# Glueless Multiple Input Multiple Output Dielectric Resonator Antenna with Improved Isolation
## 3 Results and Discussion  
Validation of simulated results can only be done by measuring the results physically. To understand concordance between simulated results and their measured counterparts, a prototype of proposed antenna design has been fabricated, as shown in the inset of Figure 4. This fabrication of prototype has been done manually using standard laboratory tools and insertion of copper rods with highest accuracy, which became an onerous task. Expected tolerance between simulated and measured results may be attributed to manual fabrication process. Measurement of far field results have been accomplished in an anechoic chamber with horn antenna as transmitter antenna and by keeping the other port of the proposed antenna, which has been matched with 50 \(\Omega\), as displayed in Figure 4. Cartesian coordinates are also shown in the Figure 4 for the antenna under test and the reference antenna. Angle theta varies are given for \(-180^{\circ}\) to \(180^{\circ}\) for \(\phi=0\) and \(\phi=90^{\circ}\), which provide E-plane and H-plane radiation patterns. Scattering parameters have been measured using Keysight Technologies-N5227A Vector Network Analyzer. Simulated and measured S\(-\)parameters of the proposed MIMO DRA are shown in Figure 5. S22 identifies with \(S11\) owing to symmetrical structure of proposed design, hence omitted here for brevity. Simulated and measured radiation patterns for \(\phi=0\) and \(\phi=90^{\circ}\) of the proposed MIMO DRA at 8.4 GHz are shown in Figure 6. Measured IBW of fabricated prototype is 10.5% (8.05-8.95 GHz), with more than \(-15\) dB isolation (between ports) bandwidth between 8.2-9.2 GHz. It has been perceived that the maximum gain of the  
Figure 4: Measurement of far field radiation parameters in anechoic chamber. Figure 3: Simulated E-Field of proposed model in Eigen mode solver at 8.8 GHz. (In scale E Field 1.0000E+06 is \(1\times 10^{6}\) V/m). proposed DRA is 6.2 dBi, and the simulated radiation efficiency of the antenna is above 0.90, as shown in Figure 7.  
Figure 5: Simulated and measured S\(-\)parameters of proposed Antenna. Figure 6: Simulated and measured radiation pattern of proposed antenna at 8.4 GHz. For a dual-port MIMO system, \(\rho\) is expressed in Equation (1) [12]. \(\rho\) describes properties of communication channel with each other, such as isolation and correlation [27]. \(\rho\) can be measured using two methods: (i) using S\(-\)parameters; and (ii) using radiation pattern. For S\(-\)parameters, method radiation efficiencies for each port and at each frequency are also to be computed, which is difficult. It is also found that radiation pattern method of finding \(\rho\) is more accurate than the earlier one [8; 27; 28; 29]. \[\rho_{12}=\frac{\big{|}\iint_{4\pi}\left[\overrightarrow{F_{1}}(\theta,\phi)* \overrightarrow{F_{2}}(\theta,\phi)\right]d\Omega\big{|}^{2}}{\iint_{4\pi} \big{|}\overrightarrow{F_{1}}(\theta,\phi)\big{|}^{2}d\Omega\iint_{4\pi} \big{|}\overrightarrow{F_{2}}(\theta,\phi)\big{|}^{2}d\Omega} \tag{1}\]  
where \(\overrightarrow{F_{i}}(\theta,\phi)\) is three dimensional field radiation pattern of MIMO antenna when port-\(i\) is excited. \(\Omega\) is solid angle and \(*\) represents the product operator. Equation (2) is expanded version of Equation (1). Figure 4.0  
where \(\delta\) for \(i^{th}\) port calculated using Equation (3)  
Figure 4.1  
where \(E_{\theta 1}\) and \(E_{\phi 1}\) are elevation and azimuthal radiated field components for port-1 when other port is matched with 50 \(\Omega\) termination and similarly for port-2 are \(E_{\theta 2}\) and \(E_{\phi 2}\). XPR is the cross-polarization discrimination factor, which is the ratio between average power of vertically and horizontally polarized components of the transmitting wave (\(XPR=P_{V}/P_{H}\)), and \({}^{*}\) represents the complex conjugate.