A W-band balun integrated probe with common mode matching network

There has been a growing interest in developing differential Millimeter-wave Monolithic Integrated Circuits (MMICs) in recent years. The characterization infrastructure for these differential devices however, is still limited at higher frequencies. In this paper, a balun integrated probe is designed to cover the entire W-band (75 - 110 GHz) with the potential to be scaled to even higher frequencies. Test structures of the balun are characterized and found to agree well with simulated results for the entire W-band, while the balun integrated probe is characterized from 90 to 115 GHz, also agreeing well with simulation. Over the frequency range measured, the balun integrated probe has lower than -22 dB coupling between the single-ended input and common mode output, as well as between the common and differential modes. Furthermore, the return loss for the differential output and single-ended input modes are better than 10 dB, while the common mode return loss is also better than 10 dB.