Flat-field planar structures designed for small and large aspect ratios

We consider novel designs that provide field flatness of fundamental mode in transverse dimensions of planar RF structures. These designs include waveguides with slotted irises and/or dielectric loaded side openings. The specially modified, advanced planar structures can be produced with available technology for a number of purposes. High-aspect ratio structures are suitable for mm-wave generation in sheet-beam klystrons (SBK) and for industrial, medical and research linacs. Small aspect-ratio planar structures having "flat" impedance in central area may be applicable to linear colliders. Impedance flatness better than 1/1,000 over half of aperture cross-section is demonstrated in simulations done for sample structures.