In this paper, the concept of perturbation theory is applied to derive a general electric field (E-field) expression for any arbitrary-shaped microstrip patch antenna. The arbitrary shape is created by adding small perturbation in a regular patch shape, which is used to find perturbed and unperturbed electromagnetic wave solutions for resultant E-field of patch antenna. Ansoft HFSS simulator is used to validate the derived field expression in curvilinear coordinates for a regular circular-shaped patch. Then the proposed field analysis is applied to develop two new arbitrary-shaped patches in C-band for desired E-field patterns.

In this paper, a vase-shaped monopole antenna is presented for dual band notch (WiMAX IEEE802.16 3.30–3.80 GHz with C-band 3.80–4.20 GHz and WLAN IEEE802.11a/h/j/n 5.15–5.35 GHz, 5.25–5.35 GHz, 5.47–5.725 GHz, 5.725–5.825 GHz) UWB and other wireless services (close range radar: 8–12 GHz in X-band & satellite communication: 12–18 GHz in Ku-band). Measured VSWR of proposed antenna shows a high band-rejection for WiMAX along with C-band with VSWR = 25.33 at 3.77 GHz and WLAN with VSWR = 6.0 at 5.64 GHz is achieved by cutting two C-shaped slots on the radiating patch. Designed antenna covers a wide usable fractional bandwidth 160% (2.58–20.39 GHz). Furthermore, the measured gain of antenna is relatively stable across the impedance bandwidth except band-notched. In addition, antenna offers omni-directional pattern, reasonably small 20 × 20 × 0.787 mm3 and easy to construct structure.

A miniaturized dual-band CPW-fed metamaterial antenna is presented and developed in this paper. Zeroth-order mode is originated by realizing open-ended composite right/left-handed transmission line. A dual split ring resonator is introduced to obtain another mode. The antenna is operated in the frequency region 1.60–1.64 and 2.76–2.79 GHz. Shunt inductance is offered by means of thin stripline connecting ground planes. It is demonstrated that by applying metamaterial loading (thin stripline) proposed antenna is capable to achieve 51.9% miniaturization with respect to the antenna without metamaterial loading. The presented antenna has an electrical size of 0.162 λ0 × 0.108 λ0 × 0.008 λ0 at f0 = 1.62 GHz. The antenna exhibits simulated gain of 1.05 and 2.59 dB in the broadside directions at 1.62 and 2.78 GHz, respectively. Beside that this antenna offers dipolar-type pattern and omnidirectional pattern in the xz-and yz-planes respectively at both bands, which is beneficial to be used in modern wireless applications. The design methodology of the proposed antenna is described with the help of current distributions and parametric analysis.

Wide-band circularly polarized multi-input multi-output (MIMO) antenna array with a 2 × 4 feed network was proposed for C-band application. Different unique techniques were utilized in the proposed array to enhance the antenna characteristics, such as gain, 3 dB axial ratio bandwidth (ARBW), impedance tuning, and ruinous mutual coupling effects. A miniaturized dual-feed Tai chi-shaped antenna element with a pair of feeding points and a pair of eyebrow-shaped strips was presented for enhancing circular polarization (CP) purity and impedance matching. For a better improvement of CP features, a 2*4 MIMO sequentially rotated (MIMO-SR) feed network was used to achieve broader 3 dB ARBW. Besides, the MIMO feature of the feed network could control the left- and right-handed CP, respectively. Ultimately, specific forms of slot and slit structures were applied onto the top layer of MIMO feed network that provided a high isolation between the radiating elements and array network. Furthermore, the diversity gain (DG) was studied. The extracted measured results illustrated an impedance bandwidth of 3.5–8.2 GHz at port 1 and 3.5–8.3 GHz at port 2 for VWSR < 2 and 3 dB ARBW of 4.6–7.6 GHz at port 1 and 4.6–7.5 GHz at port 2. The peak gain of 9.9 dBi was at 6 GHz.

In this paper, a simple conical-shaped dielectric resonator antenna operating in HEM11δ mode is presented for X-band wireless applications. A rectangular slot with a running microstrip line is used for excitation purpose. By placing a FR-4 based superstrate at 7 mm height from the ground FR-4 substrate and incorporating a set of modified ground plane on either side of the feed line, gain is improved by 42.85% and bandwidth by 68.92%, simultaneously. A prototype of designed antenna is fabricated and characterized. The measured results are found to be good in matching with the simulated ones.

In this paper, a novel design of compact Coplanar Waveguide-fed planar monopole antenna with enhanced bandwidth and multiband characteristics has been proposed. Two rectangular rings have been incorporated in a rectangular patch to obtain multiband operation for Wireless Local Area Network (WLAN) (2.4/5.2/5.8 GHz) and Worldwide Interoperability for Microwave Access (WiMAX) (2.3/2.5/5.5 GHz) bands. A parasitic strip and meandering along with double-ringed structure have been used to achieve enhanced impedance bandwidth in WLAN (from 2.26 to 3.03 GHz) and WiMAX (from 4.48 to 6.85 GHz) bands. The parametric analysis is carried out to study effect of varying dimensions on antenna performance. The proposed antenna is optimized and prototype is designed and fabricated. Simulated and measured radiation patterns in elevation and azimuthal planes are also observed. The antenna shows significant gain of 7.33 dBi at 6.54 GHz frequency.

Multiple input multiple output (MIMO) antenna is at core of the presently available wireless technologies. The design of MIMO antennas over a limited space requires various approaches of mutual coupling reduction, otherwise gain, efficiency, diversity gain, and radiation patterns will be severely affected. Various techniques have been reported in literature to control this degrading factor and to improve the performance of the MIMO antennas. In this review paper, we have carried out an extensive thorough investigation of diversity and mutual coupling (correlation) reduction techniques in compact MIMO antennas.