Slots or defects integrated on the ground plane of microwave planar circuits are referred to as Defected Ground Structure. DGS is adopted as an emerging technique for improving the various parameters of microwave circuits, that is, narrow bandwidth, cross-polarization, low gain, and so forth. This paper presents an introduction and evolution of DGS and how DGS is different from former technologies: PBG and EBG. A basic concept behind the DGS technology and several theoretical techniques for analysing the Defected Ground Structure are discussed. Several applications of DGS in the field of filters, planar waveguides, amplifiers, and antennas are presented.

This article presents a coplanar waveguide fed global system for mobile communications band integrated ultra wide band (UWB) multiple input multiple output (MIMO) antenna with single and dual notch band characteristics. The novelty of the antenna lies in its design as all the unit cells of the proposed UWB MIMO antenna structure are orthogonal to each other therefore the additional isolation elements responsible for achieving high isolation are not required consequently making proposed antenna design simple and easy to fabricate. In this context, 2 MIMO systems have been designed. The first MIMO system is consisting of a dual port antenna whereas the second MIMO system is a printed quad port antenna; further single and dual notch band are achieved in the proposed multi-port MIMO antenna. The antenna shows pattern diversity throughout the impedance bandwidth range. The gain of the antenna varies from 4 to 8.48 dBi. The 2 band notches are achieved at 4.8 and 7.7 GHz in the UWB range. The proposed antenna is fabricated and it is found measured results are in good agreement with simulated results.The emerging wireless and mobile communication applications demand diverse and versatile antennas which are low profile, easy to fabricate and integrable with the handheld integrated circuit along with high data rate and superior quality of service. In recent wireless communication systems, the major problem is multipath fading which is due to reflection, refraction and diffraction of electromagnetic waves in free space. The problem of multipath fading can be resolved by making use of frequency diversity, spatial diversity, or polarization diversity technique. The concept of multiple input multiple output (MIMO) is very much useful for reducing the multipath fading effects thereby achieving superior data rate, range and reliability without increasing any transmit power or bandwidth. However, due to limited availability of space in the handheld devices, the placement of multiple antennas inside the device is a challenging task. Because of closely operating frequencies and space limitations the radiating elements are exposed to high mutual coupling amongst them. Therefore, there is a need for compact and efficient MIMO antenna with low mutual coupling, high isolation and unwanted frequency band suppression.As per Federal Communication Commission, the bandwidth allocated for unlicensed ultra wide band (UWB) spectrum range is from 3.1 to 10.6 GHz. 1 Due to such large operating range UWB antennas can be employed for shortrange radars, medical imaging, high data rate transmission, broadband wireless applications, and so forth. In the last few years, various designs of UWB MIMO antennas have been proposed by a number of researchers. A few of them employ simple monopole antennas with rectangular, circular, elliptical, and trapezoidal shapes with wide impedance bandwidth and improved radiation properties, 2-6 therefore, covering several mobile wireless standards. In 2 antenna structure with 2 radiating element is proposed with common...

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A four‐port MIMO antenna design focused on the sub‐6 GHz fifth generation wireless communication application is presented. The design does not need any other decoupling structure for achieving isolation between multiple ports. A combination of four single wideband antenna units results in the formation of a circular‐shaped metallic disc in the ground plane of the proposed antenna. This disc acts as a pool of current with 180° phase difference leading to isolation between various ports. Diversity performance of the antenna is shown with the help of an envelope correlation coefficient using both S‐parameter and far‐field data. The radiation pattern of the proposed antenna has four lobes in four quadrants for proper reception of signals from different directions. A prototype of the designed antenna is fabricated and measured successfully.

The authors would like to acknowledge the support of Prince Sultan University for paying the Article Procesfsing Charges (APC) of this publication.

the paper presents a coplanar waveguide (cpW)-fed ultra-miniaturized patch antenna operating in Industrial, Scientific and Medical (ISM) band (2.4-2.5 GHz) for biotelemetry applications. The proposed antenna structure is circular in shape and its ground plane is loaded with a pair of slots for obtaining circular polarization. In the proposed design, asymmetric square slots generate phase condition for right-hand circularly polarized (RHCP) radiation. And, by merely changing the position of the slots, either RHCP or left-hand circularly polarized (LHCP) radiation can be excited. In the proposed design, a meandered central strip is used for miniaturization. The simulations of the proposed antenna are carried out using Ansys HFSS software with a single-layer and multilayer human tissue models. The antenna shows good performance for different tissue properties owing to its wide axial ratio bandwidth and impedance bandwidth. The antenna is fabricated and measurements are carried out in skin mimicking phantom and pork. Simulated and measured performances of the antenna are in close agreement. The power link budget is also calculated using an exterior circularly polarized (CP) receiving antenna.Recent advances in technology lead to the design of small and low-power consuming biomedical devices that can be implanted inside a patient's body through surgical operation or ingestion. These embedded devices can sense data from inside the human body in real-time, offering a unique opportunity for early diagnosis and treatment of diseases. The embedded devices communicate with the external world in terms of telemetry. Telemetry includes data transmission from the implanted device to an external one and vice-versa.The standard requirement of all implantable medical devices (IMD) is the wireless operation of equipment and bidirectional data communication. The implantable antenna is one of the critical components for IMD for exchanging body anatomy data with installed base stations 1,2 . In the last few years, several prototypes of implantable patch antennas are proposed; but their radiation efficiency lacks in one or the other parameters such as gain, impedance bandwidth, axial ratio bandwidth; in few cases, antenna footprints are also large for implantation 3-11 . In 12-16 , dimensions of the antenna are significantly reduced making them best prototypes for implantation, but are prone to multipath fading because of their omnidirectional linearly polarized radiations. Though these antenna designs are highly compact, their gain, and impedance bandwidths are very less. Various types of antennas with a defected ground, fractal shape, spiral, slotted, PIFA have been proposed in the literature for wide impedance and axial ratio bandwidth [17][18][19][20] . However, most of the proposed antennas are linearly polarized with large and complex geometry. Few antennas reported consist of ground plane as the primary radiator, but most of them are linearly polarized and proposed for wireless applications. Since the profile of such antennas is...

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