Subharmonically pumped 210 GHz I/Q mixers

Two subharmonically pumped 210 GHz I/Q mixer MMICs have been successfully realized in a 100 nm gate length metamorphic high electron mobility transistor (mHEMT) technology. The mixers have been designed using a branchline and a Lange coupler to generate the 90° phase shift between the I and Q ports. A conversion gain of more than -19 dB has been achieved with both mixers. The measured LO to RF isolation of the second harmonic is better than 21 dB.