## 4 Results Analysis  
As we saw in the previous section, the measurement and the simulation results are not in good agreement in the OFF state. The resulting frequency shift leads to poor radiated power and then poor connectivity. From the beginning, we knew that the 3D model would not be as accurate as the real one. The permittivity and the dissipation factor of the enclosure were set approximatively to the typical values and not those measured; the same with the photopolymer resin, we took approximate values of the permittivity and the dissipation factor issued from [35].  
Step 1: in this configuration, the matching network contains only 0 \(\Omega\) resistors on the signal path to make a short circuit. The lumped components implemented in the signal  
Figure 12: Simulated and measured S11 of the antenna in OFF configuration: (**a**) at 401 MHz; (**b**) at 868 MHz.  
Figure 13: Simulated and measured S11 of the antenna in ON configuration.  
path of the 401/868 MHz are also replaced with 0 \(\Omega\) resistors. We see that the resonant frequency predicted in simulation is at 483 MHz (Figure 14). However, the measurement shows that the resonant frequency is at 468 MHz, the delta f between simulation and measurement is 15 MHz. In simulation, we can shift the resonant frequency from 483 to 468 MHz by setting the inductance value of the inductor L3 to 2.8 nH. Thus, rather than implementing 17 nH found in the simulation, we implement 14.2 nH = 17 nH \(-\) 2.8 nH.  
Step 2: after compensating the frequency shift between the simulation and measurement, we replaced the inductor L3 (17 nH) by an inductor of 14.2 nH. The results of the simulation and measurement performed with the inductor L3 = 14.2 nH are shown in Figure 15. We see a frequency shift of 4 MHz for the lower frequency around 410 MHz and 21 MHz for the higher frequency close, 900 MHz. The frequency shift of the higher resonant frequency can be compensated with the diode capacitance Cp, as shown in the parametric studies subsection.  
Step 3: in this step, we show the resonant frequency locations in the presence of the PIN diode. This step is key toward understanding the PIN diode effect. We have seen from the parametric study on the parallel capacitance Cp that the PIN diode does not impact so much the lower frequency (a shift of 1 MHz/10 fF). This is true, but not so quantitatively. We see that the PIN diode shifts the higher resonant frequency from 912 to 825 MHz with a delta f of 113 MHz and the lower resonant frequency from 410 to 390 MHz (Figure 16).  
Figure 14: Simulated and measured S11: step 1.  
Figure 15: Simulated and measured S11: step 2.  
At this stage, we understand that the huge difference between simulation and measurement results is due to the PIN diode.  
Step 4: in step 3, we showed the effect of the presence of the PIN diode. To compensate the shift in frequency caused by the PIN diode, we proceed with same way as in step 1, by tuning the inductance value of the inductor L3. By setting the inductance value of the inductor L3 to 13 nH (1 nH for L2 and 12 nH for L3), the resonant frequencies shift to 401 and 871 MHz for the lower and higher frequencies, respectively (Figure 17). We see that we do not need to even use a matching network to match the antenna.