Active, monolithically integrated S-band (1.1-2.2 GHz) and C-band(2.2-4.4 GHz) frequency/phase doublers with ultra-compact circuitareas of less than 0.6 mm/sup 2/ and 0.5 mm/sup 2/, respectively,are presented using a commercial 0.6 /spl mu/m GaAs MESFET technology.These circuits were designed for low-power-consuming adaptive antennareceivers, operating in accordance with the high-performance radiolocal area network (HIPERLAN) and 802.11a standards. Cascading ofthe two doublers enables phase control range quadruplication of lowcost phase shifters with 90/spl deg/ phase control range in the localoscillator (LO) path. Thus, a phase control range of 360/spl deg/with low amplitude variations is reached in the radio frequency (RF)path, as required for adaptive antenna combining. Simulations performedusing the modified MESFET large signal model show excellent agreementwith measured results. At an ultra-low supply voltage of 0.9 V, asupply current of 5.8 mA and an input power of only -8 dBm, a conversiongain of 0.5 dB was measured for the quadrupler circuit. To the knowledgeof the authors, the circuits present the best results for frequencymultipliers in terms of power consumption and miniaturisation, reportedto date.