Electromagnetic Field Analysis for a Coaxial Cable with Periodic Slots

The analysis deals with the excitation of coaxial structures with periodic apertures in the outer cylindrical shield. These apertures are taken to be finite circumferential slots of thin width. A quasistatic method is employed that reduces the problem to a field matching of angular wave functions over the angular extent of the slots. An approximate averaging technique is then used to obtain expressions for the effective admittance of the cable. It is then argued that this can be used to characterize the cable in more complicated environments.