A 60 GHz MMIC pHEMT image reject mixer with integrated ultra wideband IF hybrid and 30 dB of image rejection ratio

A 60 GHz image reject mixer (IRM) with an integrated ultra wideband IF hybrid has been designed, fabricated and characterized in a commercial pHEMT MMIC process. A measured conversion loss (L_c) of 10.2 to 11.4 dB over the frequency range 55 to 65 GHz is obtained with a state-of-the-art image rejection ratio (IRR) of 30 dB at the 60 GHz center frequency. For an IF frequency between 2 and 3 GHz, the variation in L_c is less than 1 dB, and the IRR is better than 24 dB which is the best reported figures for an IRM operating at mm-wave frequencies with integrated IF hybrid. LO power as low as 1 dBm is sufficient to obtain the reported L_c and IRR. The mixer consumes virtually zero DC power since resistive mixers are used for the actual down conversion. To further minimize the overall power consumed by the system in which the IRM will be used, the combination of the two 90° out of phase IF signals are performed on-chip in an ultra wideband lumped element hybrid. This allows the system to use only one instead of two power-consuming analog to digital converters (ADCs) which thereby significantly reduces the power consumption for the overall system.