# A Frequency-Selective Reconfigurable Antenna for Wireless Applications in the S and C Bands
## 4 Experimental Results and Discussion
In the simulation, the three main resonances were located at \(2.04\), \(4.44\), and \(6.42\) GHz, while, on the fabricated antenna, they were found at \(2.07\), \(4.63\), and \(6.22\) GHz. The deviation between the three cases is \(30\), \(190\), and \(200\) MHz, respectively, or \(1.4\%\), \(4.2\%\), and \(3.1\%\). Also, the experimental results show a better functionality of the antenna at \(4.63\) GHz, than the one suggested by the simulation at \(4.44\) GHz. Furthermore, the radiation patterns of the fabricated antenna show better gains than those seen in the simulation. For the \(2,4\), and \(6\) GHz bands, the maximum simulation gain was \(0.58\), \(1.75\), and \(5.64\) dBi, respectively, while the corresponding measured gains were found as \(5.48\), \(3.97\), and \(12.79\) dBi, which are \(4.9\), \(5.72\), and \(7.15\) dBi higher than those suggested by the simulation. The deviations between the simulation and the experimental results are overall insignificant, except for the simulated and measured gain. These deviations were expected since many factors were not accounted for in the simulation. Such factors are the effects of solder used for the SMA connector, the PIN diode, and the effects of the pins used for applying voltage on the diode. Also, the antenna was tinned to avoid oxidation, which could also have some effect on its functionality. But more importantly, the deviations could be due to the R and C values selected for the diode's equivalent circuit in the simulation. Both these parameters, but mostly R, are frequency-dependent. Because the simulation tool does not support nonlinear elements in the simulations, they were both considered constant over the whole simulated frequency range, from \(0\) to \(8\) GHz. Furthermore, the graphs in the diode's datasheet describe these values for frequencies only up to \(2\) GHz. Thus, the R and C behavior for higher frequencies was considered to be similar, which might not be the case. This probably is the reason that the deviation appears to be minimal at the \(2\) GHz  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Frequency (GHz)**} & \multirow{2}{*}{**S11 (dB)**} & \multirow{2}{*}{**VSWR**} & \(\begin{matrix}-\mathbf{10}\text{\ \ dB}\\ \text{\ \band. Finally, the deviations in the radiation patterns, and primarily in the gain, might be due to reflections occurring in the vicinity of the antenna, or due to the prime resonances of the fabricated antenna not being identical to those indicated by the simulation. The compact patch re-configurable antenna is controlled by a single PIN diode, in contrast to several other works that require multiple diodes. The antenna has three modes of operation with a total bandwidth of 974 MHz over prevailing tuning in the three frequencies. Furthermore, it has a low cost, volume, and weight and can be easily implemented even in a lab-based environment. The antenna also achieved quasi-omnidirectional radiation patterns that make it ideal for wireless applications where omnidirectional coverage is usually required.