Although the harmonics are suppressed at 15 GHz, the RL is still present. This resonance can cause radiation at 15 GHz from the circuit. At 7.5 GHz the passband selectivity is destroyed with a maximum RL value of 17.5 dB. Therefore, with the inclusion of U-PBGS, the match at fundamental frequency has improved and the spurious transmission is significantly suppressed. It is worthwhile to note here that the RL plot with UC-PBGS is not produced in [1]. Since UC-PBGS is a uniform distribution, we suspect that the complete suppression of the S 11 parameters was not possible. We encourage the reader to verify the results for the design of a UC-PBG-engineered BPF.
3.4. BPF on B-PBGSs
Finally, we tested the BPF on the B-PBGSs and the measured S-parameter results are shown in Figure 4(b). It can be seen that the B-PBGS suppresses both resonance and spurious transmission significantly. At 15 GHz, the RL is about 0 dB and the transmis-sion co-efficient is found to be 48 dB. At 7.5 GHz, the maximum RL is found to be 12 dB, which is more than the reference BPF. Therefore, performance superior to that for the BPF on U-PBGS is achieved.
4. CONCLUSION
From the measured results of all the BPF designs presented in this work, it can be seen that both U-PBGSs and B-PBGSs can suppress unwanted spurious transmission in a BPF. In the case of U-PBGSs, the RL is suppressed by 5.5 dB and the transmission coefficient by 31 dB at 15 GHz. However, the selectivity of the BPF is destroyed at the fundamental frequency of 7.5 GHz with a 9-dB improvement in RL performance. On the other hand, at 15 GHz, the B-PBGSs stem better harmonic suppression, thus providing 44-dB suppression for the transmission co-efficient and full suppression for the RL. The RL at 7.5 GHz also improves by 3.5 dB, as compared to that for the reference BPF. Therefore, B-PBGSs can find potential application in harmonic suppression, as compared to the available work in the open literature.