A.R. Chandran

Queen's University Belfast, Belfast, NIR, United Kingdom

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Publications (16)3.47 Total impact

  • A.R. Chandran, W.G. Scanlon
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    ABSTRACT: Dual-band operation is highly desirable for wearable devices that need to connect with a range of wireless systems. We present a series of microstrip-line fed, dual-band compact patch antennas designed to operate in the common 2.45 GHz and 5.8 GHz bands for body-centric communications. All of the designs are low-profile and, with further study, may be suitably implemented in flexible or fabric materials. Our best performance was obtained with a shorted parasitic patch element close to a rectangular patch operating at the TM<sub>10</sub> mode. This design, with an overall height of less than ¿/24, had a radiation efficiency of 91% at 2.45 GHz and 95% at 5.8 GHz in free space. When placed 2 mm above a muscle tissue phantom at 2.45 GHz, an efficiency of 52% and a 2:1 impedance bandwidth of 95 MHz was obtained. The bandwidth at the 5.8 GHz band was 400 MHz in free space.
    Antenna Technology (iWAT), 2010 International Workshop on; 04/2010
  • A.R. Chandran, W.G. Scanlon
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    ABSTRACT: This paper introduces a compact, low profile shorted patch antenna designed for on-body communication at 2.45 GHz. The proposed antenna operates with a small (~¿/5 dimension) groundplane yet maintains a reasonable radiation efficiency of 50.9 % when in close proximity to a muscle tissue phantom. The antenna has more than sufficient impedance bandwidth for the 2.45 GHz band (126 MHz for |S<sub>11</sub>|<-10 dB), yet its overall height is only 5.75 mm or ¿/21. For on-body communications, a maximum |S<sub>21</sub>| path gain of -44.7 dB was obtained at 2.45 GHz.
    Antennas & Propagation Conference, 2009. LAPC 2009. Loughborough; 12/2009
  • A.R. Chandran, G.A. Conway, W.G. Scanlon
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    ABSTRACT: The ability to switch between propagating modes is important for body-centric applications such as medical body area networks where a single node may need to be able to optimise communications for either on-body sensor links or off-body links to the wider network. Therefore, we present a compact 2.45 GHz active mode-switching wearable antenna for both on-body and off-body wireless communications. The single-layer patch antenna was pattern-switched using shorting pins and had an impedance bandwidth of 253 MHz and 217 MHz for the on-body and off-body radiating modes, respectively. An efficiency of 57 % and 56.8 % was obtained for on-body and off-body mode respectively when placed in close proximity to a phantom that represents a muscle issue at 2.45 GHz.
    Antennas and Propagation, 2009. EuCAP 2009. 3rd European Conference on; 04/2009
  • W.G. Scanlon, A.R. Chandran
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    ABSTRACT: The ability to electronically switch between off-body and on-body communications is a useful feature for wearable antenna applications. Therefore, we present a novel stacked-patch antenna with a switched propagation mode for body-centric communications at 2.45 GHz. Mounted 2 mm above a muscle-tissue phantom and in the on-body mode, the proposed single-port antenna had an efficiency of 62% and an impedance bandwidth of 70 MHz. The antenna performance increased in the off-body mode with an efficiency of 80% and an impedance bandwidth of 247 MHz. In terms of on-body coupling in anechoic conditions, peak |S<sub>21</sub>| path gains of -39.6 dB and -48.0 dB were obtained for the on-body and off-body configurations, respectively. These results clearly demonstrate the mode isolation obtained.
    Antenna Technology, 2009. iWAT 2009. IEEE International Workshop on; 04/2009
  • Z. Duan, D. Linton, W. G. Scanlon, A. R. Chandran
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    ABSTRACT: In this paper, a single layer split ring resonant (SRR) antenna with a lumped capacitor based on CPW (coplanar waveguide) excitation is studied to offer a low profile and compact ground plane structure. The effects of basic structural parameters are investigated to give a practical insight. A double layer SRR is examined for comparison. The human body effects are considered as its potential application is in body worn devices. The antenna efficiency (in free space and on a human phantom) is validated in a reverberation chamber.
    01/2009;
  • A.R. Chandran, G.A. Conway, W.G. Scanlon
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    ABSTRACT: An extremely compact patch antenna suitable for use in medical body area network (MBAN) applications is reported. The antenna is loaded with rectangular slots, placed symmetrically on either side of the feed post, and it uses shorting pins to generate an over-the-body-surface propagating mode. Furthermore, from the measured and FDTD simulated results it is verified that for an on-body path the performance of the new antenna was similar to that of a full size lambda/4 monopole. The antenna provided a 2:1 impedance bandwidth of 2.1%. Despite being electrically small and in close proximity to a muscle tissue phantom, the simulated radiation efficiency of the antenna was 54 %.
    Antennas and Propagation Society International Symposium, 2008. AP-S 2008. IEEE; 08/2008
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    A.R. Chandran, G.A. Conway, W.G. Scanlon
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    ABSTRACT: The development of a compact and highly efficient antenna operating at 868 MHz for communication in ISM-band body area networks is reported. With symmetrical slots and shorting pins on either side of the feed, the antenna exhibited a radiation pattern similar to that of a monopole/dipole antenna with an efficiency of 52.3% and an impedance bandwidth of 9.3 MHz (1.1%) when placed in close proximity (1 mm) from a muscle tissue phantom. The maximum dimension of the proposed design is reduced by more than 66% compared to a conventional lambda/2 microstrip patch antenna. Furthermore, for a simulated on-body path the performance of the new antenna was within 2 dB of a lambda/4 monopole.
