Investigation of modulated corrugated aerial for frequency scanning

An investigation has been carried out on the characteristics of an array of periodically modulated corrugated trough elements for application as a phase-frequency scanning aerial. The theoretical analysis is based on the assumption that the corrugated surface is adequately approximated to by an equivalent surface reactance, and simple equations are presented for the propagation coefficient of the mode as functions of the structural dimensions and also of the frequency. The analysis takes into account the influence of the finite wall height of the trough, which is found to be an important parameter and must be chosen to maintain a constant value of attenuation coefficient over a limited frequency band. This is an extension of the work presented earlier by Oliner and Hessel. Experimental results are given for a 7-element array which adequately demonstrates the validity of the design equations, and therefore allows a practical aerial design to be carried out with ease.