# Approach-Based Analysis on Wireless Power Transmission for Bio-Implantable Devices
## 3 Analysis of Various WPT Approaches
### WPT Systems Based on Antenna Modifications

Table 4: WPT systems based on antenna modifications. its range is 402-405 MHz. The second band is the mid-range frequency band between 1.45-1.6 GHz. The last band is the industrial, scientific and medical (ISM) band and its range is 2.4-2.45 GHz. These bands are used for wireless telemetry, WPT, and energy-saving biomedical devices. To extend the range of such antenna to apply in on ingestible devices, the performance of said antenna has been measured with minced pork in the ISM frequency band. An altered form of the midfield energy transferring model has been assimilated to depict the WPT scheme in the implantable 3-dimensional printed capsule. In addition, an NFP plate has been used to manage the power dissipation of the WPT transmitter. In this work, authors discovered that using a ground slot portion in the Rx antenna, antenna performance could be improved and SAR could be reduced. Additionally, it is shown that by involving an NFP plate in the WPT transmission of medium field, the power transferring performance and efficiency of WPT can also be increased. A resonator for implants (subcutaneous) was developed, which provides a new pattern for impedance matching to the existing loop antenna [47]. The metal pad, which is made of concentric model-tuning components, was put up and distributed inductance and capacitance to inductive loop (planar model), which improved the resonance highly. This gives a good qualification factor to attain proper coupling. In another approach [48], an embedded receiving antenna, which is polarized circularly and integrated with a voltage-doubler rectifier for wireless microwave power transfer in the 2.4-2.48 GHz ISM band, was studied and presented. Similarly, another approach for RF energy collection and data transmission was presented [49]. The authors introduced multiple radiating branches and etched C-shaped slots to create multiple resonant frequencies. This created a wide double band and improved the WPT. [PERSON] et al. [41] propose a triple-loop WPT system with an imperium power control mesh, automatic resonant tuning (ART) receiver (Rx) and transmitter resonant compensation (TRC). The system cancels the load and coupling swing and also reimburses for variations in the inductive connection to improve the PTE of implantable medical devices. Tx had been constructed in a commercially off-the-shell radio frequency identification reader working at a frequency of 13.56 MHz. By varying the value of varicap, the Tx mesh determines the optimum capacitance, which is in parallel with the transmitting coil. The imperium power control mesh keeps the Rx power at the required range in response to the distance of coupling, misalignment of the position of coil and load changes. The Rx loops are carried out in special integrated circuits (IC) called power management IC to skip or prevent any degradation in PTE and process variability by Rx coil surroundings. This three-loop system reduces the total PTE by around 10.5% compared to a same type open-loop system, and by around 4.7% compared to a similar type closed-loop system at 2 cm nominal coil spacing. Here, the TRC contributes 2.3%, and ART loops contribute 1.4% efficiency to the system's total PTE, which is 13.5%. Notably, the first WPT system, which includes three loops, aggressively reimburses for circuit and environmental fluctuations and enhances total energy efficiency that is from controller output on Tx to the respective module on Rx. Such a smooth transmission takes place by using a three-coil and three-loop model as expressed in Figure 5.  
The WPT connection consists of a double-ring groove antenna, which is used as the Rx element and a single-patch-type antenna, which is taken as the Tx element. Here, the Rx element is implanted [42] in a one-layered tissue of skin prototype and the operating frequency of patch-type antenna is 2.45 GHz in ISM, while the double-ring groove is assigned to obtain broadband properties that involve the full ISM frequency band.