## 3 Results and Discussions
### Measurement Results  
Figure 12 outlines the simulated and measured results for each state separately to examine the antenna performance along with the two different switching mechanisms, namely PIN diode and SPDT. It is clear that such a configuration with PIN diodes is advantageous in terms of ease of integration. However, nonlinear effects of switches, interference losses, and negative effects of biasing lines are disadvantages of electronic reconfigurability. The DC biasing lines required for PIN diodes cause unwanted electromagnetic coupling that may lead to losses and reduced performance. The nonlinear behavior of PIN diodes under varying bias conditions results in signal distortion. These challenges highlight the intricate trade-offs that must be considered when choosing between different reconfigurability approaches. In comparison to SPDT switches, the utilization of PIN diodes for electronic reconfigurability introduces its own set of challenges, mainly due to the DC biasing requirements. While SPDT switches can operate with minimal biasing, PIN diodes need a continuous DC bias current. It is concluded that this bias current not only consumes power but also introduces nonlinear effects, adversely impacting the overall performance of the system. Figure 11: Surface current distribution of (**a**) State-1 (ON-ON, 2.4 GHz), (**b**) State-2 (OFF-ON, 3.27 GHz), (**c**) State-3 (ON-OFF, 3 GHz), (**d**) State-4 (OFF-OFF, 3.45 GHz). Figure 12: _Cont._  
The frequency-reconfigurable microstrip antenna proposed in this study exhibits variations in return loss across different switch states. This phenomenon arises from the intricate interplay between the antenna's electromagnetic properties and the presence of switching components, including the PIN diode (BAR64-02V) and SPDT switches (CG2415M6 models). When the PIN diode is in an \"ON\" state, its additional impedance element alters the effective electrical length of the antenna, resulting in modified resonant frequencies and impedance matching characteristics. This leads to observable variations in the return loss due to the changes in impedance relationships between the antenna and the feeding network. Similarly, the SPDT switches introduce alterations to the antenna's configuration, affecting its radiating properties and resonance frequencies. Coupling effects between the switching components and the antenna's inherent geometry further contribute to the observed differences in the return loss. These intricate interactions emphasize the sensitivity of the proposed antenna's performance to the active switching elements, underscoring the need for precise control and understanding of the switch states for optimal operation. Measurement of the radiation pattern and gain of a proposed antenna is of paramount importance for performance analysis, including its directional capability, efficiency, tuning, and compliance with various applications. Measuring the radiation pattern and gain of an antenna requires special equipment and techniques such as an antenna test range, turn table, antenna range controller, far field or near field probe, and software. These are some of the primary equipment commonly used in antenna measurement setups. Unfortunately, due to the limitations of the current laboratory facilities, only the reflection coefficient measurement results are given for the designed antenna. In combination, the ring resonator and switches provide a mechanism for frequency reconfigurability in the antenna. By controlling the states of the switches and the dimensions of the ring resonator, the resonant frequencies and bandwidths of the antenna can be adjusted to meet the requirements of different communication standards, frequency bands, and system specifications. In essence, the proposed antenna design embodies these distinctive features, showcasing a significant leap in the field of versatile and adaptable antennas for wireless communication systems.