Variation of slotline characteristic impedance and wavelength in a Vivaldi antenna and their effect on radiation characteristics

A method is presented for evaluating the variation in slotline characteristic impedance and wavelength along the taper of a Vivaldi antenna, and therefore its effect on the matching of the antenna to free space and the phase difference accrued by the guided wave as it propagates along the taper. The method involves using a stepped approximation to the Vivaldi taper and analysis of the slot wavelength and characteristic impedance for each discretised section. Results are presented for Vivaldi antennas that use various dielectric substrates/thicknesses.