**4. Antenna design and testing**

#### **4.1 Antenna design**

While designing an antenna one should follow the following characterization of implantable antenna:


Following commercial tools are used for designing an implantable antenna such as computer simulation tool (CST) Microwave Studio, High-Frequency Structure Simulator (HFSS), Advanced Designed System (ADS), and XFDTD. In [55] for analyzing electromagnetic characteristics of the implantable antenna inside head and body, Finite-difference-time-domain (FDTD) and Spherical dyadic Green's function (DGF), etc. functions are applied. In [83] Antenna simulated using FDTD overall efficiency improved and suitable design obtained in minimal time with help of a genetic algorithm.

In general, a one-layer skin model is widely used for implantable antenna design. Although, 2/3 muscle model and three-layer tissue (skin, fat, muscle) mode are also typically for antenna designing. These three models make simulation efficient and measurement easier as this model is made from different materials to active accurate permittivity and conductivity.

In [26] implantable antenna designed with FDTD method including 2/3 muscle model. In [28, 33] antenna simulated in HFSS and CST respectively and a singlelayer skin model is used. To design an implantable antenna in a realistic environment then it must evaluate within accurate human body models such as the human Voxel model shown in **Figure 3**. For neural recording systems and wireless



*Microwave Antennas Suggested for Biomedical Implantation DOI: http://dx.doi.org/10.5772/intechopen.101060*

> **Table 5.**

*Volume occupied by MICS, ISM and medradio band implantable antenna and its miniaturized techniques: A literature.*

**Figure 3.** *Front and side view of CST human voxel mode used for simulation testing of various antenna.*

endoscope systems, an accurate human model is required. For different biomedical applications, the implant's position and depth could be a different and single layer or three-layer modeling used according to application. In **Figure 4** one-layer tissue model is shown.
