# Revisiting the Analysis of Radiative Mid-Range Wireless Link for Pacemakers
## 3 Results
### Measurement  
The anechoic chamber measurements were performed to verify the validity of both the computed and simulated results. The setup for the indoor measurement is shown in Figure 7. A phantom fluid that provides the characteristics of the human skin was applied to the measurements. The product (SKIN350-500V2) manufactured by Schmid & Partner Engineering AG company, Zurich, Swiss is used. An acrylic tank is used to contain the fluid for the implanted patch antenna. The size of the acrylic tank is set as (height \(\times\) length \(\times\) width) = (31.6 cm \(\times\) 31.6 cm \(\times\) 10 cm), which can be filled with one liter of the fluid. The implanted patch antenna is situated inside the fluid, while the reader patch antenna moves along the boresight direction of the two antennas. An important aspect of this work is the investigation of wireless power transmission to implanted antennas which are immersed with different depths of 4 mm and 8 mm. The depths of the human skin were determined by measuring the distance between the implanted antenna and the wall of the tank. The power transmission was measured using a vector network analyzer by varying the separation distance from \(R\) = 1 \(\lambda\) to \(R\) = 5 \(\lambda\). A comparison of the simulated results and measured results is shown in Figure 8.  
Figure 6: A comparison of the power transmission obtained from the FEKO simulation and the integral coupling formula at 400 MHz within a valid angular range at \(R\) = 1\(\lambda\) between: (**a**) the reader patch antenna and the implanted patch antenna immersed with 4 mm thickness of the human skin and (**b**) the reader patch antenna and the implanted patch antenna immersed with 8 mm thickness of the human skin.  
An excellent agreement between the simulated and measured results is observed for the different depths of the human skin. It is noted that the simulated coupling level at the shortest distance is slightly smaller than the one of Figure 8, since the shortest distance of \(R=1\lambda\) for the measurement is greater than the one of \(R=0.8\lambda\) for the simulation. For the impedance matching, the simulated and measured results are similar in terms of the magnitude of the reflection coefficients, while a 3-5% shift of the center frequency between the simulated and measured results is generated. The discrepancy between the simulated and the measured one might be attributed to the use of a relatively smaller  
Figure 8: A comparison of the simulated results and the measured results for: (**a**) the power transmission between the reader patch antenna outside the human body and the implanted patch antennas with different thicknesses of the human skin at 400 MHz, and (**b**) the impedance matching of the implanted antennas with different thicknesses of the human skin.  
Figure 7: Photographs of the measurement setup for: (**a**) the on-axis power transmission between the implanted patch antenna and the reader patch antennas outside human body at 400 MHz, and (**b**) the patch antennas located in the tank filled with phantom fluid.  
size of the tank than the human tissue model used in the simulation. The effect from the dispersive phantom fluid can be reduced due to the limited size of the tank, which results in higher resonant frequency than the full-wave simulation. The measured results provide a good agreement with the simulated results for both the power transmission and impedance matching.