5-GHz CMOS wireless LANs

This paper first provides an overview of some recently ratified wireless local-area network (WLAN) standards before describing an illustrative 5-GHz WLAN receiver implementation. The receiver, built in a standard 0.25-/spl mu/m CMOS logic technology, exploits several recent developments, including lateral-flux capacitors, accumulation-mode varactors, injection-locked frequency dividers, and an image-reject low-noise amplifier. The receiver readily complies with the performance requirements of both IEEE 802.11a and ETSI HiperLAN. It exhibits a 7.2-dB noise figure, as well as an input-referred third-order intercept and 1-dB compression point of -7 and -18 dBm, respectively. Image rejection for this double conversion receiver exceeds 50 dB throughout the frequency band without using external filters. Leakage out of the RF port from the local oscillators is under -87 dBm, and all synthesizer spurs are below the -70-dBm noise floor of the instrumentation used to measure them. The receiver consumes 59 mW from a 1.8-V supply and occupies only 4 mm/sup 2/ of die area, in no small measure due to the use of fractal capacitors for ac coupling.

I. Introduction to Wireless LANs

THE growing demand for wireless connectivity has motivated the industry to evolve beyond today's voice-based cellular services. Data-centric third-generation (3G) services now under development seek to provide substantially higher data rates to supplement, and occasionally supplant, wired networks. At the same time, there is a constant desire to keep power consumption and size of the communication devices to a minimum. Fortunately, continuing advances in integrated circuit (IC) technology have made possible the low-cost, compact implementation of transceivers capable of operating at multiple-GHz carrier frequencies with data rates competitive with established wired alternatives. Although the main focus of this paper is the implementation of an integrated 5-GHz wireless local-area network (WLAN) receiver in CMOS technology, the rationale underlying many of the design objectives is best appreciated after understanding the WLAN standards to which the receiver must conform. As a consequence, we undertake here a brief history of, and introduction to, some wireless local area network (LAN) standards.