Design and Analysis of a Novel Noise Cancelling Topology for Common Gate UWB LNAs - VLSI Design and Test - page 169

Design and Analysis of a Novel Noise Cancelling
Topology for Common Gate UWB LNAs

Mohd Anwar 1 , Syed Azeemuddin 1 , and Mohammed Zafar Ali Khan 2

1 Center for VLSI & Embedded Systems Technology, IIIT, Hyderabad
[e-mail], [e-mail]
2 Department of Electrical Engineering, IIT, Hyderabad
[e-mail]

Abstract. In this paper, we present a noise cancellation technique for common
gate ultra wide band (UWB) low noise amplifiers (LNAs) which not only
reduces the noise but also increases the gain. On implementing this technique
in one of the existing UWB LNAs significant reduction of noise figure (NF)
compared to same LNA without noise cancellation technique was observed.
Noise cancellation of the most dominating thermal noise source viz. the input
matching device with theoretical analysis is presented in this paper. Simulation
results with TSMC 0.18 μm CMOSRF technology shows a peak gain of 28 dB
and base NF of 3.16 dB for a 6.6 GHz (2.4-9 GHz) band LNA with noise
cancellation when compared to peak gain of 21 dB and base NF of 4.09 dB
without noise cancellation. Both theoretical analysis and simulation results are
in good agreement.

Keywords: Low noise amplifier, Noise cancellation, Ultra wide band, High
gain, Noise Contribution.

1 Introduction

In wireless receiver systems, effect of noise of all the subsequent stages is reduced by
the gain of LNA whose noise injects directly into the receiver. Thus, it is necessary to
boost the desired signal power while adding as little noise and distortion as possible so
that the retrieval of this signal is possible in the later stages in the system. Recent dem-
onstrations show that UWB LNAs ranging from few MHz to 10 GHz are included to
wireless receivers which uses single LNA for contiguous broadband signal processing
[1-3]. There are various techniques to design UWB LNA such as design using common
source (CS) configuration and common gate (CG) configuration. CS configuration
with inductive degeneration LNA provides good input matching for UWB range but
requires a passive network at the input which consist large number of high Q inductors.
Moreover, LNA of this configuration shows good noise performance for narrow band
(NB) applications but not at corner frequencies for UWB applications [4]. However,
CG LNA provides ultra wide band input matching due to its low input impedance
resulting in an improved reverse isolation and therefore provides better stability. In
contrast, noise figure of CG LNA is considerably large when compared to CS LNA but
it can be improved by using g m boosting technique which trades off with gain [5].