A LOW-FREQUENCY MODEL FOR WEDGE OR PYRAMID ABSORBER ARRAYS .1. THEORY

The interaction of electromagnetic waves with an array of absorbing we dges or pyramid cones is studied in the low-frequency limit; i.e., whe n the period of the array is small compared with wavelength. A theoret ical model is obtained using the method of homogenization, which repla ces the transversely periodic structure with a transversely uniform me dium possessing a certain (generally anisotropic) effective permittivi ty and permeability. Plane-wave reflection from such structures can th en be modeled using well-known techniques for one-dimensionally inhomo geneous media; a Riccati equation for the reflection coefficient is us ed in this work. This model is appropriate for use with absorbers foun d in anechoic chambers used for electromagnetic compatibility and elec tromagnetic interference (EMC/EMI) measurements over the frequency ran ge of 30-1000 MHz. Numerical results and application to the design of such absorbers are given in Part II of this two-part paper.