An Ultrawideband CMOS Low-Noise Amplifier for 3.1–10.6-GHz Wireless Receivers
Andrea Bevilacqua, Student Member, IEEE, and Ali M. Niknejad, Member, IEEE
Abstract—An ultrawideband 3.1–10.6-GHz low-noise amplifier employing an input three-section band-pass Chebyshev filter is presented. Fabricated in a 0.18-m CMOS process, the IC prototype achieves a power gain of 9.3 dB with an input match of 10 dB over the band, a minimum noise figure of 4 dB, and an
IIP3 of 6.7 dBm while consuming 9 mW.
Index Terms—Chebyshev filter, CMOS, low-noise amplifier (LNA), low power, RFIC, ultrawideband (UWB).
ULTRAWIDEBAND (UWB) systems are a new wireless technology capable of transmitting data over a wide spec-trum of frequency bands with very low power and high data rates. Among the possible applications, UWB technology may be used for imaging systems, vehicular and ground-penetrating radars, and communication systems. In particular, it is envi-sioned to replace almost every cable at home or in an office with a wireless connection that features hundreds of megabits of data
per second .
Although the UWB standard (IEEE 802.15.3a ) has not been completely defined, most of the proposed applications are allowed to transmit in a band between 3.1–10.6 GHz. Two pos-sible approaches have emerged to exploit the allocated spec-trum. One is a multiband approach, with fourteen 500-MHz sub-bands, OFDM modulation and, possibly, a frequency-hopping scheme . Another possibility is the so-called “impulse radio” , based on the transmission of very short pulses, with pulse position or polarity modulation.
In many ways, UWB benefits from existing wireless tech-niques and standards, as modulation schemes, multiple-access techniques, and transmitter/receiver architectures are adapted for UWB.
A UWB receiver, diagrammed in Fig. 1, will feature a low-noise amplifier (LNA) followed by a correlator that removes the carrier (or the pseudocarrier) from the received radio frequency (RF) signal. Analog-to-digital conversion will then allow for digital signal processing aimed at recovering the information data. In this context, it is clear that, regardless of what the fu-ture standard will be, a wideband LNA operating over the entire 7.5-GHz band of operation is required. Such an amplifier must
Manuscript received April 18, 2004; revised June 16, 2004.
A. Bevilacqua is with the Dipartimento di Ingegneria dell’Informazione, Università di Padova, 35131 Padova, Italy (e-mail: andrea.bevilacqua@ dei.unipd.it).
A. M. Niknejad is with the Berkeley Wireless Research Center, Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA 94720 USA.
Digital Object Identifier 10.1109/JSSC.2004.836338
Fig. 1. Block diagram of a UWB receiver. The dashed box represents the subsystem that brings the RF signal to baseband in order to recover the information signal: it can be a correlation filter followed by a sampler or, as depicted here as an example, a quadrature mixer.
feature wideband input matching to a 50- antenna for noise optimization and filtering of out-of-band interferers. Moreover, it must show flat gain over the entire bandwidth, good linearity, minimum possible noise figure (NF) and low power consump-tion.
This paper focuses on the design and implementation of a low-noise amplifier (LNA) in a 0.18-m CMOS technology for the receiver path of a UWB system. The paper is organized as follows. In Section II, the issues related to the design of a wide-band LNA are summarized, and the approach employed in this work is discussed. In Section III, the proposed circuit is ana-lyzed, and the circuit design issues are discussed in Section IV. Experiments carried out on the fabricated LNA prototypes are reported in Section V.
- DESIGN CHALLENGES
Designing wideband LNAs for wireless applications presents two levels of challenges. In the first place, having fast and low-noise transistors depends on the available technology. Tradition-ally, wideband microwave amplifiers relied on transistors re-alized with composite semiconductors, e.g., GaAs, because of the intrinsic superior frequency characteristics of such devices –. Silicon technology, on the other hand, has been em-ployed to design and fabricate amplifiers, even wideband ones, for particular applications, e.g., optical communications , , that require different specifications compared to wireless sys-tems. In wireless mobile communications systems, silicon inte-grated circuits have been widely employed in narrow-band sys-tems, where limited gain and increased parasitics are tolerable due to lower operating frequencies and the application of tuned networks.
There are few examples of development of high-frequency wideband amplifiers employing silicon transistors, in particular
0018-9200/04$20.00 © 2004 IEEE
Fig. 2. Conceptual schematic of a shunt feedback amplifier.
in CMOS technology. In this case, it is remarkable that em-ployed solutions (distributed amplifiers –) require high levels of power consumption, and they are not optimized for noise. This brings about the second challenge—finding a low-power topology that satisfies all the other design requirements, the most stringent one being the input match.
Classic shunt feedback amplifiers have limi
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