To improve communication quality by increasing the beam width in the circumferential direction of a radiated radio wave by constituting the leakage hole formed along the length, of 1st leakage holes which are cyclically arranged along the length and 2nd leakage holes which are cyclically arranged shifting from them.
First leakage holes 2 and 2nd leakage holes 3 have the same cycles and the same shape, but the 2nd leakage holes 3 are arranged shifted from the 1st leakage holes 2 by a distanced. Intervals (p) of the leakage holes along the length direction are made smaller than the wavelength (λg) of a radio wave in the leakage waveguide 1 and also the distance (d) is made less than 0.5.p, so that the beam width in the circumferential direction can be widened. Specially, when the intervals (p) are less than 0.75.λg and the distance (d) is 0.375.p, the beam width in the circumferential direction can greatly be increased. When the intervals (p) are 0.53.λg and the distance (d) is 0.29.p, the calculated value of the angle of the circumferential direction where the intensity of the radiated radio wave becomes a half is ≥130°.
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