Theoretical and experimental investigation of parasitic effects in double-Y baluns

Effects limiting the bandwidth of CPW_FGP-CPS double-Y baluns are investigated both theoretically, using 3D electromagnetic simulators and experimentally. Analysis shows two kinds of parasitic effects: (a) parasitic effects that depend on input transmission lines and they are caused by: (a) even mode and parasitic balanced mode (PBM) and (b) parasitic effects that depend on open and short circuited stubs forming the double-Y balun and they are observed in both regular mode and PBM. This theory has been experimentally proven and it enables to predict the frequency of parasitic resonances that appear in the characteristics of CW_FGP-CPS baluns and shift them out of the operating frequency bandwidth by changing the physical dimensions of the balun