DC-coupled IF stage design for a 900-MHz ISM receiver

This paper presents a DC-coupled 900-MHz ISM band RF front-end for a short-range wireless receiver. The frontend, fabricated in a 0.5-/spl mu/m CMOS process, is intended as a test vehicle to verify the proposed DC-coupled topology. In this topology, a low-frequency feedback circuit suppresses the DC offset and low-frequency noise at the mixer output. The DC-coupled topology is compared with traditional AC coupling. We show that there is a tradeoff between bandwidth and midband loss in a fully integrated AC-coupled system. The proposed DC-coupling technique does not impose this tradeoff. The DC-coupled topology was verified via simulation and measurements from the test vehicle.