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20/04/23 1
Calibration of Input-Matching and its Center Frequency for an Inductively Degenerated Low
Noise Amplifier
Laboratory of Electronics and Information TechnologiesNational school of Engineers Sfax
University of Sfax
Sami Mahersi, Hassene Mnif and Mourad Loulou
ICECS 2010, IEEE International Conference on Electronics Circuits and SystemsAthens, 12-15 December 2010
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Outline
Introduction
Technique of input matching and center frequency calibration of
an Inductively degenerated LNA
Theoretical study of the calibration technique Calibration of Input matching
Calibration of center frequency
Impact of the calibration on the LNA behaviour
Conclusion and future works
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Introduction(1)
• Several factors causes RF front-End (LNA) performance degradation:
Parasitic Effects Process variation
Power Supply voltage variation
Degrading the circuit performances
Non performant Circuitbehaviour
On-chip Capacitive couplingTemperature
Variation
Introduction(2)
Input
ADCDigital
calibration Algorithm
Sensor
Tunable LNA (Device Under
Test)Output
Sensor
DAC
Basic schema of a DUT performances Self calibration system
J. Wilson, M. Ismail, “Input match and load tank digital calibration of an inductively degenerated CMOS LNA,” Integration, the VLSI Journal, vol. 42, Issue 1, pp. 3-9, January 2009
Self Calibration systems are used for self controlling and self correcting the performances of a Device Under Test in order to compensate performances deviations
Principle: The sensors take the input and the output signals of the DUT. Transform the RF signals into DC voltage converted to digital for processing by the calibration algorithm block. The results, producing a correction signal which is fed back to the Tunable DUT.
420/04/23
In This Work
A Calibration schema for a LNA performances
• We propose a new technique to tuning two performances of an Inductively Degenerated low noise amplifier which are : the input matching and center frequency.
• The purpose is to have separate control of both characteristics
• Low impact on Amplifier other characteristics: Gain, Linearity and Noise Figure
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Technique of input match and its center frequency calibration for an Inductively degenerated LNA
Theoretical study of the calibration technique
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Schematic of LNA for calibration
RL=50Ω
VDD
Vout
Ls
Lg
M1
M2
Ld Cd
Rs= 50Ω
Vs
Zin
Cg
Cs
Cc1
Cc2
R2
R1
Zout
M3
Zin
fc
• Cs capacitor for the tuning of input matching
• Cg capacitor in parallel with Ls forthe tuning of the central frequency
Advantages compared to already proposed techniques:
• Avoid the use of the inductance tuning (complexity in the implementation)
• Having independant tuning of the parameters S12 and fo)
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501
)Re(2
gsss
smin
CCL
LgZ
totssgtotgsgss CCLLCLCLCLf
111
22
10
totssgsstotstotg CCLLCLCLCL 42 Where :
gsgtot CCC
111Where :
01
1)Im(
2
totss
sgin
CCL
LLZ
Symbolic analysis of Input impedance and resonance frequency
gsss
sm
totss
sgin
CCL
Lg
CCL
LLjZ
22 1
1
1
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Variation of resonance frequency versus the capacitors Ctot and Cs
80 85 90 95 100 105 110 115 12090
95
100
105
110
115
Ctot, Cs (%)
f0 (
%)
Cs
Ctot
• The central frequency is more dependant on the Ctot (Cg) variation • However it doesn’t vary when Cs varies
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Variation of input impedance versus capacitor Cs for different values gm and Ls
500 1000 1500 2000 2500 300042
44
46
48
50
52
54
56
58
60
Cs (fF)R
eal(Z
in)
(Ohm
)
Ls=35.971e-2 nH
Ls=37.572e-2 nHLs=39.323e-2 nH
100 200 300 400 500 600 700 800 900 100044
46
48
50
52
54
56
58
Cs (fF)
Rea
l(Zin
) (O
hm)
gm = 70e-3 A/V
gm = 35e-3 A/V
gm = 15e-3 A/V
• Decreasing gm makes the tuning range of the input impedance more wider• Decreasing Ls makes the tuning range of the input impedance more wider.
