometry having same radiating element on an infinite and finite ground planes is shown in Fig. 1 This antenna is then modified in two steps to improve its performance. Keywords CPW Feed Circular Patch with Defected Ground PlaneIn the first step of modification, two L-shaped slits are introduced one by one to make ground plane defective as shown in Fig. 2. The slit length in ground a and slit width in ground b are taken 5 mm and 3 mm, respectively. The slit width S w1 is optimised by simulating (S 11 ) parameter of antenna considering four different slit widths as shown in Fig. 2(b). Finally for the present work, slit width equal to 0.3 mm is selected because for this slit width, best performance from antenna is realised which is shown in Fig. 2(c). A comparison between simulated and measured reflection coefficient (S 11 ) as a function of frequency...
A novel single layer assembly of gap coupled elements in elliptical shape is proposed in this communication to achieve broadband performance. Among the five patches considered in the present assembly, two pairs of patches having different patch areas are arranged around an edge truncated elliptical patch. The central edge truncated elliptical patch is fed through an inset feed arrangement and the other patches are parasitically gap coupled to the central patch. With such an arrangement, an enhanced impedance bandwidth of 2.45 GHz (or 36.2%) with respect to central frequency 6.1 GHz is achieved. Three resonant modes are excited with this arrangement giving improved bandwidth and gain in comparison to a conventional elliptical patch antenna. The simulated radiation patterns of proposed arrangement of patches suggest that these are identical in shape and direction of maximum radiations is directed normally to assembly of patches.
The article proposes design investigation and experimental results of a coplanar waveguide (CPW) fed square slot antenna that gives wideband circular polarization. This circular polarization characteristic is achieved by embedding a square shape stub to left bottom corner and an L-shaped strip to the right upper corner of the slot. A high impedance bandwidth of 87.8 % (3.6–9.0 GHz), a wide axial ratio bandwidth of 73.05 % (4.2–9.0 GHz) and wide 3-dB axial ratio beamwidth of 90° in the entire frequency range of interest are achieved with this antenna structure. To improve the 3-dB axial ratio bandwidth, three slots (two horizontal and one vertical) are scratched at the exterior periphery of the ground plane. These perturbation assemblies are accountable to excite orthogonal modes and help increase an axial ratio bandwidth. The designed antenna displays the constant and steady radiation patterns in the complete frequency range of concern. The overall dimension of the presented compact antenna is 0.24λ × 0.24λ × 0.01λ.
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