Download A CMOS Low Power Current

King Fahd University of Petroleum & Minerals
KFUPM, Department of Electrical Engineering
A CMOS Low Power
Current-Mode Polyphase Filter
By
Hussain Alzaher & Noman Tasadduq
OUTLINE

INTRODUCTION




PROPOSED APPROACH
CURRENT AMPLIFIER







Introduction
Fully differential current amplifier (FDCA)
BASIC PRINCIPLE
PROPOSED FILTER


Bluetooth receiver
Available solutions
Single ended realization
Fully differential realization
EXPERIMENTAL RESULTS
COMPARISON WITH THE LITERATURE
CONCLUSION
2
INTRODUCTION

Low-IF Receiver Architecture
 Unlike
zero-IF: Low-IF = No DC offset and flicker noise
problems
 Image problem
 Solution: Polyphase bandpass filter
+45
LO1
LNA
-45
LO2
o/p
+
BPF
Amplifier Limiter
t
LPF
FSKDemodulator
-
3
INTRODUCTION
Available Solutions
 Active-RC
filters.
High dynamic range.
 Limited bandwidth.
 Relatively high power consumption.

 gm-C
filters
High frequency.
 Programmable.
 Poor linearity=Limited dynamic range.

4
PROPOSED APPROACH
Design new polyphase filter based on optimum
active element

Higher bandwidth than op-amp  lower power

Better linearity than gm  better DR
5
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
6
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
KIX
IX
KIX
X CA Zp
X CA Zn
CA with +ve output
CA with -ve output
7
CURRENT AMPLIFIER (CA)
Single Input/Dual Output CA
VDD
M13
M9
M10
M3
IB
M2
M6
M8
M14
1
K
K
M1
X
VDD
M11
1
M16 M18
1
M20
M5
M12
1
Zp
K
K
M7
M15
Zn
X CA Z
p
KIX
KIX
Zn
1
M4
M21
IX
M17 M19
ISB
1
I zp   I zn  KI x
Vx  0
VSS
Core Input
Stage
Class-AB
Output Stage
Current
Mirrors
8
CURRENT AMPLIFIER (CA)
Fully Differential Current Amplifier (FDCA)
Four terminal device, with two input and two output currents.
FDCA
I1 Io1=K(I1-I2)
I1
Zn
Zp
X CA Z
(K) p
Xp
I1
I2 Io2=K(I2-I1)
I2
Zn
X CA Z
Zn
Xn
(K) p
I2
I1
Xp
Zp
Io1
I2
Xn
Zn
Io2
I 01  I 02  2K ( I1  I 2 ) (Ideally common mode gain is zero)
Details available in:
H. Alzaher, N. Tasadduq, “Realizations of CMOS fully differential current
followers/amplifiers," IEEE International Symposium on Circuits and Systems
9
(ISCAS 2009), pp. 1381-1384.
BASIC PRINCIPLE

General Transfer function
ao / o
T ( j ) 
1  j ( / 0  c / 0 )

c  Center frequency
Q  c / BW  c / 2o
Gain  ao / o
Image Rejection
T ( jc )  ao / o
T ( jc ) 
ao / o
1  (2c / 0 )2
Image Rejection Ratio  IRR 
T ( jc )
T ( jc )
 1  16Q 2
10
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.
xI
xi

ao
s  o
j

ao
s  o
xoI
c
xo
ao
c

- aco
ao
xQ

ao
s  o
xoQ
11
PROPOSED FILTER

Single Ended Realization
T ( j ) 
R
Ii
C
A
1  j ( / 0  c / 0 )
Simple LP
filter to
complex filter
c  K 2 / RC
o  1/ RC
Q  K2 / 2
Io
C
R
II
K1IoI
CA ++
K2IoI
A  K1
 Independent
control of ωc without
changing Q using R and/or C.
K2IoQ
IQ
C
R
CA +K1IoQ
12
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=13kW,
C1=8.5pF and K2=2.1.
K1 is 1 to achieve a gain of unity.
13
PROPOSED FILTER

