Patent ID: 7495533

Claim:
A rectangular waveguide comprising: a pair of main ground electrodes disposed so as to face each other in parallel with each other with a dielectric in between; and a pair of side walls, each side wall constructed of a plurality of sub ground electrodes provided between the pair of main ground electrodes, the sub ground electrodes stacked in parallel with the main ground electrodes with a interval along a direction orthogonal to the main ground electrodes, wherein electromagnetic waves in the TM mode propagate in a region surrounded by the pair of main ground electrodes and the pair of side walls, when the interval is “a”, frequency of the electromagnetic wave is “f”, dielectric constant of the dielectric is ∈r, light velocity is “c”, and natural logarithm is “e”, the interval “a ” and a width L satisfy the following equation (1): L ×((π/ a ) 2 −(2×π× f/c ) 2 ×∈r ) 1/2 ≧1/log 10 e (1), and the width of each of the sub ground electrodes is equal to or greater than L.