A CMOS Low Power Current-Mode Polyphase Filter
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Transcript of A CMOS Low Power Current-Mode Polyphase Filter
A CMOS Low Power Current-Mode
Polyphase Filter
ByHussain Alzaher & Noman Tasadduq
King Fahd University of Petroleum & Minerals
KFUPM, Department of Electrical Engineering
2
OUTLINE INTRODUCTION
Bluetooth receiver Available solutions
PROPOSED APPROACH CURRENT AMPLIFIER
Introduction Fully differential current amplifier (FDCA)
BASIC PRINCIPLE PROPOSED FILTER
Single ended realization Fully differential realization
EXPERIMENTAL RESULTS COMPARISON WITH THE LITERATURE CONCLUSION
3
Low-IF Receiver Architecture Unlike zero-IF: Low-IF = No DC offset and
flicker noise problems Image problem Solution: Polyphase bandpass filter
INTRODUCTION
LNA
LO1
LO2
BPF-45
+45
Amplifier tLimiterFSK-
Demodulator
LPF
o/p+
-
4
INTRODUCTION
Available SolutionsActive-RC filters.
High dynamic range. Limited bandwidth. Relatively high power consumption.
gm-C filters High frequency. Programmable. Poor linearity=Limited dynamic range.
5
PROPOSED APPROACH
Design new polyphase filter based on optimum active element
Higher bandwidth than op-amp lower power
Better linearity than gm better DR
6
PROPOSED APPROACH
Current-mode processing inherently possess High BW + Low voltage Low Power High signal swing High linearity
Current Amplifier based Filter Simple filter topology Low power
7
CURRENT AMPLIFIER (CA)
Introduction Conveys input current from a low impedance input terminal
(X) to a high impedance output terminal (Z).
Gain=K, (sizing of current mirror transistors).
Two types: positive CA (input and output currents are both going in the same direction) and negative CA (having currents in opposite directions).
IX
X ZpCAKIX IX
X ZnCAKIX
CA with +ve output CA with -ve output
8
IX
XZn
ZpCA
KIX
KIX
Single Input/Dual Output CA
zp zn xI I KI 0xV
M13 M9 M10
M11VDD
M12
ISB
M3
M4
M8
M7
M6
M5
VDD
VSS
X ZpM2 M1
M20
IB Zn
M14
M15
M16
M17
M18
M19
K
1 K
1 K
K
M21
1
1
1
1
Core Input Stage
Class-AB Output Stage
Current Mirrors
CURRENT AMPLIFIER (CA)
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H. Alzaher, N. Tasadduq, “Realizations of CMOS fully differential current followers/amplifiers," IEEE International Symposium on Circuits and Systems (ISCAS 2009), pp. 1381-1384.
Details available in:
I1
XZn
ZpCA
XZn
ZpCA
I2
I1
I2
I2
I1
Io1=K(I1-I2)
Io2=K(I2-I1)
(K)
(K)
Xp
XnZn
Zp
FDCA
Xp
Xn Zn
Zp Io1
Io2
I1
I2
Four terminal device, with two input and two output currents.
(Ideally common mode gain is zero)01 02 1 22 ( )I I K I I
CURRENT AMPLIFIER (CA)Fully Differential Current Amplifier (FDCA)
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BASIC PRINCIPLE
0 0
/( )
1 ( / / )o o
c
aT j
j
General Transfer function
/ / 2
/
c
c c o
o o
Center frequency
Q BW
Gain a
Image Rejection
( ) /c o oT j a
20
/( )
1 (2 / )o o
c
c
aT j
2( )Image Rejection Ratio 1 16
( )c
c
T jIRR Q
T j
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BASIC PRINCIPLE Systematic Design
Lowpass filter can be converted to a bandpass polyphase filter centered at ωc.
Complex poles are achieved by using cross-coupling between I and Q paths.
s o
ao
c
aoj
xi xo
s o
ao
c
ao
xI xoI
xQ xoQ
c
ao
s o
ao
-
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PROPOSED FILTER Single Ended Realization
R
C
Ii Io
0 0
( )1 ( / / )c
AT j
j
2 /c K RC
1/o RC
2 / 2Q K
Independent control of ωc without changing Q using R
and/or C.
RCA+
+
C
RCA -
+C
K1IoI
K2IoI
K2IoQ
K1IoQ
II
IQ
1A K
Simple LP filter to complex filter
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PROPOSED FILTER
Nominal Values 6th order polyphase filter is implemented. The nominal center frequency of 3MHz and overall
bandwidth of 1MHz are achieved by selecting R1=13k, C1=8.5pF and K2=2.1.
K1 is 1 to achieve a gain of unity.
