Equivalent circuit of the excitation to a slot antenna and the matching to a complex impedance

The equivalent circuit of a slot antenna and the feed line was studied for the reflection characteristics depending on the tuning parameters. The antenna was a cavity-backed slot antenna and fed with a microstrip line by electromagnetic coupling. The previously proposed equivalent circuit was used to calculate the reflection coefficients depending on the tuning stub and offset lengths of the feed line. A design example for the matching to a complex impedance was also shown.