Advancement in Ultra Wideband Antennas for Wearable ...

International Journal of Scientific & Engineering Research, Volume 4, Issue 8, August 2013

341

ISSN 2229-5518

Advancement in Ultra Wideband Antennas for

Wearable Applications

Narbada Prasad Gupta, Dr. Ranjan Maheshwari, Dr. Mithilesh Kumar

Abstract- There has been a tremendous rumble in UWB research after the U.S. Federal Communications Commission (FCC) allocated a frequency range with a bandwidth of 7.5 GHz from 3.1?10.6 GHz for UWB applications. Ultra wideband (UWB) technology was earlier limited to special applications, primarily in the military area and there primarily to electronic warfare. The antennas were usually horn antennas or modified, ridged horn antennas, sometimes in combination with reflectors. Wearable intelligent textile system is an innovative fast growing field in application oriented field. In recent years, body-centric wireless communication becomes an important part of fourth generation mobile communication systems (4G). Utilization of wearable textiles in the antenna segment has been seen on the rise due to the recent miniaturization of wireless devices. Wearable and fabric-based antennas have become one of the dominant research topics in antennas for body-centric communications. The review presented here intended to disclose the unconventional antenna technology including UWB technology for wearable applications. Contributions by various researchers have been compiled keeping in mind background of UWB technology, the wearable antenna, and specification of the antenna, material for the antenna and analysis that must be done to design proper UWB wearable antennas for various applications.

Index Terms-- Body-centric communications, UWB, UWB wearable antenna, Wearable Antenna, 4G.

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1 INTRODUCTION

NTENNA becomes a part of electrical devices in

A wireless communication system after late 1888; Heinrich Hertz (1857?1894) were first demonstrated

IJSER the existence of radio waves [1]. The UWB

technology opens new door for wireless communication system, since the current wireless system increasing exponentially. The appearance of wearable intelligent textile systems revealed the necessity for WBAN (Wireless Body Area Network) system to provide standalone outfit in recent

Fig.1: FCC spectral mask for Indoor UWB Application

years. This network enables wearable computer devices to interact with each other and exchange digital information using the electrical conductivity of the human body as a data network [2]. While talking about wireless body area networks, suddenly it comes into mind that how the signals would be communicated? Well, an antenna, which is a fundamental part of the network, is the answer for this. Textile antenna is one of the most fascinating and cutting edge research areas of modern era. It provides a wearable interface between human and the machine. Since we are talking about wearable antennas, it is necessary to mention here that antennas for such applications should possess certain properties like light weight, conformal design, low

In Impulse-Ultra wideband (I-UWB) technology a very low power pulse is sent whose power is always kept below the noise threshold and also this system does not uses any carrier for transmission. Generation of UWB pulse has been described in [4]. The transmission bandwidth for such system is more than 20% of its center frequency (>500 MHz) [5], [6]. In short, the antennas to be designed for UWB systems should have sufficiently broad operating bandwidth for impedance matching and high-gain radiation in desired directions. The UWB spectral mask was defined to allow a spectral density of -41.3 dBm / MHz throughout the UWB frequency band.

cost, easy system integrable etc. So the design should be such

that antennas performance is not deteriorated even if they are 2 UWB REQUIREMENT AND SPECIFICATION

bent. UWB radio applications has gain much attention to wireless personal area networks, which address short-range, ad-hoc, and high-rate connectivity among portable electronic devices. The Federal Communication Commission (FCC) releases ultra-wide band (UWB) from 3.1GHz-10.6 GHz in 2002 for the use of indoor and hand-held systems [3]. Since then UWB antennas have gained enormous attention in both academia and industry for applications in wireless transmission systems. Figure-1 shows spectral mask for UWB applications specified by FCC.

Various studies have been devoted to evaluating the performance of UWB antennas (Agrawal et al., 1998; Amman & Chen, 2003; Hertel & Smith, 2003; Klemm et al., 2005; MaTG & Jeng, 2005). The UWB antenna must achieve almost a decade of impedance bandwidth, spanning 7.5 GHz. The UWB system must provide:

Broad operating bandwidths for impedance matching, High gain transmissions in the desired direction, Stable transmission patterns and gains, Consistent group delays,

IJSER ? 2013

International Journal of Scientific & Engineering Research, Volume 4, Issue 8, August 2013

342

ISSN 2229-5518

High transmission efficiency, and

copper film and a AgHT-8 film as substrate is presented in

Low profiles.

[15].

The design considerations of the UWB antennas and source UWB antennas should be effective in transmitting, compact,

pulses are based on investigating S parameters, transfer non dispersive, and have a good wide impedance bandwidth

functions, systems efficiency, group delay and fidelity.

properties, these features are desirable for both indoor and

outdoor hand-held UWB applications. To satisfy such

3 DESIGN PARAMETERS FOR UWB WEARABLE ANTENNA

requirements, various types of planar monopole antennas have been developed for UWB communications over the last few years. Also, variety of bandwidth enhancement

There are 14 parameters to be considered while designing the techniques have been reported, to improve the impedance conventional antenna (radiation diagram, directivity, gain, bandwidth of these antennas, such as the use of the multiple

equivalent receiving area, diffraction area, input impedance, feeds techniques [16], beveling radiating element [17], a

radiation resistance, equivalent height, bandwidth, beveling ground pattern [18], offset feeding techniques [19], polarization, front-back ratio, antenna ratio, thermal noise, feed gap optimization [20], ground plane shaping [21], a

efficiency). When we talk about design of UWB antenna for wearable applications certain parameter need to be calculated

notched ground plane [22]-[24] and so on. Following section provides the detail about development of

in addition to conventional parameters like transfer function, various techniques proposed by different authors during last

group delay etc.

few years. Various designs & theirs implementation for

For wearable antennas integrated into clothing Microstrip different applications have been compiled. All these are

antennas have been preferred among the candidates [7], [8]. presented to show that how UWB technology is being taken

In such uses Microstrip antennas with flexible conductors and up by various researchers and what are the future scope of

substrates are needed and this has led to an increased work in this technology and its implementation.

demand for electrical technical textiles (ETTs). Microstrip

antennas [9] have some significant advantages for on-body 4 DEVELOPMENT OF UWB WEARABLE

wearable applications the three major ones being their ease of

ANTENNAS

IJSER construction, their cost effectiveness and an associated

metallic ground plane that when used between the body and the radiating elements can significantly reduce energy absorbed by the body. But Microstrip antennas are low bandwidth and relatively large in size. Typically for flexible and wearable antennas the substrate

During early 1930s many wide band antennas had already been reported. All were Non-planar wideband antennas. Later, various antennas at different frequency bands like UHF, VHF etc. were introduced having planar designs and suitable for integration with ICs. Various Ultra wideband antennas have been categorized in four forms based on four

materials chosen have been textiles or plastics. Textiles tend corners of Figure-2

to low relative permittivity ( ................
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