Performance of uniform circular PBGS Assisted BPF, Performance of reference BPF, Performance of BPF on 2-D array of uniform circular PBGSs, Performance of BPF on dense 2-D array of uniform circular PBGSs, Performance of BPF with three line uniform circular PBGSs, Performance of BPF with uniform circular PBGSs under two extreme 50 ohm lines, Performance of BPF with uniform circular PBGSs under all the lines Performance of BPF with uniform circular PBGSs under all the line



    Performance of uniform circular PBGS Assisted BPF


Theoretical results are produced for different geometries of uniform circular PBGS assisted BPF. To see the effect of uniform circular PBGS in harmonic suppression the performance of reference BPF is shown. Finally the insertion loss performances of a standard BPF and uniform circular PBGS assisted BPF are shown to compare the results.

·         Performance of reference BPF

 The performance of standard asymmetric coupled line BPF is reproduced. The performance as obtained from the simulation result is shown in Fig. 5.4. The presence of spurious transmission around 15 GHz is obvious in case of a reference BPF. At this frequency maximum value of return loss is found to be 9 dB and insertion loss is found to be 2.5 dB. At 7.5 GHz, which is the frequency of interest, the maximum value of return loss is 22.5 dB and insertion loss is 0.5 dB.  For harmonic suppression 2-D array of uniform circular PBGS are used in the ground plane of a reference BPF.

Fig. 5.4: IE3D simulated S-parameters performances of a standard coupled line BPF. Substrate is RT/Duroid having dielectric constant of 10.2 and height of 0.635 mm.

·         Performance of BPF on 2-D array of uniform circular PBGSs

The harmonic is suppressed due to application of 2-D array of uniform circular PBGSs as shown in Fig. 5.5.

The return loss performance at second harmonic should ideally be zero for proper harmonic suppression. But the maximum value of return loss is here 2 dB and the value of insertion loss 9.5 dB. It is clear that the uniform circular PBGSs are not exact under the lines. So they are not strong enough to suppress the transmission at second harmonic frequency.

·         Performance of BPF on dense 2-D array of uniform circular PBGSs

Fig. 5.4  shows the simulation result of a BPF with 2-D PBGSs that are denser than conventional 2-D square lattice structure. In this case they are rectangular lattice structure. It is seen that at 7.5 GHz the maximum return loss is 25 dB and the maximum return loss at 15 GHz is about to zero dB. The insertion loss is more than 30 dB. Significant suppression is achieved here. 

·         Performance of BPF with three line uniform circular PBGSs

 The BPF is simulated where the PBGSs are under two 50-ohm line and the central coupled lines. The performance is shown in Fig. 6.24. In this structure, the uniform circular PBGSs are situated under two 50-ohm lines and the central coupled line. From the simulation results it can seen that at 15 GHz the maximum value of return loss is about 1 dB only and the insertion loss is found to be 11 dB.


Fig. 5.6:  Simulated S-parameters performance of BPF when it is loaded by dense 2-D uniform circular PBGSs. Substrate is RT/Duroid having dielectric constant of 10.2 and height of 0.635 mm.

Harmonic suppression is not satisfactory. In addition to this, the return loss performance at fundamental frequency is poor.

Fig. 6.24: Simulated S-parameters performances of a BPF with three line uniform circular PBGSs. Substrate is RT/Duroid having dielectric constant of 10.2 and height of 0.635 mm.

·         Performance of BPF with uniform circular PBGSs under two extreme 50 ohm lines

Thinking over the philosophy that the EM propagation takes place through the 50-ohm line first, uniform circular PBGSs are used under two 50-ohm lines only to see their effect in harmonic suppression. The simulation result is shown in Fig. 5.7.

It can be seen that the result is not promising at all. Rather the performance at fundamental and second harmonic frequencies the performances are worse.

·         Performance of BPF with uniform circular PBGSs under all the lines

Finally PBGS is used just under all the lines. The design provides S-parameters performances as shown in Fig. 5.8. It can be seen that at 7.5 GHz the maximum return loss is more than 30 dB. At 15 GHz the maximum return loss is zero dB and the insertion loss 30 dB. In this case significant improvements in fundamental and second harmonic frequencies are achieved. Only small ripple in transmission band is noticed that can be controlled with resizing the uniform circular PBG elements.

Fig. 5.8: Theoretical S-parameters performances of a BPF when uniform circular PBGSs are situated under all the lines. Substrate is RT/Duroid having dielectric constant of 10.2 and height of 0.635 mm.

·         Comparison of S21 Performances  

Finally optimized reference and uniform circular PBGS assisted BPF are fabricated. The measured insertion loss performances are shown in Fig. 5.9.

Fig. 5.9: Measured insertion loss performances of an optimized BPF. Substrate is Taconic having dielectric constant of 10 and height of 0.635 mm.

From the measured result it can be seen that the fundamental frequency is little bit shifted and the second harmonic also. For the reference BPF the average 3 dB insertion loss and 10 dB return loss bandwidths are 7.18% and 5.96% respectively. On the other hand uniform circular PBGS assisted BPF provides maximum 26 dB return loss at fundamental frequency. Average insertion loss at second harmonic is found to be 26 dB. 3 dB insertion loss and 10 dB return loss bandwidths are found to be 16.02% and 15.2% respectively. So uniform circular PBGS assisted BPF improves the performances in terms of return loss, insertion loss and BW.



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