Wideband Matching of a Coaxial Waveguide Feed Using an Iris Matching Network

We are designing ultra-wideband feed antennas for radio astronomy using nested coaxial waveguide horns. A limitation of coaxial waveguide horns is their poor matching to free space, and thus high reflection coefficient. In this work, we use an iris matching network to improve the aperture mismatch over a wide range of frequency. A design methodology for iris matching networks is presented and used to study bandwidth and matching tradeoffs. We present a 2-iris matching network design that reduces the overall reflection coefficient from -6.5 dB to -13 dB over a 2:1 bandwidth ratio.