Design of a Ka-Band MMIC Lange Coupler

A Lange coupler within a Ka-band (26.5 similar to 40 GHz) had been designed in a 0.15 mu m GaAs MMIC technology. The coupler uses lambda/4 wavelength lines as the coupling lines. The coupler was realized and measured by using 50 Omega resistors as terminations. The results of the coupler within 26.5 similar to 40 GHz frequency range as follows: the coupling degree -3.2dB at the center frequency of 33GHz, insertion loss less than 3.5 GHz return loss and isolation both less than -20 dB, amplitude imbalance less than 0.06 dB, phase imbalance less than 1 degrees. The proposed Lange coupler has extremely wide application scenarios in MMIC circuits such as Ka-band power amplifiers, mixers, and phase shifters and so on.