PURPOSE: To obtain an economical input filter with low loss by compressing a rectangular waveguide from both sides by a press having a conical head in a part of a rectangular waveguide in the lengthwise direction so as to reduce the inner size of the waveguide.
CONSTITUTION: Longer sides of the waveguide 8 are supported from both sides by external supports 9, 9. Shorter sides of the waveguide 8 are pressed by press machines 10, 10'. The heads of the press machines 10, 10' are formed conical so that the center of the shorter sides is pressed deepest. For example, a waveguide for 12GHz band having 19.525mm×9.525mm inner size is used, and the waveguide is pressed ranging over 100mm length in an axial direction until the inner width of the center of short sides reaches 12mm. The attenuation at the image frequency band of the waveguide is ≥80dB. Since the manufacture is easy in this way, the economical low-pass filter with low loss is obtained.
HATANO TETSUO
SAITOU TAMAO
OOKURA TOSHIHIKO
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