A third-harmonic mixer using balanced diode configuration at W-band frequencies

This paper reports on the design, fabrication and performance of a third-harmonic fixed-tuned frequency mixer, working at W-band frequencies. The mixing circuit consists of a variation of crossbar structure, a combination of the suspended stripline circuit and the microstrip matching circuit. The mixing diodes are arranged as a single balanced configuration near the end of the RF waveguide. The precise RF grounding is provided by the grounding via holes close to the diodes. For a fixed IF frequency of 2.0GHz, the mixer has a measured conversion loss (CL) of 12.5 ±1.5 dB over both the frequency range of 80-83GHz and 91-97GHz. Furthermore, the mixer exhibits wide-band CL characteristics of better than 18.0dB over 75-83GHz and 88-98GHz. The achieved LO-to-IF isolation is better than 30dB. This mixer design offers an effective and low-cost alternative solution for W-band receivers.