A planar microstrip patch antenna has been designed by amalgamating two different fractal geometries in the form of notches and cuts capable of exhibiting heptaband behavior inherited by basic fractal shapes. The suggested layout reverberate at heptad frequencies and exhibits bandwidth of 300 MHz, 110 MHz, 200 MHz, 160 MHz, 300 MHz, 300 MHz and 120 MHz respectively. Entire reverberant frequencies have admissible numbers of S11 and VSWR less than 2. The proposed structure has been designed on rectangular FR4 substrate with a square patch dimensions of 45 mm × 45 mm. Proposed antenna structure is compact and can become part of portable device. Design, analysis and simulation have been done on an electromagnetic simulator.
communication systems fractal antennas have fulfilled requirements of obtaining multiple resonances by a single antenna. So multiband but low profile antennas are very popular for various wireless applications [6][7].
The congruous architecture of Koch curve is straightforward. A Minkowski fractal is also a well known fractal geometry, due to its space filling properties it can be used to impoverish the form factor of the layout by increasing the efficiency with which extended electrical length [8]. Both the fractal curves are shown in Figure 1.
The proposed structure starts with a square microstrip patch of 45 mm × 45 mm designed on FR4 substrate measuring 56 mm × 54 mm in HFSS electromagnetic field solver.
The following mathematical expressions [9] are used for calculation of various antenna geometrical parameters:
W = ε eff = 2 f 0
C ε r + 1
2 ε r + 1 2 + ε r−1 1 + 12 h −12
2 w Leff =
c 2 f 0
ε eff ∆L = 0.412h L = Leff − 2∆L (ε eff + 0.3) w + 0.264
h (ε eff − 0.258) w + 0.8 h (1) (2) (3) (4) (5)
The designed microstrip patch antenna is shown in figure 2 has been simulated in its basic form and results were extracted. The coaxial feeding method and a simulated SMA connector was utilized for this antenna geometry. Full ground has been used at the back of the substrate.
The calculated design criteria of the suggested layout are shown in Table 1.
The next step in designing the proposed structure is by removing the patch material in the form of
Koch fractal and Minkowski fractal from the lower and upper side of the patch at 1st iteration. After
simulating this structure with coaxial probe feed, resonance has been achieved at four different
frequencies 3.1GHz, 4.4GHz, 6.1GHz and 7GHz with good values of return loss. Later iteration level
has been increased up to 2nd level. Multiband resonance has been achieved due to the self-similar
behavior of the fractal structures which generates a lot of edges, corners, segments and perimeter
[8][
Present portion portrays the analogizing and analysis of profuse outcome from the simulation of proposed antenna structure in the electromagnetic simulator. As mentioned in the prior section proposed antenna has been designed for iterations 1 and 2. A comparison of the reflection coefficient properties of the designed layout as demonstrated below .
For the simple square patch the structure resonates at two frequencies. The suggested layout structure reverberates at four un-identical frequencies at 1st iteration while it reverberates at 7 different frequencies for 2nd iteration. It has been noticed that suggested layout is compact and multiband radiating device. Table 2 displays the elaborated values of reverberate frequencies inclusive of VSWR and bandwidth. All obtained values are in an acceptable range.
Emission figure is a kind of diagrammatic illustration of dissimilarity in the field strength of the radio waves in two-dimensional stretch. Two dimensional radiation designs are more often taken at particular frequency, selected polarization and at particular plane.
1. 2. 3. 4. 5. 6. 7.
2.8 3.2 4.5 6.0 7.5 8.2 9.6
Return Loss (dB) 20.1 14 11 20 19 26.5 32
VSWR 1.21 1.49 1.85 1.23 1.25 1.09 1.05
Bandwidth (MHz) 300 110 200 160 300 300 120
In this work, a hybrid fractal microstrip patch antenna has been designed by using Koch and Minkowski fractal structures. The proposed antenna has been designed on FR4 material. Probe fed coaxial feed has been used for providing signal. Simulation is done on the HFFS electromagnetic simulator and resonance has been obtained at seven different frequencies in gigahertz are 2.8, 3.2, 4.5, 6.0, 7.5, 8.2 and 9.6 with sustainable values of return loss in decibels 20.1, 14, 11, 20, 19, 26.5, 32 respectively. Suggested layout is close packed and suitable for wireless applications. 5. References
A. Azari and J. Rowhani, “Ultra Wideband Fractal Microstrip Antenna Design,” Progress In Electromagnetics Research C, vol. 2, pp. 7–12, 2008.
H. Rhyu et al., “Multi-band hybrid antenna for ultra-thin mobile phone applications,” Electronics Letters, vol. 45, no. 15, p. 773, 2009.
M. Barthwal, “Microstrip Slot Antenna Loaded With SRR For Multiband Operation,” pp. 3–6, 1996.
L. Lizzi, R. Azaro, G. Oliveri, and A. Massa, “Multiband Fractal Antenna for Wireless Communication Systems for Emergency Management,” Journal of Electromagnetic Waves and Applications, vol. 26, no. 1, pp. 1–11, Jan. 2012.
D. H. Werner and S. Ganguly, “An overview of fractal antenna engineering research,” IEEE Antennas and Propagation Magazine, vol. 45, no. 1, pp. 38–57, 2003.