A%20System%20Level%20Design%20for%20a%20Bluetooth%20Front-end%20Receiver

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A System Level Design for a Bluetooth Front-end
Receiver
AALBORG UNIVERSITY Department of
Communication Technology
Group 789
Angela Lin Shekar Nethi Shadi Tawfik
Supervisor
Jan H. Mikkelsen
January 9, 2004
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Contents

• Introduction to Bluetooth

• Radio Receivers Architectures

• Bluetooth Receiver Design

• MATLAB Modeling

• Conclusion Future Work

• Working Process

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Introduction to BluetoothDefinition
Introduction to Bluetooth

• Bluetooth is a wireless technology standard
  intended to be a cable replacement

Radio Receivers Architectures

• Main radio specifications

• Short range (10 - 100 m)

Bluetooth Receiver Design

• Unlicensed ISM band
• (2.4 - 2.4835 GHz)

MATLAB Modeling

• GFSK Modulation
• (BT 0.5, h 0.28 - 0.35)

Conculsion Future Work
Working Process

• Bit rate of 1Mbps

• Frequency Hopping (1600 Hops/sec)

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Introduction to BluetoothBackground
Introduction to Bluetooth

• Bluetooth was first originated by Ericsson in
  1994, with the main targets being low cost, low
  power and low form factor

Radio Receivers Architectures

• In 1998, the Bluetooth Special Interest Group
  (SIG) was formed

Bluetooth Receiver Design

• SIGs initial target price of a Bluetooth
  solution 5

• Currently, average price is around 25

MATLAB Modeling

• High cost is the main problem delaying the
  widespread of Bluetooth

Conculsion Future Work

• Radio part accounts for 80 of the total cost

Working Process
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Radio Receivers ArchitecturesIntroduction
Introduction to Bluetooth

• All wireless front-end receivers employ
  downconversion to an Intermediate Frequency (IF)

Radio Receivers Architectures

• Achieve higher Q components

• Avoid high power consumption

Bluetooth Receiver Design

• Architectures can be classified according to IF
  used

• The Superheterodyne Receiver

MATLAB Modeling

• I/Q Processing Receivers

Conculsion Future Work
- The Direct Conversion Receiver
- The Low IF Receiver
Working Process
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Radio Receivers ArchitecturesThe Superheterodyne
Receiver Operation (1)
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design

• RF Band select filter

MATLAB Modeling

• reduces linearity requirements for later blocks

• avoids desensitization of the receiver

Conculsion Future Work

• Low Noise Amplifier (LNA)

Working Process

• Minimum noise added during amplification

• Mixer

• Downconverts RF signal to IF (usually IF
  RF/10)

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Radio Receivers ArchitecturesThe Superheterodyne
Receiver Operation (2)
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design

• RF image-band-reject filter

MATLAB Modeling
Conculsion Future Work
Working Process

• IF channel select filter

• High Q filter for channel selection

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Radio Receivers ArchitecturesThe Superheterodyne
Receiver Trade-offs
Introduction to Bluetooth

• High IF

Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Razavi-RF Microelectronics

• Low IF

Conculsion Future Work
Working Process
Razavi-RF Microelectronics
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Radio Receivers ArchitecturesThe Superheterodyne
Receiver Pros Cons
Introduction to Bluetooth

• Pros

• High sensitivity and selectivity ? successive
  downconversion

Radio Receivers Architectures
BPF1
BPF2
BPF3
BPF4
Bluetooth Receiver Design
VLO1
VLO2
MATLAB Modeling

• Cons

• Bulky external components

Conculsion Future Work
? Cannot be integrated
Working Process
? Expensive
? High power consumption
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Introduction to BluetoothIQ Processing Receivers
Theory
Introduction to Bluetooth

• Traditional Downconversion

• LO signal contains positive AND negative tones

Radio Receivers Architectures

• Image rejection before downconversion

Bluetooth Receiver Design
MATLAB Modeling
Conculsion Future Work
Working Process
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Introduction to BluetoothIQ Processing Receivers
Physical Realization
Introduction to Bluetooth
I
Radio Receivers Architectures
Bluetooth Receiver Design
Q
MATLAB Modeling

• Common disadvantage IQ mismatches

Conculsion Future Work
Working Process
1 gain and phase mismatch reduces IRR to 35dB
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Radio Receivers ArchitecturesDirect Conversion
Receiver Operation
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design

• DCR can be fully integrated

MATLAB Modeling
Conculsion Future Work
Working Process
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Radio Receivers ArchitecturesDirect Conversion
Receiver Problems (1)
Introduction to Bluetooth

• DC offset

• Imperfect isolation between different ports

Radio Receivers Architectures

• Distortion of downconverted signal

Bluetooth Receiver Design

• Static and dynamic DC offsets

MATLAB Modeling
Conculsion Future Work
Working Process
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Radio Receivers ArchitecturesDirect Conversion
Receiver Problems (2)
Introduction to Bluetooth

