A GaN-on-Si passive upconversion mixer for Ku-band applications

Abstract

This paper showcases a passive single side-band (SSB) subharmonically pumped (SHP) GaN on Si mixer intended for operation in the Ku band. A passive topology has been selected in order to test the viability of these kinds of designs for GaN applications. By utilising the SSB SHP mixer, it is possible to reduce the energy consumption of a complete transmission system implementation. Two techniques to enhance the performance of the mixer are tested. First, the quasi-lumped method has been employed to reduce the size of the stubs needed to implement the mixer topology. Secondly, octagonal tapered inductors were used to obtain higher quality factors and narrow the frequency response of the lumped-element hybrids. The final design occupies an area of 2720μm×1514μm, including pads. Measurements show a performance in line with the simulations, with a slight increase in its losses with respect to the simulation results. Through the measurement of a transistor of the technology, it is demonstrated that this deviation is caused by the variability of the process and its low technology readiness level (TRL). The results are very promising and prove the advantages of implementing passive mixers for high-frequency applications in GaN on Si technologies.