Wave guiding structure

Claim 1

A LADDER TYPE DELAY LINE FOR MICROWAVE TUBES HAVING THE CHARACTERISTIC OF BACKWARD PROPAGATION OF BOTH THE FUNDAMENTAL COMPONENT AS WELL AS FOR THE FIRST SPACE HARMONIC OF THE SYMMETRIC MODE, COMPRISING A SERIES OF PERIODICALLY SPACED BARS, SAID BARS BEING OF INDENTICAL DIMENSIONS AND MEANS FOR IMPARTING TO SAID DELAY LINE A BACKWARD DISPERSION FOR THE SYMMETRIC MODE OF THE FUNDAMENTAL SPACE COMPONENT AND OF THE FIRST SPACE HARMONIC INCLUDIING SUCCESSIVE ADJACENT BARS ALTERNATELY DISPLACED IN OPPOSITE LATERAL DIRECTIONS BY SUBSTANTIALLY EQUAL AMOUNTS FROM A PLANE WHICH BISECTS THE TOTAL WIDTH OF THE RESULTANT STRUCTURE, THEREBY FORMING A LONGITUDINAL PLANE OF ANTISYMMETRY FOR SAID LINE, THE EXTREMITIES OF SAID BARS BEING BENT SUBSTANTIALLY PERPENDICULAR TO THE PLANE OF SAID SERIES, AND A SUBSTANTIALLY SMOOTH BACK PLATE EXTENDING SUBSTANTIALLY PARALLEL TO SAID BARS, SAID EXTREMITIES BEING FIXED TO SAID BACK PLATE.