**6.1 The SIW BC-CSRR pair**

**Figure 17** depicts the layout of the proposed SIW BC-CSRR. It is evident that two BC-CSRRs are aligned side by side with opposite orientations to each other. A microstrip feed line is used to excite the SIW cavity. For the selected dielectric substrate with ɛ<sup>r</sup> = 2.65 and waveguide cutoff frequency of 8.15 GHz, the width of the SIW (w) is calculated to be 12.5 mm. **Figure 18** shows the simulated transmission response for the SIW integrated with the unit cell. It is evident from the response that it creates a passband with a center frequency of 5.6 GHz, which is below waveguide cutoff frequency.
