A FULLY INTEGRATED MOS-C CURRENT-MODE IF FILTER FOR

BLUETOOTH

by

Hussain Alzaher

Electrical Engineering DepartmentKing Fahd University of Petroleum & Minerals

Dhahran Saudi Arabia

Outline Introduction

• Bluetooth technology• Receiver Architecture

Requirements of IF Filter Proposed Technique

• Unity gain cells• Non-Linearity Cancellation• Fully Differential Architecture

Proposed Low IF Bandpass Filter• Filter design topology• Filter characteristics

Simulation Result• ac response• Filter specifications

Conclusions

IntroductionBluetooth technology

• small, low-cost, short-range radio link• mobile computing and communications

between wireless devices• frequency hopping spread spectrum multiple

access technique• 79-hopping channels spaced 1-MHz apart• data transmission rate of 1 Mb/s• Gaussian frequency shift keying• relaxed dynamic range, noise figure and image

rejection specifications

Introduction

Bluetooth Receiver Architecture

LNA

LO1

LO2

BPF-45

+45

Amplifier tLimiterFSK-

Demodulator

LPF

o/p+

-

Low-IF architecture

• Center frequency (fc): 3MHz

• Filter bandwidth: 1MHz

• Selectivity

0dB @ fc±1MHz

30dB @ fc±2MHz

40dB @ fc±3MHz (or more)

• Dynamic Range

IP3-Noise > 75dB

• In-band group delay < 1us

Requirements of IF Filter

Proposed Technique

Unity gain cells

Characteristics Voltage Buffer Current Follower

Relations Voutput=Vinput Ioutput = Iinput

Vinput=0

Input impedance

Very HighIdeally =infinity

Very LowIdeally=zero

Output Impedance

Very LowIdeally=zero

Very HighIdeally =infinity

Unity gain cells terminal characteristics

A CMOS Low-power Current follower

M13 M9 M10

M2 M1

M3 M7 M8

M6M5

M4

McXM11

M12

VDD

Vb

V

Z

Isb

Ibp

VDD

VSS

VSS

Proposed Technique

Unity gain cells

Proposed Technique

Unity gain cells

A CMOS Low-power Voltage-buffer

M16

Vi

Vb

Vsb

M15 M19

M3 M11

M2M1

M7

M4M19

M17

M18

Ib

Isb

VDD

VSS

Vo

Proposed Technique

Non-Linearity Cancellation

VA

V2

V2V1

VB

I1

I2

))((2 2121 BA VVVVKII

...)()())(( 332

221 SDsDSDTG VVaVVaVVVVKI

)(1

21BAoxn VV

L

WCu

V

IIG

• Ohmic Region MOSFET Current

• Linearized MOSFET Resistor

Basic Circuit

Proposed Technique

Non-Linearity Cancellation

Nonlinearity cancellation using CFs

CF x z CF x z

V B

V A I 1

I 2 I 1 -I 2 I 2 I 1 -I 2 V 1

Proposed Technique

Fully Differential Architecture

Fully differential building block topology

C Fx z

C Fx z

C M F B

Ip

In

V o p

V o n

Proposed Technique

Fully Differential Architecture

M18

M17

M16

M12

M11

MccVc

VDDVb

Vc

M15M2

M1

Mc

M4

M5M6

IsbICM/2ICM/2

ICM

VCM

Mc1 Mc2

Mc6Mc3Mc4M3 M7 M8

M10M9M13M14

M19M20

M21Mc5

Zn Xn Xp Zp

CCM RCM

CCM RCM

VM

VDD

VSS

Ibp

Vop

Von

Fully differential building block CMOS realization

Proposed Low IF Bandpass Filter

-R 2

CF x z CF x z R i

R 1

R 3

C 1 C 2

V i

Vo

RC-Unity Cells two-integrator loop filter

Filter design topology

Proposed Technique

Filter design topology

CMFBCMFB

CFx z CFx z CFx z CFx z

C1 C2

VBi

VAi VB1

VB3

VB2

VA3

VA2

VA1

CFx z CFx z CFx z CFx z

C1 C2

VBi

VAiVB1

VB3

VB2

VA3

VA2

VA1

Vi

+

-

Vo+

-

Proposed second-order bandpass filter section

Proposed Technique

Filter design characteristics

)/(/

/

2132112

1

CCGGCsGs

CsG

Vi

Vo i

21

32

CC

GGo

1

1

C

GBW

2

1

1

32

C

C

G

GGQ

Proposed Technique

Filter die photo

Simulation Result

Magnitude response

Receiver Architectures

5.4

0

340nV/ Hz

Parameters Spct. Results

VDD - 2.5V

IDD - mA

Center frequency - 3Meg

Order 12th (6th+three 2nd)

Passband gain -

Frequency tuning - 2.5-3.5Meg

Group delay <1us <0.5us

1st blocker attenuation 0dB >7dB

2nd blocker attenuation 30dB >34dB

3rd/more blocker attenuation 40dB >44dB

In-band noise input referred Noise

-

IIP3-Noise >75dB 80dB(inband)84dB(near blockers)91dB(distant blockers)

Area 1.7 mm x 1.7 mm

Conclusions

• CMOS bandpass filter for fully integrated Bluetooth receiver

• Using unity gain cells

• Utilizing linearized MOSFET resistors for tuning

• 12th order = 3 X 2nd order bandpass + 3 X 2nd order notches

• Dynamic range = 53dB for in-band signals

• Selectivity improved by cascading

• Current consumption can be optimized