## 3 Design
The phase delay can be described by the following equation:  
\[\Delta\theta=tan^{-1}\ \ \frac{\omega L-\frac{1}{\omega\mathrm{C}}}{R_{L}} \tag{6}\]  
A phase constant can be possessed by the meander line resonator, and it is as follows:  
\[\beta=\frac{2\pi}{\lambda i} \tag{7}\]  
where the symbol \(\lambda\)i represents the wavelength of the resonator. By the equations that came before it, the next equation can be expressed as follows:  
\[\Delta\theta=\beta\ l \tag{8}\]  
Or  
Figure 2:0  
Figure 2:1 (**a**) The typical structure of a meander resonator, and (**b**) its equivalent lumped element circuit. Therefore, Equations (8) and (9) might be taken into consideration within the process of designing this resonator. As shown in Figure 6, the BPF can be constructed by utilizing a series connection between the C and L terminals. This will make it possible to construct the microstrip BPF in accordance with Equation (9). All of the suggested diplexer filters are listed in Table 1, which contains their varied specs. To design and simulate the microstrip diplexer that was suggested, the AWR program was utilized. This was done to accomplish the aforementioned goals. The diplexer was initially designed to have total substrate dimensions of 32 \(\times\) 26 mm\({}^{2}\), based on FR4 substrate. The microstrip diplexer has a Chebyshev response based on frequency responses received by the AWR simulator. Each filter for the projected microstrip diplexer has only one resonator and can be considered a first-order filter. Meander line resonators, patches, SIR, and UIR components are utilized in the construction of the suggested diplexer, which is illustrated in Figure 2:2 Intended to improve band isolation and achieve satisfactory frequency responses, the diplexer was projected to operate under frequency channels of 1.66 and 2.52 GHz. The meander line resonator and SIR are two common types of resonators used in microwave and RF filter designs. The meander line has a serpentine-shaped topology, which can create resonance through induction and capacitance without the use of other stubs, perfect for impedance matching. Such an arrangement enhances compactness and it is very easy to be integrated into stripline or microstrip circuits. On the other hand, SIR, which consists of branched line sections taking different characteristic impedances connected in a series, aims to use resistance mismatch at junctions to achieve the impedance. SIR is known to enable the achievement of narrow bands, or harmonics blocking, or sharp transitions between passbands and stopbands, which can also include stubs or tuning elements to be able to adjust a certain band. In the present study, design nullification of stubs in the meander line, as opposed to the SIR, suggests a structural deviation in addition to varying operational principles. This also implies that the frequency responses demanded and the suitability of the SIR and the meander line are structured in qualitatively different ways, for a wide range of microwave and RF applications. Nearby SMA connectors and the highest points of input/output feeds, a substantial number of SIR elements are located. As a consequence of this, it is essential to implement suitable optimization strategies for each component that is a part of the circuit. Many parameters can affect the resonant frequency of the filter. These factors include the length of the filter, the turn number of meander line resonators, patches, and the existence of both UIR and SIR elements. As may be seen in Figure 7, the dimensions of the diplexer are expressed in millimeters.