pHEMT and mHEMT ultra wideband millimeterwave balanced resistive mixers

Two ultra wideband millimeterwave single balanced resistive mixers utilizing a Marchand balun for the LO-hybrid are simulated, fabricated and characterized for 30-60 GHz in both up and down conversion. Two different versions of the mixer were manufactured in a commercial pHEMT-MMIC and a mHEMT-MMIC process respectively. A measured down conversion loss of approximately 6 to 12 dB over the whole band is obtained for both versions of the mixer with external IF power combining. In spite of the balanced design, the required LO power is quite low, 2 dBm is sufficient for low conversion loss. The LO-RF isolation is excellent, often more than 30 dB for both type of mixers. Low noise figure and high IIP3 figures are obtained. It is also shown that by applying selective drain bias, up to 5 dB improvement of IIP3 can be obtained for the mHEMT mixer with small LO powers.