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.