## 2 Proposed Optimization Method
For the first time, this study presents a novel optimization-oriented method for modeling and sizing the implanted MIMO antennas, automatically. Intelligent methods are proposed in this work for firstly building the initial configuration and then sizing the implanted MIMO using the TDO and DNN methods, sequentially. All process are performed automatically with the combination of CST and MATLAB. The superior performance of the proposed method is validated by designing an implanted MIMO antenna in the multi frequency band from 4.34 GHz to 4.61 GHz and from 5.86 GHz to 6.64 GHz that are emerging wireless bands for future medical applications. The optimized MIMO antenna to be used within the human body in these emerging wireless medical bands are firstly proposed in the present work. Our proposed optimization paradigm is flexible and it can be developed by: (1) considering various biomedical tissues, (2) using various types of feeding points, (3) employing different optimization methods in configuring the initial structure of the MIMO antenna. Figure 6: Co-pol radiation pattern of the considered antenna in the E—(**left**) and H—(**right**) planes at 4.5 GHz (**top**) and 6.2 GHz (**bottom**). **Author Contributions:** Conceptualization, L.M. and L.K. ; methodology, L.K. ; software, L.K. ; validation, L.K., L.M. and I.P. ; formal analysis, L.M. ; investigation, L.K. ; resources, L.M. and I.P. ; data curation, L.K. ; writing--original draft preparation, L.K. ; writing--review and editing, L.K., L.M. and I.P. ; visualization, L.K. ; supervision, I.P. and L.M. ; project administration, L.M. and I.P. ; funding acquisition, I.P. All authors have read and agreed to the published version of the manuscript. **Funding:** This work was partially supported by a grant of the Romanian Ministry of Education and Research, CNCS--UEFISCDI, project number PN-III-P4-ID-PCE-2020-0404, within PNCDI III. **Conflicts of Interest:** The authors have no conflict of interest. ## References

* (1) [PERSON]; [PERSON]; [PERSON] [PERSON]; [PERSON] [PERSON]; [PERSON]; [PERSON] In-Body Communications Exploiting Light: A Proof-of-Concept Study Using Ex Vivo Tissue Samples. _IEEE Access_**2020**, \(8\), 190378-190389. [CrossRef]
* (2) [PERSON]; [PERSON]; [PERSON] Circularly Polarized Dual-Mode Wearable Implant Repeater Antenna With Enhanced Into-Body Gain. _IEEE Trans. Antennas Propag._**2020**, _68_, 3515-3524. [CrossRef]
* (3) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Review on Medical Implantable Antenna Technology and Imminent Research Challenges. _Sensors_**2021**, _21_, 3163. [CrossRef] [PubMedMed]
* (4) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Compact SIW Fed Dual-Port Single Element Annular Slot MIMO Antenna for 5G mmWave Applications. _IEEE Access_**2021**, \(9\), 91995-92002. [CrossRef]
* (5) [PERSON] [PERSON]; [PERSON] A Three Dimensional MIMO Channel Model for Unmanned Aerial Vehicle in Urban Environments. _IEEE Open J. Commun. Soc._**2021**, \(2\), 1419-1430. [CrossRef]
* (6) [PERSON]; [PERSON] [PERSON] A Novel and Systematic Approach to Inhomogeneous Dielectric Lens Design Based on Curved Ray Geometrical Optics and Particle Swarm Optimization. _IEEE Trans. Antennas Propag._**2019**, _67_, 3657-3669. [CrossRef]
* (7) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Optimized Corrugated Tapered Slot Antenna for mm-Wave Applications. _IEEE Trans. Antennas Propag._**2018**, _66_, 1227-1235. [CrossRef]
* (8) [PERSON]; [PERSON]; [PERSON]; [PERSON] Fabrication and Characterization of Multiband Polarization Independent 3-D-Printed Frequency Selective Structures With UltraWide Fields of View. _IEEE Trans. Antennas Propag._**2018**, _66_, 6096-6105. [CrossRef]
* (9) [PERSON]; [PERSON]; [PERSON] Mutual Coupling Reduction in Patch Antenna Arrays by Using a Planar EBG Structure and a Multilayer Dielectric Substrate. _IEEE Trans. Antennas Propag._**2008**, _56_, 1648-1655.