Abstract: Effects limiting the bandwidth of CPW_FGP-CPS double-Y balun are investigated both theoretically, using 3D electromagnetic simulators and experimentally. Analysis shows two kinds of parasitic effects: a) parasitic effects that depend on electrical length of input transmission lines for even and balanced modes and b) parasitic effects that depend on the length of open and short circuited stubs forming the double-Y balun, and they are observed in both regular odd mode and balanced mode. Developed theory enables prediction of parasitic resonances in CPW_FGP-CPS baluns and shifting them out of an operating frequency bandwidth by changing physical dimensions of the balun. Theoretical results have been experimentally verified.
Key words: Microwave, double-Y balun, coplanar waveguide, parasistic effects.