Compensated microstrip coupled line and its application on impedance transformer

The coupled line fabricated with microstrip circuits may result in the inherent transmission zeros being located at more than twice the central frequency (2f₀). Therefore, to compensate the unbalanced even- and odd-mode phase velocities, the slotted lines are employed for the microstrip coupled line in this reported work. Moreover, unwanted harmonics can be consequently suppressed by the compensated microstrip coupled line, which could be adopted for parallel-coupled line filters. However, the proposed compensated microstrip coupled line is utilised for the planar complex impedance transformer as a design example. Good agreement between measurement and simulation has demonstrated the feasibility of the proposed method.