WR-3 Band Waveguide Filter Tolerance Analysis and Surface Metallization Comparison
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WR-3 Band Waveguide Filter Tolerance Analysis and Surface Metallization Comparison Daniel Miek1
¨ 1 · Fynn Kamrath1 · Patrick Boe1 · Michael Hoft
Received: 24 June 2020 / Accepted: 6 August 2020 / © The Author(s) 2020
Abstract In this paper, a fifth-order WR-3 band waveguide filter with two transmission zeros (TZs) is presented. The design process is described and manufacturing issues are addressed. The filter is designed to fulfill a center frequency of 237.9 GHz and a fractional bandwidth of 2.64%. Three identical filters are manufactured with the classical computerized numerical control (CNC) milling technique in order to obtain information about the manufacturing repeatability for filter structures in the WR-3 band. The comparison shows that even in very high frequency regions a good repeatability can be achieved, if modern high-speed cutting (HSC) CNC milling machines are used. A comprehensive tolerance analysis is accomplished to classify the obtained results. The filters were manufactured from brass to ensure a meaningful comparability and due to the good machining qualities in CNC machines. In order to reduce the losses, the filters are afterwards sputtered with different materials (gold, silver, copper) to evaluate the effect on the insertion loss at very high frequencies. In comparison with the literature, it is shown that even narrow-band filters, which show a high sensitivity to machining tolerances, can be manufactured with high reliability and manufacturing repeatability in modern CNC milling machines. One of the measured filters shows a return loss higher than 20 dB over the whole passband. Keywords Coupled triplet filter · J-band · H-plane split block · Waveguide filter · WR-3 band Daniel Miek
[email protected] Fynn Kamrath [email protected] Patrick Boe [email protected] Michael H¨oft [email protected] 1
Kiel University, Kiel, Germany
International Journal of Infrared and Millimeter Waves
1 Introduction Increasing data rates in modern communication systems lead to a steadily increase of the carrier frequency of such systems. While in the lower GHz range several techniques are available for the realization of bandpass filters, in sub-THz bands waveguide filters are the only meaningful solution due to size and loss issues. The techniques for their realization are rather different as small sizes of the components lead to tight manufacturing constraints. Novel manufacturing techniques comprise the SU-8 photoresist technique [3, 16] as well as the deep reactive ion etching (DRIE) technique [8]. These techniques show a high potential, especially for smaller components in even higher frequency ranges. However, a common approach is to use classical computerized numerical control (CNC) milling machines as proposed by different groups in e.g. [5–7, 19]. The advantages of CNC milling techniques are the large flexibility of realizable geometries and the widespread use of this technology. In this paper, three identical fifth-order WR-3 band filters comprised of two cascaded triplets are manufactur
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