AFSIW Termination with Full- and Partial-Height Absorbing Material Loading

Abstract

In this paper, an air-filled substrate integrated waveguide (AFSIW) termination is introduced. To the authors' knowledge, it is the first time such essential component found in most microwave and millimetre-wave systems is reported based on the AFSIW technological platform. First, a full-height absorbing material loaded AFSIW termination is studied, with a design based on the theory of multi-section transformer. Second, an improved partial-height absorbing material loaded AFSIW termination is introduced to reduce the termination size as well as to improve the distribution of energy dissipated in the absorbing material. This second design is based on the effective permittivity calculation of a multilayer dielectric model inspired by the Wienner analytical model. For demonstration purposes, an optimized partial-height absorbing material loaded AFSIW termination, operating in the downlink Ka-band satellite communication frequency band (17.7 to 21.3 GHz), was designed and fabricated based on a shorted AFSIW transmission line loaded with a laser cut absorbing material sheet to fabricate the desired absorber geometric shape. The measured results show a reflection coefficient better than -20 dB over the entire frequency range of interest with a termination total length as small as 15 mm.