# Miniaturized Compact Reconfigurable Half-Mode SIW Phase Shifter with PIN Diodes
## 3 Results and Discussion of Varied Solutions  
The proposed structure was designed in numerical full wave simulation software according to the geometry of Figure 2. In light of the scattering parameters, the geometry was tuned to provide suitable performance across the frequency range. The background surface is applied with a perfect electric conductor as the boundary condition. Other directions are chosen as open added-space boundaries. Two ideal waveguide ports with larger areas are added to the two microstrip lines at the corners. The frequency of analysis in the simulation software is 2 to 9 GHz. Various simulation software, including CST, ANSYS HFSS, and a circuit analyzer (ADS), is used to verify the structure before a concrete measurement study. To further evaluate a HM-SIW phase shifter microwave component, the proposed structure is fabricated as shown in Figure 7. Two SMA connectors are soldered to the input and output ports. In the figure, the metallic surface of the HM-SIW is covered with copper and solder paste. A portable network analyzer from Keysight (N9950B) is connected to investigate the scattering parameters for two ports, including reflection and coupling values both in dB and phase units. Before performing the scattering parameter measurements, a mechanical 2-port calibration is conducted (based on a broadband SOLT kit). PIN diodes and resistors are soldered to the board. Then, a DC source is employed to change the diode situation using key control. For better soldering on the same SIW surface, three extra arms connected in one direction to the diode are provided. On the opposite side of the background, the diodes are connected to a DC source in the other direction. Figure 6: Analysis of the effects of adding parallel stubs to the transmission line. Charts of (**a**) scattering parameter magnitudes and (**b**) transmission phase when the HM-SIW is alone (reference) and by adding a parallel diode (ON state) are prepared. There are three diodes in the design; therefore, eight different formations of diode states can be explored. The first state, 000, shows that all three diodes are OFF. Moreover, 111 indicates that all three diodes are in the ON state. The magnitude of scattering parameters in dB is obtained in these two situations from varied solutions. In Figure 8, the scattering coefficients for both ports are acceptable from 4.5 to 7 GHz for both scenarios. Based on the different solutions, the reflection coefficients of both ports were below \(-10\) dB, and the coupling parameter was below \(-2\) dB considering the assigned frequency band. The coupling parameter was not acceptable to work at frequencies exceeding 7 GHz in the experiment because of loss in the connectors. Once proper wave transmission has been carried out in the allocated frequency band, both solutions are examined to determine the phase of transmission. Since three PIN diodes are integrated in the transmission line, there would be eight different situations for diodes. State 000 assigns the first and reference situations. Then, by changing the states of the diodes one by one, the transmission phase variation is analyzed. The phase variation can be controlled digitally with this reconfigurable phase shifter. Figure 9 presents the phase difference resulting from normalizing different diode states to the reference 000 formation. A maximum 55\({}^{\circ}\) phase shift is achieved when all diodes are ON (as shown in Figure 9a). For the entire frequency range, a nearly stable response is achieved. Moreover, different diode formations lead to a quantitative feature in the phase shifter. Only phase shift performance in the 4.5 to 7 GHz frequency range is shown in the charts. Ideally, phase shifters should provide a constant phase shift and dominant signal transmission. The signal coupling parameter in Figure 8 shows high quality wave transmission. In addition, a nearly constant phase difference is achieved based on the analysis of Figure 9, considering every frequency point.