Multi-band Microstrip to Co-planar Stripline transitions based on electromagnetic coupling

Novel designs of planar Microstrip (MS) to coplanar stripline (CPS) transitions are presented in this paper. These transitions convert unbalanced transmission line Microstrip to a balanced transmission line coplanar stripline using an exponential taper. Measured insertion loss of one of the transition is less than 0.85 dB and return loss is better than 10 dB in the frequency bands around 1.7GHz, 5.1GHz and 8.5GHz. Design guidelines are provided and structure of this transition can be slightly adjusted to meet the desired output impedance and bandwidth. Transition designs are validated by back-to-back balanced and unbalanced configurations and measured using Vector Network analyzer. Measurement results agree well with the simulated ones.