# A Comprehensive Review of In-Body Biomedical Antennas: Design, Challenges and Applications
## 3 Antenna Design, Manufacture and Testing  
Figure 4 shows the generalized steps for designing, manufacturing and testing in-body antennas. In the first step, the researchers benchmark the antenna parameters based on the specifications provided in Section 2. These parameters are then used to generate an analytical model, which leads to analysis and simulation in programming and numeric computing platforms, such as MATLAB [59; 60; 61; 62; 63; 64]. This is an important step of optimizing the antenna to accomplish the best performance [65]. In the next step, the data generated from the analytical model are used to build a 3D antenna simulation environment using electromagnetic (EM) software, such as Ansys high frequency structure simulator (HFSS) [66] [[https://www.ansys.com/en-gb/products/electronics/ansys-hfss](https://www.ansys.com/en-gb/products/electronics/ansys-hfss)]([https://www.ansys.com/en-gb/products/electronics/ansys-hfss](https://www.ansys.com/en-gb/products/electronics/ansys-hfss)) (accessed 15 May 2023), Dassault Systems CST microwave suite [67] [https://www.3 ds.com/products-services/simulia/products/cst-studio-suite/](https://www.3 ds.com/products-services/simulia/products/cst-studio-suite/) (accessed 15 May 2023), finite difference time domain (FDTD) [68] [[https://optics.ansys.com/hc/en-us/articles/360034914633-Finite-Difference-Time-Domain-FDTD-solver-introduction](https://optics.ansys.com/hc/en-us/articles/360034914633-Finite-Difference-Time-Domain-FDTD-solver-introduction)]([https://optics.ansys.com/hc/en-us/articles/360034914633-Finite-Difference-Time-Domain-FDTD-solver-introduction](https://optics.ansys.com/hc/en-us/articles/360034914633-Finite-Difference-Time-Domain-FDTD-solver-introduction)) (accessed 15 May 2023), Altair FEKO [69] [[https://altair.com/feko](https://altair.com/feko)]([https://altair.com/feko](https://altair.com/feko)) (accessed 16 May 2023) and COMSOL [64] [[https://www.comsol.com/rf-module](https://www.comsol.com/rf-module)]([https://www.comsol.com/rf-module](https://www.comsol.com/rf-module)) (accessed 16 May 2023). Furthermore, Ansys Maxwell 3D [70] and Dassault Systems Simulia are low frequency solvers used to design in-body antennas with lower MHz to kHz frequency ranges. The analytical model and EM software simulation results are compared to verify and confirm the antenna parameters before manufacturing in-body antennas. Figure 4: Generalized steps for designing, manufacturing and testing in-body antennas. Detailed methodology of the manufacturing process of an in-body patch-type planar antenna has been outlined in Ref. [65]. In antenna manufacturing, a photolithography mask is first produced to confirm the antenna geometry, including antenna layers, which are going to be stacked on the plane. In the next step, the antenna layers are etched according to the antenna geometry using the photolithography mask. Furthermore, the lower substrate comprises the ground and lower patch; the upper substrate comprises the upper patch; and the superstrate is positioned on the top. Additionally, a circular-shaped hole is etched as per the patch geometry, where four pins are located at the base of the mask. Afterward, all the layers are machined to the circular format, and the layers of the antenna are positioned in a straight line. This process must be conducted without putting much more mechanical stress on the antenna. Finally, the layers of the antenna are organized in a mountain format and glued to attach all the layers in case of a multi-layered structure. This step is not required for single-layer microstrip patch planar antenna. In the next step, the shorting pin is attached to the ground plane and lower patch. Therefore, the outer conductor of the co-axial feeding point is connected to the ground. Furthermore, the inner conductor is soldered to the lower and upper patch. This methodology is commonly used in research laboratories to validate the antenna parameters with respect to simulation.