    Antennas and Propagation Conference, 2008. LAPC 2008. Loughborough; 04/2008
  • D. Das Krishna, A.R. Chandran, C.K. Aanandan
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    ABSTRACT: A compact dual band microstrip patch antenna with fractal based slots is proposed in this paper. The structure consists of a square patch with modified Sierpinski gasket based slots, electromagnetically fed by a microstrip line. The antenna resonates at two distinct frequencies with linear polarization in the same plane. The simulated current distribution over the antenna establishes that the higher resonance is due to the smaller slots and the lower due to the central slot. In addition to the dual frequency behaviour, the antenna exhibits a size reduction of 77% at the lower resonance. Also it has broad radiation characteristics with cross-polarization levels better than -20dB.
    Microwave Conference, 2007. European; 11/2007
  • D.D. Krishna, A.R. Chandran, C.K. Aanandan
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    ABSTRACT: A compact dual band microstrip patch antenna with fractal based slots is proposed in this paper. The structure consists of a square patch with modified Sierpinski gasket based slots, electromagnetically fed by a microstrip line. The antenna resonates at two distinct frequencies with linear polarization in the same plane. The simulated current distribution over the antenna establishes that the higher resonance is due to the smaller slots and the lower due to the central slot. In addition to the dual frequency behaviour, the antenna exhibits a size reduction of 77% at the lower resonance. Also it has broad radiation characteristics with cross-polarization levels better than -20dB.
    Wireless Technologies, 2007 European Conference on; 11/2007
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    ABSTRACT: The scattering behaviour of fractal based metallo- dielectric structures loaded over metallic targets of different shapes such as flat plate,cylinder and dihedral corner reflector are investigated for both TE and TM polarizations of the incident wave. Out of the various fractal structures studied,square Sierpinski carpet structure is found to give backscattering reduction for an appreciable range of frequencies. The frequency of minimum backscattering depends on the geometry of the structure as well as on the thickness of the substrate. This structure when loaded over a dihedral corner reflector is showing an enhancement in RCS for corner angles other than 90◦.
    Progress in Electromagnetics Research-pier - PROG ELECTROMAGN RES. 01/2007;
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    ABSTRACT: In this paper, we present a detailed study of a printed square monopole antenna for Ultra Wide Band (UWB) communication applications. The 2:1 VSWR bandwidth of the proposed antenna is from 2.87–14 GHz. The antenna can be made to reject particular frequency bands by introducing narrow slits on the patch. In addition, the rejection band can be easily tuned for centre frequency, VSWR and rejection bandwidth by adjusting the slit parameters. In the proposed antenna, slits are introduced to reject the IEEE802.11a and HIPERLAN/2 bands used for WLAN applications. The antenna is analyzed in both frequency and time domains. Radiation patterns of the antenna are omnidirectional with appreciable gain throughout the band. Transient analysis indicates linear phase response and minimum pulse distortion.
    Journal of Electromagnetic Waves and Applications 01/2007; 21:1525-1537. · 1.40 Impact Factor
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    ABSTRACT: Effective use of fractal-based metallo-dielectric structures for enhancing the radar cross-section (RCS) of dihedral corner reflectors is reported. RCS enhancement of about 30 dBsm is obtained for corner reflectors with corner angles other than 90deg. This may find application in remote sensing and synthetic aperture radar
    Electronics Letters 10/2006; · 1.04 Impact Factor
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    ABSTRACT: Scattering behaviour of various metallo-dielectric structures based on the modified design of Sierpinski carpet fractal geometry for the elimination of backscattered power is reported. The reduction in backscattered power is obtained for a wide range of frequencies in X-band. A bandwidth of 1.26 GHz at -20 dB is obtained for the structure based on octagonal Sierpinski. Simultaneous reduction in backscattered power is obtained for both TE and TM polarisations.
    Antennas and Propagation Society International Symposium, 2005 IEEE; 08/2005
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    ABSTRACT: Electromagnetic scattering behaviour of a superstrate loaded metallo-dielectric structure based on Sierpinski carpet fractal geometry is reported. The results indicate that the frequency at which backscattering is minimum can be tuned by varying the thickness of the superstrate. A reduction in backscattered power of ∼44 dB is obtained simultaneously for both TE and TM polarisations of the incident field.
    Electronics Letters 10/2004; · 1.04 Impact Factor
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    ABSTRACT: A novel dual frequency, dual polarized operation of a compact single feed square microstrip patch antenna embedded with a hexagonal slot is presented. The proposed antenna provides a size reduction up to 45% and 36% for the two resonant frequencies compared to standard rectangular patches. This design also gives enhanced bandwidth, as high as 2.86% and 2.34%, for the two frequencies with a very low operating frequency ratio.
    Antennas and Propagation Society International Symposium, 2004. IEEE; 07/2004
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    ABSTRACT: The development of a low backscattered dual polarized metallodielectric structure based on Sierpinski carpet fractal geometry is reported. A backscattering reduction of 32 dB for normal incidence is obtained for the third iterated stage of the fractal geometry. The scattering behaviour is found to be similar for both the TE and TM polarizations, owing to the symmetry in the structure of Sierpinski Carpet.
    Antennas and Propagation Society International Symposium, 2003. IEEE; 07/2003