PURPOSE: To make a coupling hole small without deteriorating branching characteristics to low frequencies and to obtain excellent passing characteristics to high frequencies by providing a waffle iron type filter between the coupling hole and a branch waveguide.
CONSTITUTION: The coupling hole 5 and branch waveguide 9 are connected together by a tapered filter 10. When waves of fH and fL enter a corrugate horn 1, the wave of fH propagates to a corrugate circular waveguide 2 without coupling with the branch waveguide 9 and the wave of fL is reflected completely by the cutoff characteristics of the corrugate horn 1 and couples with the filter 10 through four coupling holes 5 provided at proper positions. The filter 10 decreases in the lateral width of the waveguide, but its cutoff frequency is low because of the operation of a projection part 10, so the wave of fL is not cut off, but propagates to the branch waveguide 9. This branching filter is provided with the waffle iron type filter 10 to make the coupling holes 5 small without deteriorating branching characteristics to fL and obtain excellent passing characteristics to high frequencies.
ISODA YOUJI
TAKEDA FUMIO
