# Metamaterial Integrated Folded Dipole Antenna with Low SAR for 4G, 5G and NB-IoT Applications
## 3 Antenna Design and Result Analysis
They can be assumed to be further divided into four close bands. The first of these can be designated as low frequency LTE bands and consists of band nos. 35, 39, 33, 37 and 36. The two middle frequencies LTE bands can be identified as band nos. 34 and 40, 41, 38 respectively. The last high frequency bands consist of LTE band nos. 42, 43 and NR n78. The NB-IoT bands almost coincide with the LTE bands, so they are not assumed separately for wideband accomplishment. These close bands can be obtained by dipole elements 1 and 3 for low frequency LTE bands and elements 5 and 2 for middle frequency LTE bands. Similarly, high frequency bands can be achieved through dipole element 4. The simulations were performed using CST microwave studio with the length and width of the feeding strip of 5.6 and 4.7 mm, respectively. The ground layer is considered to be infinite with some extra spacing for the substrate in addition to the maximum width and length of the dipole to compensate for the  
The initial tuning operations are obtained using the common width dipole elements such that the variable width dipole antenna acts as a single thin dipole antenna. The common width dipole resonates at a frequency of 1.8 GHz and is in good agreement with the second resonance frequency, as per the theoretical calculations of Equation (9). The scatter plot obtained for the same is illustrated in Figure 8 as case 1. The resonance and bandwidth can be controlled further according to the equivalent length and width combination of the five element dipoles. The 350 MHz bandwidth obtained in case 1 is escalated in case 2 by increasing the elements widths and slightly decreasing the length to incorporate the high frequencies. However, the 420 MHz bandwidth obtained in case 2 is not sufficient to include the middle and high bands. Thus, the length and width of the dipole elements are further optimized to include the higher frequency bands. Case 3 resonates for two frequencies; the lower resonating frequency of 1.8 GHz is due to the total equivalent length and the higher resonating frequency of 2.3 GHz is supported by the sub-combinations of dipole element lengths. The total bandwidth achieved in case 3 is 800 MHz, in comparison to 420 MHz obtained in case 2. However, all three cases are not able to cover the high frequency bands. It should be noted that there is a small gap between the middle and high frequency bands. The same process was attempted to be incorporated in case 4, by emphasizing dipole element 4, which nearly covers low frequency and high frequency bands with bandwidths of 270 and 850 MHz, respectively. The essential operational bandwidth can be achieved in the same escalating manner but will result in a bulky antenna. The basic compact size requirement of the radio device is obtained by folding the elements of the dipole in the minimum possible substrate space with a cross-section area of 35 \(\times\) 48 mm\({}^{2}\), as illustrated in \[R_{in}=24.7\,\left(\frac{\beta L_{d}}{2}\right)^{2.5} \tag{1}\]5 However, the size minimization may result in bandwidth depletion because of the finite, rather than infinite, ground, and this can be addressed by a defective ground structure with an optimized length of 4 mm, as shown in \[R_{in}=24.7\,\left(\frac{\beta L_{d}}{2}\right)^{2.5} \tag{1}\]6 The length and width of the feeding element are optimized to 5.6 and 10 mm, respectively.