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PROPOSED FILTER Fully Differential Realization
Zp1
Zn1
Zp2
Zn2
Xp
Xn
Iip
Iin
C
CR
R
Zp1
Zn1
Zp2
Zn2Xp
Xn
Iqp
Iqn
C
CR
R
(to next stage)Ioip
Ioin
Ioqp
Ioqn
}
(to next stage)}
FDCA
FDCA
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PROPOSED FILTERFDCA with four outputs
FDCA
Zp1
Zn1
Zp2
Zn2
Xp
Xn
I1
I2
CA
Zp1
Zn1
Zp2
Zn2
Xp
(K1)
(K2)
CA
Zp1
Zn1
Zp2
Zn2
Xn
(K1)
(K2)
I1
I2
Io1a=K1(I2-I1)
Io2a=K1(I1-I2)
Io1b=K2(I1-I2)
Io2b=K2(I2-I1)
Zp1
Zn1
Zp2
Zn2
FDCA (with four outputs)
01 02 1 1 22 ( )a aI I K I I
01 02 2 1 22 ( )b bI I K I I
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FOUR OUTPUT CA REALIZATION
9 10M M BI I I ; 15 25M M S BI I I ; 8 17 19 23 0.5M M M M SBI I I I I 3M S BI I ;
Core biasing circuit of IB=9A and ISB=3A is shared for all FDCATotal biasing current is(2 6 )x4x6 0.88mAB S B B S BI I I I
M13 M9 M10
M11VDD
M12
ISB
M3
M4
M8
M7
M6
M5
VDD
VSS
X Zp1M2 M1
M20
IB Zn1
M17
M16
M19
M18
M23
M22
1
1 0.5
M21
1
1
1
1
M15
M14
Zp2
1.05
Zn2
M25
M24
0.5 1.05
1.050.50.5 1.05
6M S BI I ;
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EXPERIMENTAL RESULTS
Standard 0.18m CMOS process. Supply Voltage ±1.35V.Total Supply Current 0.88mA.Center frequency 3MHz.Bandwidth 1MHz.Center frequency tuning using
capacitor arrays.
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EXPERIMENTAL RESULTS Signal magnitude response showing center frequency tuning
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EXPERIMENTAL RESULTSFeatures Proposed Filter
fc 3MHz Bandwidth 1MHz Supply voltage 2.7V Total current 0.88mA Tuning Range 1.8-4.5 MHz ATTENUATION 1st Blocker @4MHz 2nd Blocker @5MHz 3rd Blocker @6MHz
14dB (BT specifies 0dB) 37dB (BT specifies 30dB) 52dB (BT specifies 40dB)
IIP3 In-band Out-of-band
29.2dBm 45dBm
Total noise -68dBm SFDR (Inband) 64.7dB (BT specifies more than 50dB) Image rejection >54dB
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COMPARISON WITH LITERATURE
1. B. Shi, W. Shan, and P. Andreani, 2002, “A 57dB image band rejection CMOS gm-C polyphase filter with automatic frequency tuning for Bluetooth,” Proc. Int. Symp. Circuits and Systems, ISCAS’ 2002., vol. 5, pp. V-169 - II-172, 2002.
2. A. Emira, and E. Sánchez-Sinencio, “A pseudo differential complex filter for Bluetooth with frequency tuning,” IEEE Trans. Circuits and Syst.-II, vol. 50, pp. 742 – 754, October 2003.
3. B. Guthrie, J. Hughes, T. Sayers, and A. Spencer, “A CMOS gyrator Low-IF filter for a dual-mode Bluetooth/ZigBee transceiver,” IEEE J. Solid-State Circuits, vol. 55, no. 9, pp. 1872-1878, Sep. 2005.
4. C. Psychalinos, “Low-voltage log-domain complex filters,” IEEE Trans. Circuits and Syst.-II, vol. 55, no. 11, pp. 3404- 3412, Dec. 2008.
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COMPARISON WITH LITERATURE
Features [1] [2] [3] [4] Proposed
Filter Technology 0.35m 0.35m 0.18m 0.35m 0.18m
Order 6th 7th 5th 6th 6th Application BT BT BT BT BT
fc 2MHz 3MHz 1MHz 2MHz 3MHz Active
Element gm-C gm-C gm-C
gm-C log dom
CF-C
Tuning gm gm gm gm Cap arrays Supply voltage
2.7V 3.3V 3.6V 1.2V 2.7V
Total current
4.7mA 3.8mA 0.53mA 9.1mA 0.88mA
Power/pole 2.1mW 1.8mW 0.38mW 1.8mW 0.4mW Image
rejection >45dB >57dB >48dB >45.7dB >54dB
SFDR (Inband)
45.2dB 53dB NA 36.9dB 64.7dB
Total Area 1.32mm2 0.54mm2 0.23 mm2 Sim. 0.61 mm2
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COMPARISON RESULTS
Power consumption/pole Proposed filter and [3]
Image rejection Propsed filter and [2]
SFDR Proposed filter
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CONCLUSION
CA based filters inherently exhibit higher bandwidth than active-RC and better linearity than gm-C.
This is demonstrated by a new polyphase filter with improved SFDR and IRR while using relatively lower power.
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Thank You,