International Research Journal of Engineering and Technology (IRJET) Volume: 04 Issue: 02 | Feb -2017
e-ISSN: 2395 -0056
www.irjet.net
p-ISSN: 2395-0072
Isolation Enhancement of a Very Compact UWB-MIMO Slot Antenna With Two Defected Ground Structures Used in Multi band Applications Maddula Sai Teja1 , P.Srinivas Rao2 Department of Electronics , St.Ann’s College of Engineering and Technology, Chirala, INDIA ---------------------------------------------------------------------------------****---------------------------------------------------------------------------------------------Abstract—A multiple-input multiple-output (MIMO) antenna available in portable devices will inevitably cause severe which has a compact size of 22×26 mm² that operates in ultra mutual coupling and significantly degrade the diversity wide band range of 3.1-10.6 GHz is presented. The antenna performance. Thus, one of the main challenges to employ exhibits high isolation to improve the impedance matching MIMO technology in portable devices is the design of the characteristics in low frequencies as well as reduces mutual small MIMO antennas with low mutual coupling. coupling less to than 18db for high frequencies. A T shaped slot is cut from the ground. The performance of this antenna is Some MIMO antennas for UWB applications were proposed studied and measured by simulation. The results indicate that the proposed antenna is a good candidate for UWB applications. in the past few years [6]–[10]. In order to achieve the best
I. INTRODUCTION ULTRAWIDEBAND (UWB) is a rapidly growing technology which makes use of wide frequency band to transmit signals at low energy level. It has promising applications in short-range high-data-rate transmission, radar imaging and cancer sensing, etc. Since the authorization from the Federal Communications Commission in the US for the unlicensed use of 3.1–10.6 GHz spectrum for applications with low power emission in 2002 [3], UWB systems have attracted much attention. Like other wireless communication systems, UWB systems suffer from multipath fading. It is well-known that multiple-input- multiple-output (MIMO) technology can be used to provide multiplexing gain and diversity gain to improve the capacity and link quality, respectively, of wireless systems. UWB systems using huge bandwidths already have high data rates, so MIMO technology can be used for fade countermeasure through diversity gain.
performance of the MIMO systems, high isolation is accomplished by orthogonally feeding [6]–[8], introducing defected ground structure (DGS) to suppress surface wave [8], [9], using directional antenna elements [9], adding protruding ground stub or parasitic element as reflective component [6], [7], [10], and adopting a neutralization line to cancel out the original coupling [11]. All of the decoupling methods can reduce the mutual coupling to - dB or less. To integrate multiple antennas at the user terminals that are becoming smaller and thinner each day, the design of a very compact UWB-MIMO antenna covering the whole operating frequency band is one of the most essential requirements. However, reducing the size of a MIMO antenna usually brings about reduced operating bandwidth and strong coupling between antenna elements. Moreover, most decoupling structures bring occupation of too large space, which are not suitable for a very small MIMO antenna.
The basic concept of MIMO/diversity is to use multiple antenna elements to transmit or receive signals with different fading characteristics. Since it is unlikely that all the received signals will experience deep fading at the same time, the system reliability can be increased by proper selection/combining of the received signals. However, installing multiple antenna elements on the small space
In this letter, a very compact MIMO antenna with high isolation is presented for UWB systems. The antenna measures only 26×26 mm . In order to improve isolation of such a compact MIMO antenna, two defected ground structures are utilized. The T-shaped slot etched on the ground has two functions, extending the current path, which can reduce the first resonant frequency of the antenna, and suppressing surface currents, enhancing isolation at the band of 4–10.6 GHz. To reduce the coupling at the band of 3–4 GHz, a line slot is used to bring new coupling to cancel out the original coupling, which works as a novel neutralization line and has a very small occupied space. Compared to the traditional neutralization line technology, which is connected at radiation patch or feeding line to produce an additional
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With increase of demand of wireless communication systems, personal communication devices are required to operate at multiple frequencies to cater to different applications. In addition to multiband operation, it is necessary that the antenna is small with light weight, low profile and easy integration with other circuit structures.
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