Matching evanescent open-ended waveguide antennas using the Imaginary Smith Chart

In this paper we propose a means by which the Imaginary Smith Chart may be used to simplify the design of evanescent open-ended waveguide antennas. WR90 waveguide (which has a cutoff frequency of 6.56GHz) was used in the design process. An open-ended waveguide antenna design is presented that operates at 4.5GHz with a bandwidth of 3.2% for return loss <;-10dB and a maximum realised gain of 3.71dBi.