Evaluation of the normalized impedance of a transverse slot in the image plane of an image NRD guide

A transverse slot placed in the image plane of the image NRD guide that has a low loss nature similar to that of the NRD guide in a millimeter wave circuit can be designed using waveguide array theory. In this paper, a method is presented to derive the normalized impedance of the transverse slot needed for the design from standing wave measurement. Near the slot, the standing wave distribution is disturbed by the field scattered from the slot. A method is given to derive the minimum distance for which no effect of the scattered field is received. From the standing wave distribution in the range where this condition is satisfied, the normalized impedance is evaluated. Further, in order to determine the validity and effectiveness of the evaluation method, an analysis based on the finite difference time domain (FDTD) method is carried out and the results are compared with the experimental data. Finally, a design example of an array antenna is presented. A possibility for applications of the proposed measurement method and the derived normalized impedance to the array antenna design is confirmed. © 2002 Scripta Technica, Electron Comm Jpn Pt 1, 85(5): 25–33, 2002