A Tunable Microstrip-to-Waveguide Transition for Emergency Satellite Communication Systems

A tunable microstrip-to-waveguide transition is proposed for the ground station of emergency satellite communication systems. The proposed transition, consisting of a microstrip, three matched patches, three waveguides, and three metal screws, can not only convert the microstrip’s TEM-dominated mode into the waveguide’s TE mode within the transmitting frequency band, but also possesses the ability to filter out the amplified noise signals within the receiving frequency band around 12.5 GHz. Importantly, by adjusting the screws’ lengths, it is feasible to change the suppression frequency within the receiving frequency band and keep a good match within the transmitting frequency band. The measured results demonstrate that the proposed transition has a return loss of over 10 dB from 14 to 14.5 GHz and an out-of-band suppression of over 20 dB, from 12.25 to 12.7 GHz, with a typical value of −48 dB around 12.55 GHz. This unique feature eliminates the need for additional waveguide filters that prevent the amplified noise signal, thereby contributing to the miniaturization of the ground station.