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ABSTRACT In this article, an X-band to Ka-band up-converter circuit designed for the transmitting chain of Satcom-on-the-move terminals is presented. The circuit is implemented using a 0.25 µm GaAs pHEMT microwave monolithic integrated circuit commercial process. It operates at fixed LO frequency of 22 GHz, IF input frequency within the band (8-9) GHz and corresponding RF output frequency within (30-31) GHz band. The up-converter circuit is composed of a resistive FET mixer, a K-band LO buffer amplifier, and a Ka-band medium power amplifier at the RF output. The bias operating condition of the entire multifunction chip is Vdd = 2.8 V, Idq = 322 mA, for a power consumption of 900 mW, when the Ka-band high power amplifier (HPA) operates in linear conditions. The chip dimensions are 3.4 × 2.8 mm2. The up-converter provides more than 12 dB conversion gain over the full bandwidth, when operated with LO input power of 0 dBm and IF fixed input power of −5 dBm. It also achieves 25 dBc of LO isolation at the RF output port. The high 1 dB compression point P1dB > 19 dBm, along with an OTOI in excess of 29 dBm, make the circuit suitable to directly drive Ka-band high power amplifiers in very linear operating conditions. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2649-2656, 2014 [ABSTRACT FROM AUTHOR]