A compact hexagonal Sierpinski fractal antenna for super wideband applications is presented. It consists of hexagonal radiation patch with two iterations of Sierpinski square slots and coplanar waveguide feeding. An impedance bandwidth of 3.4–37.4 GHz is achieved. The achieved bandwidth ratio is 11:1. Desirable radiation performance characteristics including relatively stable and omni‐directional radiation patterns are obtained over this range. A good agreement is achieved between the simulated and experimental results. The designed antenna has advantages of wider bandwidth and miniaturised size over the previously reported structures.

The present technology fulfills the requirement of high data rate and high channel capacity using multiple input multiple output (MIMO) technology. The MIMO capacity of the system is increased linearly but due to the multiple antennas placed near to each other, problem of mutual coupling exists, which degrades the maximum achievable performance of the system. The problems of multipath propagation can be solved using MIMO system. The isolation improvement methods decrease the mutual coupling among antenna elements, and improve the gain and efficiency of the system. In this paper, decoupling network isolation approach, parasitic element approach, defected ground structure, Neutralization line, isolation improvement based on metamaterials, isolation improvement using PIN diode, varactor diode, and feeding structure have been incorporated, and their merits and demerits have been discussed. The effect of different permittivity material on antenna parameters has also included.

In this article, a compact third iteration inner tapered tree‐shaped fractal antenna for ultrawideband applications is presented. The bandwidth is enhanced by using CPW ground plane and increasing the number of iterations. An impedance bandwidth of 4.3–15.5 GHz (113%) is achieved. The proposed third iteration antenna has nearly omnidirectional patterns at its resonance frequencies with an acceptable value of gain. The experimental and simulation results are found to be in good agreement. The proposed antenna has improved return loss performance and miniaturized size. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:559–567, 2015

A coplanar waveguide (CPW)‐fed octagonal super‐wideband fractal antenna is presented. It comprises four iterations of an octagonal slot‐loaded octagonal radiating patch, CPW feedline, and modified ground plane loaded with a pair of rectangular notches. An impedance bandwidth of 3.8–68GHz (179%) – i.e. a17.89:1 ratio bandwidth – is achieved. Desirable radiation performance characteristics, including relatively stable and omnidirectional radiation patterns, are obtained over this range. The experimental and simulation results are found to be in good agreement. The designed antenna has the advantages of wider bandwidth and miniaturised size over the previously reported structures.

A microstrip line fed star‐star fractal antenna with notch loaded semi‐elliptical ground plane is presented for super wideband applications. An impedance bandwidth of 4.6–52 GHz, i.e., a bandwidth ratio of 11.31:1 is achieved for VSWR < 2. The antenna structure has advantages of compact dimensions and wider bandwidth over previously reported SWB structures. Radiation characteristics, i.e., co and cross polar radiation patterns, peak gain, and efficiency has been presented and discussed. The simulated and experimental results are found to be good agreement. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:624–630, 2017