A 2.4/5.8 GHz microstrip (MS)-to-coplanar stripline (CFS) transition (industrial-scientific-medical bands) is presented in this paper. The transition can operate at two bands simultaneously with a stepped impedance transformer and stepped impedance open stub. The circuit is proven with a design on RF060 substrate. Simulated and experimental results of the transitions connected in back-to-back style are in good agreement. The back-to-back transition exhibits return and insertion losses, which are better than 15 dB and 3 dB, respectively.
