Compact and Flexible Monopole Antenna for Ultra-Wideband Applications Deploying Fractal Geometry

  • Geetha, G (Department of ECE, College of Engineering, Guindy, Anna Univeristy) ;
  • Palaniswamy, Sandeep Kumar (Department of ECE, SRM University) ;
  • Alsath, M. Gulam Nabi (Department of ECE, SSN College of Engineering) ;
  • Kanagasabai, Malathi (Department of ECE, College of Engineering, Guindy, Anna Univeristy) ;
  • Rao, T. Rama (Department of ECE, SRM University)
  • Received : 2017.06.04
  • Accepted : 2017.08.30
  • Published : 2018.01.01


This paper presents a compact ultra-wideband (UWB) flexible monopole antenna design on a paper substrate. The proposed antenna is made of iterations of a circular slot inside an octagonal metallic patch. This fractal-based geometry has been deployed to achieve compactness along with improved bandwidth, measured reflection coefficient -10 dB bandwidth ranging from 2.7 to 15.8 GHz. The overall size of the antenna is $26mm{\times}19mm{\times}0.5mm$, which makes it a compact one. The substrate used is paper and the main features like environment friendly, flexibility, green electronics applications and low cost of fabrication are the key factors for the proposed antenna. The aforementioned UWB prototype is suitable for many wireless communication systems such as WiMAX, WiFi, RFID and WSN applications. Antenna has been tested for the effect of bending by placing it over a curved surface of a very small radius of 10 mm.

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Fig. 1. Dimension details of the proposed UWB fractal-based monopole antenna where R0 - radius of thezeroth iteration (9.2 mm), R1 - radius of the firstiteration (6.8 mm) and R2 - radius of the seconditeration (5.03 mm). All dimensions are in mm

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Fig. 2. Evolution of the proposed fractal based monopoleantenna and the corresponding reflection charac-teristics

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Fig. 3. Iteration Factor (IF=R0/R1=R1/R2=....= Rn/Rn+1)evolution of the proposed fractal based monopoleantenna.(a) IF = 1.2, (b) IF = 1.25, (c) IF = 1.3 and(d) IF = 1.35

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Fig. 4. Iteration order Evolution of the proposed fractalbased monopole antenna: (a) Zeroth iteration, (b)First iteration and (c) Second iteration

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Fig. 5. Magnitude plot of surface current distribution at (a)3.5 GHz (b) 7.5 GHz (c) 10.5 GHz

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Fig. 6. Simulated and measured reflection coefficientcharacteristics of the proposed antenna.

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Fig. 7. Photograph of the fabricated prototype under flatand bent conditions (a) Front view (b) Rear view (c)X- bent, and (d) Y- bent

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Fig. 8. Measured reflection coefficient characteristics ofthe prototype under flat and bent conditions

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Fig. 9. Measured radiation pattern of the proposed antennaalong E-plane (yz-plane) and H-plane (xz-plane) at3.5 GHz, 7.5 GHz and 10.5 GHz

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Fig. 10. Gain and efficiency of the proposed papersubstrate antenna

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Fig. 11. Group delay of the proposed antenna (face- faceorientation and side-side orientation)

Table 1. Performance comparison of the proposed antenna with the other flexible UWB antennas reported in literature

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