High-performance V-band cascode HEMT mixer and downconverter module

A high-performance V-band cascode HEMT mixer is presented together with a compact downconverter module integrating the mixer with other receiver MMICs. The cascode mixer was optimized for conversion gain and/or linearity by employing the low-pass interstage networks and by optimizing the bias voltages. The low-pass interstage network effectively filters out the unwanted harmonics and spurious signals, and therefore, enhances the gain and the linearity of the cascode mixer. On a two-tone test, the cascode mixer showed a high conversion gain of 6.3 dB with an LO power of 2.6 dBm at 60 GHz. When the gate bias to the upper common-gate HEMT was tuned for the intermodulation distortion "sweet spot" theoretically predicted by the authors , the mixer showed a high third-order intercept point of 11.2 dBm with a decent gain of 4.1 dB under a small DC power consumption of 8 mW. To benchmark the performance of the cascode mixer of this work, a waveguide-based compact V-band downconverter module was built by integrating the mixer with an MMIC LNA, a VCO, and a LO driving amplifier. The downconverter module showed a conversion gain higher than 20 dB from 57.5 to 61.7 GHz. This paper shows the potential of the cascode FET mixer for high-performance compact downconverter applications at millimeter-wave frequencies.