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.

在本文中，提出了具有两个透射零（TZ）的五阶WR-3带波导滤波器。描述了设计过程并解决了制造问题。该滤波器旨在满足237.9 GHz的中心频率和2.64％的分数带宽的要求。用经典的计算机数控（CNC）铣削技术制造了三个相同的滤波器，以便获得有关WR-3波段滤波器结构的制造重复性的信息。比较表明，如果使用现代高速切削（HSC）CNC铣床，即使在非常高的频率区域也可以实现良好的重复性。完成全面的公差分析以对获得的结果进行分类。过滤器由黄铜制成，以确保有意义的可比性，并且由于CNC机床具有良好的加工质量。为了减少损耗，随后用不同的材料（金，银，铜）溅射滤波器，以评估在非常高的频率下对插入损耗的影响。与文献比较表明，即使是对加工公差表现出高灵敏度的窄带滤波器，也可以在现代CNC铣床中以高可靠性和可重复性制造。被测滤波器之一显示在整个通带上的回波损耗均高于20 dB。铜）以评估其在极高频率下对插入损耗的影响。与文献比较表明，即使是对加工公差表现出高灵敏度的窄带滤波器，也可以在现代CNC铣床中以高可靠性和可重复性制造。被测滤波器之一显示在整个通带上的回波损耗均高于20 dB。铜）以评估在非常高的频率下对插入损耗的影响。与文献比较表明，即使是对加工公差表现出高灵敏度的窄带滤波器，也可以在现代CNC铣床中以高可靠性和可重复性制造。被测滤波器之一显示在整个通带上的回波损耗均高于20 dB。