This is to be considered when designing the LNA and a compromise can be reached when setting the values of gm and Ls
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Technique of input matching and its center frequency calibration for an Inductively degenerated LNA
Calibration of Input matching
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Initial performances of LNA at 2.45GHz
Parameter Value
S21 (dB) 20.5
S11 (dB) -58.6
Real(Zin) (Ω) 50.09
Imag(Zin) (Ω) -0.07
S22 (dB) -47.6
Real(Zout) (Ω) 49.6
Imag(Zout) (Ω) 0.09
NF (dB) 1.98
CP1 (dBm) -23.6
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Calibration of Input matching
2.440 2.445 2.450 2.455 2.460 2.4652.435 2.470
-60
-40
-20
-80
0
freq, GHz
dB(S
(1,1
))
2.450G-28.59
m1
2.450000G-28.58573
m2
2.450000G-28.58573
m3
m1freq=dB(S(1,1))=-57.965Cs=1.505000E-12
2.450GHzm2freq=dB(S(1,1))=-40.773Cs=1.006667E-12
2.450GHzm3freq=dB(S(1,1))=-28.586Cs=3.000000E-12
2.450GHz
2.42 2.43 2.44 2.45 2.46 2.472.41 2.48
40
45
50
55
35
60
freq, GHz
real
(Zin
1)
2.450000G53.86025
m4
2.450000G53.86025
m5
m4freq=real(Zin1)=47.341Cs=1.000000E-14
2.450GHz
m5freq=real(Zin1)=53.860Cs=3.000000E-12
2.450GHz
• Cs is swept around 1500fF (nominal value ) : [10fF – 3000fF]
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Impact of input matching calibration on the other LNA performances at 2.45GHz
Parameter Variation range
S21 (dB) [20.21 , 20.74]
Im(Zin) (Ω) [-0.19 , -0.03]
S22 (dB) [-53.14 , -43.08]
Re (Zout) (Ω) [49.3 , 49.83]
Im (Zout) (Ω) [0.049 , 0.138]
NF (dB) [1.98 , 1.99]
CP1 (dBm) [-23.3 , -23.87]
Low variation of LNA gain, Noise Figure and linearity when calibrating the input impedance
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Technique of input matching and its center frequency calibration for an Inductively degenerated LNA
Calibration of input match center frequency
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Calibration of input match center frequency
2.2 2.3 2.4 2.5 2.6 2.7 2.82.1 2.9
-60
-40
-20
-80
0
freq, GHz
dB
(S(1
,1))
2.448G-64.93
m1
2.349G-21.79
m2
2.563G-6.086
m3
m1freq=dB(S(1,1))=-64.930Cg=3.132857E-13
2.448GHzm2freq=dB(S(1,1))=-21.789Cg=3.750000E-13
2.349GHzm3freq=dB(S(1,1))=-26.816Cg=2.670000E-13
2.563GHz
2.42 2.43 2.44 2.45 2.46 2.472.41 2.48
40
45
50
55
35
60
freq, GHz
real
(Zin
1)
2.450G50.09
m4
m4freq=real(Zin1)=50.095Cg=3.750000E-13
2.450GHz
Center frequency tuning band = 214MHz
It is clear that when tuning center frequency there is no impact on input matching
• Cg is swept in the range [267fF – 375fF]
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Parameter Variation range
S21 (dB) [20 , 20.5]
S22 (dB) [-48.42 , -31.29]
Real(Zout) (Ω) [47.77 , 50.14]
Imag(Zout) (Ω) [-2.16 , 1.45]
NF (dB) [1.77 , 2.41]
CP1 (dBm) [-23.15 , -23.62]
Impact of center frequency calibration on the other LNA performances at 2.45GHz
Gain and linearity are not affected by Noise figure varies a little but still lower than 3dB
20/04/23 18
Conclusion and future works
• A technique is proposed for calibrating the input matching and central
frequency for an Inductively Degenerated Low Noise Amplifier operating at 2.45GHz.
• We studied the impact of each perfomance calibration on the others
performances of the LNA at 2.45GHz, good results are observed since
these calibrations have no significant effect on the other
characteristics of the LNA.
• In the future: we will investigate on some other calibration techniques
for the other LNA performances (Gain, Noise figure, linearity)
THANK YOU