Design and Simulation of multi mode Continuous Time Delta Sigma Modulator for wireless communication standards
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Sahand University of Technology
Design and Simulation of multi mode
Continuous Time Delta Sigma Modulator
for wireless communication standards
Types of ADC from the point of sampling frequency view
ADCs
Nyquist  Rate ADCs
Over sampling ADCs
Typical Nyquist  Rate ADCs ( FLASH )
Vin
R/2
Vout

+
R
Flash ADCs
R





+
+
+
+
+
Encoder
R
R
R/2
Over Sampling
Noise Shaping
1bit quantizer
∑ / ∫
∆
Advantages:
very high resolution(1224 bit)
Analog part small area
robustness to circuit imperfections
Disadvantage :
Moderate bandwidth due to oversampling
Low speed

+
1224 bit Resolution
Wow !!!!!!!!!!!
DeltaSigma Concepts : quantization noise
ADC
X(n)
DAC
Y1(n)
e(n)
Se(f)
X(n)
kx
Quantization noise power density
Y1(n)
t
fs/2
fs/2
f
e(n)
Δ/2
t
Δ/2
DeltaSigma Concepts : over sampling
Quantization noise and inband noise for OSR = 1
Quantization noise and inband noise for OSR = 4
DeltaSigma Concepts : DT and CT
DT Δ Σ modulator
CT Δ Σ modulator
Continuous Time
AAF
DSM
Decimation
DSM
Decimation
H(z)
H(s)
fs
fs
DeltaSigma Concepts : DT and CT
STF : Signal Transfer Function
NTF : Noise Transfer Function
DeltaSigma Concepts : comparison between CT & DT
Continuous Time
Discrete Time
DeltaSigma Concepts : DSM structures
E1(z)
2nd order DSM
2nd order DSM
X(z)
g
Y2(z)
Y1(z)
H1(z)
H1(z)
Y(z)
Verifying the performance of system
Design Flow
System
Level
Device
Level
Systemlevel simulation is a great benefit before circuitlevel simulation
Clock jitter at the comparator
Integrator leakage due to finite gain
Practical
Ideal
Practical
Critical opamp DC gain
Slew Rate and Finite Bandwidth
Critical opamp BW
350 MHz
Critical opamp Slew Rate
340 V/us
Problems
Solution
Before scaling
After scaling
Scaling coefficients of the Delta Sigma Modulator
Out put of second int.
Quantizer input
Out put of first int.
Europe : GSM900 / DCS1800 / UMTS
WCDMA
3G
UnitedStates : IS95 / CDMA2000
China : TDSCDMA
Gabon : GSM900
Standards evolution on mobile terminals
1G
AMPS
NMT
2G
EDGE
GPRS
GSM
WiMAX
WLAN
WiFi
4G
Next Generation
Chip area restrictions
Why multistandard ????
Base band
RF band
Multi standard solution
Multi standard receiver
WLAN
Worldwide Communications Systems
Bistandard or tristandard mobile phones
VOICESMSDATAVIDEO…
Single chip
WCDMA
Design of a reconfigurable RF transmitter IC able to address every standard
Different wireless standards and some basic characteristics
Quality of Service (QoS)
Design approach
GSM
WCDMA
WLAN
Baseband
signal
processor
GSM mode DSM
0.2 MHz
WCDMA mode DSM
WLAN mode DSM
2 MHz
20 MHz
Design approach
worstcase set of specifications ( WLAN)
Very inefficient
Consume way too much power for most of the standards and operation modes
Design approach
0.2 MHz
GSM
WLAN
Flexible / Reconfigurable
WCDMA
2 MHz
20 MHz
Golden key
DR : Dynamic range
L : Order of modulator
OSR : Over Sampling Ratio
B : Quantizer Resolution
fs : Sampling Frequency
f0 : Modulator Bandwidth
SYSTEM ARCHITECTURE : Drawbacks and Suggestion
Increasing the order of the modulator
Increasing the resolution of the quantizer
Increasing the Sampling frequency
Drawbacks
Suggestion
Drawbacks
Suggestion
Drawbacks
Suggestion
Stability concerns
higher order digital filter downstream
power dissipation
circuit area
feedback DAC DEM technique considerable complexity to the design
power in the quantizer and feedback DAC
process limitations in 0.18μm 500MHz is reasonable
A MultiMode SigmaDelta ADC for GSM / WCDMA / WLAN Applications [Babita R. Jose]
GSM mode
WCDMA mode
GSM mode
WLAN mode
WCDMA mode
WLAN mode
A 1.2V DualMode WCDMA/GPRS ΣΔ Modulator [Alessandro Dezzani]
A TripleMode SigmaDelta Modulator for MultiStandard Wireless Radio Receivers [ANA RUSU]
GSM mode
WCDMA mode
WLAN mode
0.2 MHz
2 MHz
20 MHz
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A.Rusa, A. Borodenkov,M. Ismail, and H.Tenhunev “A triplemode SigmaDelta modulator for multistandard wireless radio receivers,” Analog Integrated Circuits and Signal Processing, Springer Science + Business Media, vol. 47, pp. 113–124, 2006.
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G. Gomez, and B. Haroun,“ A 1.5V 2.4/2.9mW 79/50 dB DR ΣΔ Modulator for GSM/WCDMA in a 0.13μm Digital Process,” In IEEE ISSCC Conference Digest of Technical Papers, pp. 242–244, 2002.