An application of defected ground structure (DGS) to reduce out-of-band harmonics has been presented. A compact, proximity feed fractal slotted microstrip antenna for wireless local area network (WLAN) applications has been designed. The proposed 3rd iteration reduces antenna size by

Printed antennas have been widely used because of their advantages like low profile, easy fabrication, low cost, small size, and so forth [

In this paper, an application of the DGS to suppress higher harmonics and thus to improve radiation efficiency of the planar antenna is demonstrated. Moreover, this paper also shows the significant role of the fractal geometry for size miniaturization of the radiating element of the patch antenna.

The geometry of the proximity coupled patch antenna is presented in Figure ^{2}. The microstrip line with 50 Ω impedance, width ^{2} is fabricated on upper side of upper substrate. From that patch, plus shape slot is taken out. This procedure is repeated for next two iterations as shown in Figure

Geometry of proximity coupled plus shape fractal slot antenna.

Geometry of plus shape fractal slot: (a) 1st iteration (b) 2nd iteration, (c) 3rd iteration.

Design geometry of 3rd iterated plus shape patch.

Design geometry of DGS on the ground plane of the proposed antenna.

Initially, H-DGS is considered below the 50 Ω microstrip line as shown in Figure

Setup of H-DGS under 50 Ω strip line in CST Microwave Studio to extract

Effect of variation of

Effect of variation of

Effect of variation of

The

Equivalent

The geometry of the proposed microstrip antenna has been optimized and simulated with CST Microwave Studio. Figure

Comparison of conversional rectangular patch antenna with various fractal slot iterations of antenna.

Iteration | Resonating frequency (GHz) | Number of higher harmonics | Return loss (dB) | VSWR | Gain (dB) | Radiation efficiency (%) | Bandwidth of fundamental resonance frequency (%) | higher harmonics | Bandwidth of 2nd harmonics (%) | Patch size (mm^{2}) |
Size reduction (%) |
---|---|---|---|---|---|---|---|---|---|---|---|

0 | 2.42 | 1 | −12.53 | 1.61 | 6.3 | 67.6 | 2.46 | 2.90 | — | 1725 | — |

1st | 2.43 | 2 | −13.44 | 1.54 | 3.3 | 55.4 | 3.27 | 2.64 | 5.08 | 983.25 | 43 |

2nd | 2.42 | 2 | −22 | 1.17 | 3.8 | 51.2 | 3.30 | 9.19 | 4.34 | 983.25 | 43 |

3rd | 2.42 | 2 | −27 | 1.2 | 4.16 | 51.5 | 3.27 | 2.29 | 4.93 | 983.25 | 43 |

3rd with H-DGS | 2.45 | 0 | −23.26 | 1.14 | 4.46 | 63.8 | 3.68 | — | — | 932 | 46 |

Simulated return losses

Table

Comparison of return loss of 3rd iterated antenna with and without DGS.

Figure

Current distribution in 3rd iteration fractal slot antenna witH-DGS.

Simulated radiation pattern of 3rd iteration fractal slot antenna witH-DGS: (a) E-plane, (b) H-plane.

To obtain an impedance matching, high radiation efficiency, higher harmonic suppression, and the size reduction, a novel type of 3rd iteration plus shape fractal slot antenna has been proposed. By introducing fractal slots, VSWR improves and the size of an antenna reduces, but it also generates higher harmonics. To suppress higher harmonics, H shape DGS and its equivalent circuit have been proposed. The parameter extraction method for the proposed H-DGS has also been explained. Furthermore, by employing the extracted parameters, the band stop characteristics of H-DGS are explained, which suppressed higher harmonics. The radiated power of the proposed antenna in 1st and 2nd harmonic frequency is very low. The proposed DGS unit and its equivalent circuit could also find applications like microwave filter, coupler, power divider, and so forth.

The author declares that there is no conflict of interests regarding the publication of this paper.

The author is thankful to G. H. Patel College of Engineering and Technology, Gujarat, for providing access of ADS Simulation software and the management of A. D. Patel Institute of Technology and Charutar Vidyamandal, Gujarat, India, for motivation and support for the research work.