# A Multi-Bandwidth Reconfigurable Patch Antenna for Devices in WLAN and UWB Technology Applications
## 3 Experimental Results and Discussion  
We fabricated and measured a hardware prototype to validate the simulation results and check the actual antenna behavior. In this case, a commercially available substrate was used to fabricate the proposed PA (shown in Figure 9a), which was then measured using a vector network analyzer (VNA) and an anechoic chamber to determine its return loss. The anechoic chamber and the antenna under measurement can be seen in Figure 9b,c. Additionally, to measure the far-field parameters of the antenna, such as its radiation pattern, an electromagnetically isolated RF anechoic chamber was used. By measuring the radiation pattern in the anechoic chamber, the antenna's performance can be characterized, and any deviations from the simulation results can be identified and analyzed. Figure 8: Surface current distribution of the proposed antenna design at a frequency of 4 GHz. (**a**) Both PIN diodes are on. (**b**) Left diode is on the right is off. (**c**) Left diode is off and the right is on. (**d**) Both PIN diodes are off. The reflection coefficient of the antenna was measured for its different operation states. Figure 10 shows the results of the measurements compared to the simulations performed for two of the operation states: when both diodes are on (and the antenna shows two operations bands) and when diode D1 is off, and diode D2 is on (and there is a wide band around 2.41 GHz). When both diodes are active, the fabricated antenna covers both the WLAN and low-ultra-wideband spectrum in the ranges of 2.4-2.5 GHz and 4.1-5.1 GHz, respectively. The simulation and the measurements agree very well on the positions of the bands and approximately well on the widths of the bands. When diode D1 is off, both measurements and simulations yield a featureless reflection coefficient with no bands, even if the particular shape of \(S_{11}\) differs. The absence of features is due to the change in the electrical size of the antenna caused by the operation states of the diodes. When PIN diode D1 is _off_ and PIN diode D2 is _on_, the semicircular patch is disconnected and the rectangular part is connected, respectively. In this configuration, the electrical length of the antenna is such that the resonances are outside the frequency range covered in Figure 10.  
The simulated and measured reflection coefficients of the antenna are in good agreement for both frequency bands, further validating the accuracy of the simulation process used to model the antenna's behavior. The antenna design process can be reliably modeled using simulation tools. Figure 10: Comparison of measured and simulated reflection coefficient of the proposed PA.  
Figure 9: (**a**) Fabricated prototype. (**b**) Antenna under test. (**c**) Measurement of the far-field parameters in facilities at KU Leuven. Figure 11 illustrates the simulated and measured 2D radiation patterns in the E- and H-planes for the proposed antenna. The E-plane (or azimuth) represents the radiation in the plane perpendicular to the antenna's feeding mechanism. It shows how the antenna radiates energy in the horizontal plane around the antenna. The H-plane (or elevation) represents the radiation in the plane containing the antenna's feeding mechanism. It shows how the antenna radiates energy in the vertical plane, typically above or below the antenna. The results show strong agreement between the simulation and the measurements, indicating the accuracy of the antenna design. The antenna provides relatively stable radiation patterns at all resonating frequencies, ensuring its wideband operation. In the H-plane, the antenna offers a nearly omnidirectional radiation pattern at the first resonant frequency and a quasi-omnidirectional radiation pattern at higher frequencies, ensuring coverage over a broad range of frequencies.