Fully Differential Realization
C
Iip
R
Zp1
Z
FDCA n1
Zp2
Xn
Zn2
Xp
Iin
R
Ioip
Ioin }
(to next stage)
Ioqp
Ioqn }
(to next stage)
C
C
Iqp
R
Zp2
Zn2
FDCA Z
p1
Xn
Zn1
Xp
Iqn
R
C
14
PROPOSED FILTER
FDCA with four outputs
FDCA (with four outputs)
I1
Xp
Z
(K1) p1
Z
CA Zn1
(K2) p2
Zn2
Io1a=K1(I2-I1)
Zp1
Io2a=K1(I1-I2) Zn1
I1
I2
I2
Xn
Zp1
Z
CA Zn1
(K2) p2
Zn2
(K1)
Zp1
Z
FDCA Zn1
p2
Xn
Zn2
Xp
Io1b=K2(I1-I2) Zp2
Io2b=K2(I2-I1) Zn2
I 01a  I 02a  2K1 ( I1  I 2 )
I 01b  I 02b  2K2 ( I1  I 2 )
15
FOUR OUTPUT CA REALIZATION
VDD
M13
M9
M10
M3
M6
1
IB
M2
M15 M17
0.5
1.05
X
Zp1
1
0.5
1.05
0.5
M5
M7
M14
M16
M1
VDD
M11
M8
0.5
M19 M23
1
1
Zp2
M25
1.05
Zn1
1
1
Zn2
1.05
M4
M21
M20
M12
M18 M22
M24
ISB
VSS
I M 9  I M 10  I B ; I M 3  I S B ; I M 6  I S B ; I M 15  I M 25  I S B ; I M 8  I M 17  I M 19  I M 23  0.5I SB
Core biasing circuit of IB=9mA and ISB=3mA is shared for all FDCA
Total biasing current is (2 I B  6 I S B )x4x6  I B  I S B  0.88mA
16
EXPERIMENTAL RESULTS
 Standard
0.18mm CMOS process.
 Supply Voltage ±1.35V.
 Total Supply Current 0.88mA.
 Center frequency 3MHz.
 Bandwidth 1MHz.
 Center frequency tuning using capacitor arrays.
17
EXPERIMENTAL RESULTS

Signal magnitude response showing center frequency tuning
18
EXPERIMENTAL RESULTS
Features
Proposed Filter
fc
Bandwidth
Supply voltage
Total current
Tuning Range
ATTENUATION
1st Blocker @4MHz
2nd Blocker @5MHz
3rd Blocker @6MHz
IIP3
In-band
Out-of-band
Total noise
SFDR (Inband)
Image rejection
3MHz
1MHz
2.7V
0.88mA
1.8-4.5 MHz
14dB (BT specifies 0dB)
37dB (BT specifies 30dB)
52dB (BT specifies 40dB)
29.2dBm
45dBm
-68dBm
64.7dB (BT specifies more than 50dB)
>54dB
19
COMPARISON WITH LITERATURE
1.
2.
3.
4.
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.
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.
B. Guthrie, J. Hughes, T. Sayers, and A. Spencer, “A CMOS gyrator LowIF filter for a dual-mode Bluetooth/ZigBee transceiver,” IEEE J. Solid-State
Circuits, vol. 55, no. 9, pp. 1872-1878, Sep. 2005.
C. Psychalinos, “Low-voltage log-domain complex filters,” IEEE Trans.
Circuits and Syst.-II, vol. 55, no. 11, pp. 3404- 3412, Dec. 2008.
20
COMPARISON WITH LITERATURE
Proposed
Filter
0.18mm
6th
BT
3MHz
Features
[1]
[2]
[3]
[4]
Technology
Order
Application
fc
Active
Element
Tuning
Supply
voltage
Total
current
Power/pole
Image
rejection
SFDR
(Inband)
0.35mm
6th
BT
2MHz
0.35mm
7th
BT
3MHz
0.18mm
5th
BT
1MHz
gm-C
gm-C
gm-C
gm
gm
gm
0.35mm
6th
BT
2MHz
gm-C
log dom
gm
Cap arrays
2.7V
3.3V
3.6V
1.2V
2.7V
4.7mA
3.8mA
0.53mA
9.1mA
0.88mA
2.1mW
1.8mW
0.38mW
1.8mW
0.4mW
>45dB
>57dB
>48dB
>45.7dB
>54dB
45.2dB
53dB
NA
36.9dB
64.7dB
Total Area
1.32mm2
0.54mm2
0.23 mm2
Sim.
0.61 mm2
CF-C
21
COMPARISON RESULTS

Power consumption/pole


Image rejection


Proposed filter and [3]
Propsed filter and [2]
SFDR

Proposed filter
22
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.
23
Thank You,
24