Equivalent Circuits of Microstrip Impedance Discontinuities and Launchers

Experimental results obtained indicate that an excess phase shift is the most pronounced high-frequency parasitic effect resulting from a microstrip quarter-wave transformer impedance discontinuity. An empirically derived design-oriented model describing the dominant parasitic reactance associated with a microstrip impedance discontinuity at X-band frequencies is described. A description is also given of the dominant parasitic reactance associated with a number of commercially available coaxial-to-microstrip launchers.