Folded stubs for compact suspended stripline circuits

Coupled line sections using both sides of a suspended stripline substrate can be regarded as stubs folded closely parallel to the stripline, giving a number of advantages such as compact setup, a simple, one-channel stripline mount, no waveguide modes, and additional degrees of freedom for circuit design. It is shown that, by an appropriate design, open and short-circuited series and shunt stubs covering a wide range of stub impedances can be realized. As examples of their application, bandpass, highpass and bandstop filters are presented.<>