Time Division Multiplexing Front-Ends for Multiantenna Integrated Wireless Receivers

The approach of time division multiplexing (TDM) within an integrated wireless receiver to reduce the power, area and cost of multiple antenna receivers is studied. A solution is proposed to address the cross-interference between multiplex channels that affected previous attempts at TDM for multiple receive antennas. Detailed analysis from a radio system viewpoint is provided for when TDM is used as a low complexity hardware technique for managing multiple antenna channels. Simple closed form noise figure relations in terms of the number of multiplex channels and the anti-alias filter rejection are developed. Noise figure expressions that relate an individual TDM amplifier or TDM amplifier array's noise figure to that of a regular static amplifier are also given. These simple relations provide a quick method of determining expected noise figure of such systems. A four-antenna 2.4 GHz LNA array circuit in CMOS is designed in a 0.18-mu m technology. The noise and linearity performance of this circuit is measured to verify the developed theory. The results obtained show close agreement with the developed model of the TDM-based multiantenna receiver system.