Broadband Microstrip-to-Microstrip Vertical Transition Design

This letter presents a broadband microstrip-to-microstrip vertical transition. Basically, the transition is based on broadside coupling between the upper and lower microstrip patches through a wide slot etched on the ground plane. In order to enhance bandwidth of the transition, a patch introducing a half wavelength resonance into the passband is added on the ground plane. A demonstrator transition has been designed, fabricated and measured. Results show that a frequency range of 2.8 to 8.5 GHz (referred to return loss of 10 dB) is obtained.