• Flicker noise ? major noise contributor in MOS
  devices

Radio Receivers Architectures

• Even order non-linearities

Bluetooth Receiver Design
MATLAB Modeling
Conculsion Future Work
Razavi-RF Microelectronics
Working Process

• LO leakage ? in-band interference for other
  receivers

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Radio Receivers ArchitecturesLow IF Receiver
Operation
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling

• Image rejection ? Polyphase filter

Conculsion Future Work
Working Process
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Radio Receivers ArchitecturesLow IF Receiver
Pros Cons
Introduction to Bluetooth

• Pros

• Integrability

Radio Receivers Architectures

• DC offsets, flicker noise and even order
  distortion can be easily removed

Bluetooth Receiver Design
Combined advantages of Superheterodyne and DCR

• Cons

MATLAB Modeling

• IQ mismatches are a major concern

Conculsion Future Work
Working Process
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Radio Receivers ArchitecturesSummary
Introduction to Bluetooth
Performance Cost Power Consumption Form Factor
Superheterodyne High High High High
Direct Conversion Low DC offset Flicker noise Even order distortion LO leakage Low Low Low
Low IF Low IQ mismatches Low Low Low
Radio Receivers Architectures
Off-chip Components
Bluetooth Receiver Design
Full Integration
MATLAB Modeling
Conculsion Future Work
Full Integration
Working Process
A low IF architecture is found suitable for a
Bluetooth receiver
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Bluetooth Receiver DesignStrategy
Introduction to Bluetooth
Overall Receiver Parameters Calculation
Radio Receivers Architectures
Bluetooth Receiver Design
Verification
MATLAB Modeling
Block Level Design
Conculsion Future Work
Working Process
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Bluetooth Receiver DesignOverall Parameters
Total Noise Figure
Introduction to Bluetooth
Radio Receivers Architectures

• From Bluetooth radio specifications

• Sensitivity (PMIN) -70 dBm

Bluetooth Receiver Design

• Bandwidth (B) 1 MHz

• (BER)MAX 10-3
• ? Mapping for GFSK ? (SNRo)MAX 21 dB
• ? But, Carrier-to-Co-Channel interferenece
  (C/ICO-CH) 11 dB

MATLAB Modeling
Conculsion Future Work
(SNRo)MAX 11 dB
Working Process
NFTOT 33 dB
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Bluetooth Receiver DesignOverall Parameters
Linearity
Introduction to Bluetooth
Radio Receivers Architectures

• IM test requirements

• Desired signal (C) -70 dBm

Bluetooth Receiver Design

• Two interferers
• ? sine signal, PINT1 -39 dBm
• ? GFSK modulated signal, PINT2 -39 dBm

MATLAB Modeling
PINT -39 dBm
Conculsion Future Work

• Carrier-to-Co-Channel interferenece (C/ICO-CH)
  11 dB

Working Process
IP3i,TOT 21dBm
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Bluetooth Receiver DesignOverall Parameters
SFDR
Introduction to Bluetooth

• Sensitivity level (PMIN) -70 dBm

Radio Receivers Architectures

• Maximum interference power level (PINT,MAX)
• ? Follows from definition of SFDR
• ? Total noise figure (FTOT) 32 dB
• ? Total 3rd order Intercept Point (IP3iTOT)
  -20 dBm

Bluetooth Receiver Design
MATLAB Modeling
Conculsion Future Work
Working Process
PINT,MAX -40.6 dBm
SFDR 29.3 dB
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Bluetooth Receiver DesignOverall Parameters
AGC Range
Introduction to Bluetooth
Radio Receivers Architectures

• Sensitivity level (PMIN) -70 dBm

• Maximum signal level (PMAX) -20 dBm

Bluetooth Receiver Design

• ADC full scale power (PFS,ADC)
• ? ADC Full scale voltage (VFS,ADC) 0.8 V
• ? ADC Input resistance (Rin,ADC) 6 kW

MATLAB Modeling
Conculsion Future Work
Working Process
PFS,ADC -12.73 dBm
GTOT,MAX 57.27 dB GTOT,MIN 7.27 dB
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Bluetooth Receiver DesignOverall Parameters
In-band Filtering Requirements
Introduction to Bluetooth

• In-band blockers test specifies a desired signal
  power level of - 60 dBm

Radio Receivers Architectures
In-band interferers power levels
Overall filtering requirements for in-band
interferers
Bluetooth Receiver Design
MATLAB Modeling
Conculsion Future Work
Working Process
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Bluetooth Receiver DesignOverall Parameters
Out-of-band Filtering Requirements
Introduction to Bluetooth

