The structure in Figure 7 is fabricated (see Figure 10) and tested to validate the design of the three-section filter. Test results are shown in Figure 11 in comparison with simulation. Differences are mainly due to substrate losses and manufacture tolerances.

Figure 10

Figure 10 Metamaterial resonator permittivity, permeability and refractive index (a), and frequency response (b).

Figure 11

Figure 11 Frequency response of the three section SIW bandpass filter, measurement versus simulation.

CONCLUSION

A broadband bandpass filter design provides good performance implemented in three different topologies (see Table V). The goal, however, is to provide a miniaturized form factor that can be fabricated with low cost manufacturing techniques and be integrated easily with other circuit components.

t5.jpg

The baseline design is a rectangular waveguide filter with symmetrical irises. Excellent results are achieved but its structure (15 mm×7.5 mm×47.7 mm) is large, difficult to manufacture at low cost and not easily integrated with other circuits, which are often planar.

To address integration, the filter is fabricated in SIW with irises formed by metallic vias. The size problem remains, however, because the structure requires relatively long transitions at its two ports, making the global structure 43 percent longer than that of the waveguide filter.

A final solution combines the SIW medium with a novel metamaterial filter shape that reduces length by more than 50 percent, width by more than 40 percent and height by more than 90 percent with respect to the waveguide baseline.

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