IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 41, NO. 4, APRIL 2006 981 A 0.13 m CMOS Front-End, for DCS1800/UMTS/ 802.11b-g With Multiband Positive Feedback Low-Noise Ampliﬁer Antonio Liscidini, Member, IEEE, Massimo Brandolini, Member, IEEE, Davide Sanzogni, Student Member, IEEE, and Rinaldo Castello, Fellow, IEEE Abstract—This paper presents a fully integrated CMOS receiver front-end based on a direct conversion architecture for UMTS/802. 11b-g and a low-IF architecture at 100 kHz for DCS1800. The two key building blocks are a multiband low-noise ampliﬁer (LNA) that uses positive feedback to improve its gain and a highly linear mixer. The front-end, integrated in a 0.13 m CMOS process, exhibits a minimum noise ﬁgure of 5.2 dB, a programmable gain that can be varied from 13.5 to 28.5 dB, an IIP3 of more than 7.5 dBm and an IIP2 better than 50 dBm. The total current consumption is 20 mA from a 1.2 V supply. Index Terms—CMOS, direct conversion, feedback ampliﬁer, high linearity, low-noise ampliﬁer (LNA), mixer, multiband, multistandard, positive feedback, RF receiver. I. INTRODUCTION I N RECENT YEARS, the evolution of wireless communica- tions has motivated a strong interest toward the development of multistandard mobile terminals [1]. In particular, the conver- gence of cellular and wireless local-area networks (WLANs) is becoming more and more attractive since it offers the possi- bility of cost savings for the users through the use of WLAN as access points for lower cost wide-area connections. This creates a strong interest toward the merging in a single handheld ter- minal of both cellular and 802.11b-g standards in a compact and economical way. Within this framework, a natural choice is to use a standard CMOS technology also for the RF front-end as a ﬁrst step toward a single-chip version of the complete trans- ceiver. Furthermore, the ability of sharing the hardware through the use of reconﬁgurability represents one of the most important aspects in the design of this kind of terminal, given the poten- tial reduction in the form factor, cost, and power consumption that it can produce. In fact, simply placing in parallel several in- dependent transceiver chains not only enlarges the die area, but also increases the pin count (and consequently the number of Manuscript received September 5, 2005; revised December 19, 2005. This work was supported by the Italian National Program F.I.R.B. under Contract RBNE01F582. A. Liscidini, D. Sanzogni, and R. Castello are with the Laboratorio di Microelettronica, Department of Electronics, University of Pavia, I-27100 Pavia, Italy (e-mail: antonio.liscidini@unipv.it; davide.sanzogni@unipv.it; rinaldo.castello@unipv.it). M. Brandolini was with the Department of Electronics, University of Pavia, I-27100 Pavia, Italy. He is now with Broadcom Corporation, Irvine, CA, 92618 USA (e-mail: brandom@broadcom.com). Digital Object Identiﬁer 10.1109/JSSC.2006.870890 Fig. 1. Proposed compact zero/low-IF multistandard front-end. external components) and in some cases can also increase the power consumption. The advantages of a single reconﬁgurable transceiver chain become even more signiﬁcant when combined with the possibilities offered by recent developments that have made available multiband antennas and even tuneable SAW ﬁl- ters [2]. Consistently with the above scenario, a very high level of hardware sharing is obtained with the solution proposed in Fig. 1, where no RF switches are needed and the number of external components and input pins is minimized. Within this architecture, the low-noise ampliﬁer (LNA) design can take two different directions: either a wideband topology capable of simultaneously receiving all the different standards, or a reconﬁgurable one able to select only the desired frequency [3], [4]. While a wideband approach allows the con- current reception of more than one signal band, a reconﬁgurable one, preserving frequency selectivity, improves the immunity of the receiver from out-of-band interferers, although at the cost of allowing only one signal band to be received at one time. This paper presents a new topology of multiband reconﬁg- urable LNA based on positive feedback. The feedback loop al- lows to easily reconﬁgure the frequency interval in which the LNA is matched to the signal source thanks to a partial reﬂec- tion of the load to the input. In addition, the use of a shunt positive feedback conﬁguration provides enhanced current gain compared with other feedback topologies, thereby improving the overall receiver noise ﬁgure. Based on this LNA, a zero/low-IF DCS/UMTS/802.11b-g front-end has been developed which also includes two high-dy- namic-range Gilbert cell mixers that perform the I and Q 0018-9200/$20.00 © 2006 IEEE