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An Ultra-Wide-Band 1.0 -11.6GHz LNA in 0.18µm CMOS technology
RF Communication Systems-on-chipSpring 2007
Index of Contents
A brief introduction to UWB Potential applications
Design of the LNA Performance criteria First stage: a common-gate Second stage: a common-source
System simulation Comparison with the original paper
Conclusions
2
A brief introduction to UWB
3
A brief introduction to UWB
A technology for transmitting information spread over a large bandwidth that should be able to share spectrum with other users.
The Federal Communications Commission (FCC) authorized the unlicensed use of the 3.1 to 10.6GHz band under strict power restrictions.
4
OFDM vs. Pulse-transmissionOFDM vs. Pulse-transmission
Potential applications
Wireless Communications Systems Local and Personal Area Networks (LAN/PAN) Roadside info-station Short range radios Military Communications
Radar and Sensing Vehicular radar Ground penetrating radar Through wall imaging Medical imaging Surveillance
5
Design of the LNA6
As any Low-Noise Amplifier, an UWB LNA should have: Low noise figure (i.e., below 6dB) High gain (i.e., above 10dB) Input matching to 50Ω (i.e., S11 below -10dB) Output matching to 50Ω (i.e., S22 below -10dB)
But also, with a flat response in the whole 3.1-10.6GHz band.
Performance criteria7
Two-stage amplifier The first stage
fixes the input impedance of the system and defines a low frequency resonance.
The second stage drives the LNA total gain by fixing a second resonance in the high frequency part of the band.
Circuit description (I)8
The common-gate stage Input impedance
There is a resonance near DC. At high frequencies, gm1
becomes the dominant term.
Circuit description (II)9
1
in
1 1 11S
m gs S
sLZ
g sC sL
With RL1=320Ω, WM1=55µm and VG1=0.7V, gm1 is in the order of
20mS
With RL1=320Ω, WM1=55µm and VG1=0.7V, gm1 is in the order of
20mS
The common-source stage Defines a second resonance in
the high part of the band. Provides the gain to the system.
The output buffer was already given: WM4=55µm and Ibias=5.7mA.
Circuit description (III)10
With RL2=60Ω, WM2=WM3=120µm and VG2=1V, both transistors are
still in the saturation region
With RL2=60Ω, WM2=WM3=120µm and VG2=1V, both transistors are
still in the saturation region
Circuit simulation11
11
Circuit simulation (I)12
Effect of changing LD2
from 1nH to 3nH
Taking into account the UWB FCC mask already shown, trying to move the first resonance far below
the 3GHz is not necessary.
Taking into account the UWB FCC mask already shown, trying to move the first resonance far below
the 3GHz is not necessary.
Effect of changing LS1
from 2nH to 10nH
Gain (dB) Gain (dB)
Circuit simulation (II)13
Effect of changing VG2 from 0.6V to 1.6V
A good compromise between total gain and power consumption is achieved, for example, with 120µm
and a VG2 equal to 1.2V.
A good compromise between total gain and power consumption is achieved, for example, with 120µm
and a VG2 equal to 1.2V.
Effect of changing WM2
and WM3 from 40µm to 200µm.
Gain (dB) Gain (dB)
Final results14
L0.18μm
WM1 60μm
WM2 120μm
WM3 120μm
WM4 55μm
LS1 3.6nH
LD21.84nH
RL1 320Ω
RL2 60Ω
VG1700mV
VG2 1.2V
Design comparison15
Figure Current circuit Original circuit
Maximum Gain 13dB 12.4dB
BW-3dB 1.0-11.6GHz 0.4-10GHz
Noise Factor 3.6-4.8dB 4.4-6.5dB
IIP3 ( @ 6GHz ) -2.74dBm -6dBm
P-1dB ( @ 6GHz ) -16.27dBm -15dBm
Power consumption
15.6mW 12mW
Very similar results have been obtained.Very similar results have been obtained.
Conclusions
A two-stage LNA amplifier from 1.0 and up to 11.6GHz has been designed.
A common-gate stage fixes the input impedance of the system and creates a first resonance at low frequencies.
A common-source stage drives the system gain and introduces a resonance in the high part of the band.
A nearly flat gain of 13dB and a noise figure of 4dB are achieved within this topology.
16
