# A Novel Dual-Band Implantable Antenna for Pancreas Telemetry Sensor Applications
## 2 Methods and Results
### Radiation Performance Analysis
#### 2.2.4 Electric Current Distribution  
In general, complex phenomena were observed in the electric field due to the small size of the antenna so it was difficult to predict its distribution. However, we can draw some useful conclusions. For 1 W input power at the feed, the maximum electric field at 402.5 MHz was 3408 V/m, and at 2.45 GHz, it was 3770 V/m. The peak values of the electric field for both frequencies are shown in the Table 3.  
Electric field distribution at 402.5 MHz when every component is inserted is shown in Figure 16. Initially, the electric field of the plane microstrip antenna was very weak, with a maximum value 47 V/m and equally distributed in the conductive surface. As we inserted the shorting pin, the electric field concentrated on the edges, and the maximum value changed to 1007 V/m. This also shows why the resonance occurs when we insert the pin. When the U slots are added, the electric field distribution did not present significant changes, and the maximum values increased to 3408 V/m for the proposed antenna, which explained why the tunning improved with these structure modifications. Obviously, we fully exploited the antenna surface to achieve maximum radiation.  
\begin{table}
\begin{tabular}{c c c} \hline
**Frequency** & **Realized Gain (dB)** & **Realized Gain (dB)** \\  & **at 402.5 MHz** & **at 2.45 GHz** \\ \hline Without Elements & \(-42.4\) & \(-24.6\) \\ Shorting pin & \(-35\) & \(-22.3\) \\ Shorting pin and U-slot & \(-30.8\) & \(-24.1\) \\ Proposed Antenna & \(-31\) & \(-22\) \\ \hline \end{tabular}
\end{table}
Table 2: Results of maximum Realized Antenna Gain extracted from simulations.  
Figure 15: Realized gain at (a) 402.5 MHz and (b) 2.45 GHz.  
\begin{table}
\begin{tabular}{c c c} \hline
**Structure** & **Electric Field (V/m)** & **Electric Field (V/m)** \\
**Modifications** & **at 402.5 MHz** & **at 2.45 GHz** \\ \hline Without Elements & 47.7 & 2501.6 \\ Shorting pin & 1007.5 & 1885.9 \\ Shorting pin and U-slot & 3554 & 4784.5 \\ Proposed Antenna & 3408.6 & 3770.6 \\ \hline \end{tabular}
\end{table}
Table 3: Maximum Electric Field and Antenna Structure Modifications extracted from the simulations.  
Figure 17 shows the electric field distribution of the proposed antenna at 402.5 MHz displayed in two- dimensional and three-dimensional space as displayed from our simulations.  
The electric field distribution at the ISM band, displayed in Figure 18, was similar in all steps of the design procedure, as the resonant mode already existed from the plain microstrip patch antenna before inserting any elements. It was observed that the maximum electric field distribution was found on the edges and the maximum value was at 2501 V/m before any modification while it increased to 3770 V/m after adding all the elements. In this case, antenna radiation mechanisms changed. Less than half of the antenna volume is now used, and resonance is along the x axis.  
Figure 16: Electric field distribution of the modified antenna at 402.5 MHz without structure modifications (**a**), after inserting the sorting pin (**b**), after inserting the first U-slot (**c**), and after inserting the second U-slot (**d**).  
Figure 17: Electric field distribution of the proposed antenna at 402.5 MHz displayed in two- dimensional (**a**) and three-dimensional space (**b**) as displayed from our simulations.  
Figure 19 shows the electric field density of the proposed antenna at 2.45 GHz displayed in two- dimensional and three-dimensional space.