An unconventional design of microstrip to waveguide ridged transition at Ka-band

This paper presents the development of an unconventional waveguide-to-microstrip transition at Ka-band. Multi-section ridge transformer has been adopted. The lengths of the sections are different from conventional λg/4 length. A Ka-band prototype has been fabricated and measured. It shows 42.5% matching bandwidth with an insertion loss of about 0.33dB at the centre frequency and lower than 0.6dB over the complete bandwidth. The transition has been efficiently integrated with MMIC based Ka-band Low Noise Amplifier (LNA) and a Medium Power Amplifier (MPA).