# A Metamaterial Inspired AMC Backed Dual Band Antenna for ISM and RFID Applications
## 3 Results
### Results of the Antenna with AMC Backing  
The simulated and fabricated reflection coefficient and VSWR outcomes of the prototype design are shown in Figure 16. The antenna was placed by spacing a 25 mm gap against the periodic array of the unit cell. Figure 16a illustrates the S-parameter of the antenna with the AMC backing. It was observed that the antenna with the AMC backing provides dual band frequencies at 0.915 GHz and 2.45 GHz. Figure 16b represents the VSWR result of the antenna with AMC backing. Figure 16c depicts the photograph of the antenna results using VNA with the AMC Backing. Figure 14: Simulated Gain of Antenna without AMC Backing (**a**) at 0.915 GHz (**b**) at 2.45 GHz. Figure 15: Simulated and Measured Radiation Pattern of the Antenna without AMC Backing. (**a**) Along E-Plane (**b**) Along H-Plane. The simulated bandwidth obtained at 0.915 GHz and 2.45 GHz frequencies, when the antenna was placed in front of the AMC structure, was (0.902-0.920 GHz) 0.018 GHz, and (2.378-2.508 GHz) 0.13 GHz. Figure 17a,b illustrates the simulated gain results at 0.915 GHz and 2.45 GHz frequencies for the antenna with the AMC backing. The simulated gain obtained at 0.915 GHz was 2.87 dBi and at 2.45 GHz was 6.8 dBi. The most attractive part of this AMC structure was that it enhanced the gain without influencing the antenna's bandwidth. The simulated results of the antenna show that the gain had improved from 1.53 dBi to 2.87 dBi at 0.915 GHz, and 4.49 dBi to 6.8 dBi at 2.45 GHz, without affecting the bandwidth of the antenna, both with and without the AMC backing. Figure 16: Simulated and Fabricated results of the antenna with AMC Structure (**a**) Reflection Coefficient (**b**) VSWR (**c**) Snapshot of the antenna with AMC Backing Results. Figure 17: Simulated Gain of Antenna with AMC Backing, (**a**) at 0.915 GHz, (**b**) at 2.45 GHz. Figure 18a,b shows the radiation pattern of the prototype antenna with the AMC backing. The radiation patterns along the E and H planes were observed at 0.915 GHz and 2.45 GHz frequencies. The red line depicts the radiation pattern of 0.915 GHz along the E-Plane and the H-Plane while, the blue line depicts the radiation pattern at 2.45 GHz along the E and H-Plane. The proposed antenna with the AMC backing exhibited the desired directional radiation pattern characteristics along both planes at dual operating frequencies. In addition to the above, it was noticed that there was a good agreement between the simulated and measured outcomes. The radiation efficiency plots concerning the frequency in GHz of the antenna with and without the AMC Backing is presented in Figure 19. The red and blue lines depict simulated and measured results, respectively. It was observed that 93% and 90% radiation efficiencies were obtained at 0.915 GHz and 2.45 GHz frequency without the AMC Backing. When the AMC was loaded, radiation efficiencies were increased to 96% and 93%, respectively, at lower and higher frequency bands. The simulated and measured gain versus frequency results of the antenna with and without the AMC Backing is depicted in Figure 20. Figure 20a portrays the gain versus frequency plot without the AMC while, the red lines illustrate the antenna's simulated results, and the blue lines depict the measured results. Figure 20a shows that the gain at the operating frequency was 1.83 dBi at 0.915 GHz and 4.38 GHz at 2.45 GHz frequencies,  
Figure 19: Radiation Efficiency results of the antenna (**a**) without the AMC Backing (**b**) with the AMC Backing. Figure 18: Simulated and fabricated Radiation Pattern of AMC backing Antenna (**a**) Along the E-Plane, (**b**) Along the H-Plane. respectively, for the antenna without an AMC-backed structure. From Figure 20b, it can be observed that the gain has an improvement of 4.3 dBi at 0.915 GHz and 6.64 dBi at 2.45 GHz for the antenna with the AMC backed structure. Considering the above, at the operating frequencies of 0.915 GHz and 2.45 GHz, the gain characteristics were increased by placing the antenna in front of the AMC structure.