As 6G wireless communications push the operation frequency above 110 GHz, it is critical to have low-loss devices that can be accurately tested. To this end, D-band (110 GHz to 170 GHz) substrate-integrated waveguides (SIWs) and SIW-based circuits are designed on 100-µm or thinner SiC substrates. With the input/output of SIWs transitioned to grounded coplanar waveguides (GCPWs), the fabricated SIWs are probed in a single sweep from 70 kHz to 220 GHz under both small- and large-signal conditions and compared with the simulated characteristics. In general, the small-signal model predicts well but the large-signal model fell short. In the future, the large-signal model can be improved by using our newly established ultra-wideband capability for large-signal characterization of a sub-THz transistor up to its third harmonics. These results demonstrate the potential of using SIWs to interconnect transistors, filters, antennas, and other circuit elements on a monolithically integrated RF front end.
James Hwang is a professor in the Department of Materials Science and Engineering at Cornell University. He graduated from the same department with a Ph.D. degree. After years of industrial experience at IBM, Bell Labs, GE, and GAIN, he spent most of his academic career at Lehigh University. He cofounded GAIN and QED; the latter became the public company IQE and remains the world's largest compound-semiconductor epitaxial wafer supplier. He has been a consultant for the US Air Force Research Laboratory since 1989. He used to be a Program Officer at the U.S. Air Force Office of Scientific Research for GHz-THz Electronics. He used to be a visiting professor at Cornell University in the US, Marche Polytechnic University in Italy, Nanyang Technological University in Singapore, National Yang Ming Chiao Tung University in Taiwan, and Shanghai Jiao Tong University in China. He is an IEEE Life Fellow and an editor for the IEEE Transactions on Microwave Theory and Techniques. He has published approximately 400 refereed technical papers and been granted eight U.S. patents. He has researched the design, fabrication and characterization of electronic, opto-electronic, and micro-electromechanical devices and circuits. His current research focuses on devices and circuits above 110 GHz for 6G wireless communications.