## 3 Wireless Communication and Power Transmission
### Antenna Design
This antenna achieves the goal of miniaturization through a meandering line design and ensures the performance of the circularly polarized antenna by adopting a U-shaped structure. Inverted F Antenna (PIFA): The device features a relatively compact size. The radiation pattern and input impedance can be accurately tuned by means of designing the pointing direction and feeding position, enabling personalized adjustment. [PERSON] put forward the first implantable antenna with polarization reconfigurability. By employing two sets of PIN diodes as RF switches, it is capable of switching between two orthogonal linear polarizations, thereby preventing communication link failures and demonstrating excellent robustness in complex implantation scenarios. In vitro experiments were carried out in a tissue-mimicking liquid. Under different reconfigurable states, the overlapping impedance bandwidth ranging from 2.3 GHz to 2.52 GHz is 9.1% [113]. In demanding implantation environments like retinal surgery, [PERSON] designed a three-layer PIFA antenna based on microstrip technology. Through its compact size design, its perfor  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Reference** & **Frequency Band** & **Energy/Bandwidth** & **Size** \\ \hline \multirow{4}{*}{Dual-frequency implantable antenna [110]} & \multirow{4}{*}{402–405 MHz/2.4-2.48 GHz} & The bandwidth of the \(-\)10 dB bandwidth MICS band is 35.3\%, and the bandwidth of the ISM band is 7.1\% & 22.5 mm \(\times\) 22.5 mm \(\times\) 2.5 mm \\  & & The peak gain of the \(-\)external component is \(-\)10 dB bandwidth MICS band is 35.3\%, and the bandwidth of the ISM band is 7.1\% & \\  & & The peak gain of the \(-\)external component is \(-\)10 dB bandwidth MICS band is 35.3\%, and the bandwidth of the ISM band is 7.1\% & \\  & & The peak gain of the \(-\)external component is \(-\)10 dB bandwidth MICS band is 2.4 GHz, while that of the internal component is 7.8 decibels & \\  & & The peak gain of the \(-\)external component is \(-\)10 dB bandwidth MICS band is 2.4 GHz, while that of the internal component is 7.8 decibels & \\  & & The peak gain of the \(-\)external component is \(-\)10 dB bandwidth MICS band is 2.4 GHz & \\  & & The peak gain of the \(-\)external component is \(-\)10 dB bandwidth MICS band is 2.  
mance surpasses that of other previously proposed implantable antennas, with a gain of \(-24.31\) dB and a radiation efficiency of \(8.72\%\)[114]. Coupled antenna: A typical planar LCR resonator is composed of a capacitor in series with a planar coil. An additional manufacturing step is required to establish the electrical connection between the inductor and the capacitor. [PERSON] designed a dual-inductor coil structure [115]. In this structure, two coils are simply stacked, and a 50-micron-thick polylactic acid (PLLA) layer is used as an insulating medium in the middle (Figure 3c). This design does not require any additional electrical connections. It achieves the separation of the position of the pressure-sensitive area and the position of the wireless connection, significantly reduces the complexity of sensor manufacturing, and improves the overall stability of the device at the same time. Conformal antenna: Conformal antennas possess the ability to adapt to the geometries of complex implantation sites and are well-suited for placement on the surfaces of irregularly shaped objects, such as organ tissues. [PERSON] employed a method that combines a miniature coplanar implanted antenna with a sensor module, which can be utilized for intracranial pressure monitoring. The recorded intracranial pressure is transmitted to the skull, and a link budget within the range of 0.5-1 m is established. This constitutes an integral part of the minimally invasive intracranial pressure monitoring technology. Intracranial pressure is monitored at 2.45 GHz by means of a circular slot antenna. The radiation efficiency of this antenna outperforms that of previously utilized strip antennas, such as the printed inverted F antenna [116].