Low power down-conversion RF mixers based on the Gilbert cell approach

Three down-conversion mixers for low-voltage, balanced 900 MHz wireless applications are introduced. The mixers are implemented in a 0.8 μm BiCMOS process and based on the four transistor BJT switching quad widely used in Gilbert cells. The mixers are designed to operate at a supply voltage of 1.5 V and without external components. The implemented mixers have a few decibels of conversion loss, a third-order input intercept point of a few dBm and a single sideband noise figure of about 15 dB. It is demonstrated that modest mixer operation performance is achieved with a DC power consumption of only 1 mW. Also planar inductors on silicon and bond-wire inductors are shown to be valuable to achieve a return loss of about 9 dB for input and output ports of a mixer. The measurement results for the mixers as well as the lumped element models for the used planar inductor and for the bondwire are presented.