CMOS RF integrated circuits at 5 GHz and beyond

TLDR

Demand for wireless products and spectrum, coupled with the need for higher performance at lower power and cost, has driven RFIC technology to exploit Moore’s law, improve passive components, deepen noise understanding, and revive legacy circuit ideas. The paper surveys low‑power RF CMOS developments, focusing on a 5‑GHz wireless LAN receiver implemented in 0.25‑µm CMOS. It examines how advances in passive components, active circuit designs, and scaling enable the receiver’s implementation. The receiver consumes ~37 mW, has a 5 dB noise figure, an IIP3 of –2 dBm, and the study shows that 5 GHz is not an upper bound, with active circuits operating beyond 15–20 GHz and transmission lines up to 50 GHz.

Abstract

A strong demand for wireless products, an insatiable thirst for spectrum that pushes carrier frequencies ever upward, and the constant quest for higher performance at lower power and cost, have recently driven the development of radio frequency integrated circuit (RFIC) technology in unprecedented ways. These pressures are stimulating novel solutions that allow RFICs to enjoy more of the benefits of Moore's law than has been the case in the past. In addition to regular raw transistor speed increases, the growing number of interconnect layers allows the realization of improved inductors, capacitors, and transmission lines. A deeper understanding of noise at both the device and circuit level has improved the performance of low noise amplifiers (LNAs) and oscillators. Finally, an appropriate raiding of circuit ideas dating back to the vacuum tube era enables excellent performance, even when working close to the limits of a technology. This paper surveys some of these developments in the context of low-power RF CMOS technology, with a focus on an illustrative implementation of a low-power 5-GHz wireless LAN receiver in 0.25-/spl mu/m CMOS. Thanks to these recent advances in passive components and active circuits, the blocks comprising the receiver consume a total of approximately 37 mW. These blocks include an image-reject LNA, image-reject downconverter, and a complete frequency synthesizer. The overall noise figure is 5 dB, and the input-referred third-order intercept (IIP3) is -2 dBm. To underscore that 5 GHz does not represent an upper bound by any means, this paper concludes with a look at active circuits that function beyond 15-20 GHz, and a characterization of on-chip transmission lines up to 50 GHz, all in the context of how scaling is expected to shape future developments.