The proposed antenna with and without super-substrate is simulated using CST Microwave studio. The plot of frequency versus S11 of the proposed antenna configuration is plotted in Fig. 8. The antenna without super-substrate is simulated and observed two wideband operations. With a − 10 dB impedance bandwidth of 65%, this antenna produces first wideband resonance from 3.1 GHz-6.1GHz. The second wideband operation ranges from 6.4 GHz-10.4 GHz with a -10 dB impedance bandwidth of 47%. After that, the simulation with the proposed metamaterial super-substrate is performed. In compared to the antenna without the super-substrate, the S11 performance suffers only little degradation. The two-layer antenna, on the other hand, has a substantially higher gain. Three wideband operations are visible in the final antenna design. Firstly, the antenna has an S11 of less than − 10 dB from 3.1 to 4.5 GHz and a 39% impedance bandwidth. With an impedance bandwidth of 18%, the second wideband response is achieved between 5.1 and 6.15 GHz. Next, with an impedance bandwidth of 47%, wideband operation is found from 6.5 GHz to 10.5 GHz. Further investigation was carried out to determine the impact of various parameters on impedance bandwidth and return loss.
Initially, the effect of circle thickness on S11 performance is studied by varying t1. It can be seen from the Fig. 9 that the antenna achieves optimum performance when t1 = 1 mm. On changing t1, the resonance peak becomes weak in some frequency and bandwidth is also reduced. Figure 10 shows variation of S11 with respect to frequency on varying t2. It can be observed that when t2 = 1 mm the antenna achieves better performance in terms of S11 and gain. Finally, the effect of length of the patch that connects the inner arcs (wt) is studied using simulation. The S11 performance for various values of wt is plotted in Fig. 11. It is observed from the simulation results the antenna achieves better performance when wt=5.2 mm.
Figure 12 shows the surface current distribution of the proposed patch antenna top surface at 3.5GHz, 4.2GHz, 5.5GHz, and 10.1GHz. At 3.5 GHz, the arc-shaped patch connected to the CPW feed exhibits a high intensity of current flow. Concentric circle-shaped patches provide the second resonance peak at 4. 2 GHz. Also the current distribution at 5.5 and 10.1 GHz is high at the edges of the circles. The proposed antenna configuration is fabricated and measured. The front view of the patch and metasurface is shown in Fig. 13. The three dimensional view of the fabricated antenna is shown in Fig. 14a. The radiation pattern measurement has been performed in anechoic chamber as shown in Fig. 14b. The antenna with and without metamaterial super-substrate is considered for measurement. Anritsu Vector Network Analyzer was used to test the antenna prototype. The corresponding results are plotted in Fig. 15. It is found from Fig. 15, the experimentally measured S11 < -10dB without super-substrate has been achieved from 3.0 GHz to 10.3 GHz with an impedance bandwidth of 109%. The measured S11 for the proposed antenna with super-substrate exhibits three wideband responses, i.e. 3.06GHz − 4.72GHz (B.W of 42%), 4.94GHz-6.19GHz (B.W of 22%) and 6.50 GHz − 10.56 GHz (B.W of 47.5%). The discrepancies between simulated and measured results might have been occurred due to fabrication tolerances.
The proposed antenna's simulated and measured gains are almost identical as shown in Fig. 16. The addition of a metasurface to a simple conventional patch results in a gain enhancement of 6.2 dBi in the developed antenna. The proposed antenna's radiation pattern characteristics in the E-plane and H-plane have been measured in the anechoic chamber and shown in Fig. 17 and Fig. 18, respectively. At 3.5 GHz, 4.2 GHz, 5.5 GHz, and 10.1 GHz, the radiation characteristics of the proposed antenna arrangement are simulated and measured. Radiation from the antenna is stable in all directions.
Table 3 compares the proposed antenna's performance to that of some of the previously reported high-performance antennas. According to the findings, the proposed low profile design has significantly increased gain while reducing size.
Table 3
Comparison of the proposed antenna with the existing antennas
Reference
|
Dimension (mm)
|
Maximum Bandwidth (%)
|
Max. Gain (dBi)
|
Operating frequency (GHz)
|
[12]
|
28 × 28
|
19%
|
7.57
|
9.24–11.25
|
[22]
|
78.6 × 42.5
|
28%
|
6.72
|
(0.865–1.060),
(2.240–2.520),
(3.250–4.310),
(4.900–6.500)
|
[23]
|
28.8 × 32
|
126%
|
7.3
|
3-13.25
|
[24]
|
48 × 48
|
13%
|
4.72
|
(1.710–1.880),
(1.880–2.200),
(3.400–3.800)
|
[25]
|
67.2 ×67.2
|
16.58%
|
12
|
9.4–11.2
|
Proposed work
|
28 × 28
|
47.5%
|
6.2
|
(3.06–4.72),
(4.94–6.19),
(6.5–10.5)
|