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Once the insertion loss of each device is measured, an effective conductivity is determined for each one (the values are shown in Figure 5). This effective equivalent conductivity includes the effect of non-ideal metallic conductors, roughness, and other possible issues during the manufacturing process. In Figure 5 comparison between measurements and simulations with different equivalent conductivities is shown. At 100 GHz, the insertion loss is 0.70 dB for the E-plane case and 0.88 dB for the H-plane case. Both values of insertion loss are of the same order in magnitude (slightly better for the E-plane case), meaning a good electrical contact between two halves for the H-plane case.

4. Conclusions

Two all-pole filters operating at W-band have been machined by different techniques (electro-discharge and milling) and split-block (H-plane and E-plane). Good results have been obtained for both designs with central frequency deviation of 500 and 200 MHz and insertion loss level of 0.70 and 0.88 dB, respectively. Furthermore, a comparative study between different machining techniques and split-block has been presented. Important practical information, such as tolerances and effective conductivities, have been obtained. The insertion loss level obtained is comparable with the actual state-of-the-art for waveguide filters at this frequency.[6,7]

Acknowledgments

The authors thank the companies Inmepre and Bazus, Spain for the manufacturing and Centro Astronómico de Yebes, Spain, specially Félix Tercero and Tim Finn for their valuable help with the measurements.

References

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cuit elements for the 88 to 100 GHz frequency range. In: IEEE MTT-S International Microwave Symposium Digest. 1984 May 30–Jun 1; San Francisco, CA, USA. p. 233–235.

[2]Vahldieck R, Bornemann J, Arndt F, Grauerholz D. W-band low-insertion-loss E-plane filter (Short Paper). IEEE Trans. Microwave Theory Tech. 1984;32:133–135.

[3]Morini A, Venanzoni G, Farina M, Rozzi T. Practical design of a high-power tuning-less

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[5]Cameron RJ, Kudsia CM, Mansour RR. Microwave filters for communications systems: fundamentals, design and applications. Hoboken (NJ): N. Wiley-Interscience; 2007.

[6]Song S, Yoo C-S, Seo K-S. W-band bandpass filter using micromachined air-cavity resonator with current probes. IEEE Microwave Compon. Lett. 2010;20:205–207.

[7]Leal-Sevillano CA, Montejo-Garai JR, Ruiz-Cruz JA, Rebollar JM. Low-loss elliptical response filter at 100 GHz. IEEE Microwave Compon. Lett. 2012;22:459–461.