| 摘要 |
PROBLEM TO BE SOLVED: To obtain stable performance with no adjustment, a simple configuration without any special precision of size and to reduce the cost by specifying the size of an open window at a folded part in a folded waveguide. SOLUTION: The folded waveguide 20 is formed by folding a wide wall face of a square waveguide whose wide wall face width (lateral width) is (a) and whose narrow wall face width (height) is (b) at the angle of nearly 180 deg., and made up of a lower waveguide 21a, an upper waveguide 21b being in a laminated state and a folded part 22 to combine them. The size of an open window of the folded part 22 with respect to the waveguides 21a, 21b is selected to be a×h, and the value (h) is obtained by a relational equation h=(±/2)/(β1-β2), whereβ1 is a propagation constant of the square waveguide whose size is a×2b in the TE10 mode,β2 is a propagation constant of the square waveguide whose size is a×2b in the TE11 mode, 2b is selected to be a relation of 2b>λ0/2, andλ0 is a free space wavelength.
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