• Out-of-band blockers test specifies a desired
  signal power level of - 67 dBm

Radio Receivers Architectures
Out-of-band interferers power levels
Overall filtering requirements for out-of-band
interferers
Bluetooth Receiver Design
MATLAB Modeling
Conculsion Future Work
Working Process
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Bluetooth Receiver DesignOverall Parameters
Desensitization Blocking (1)
Introduction to Bluetooth

• Main Assumption

• Overall gain reduction is due to gain reduction
  in LNA only

Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Conculsion Future Work
Working Process
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Bluetooth Receiver DesignOverall Parameters
Desensitization Blocking (2)
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design

• Typical values for CMOS LNAs

• GLNA 15 dB

MATLAB Modeling

• NFLNA 4 dB

Conculsion Future Work
Working Process
DNF 3 dB
GLNA 15.5 dB
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Bluetooth Receiver DesignOverall Parameters
Desensitization Blocking (3)
Introduction to Bluetooth
Radio Receivers Architectures

• To obtain a3

Bluetooth Receiver Design
MATLAB Modeling
Conculsion Future Work

• Using a typical value for a CMOS LNA ? IP3i,LNA
  - 9 dBm

Working Process

• Referring to a 50 W load

a3 0.6 mV-2
B 1.37 mV
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Bluetooth Receiver DesignOverall Parameters
Desensitization Blocking (4)
BMAX 1.37 mV
Introduction to Bluetooth
Radio Receivers Architectures

• Referring to a 50 W load

Bluetooth Receiver Design
PBL,MAX 17.3 dBm
MATLAB Modeling

• 8 dB attenuation required before LNA

Conculsion Future Work
Working Process
Bluetooth specifications v1.1
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Bluetooth Receiver DesignBlock Level Design
Assumptions
Introduction to Bluetooth

• Assumptions for unavailable values

Radio Receivers Architectures

• RF band select filter is almost perfectly linear
  ? IP3i,RF 30 dBm

• RF band select filter attenuation for f 6 GHz
  continues constantly for higher frequencies

Bluetooth Receiver Design

• Polyphase channel select filter for adjacent
  channels (Df 3 MHz) extracted from a LPF of the
  same order

MATLAB Modeling
Conculsion Future Work
Working Process
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Bluetooth Receiver DesignBlock Level Design
Parameters
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Conculsion Future Work
Working Process
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Bluetooth Receiver DesignSummary and Conclusion
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Conculsion Future Work
Working Process
A low cost Bluetooth low IF receiver can be
implemented in a standard CMOS process
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MATLAB ModelingAim and Accomplishments
Introduction to Bluetooth

• Previous calculations use approximate formulas

Radio Receivers Architectures

• Building the front-end receiver in a simulation
  environment is a further step towards more
  accurate evaluation of performance

Bluetooth Receiver Design

• The group was able to build behavioral models in
  MATLAB for the following

MATLAB Modeling

• RF noise

Conculsion Future Work

• RF band select filter

• LNA (Mixer)

Working Process

• Polyphase filter

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MATLAB ModelingRF Simulation Problem
Introduction to Bluetooth

• A computer can only deal with discrete time
  signals

• Sampling of input band-pass signal is required

Radio Receivers Architectures

• Still bounded with Nyquist Sampling Theorem

fs 2fmax
Bluetooth Receiver Design

• For RF signals, sampling frequency would be very
  high

MATLAB Modeling

• Huge number of samples

• Computationally inefficient

Conculsion Future Work

• Therefore, use base-band representation of
  band-pass signals

Working Process

• Model built to deal with base-band form input

• Model gives output in base-band form

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MATLAB ModelingBase-Band Representation of
Band-Pass Signals
Introduction to Bluetooth

• Any band-pass (modulated) signal can be written
  as

Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling

• Consequently, the band-pass signal can be
  written as

Conculsion Future Work
Working Process

• I(t) and Q(t) are real signals

• Canonical forms of transmitters and receivers

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MATLAB ModelingGFSK Signal Generation Basic
Principle
Introduction to Bluetooth
g(t )
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Conculsion Future Work
Working Process
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MATLAB ModelingGFSK Signal Generation - Waveforms
Gaussian shaped bits
Bipolar bits stream
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
PSD of GFSK signal
Conculsion Future Work

• BT 0.5

Working Process

• modulation index 0.35

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MATLAB ModelingRF Noise Model Basic Principle

• The PSD of white noise is infinite

Introduction to Bluetooth

• Direct simulation of white noise is impossible

Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling

• Usually, we have a limited bandwidth of interest

Conculsion Future Work
Working Process
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MATLAB ModelingRF Noise Model Algorithm
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Conculsion Future Work
Working Process
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MATLAB ModelingRF Noise Model Results
PSD of generated RF noise
Introduction to Bluetooth

• Simulation parameters

Radio Receivers Architectures

• Two sided PSD NF 3dB

Bluetooth Receiver Design

• Center frequency 200 MHz

• Noise bandwidth 100 MHz

MATLAB Modeling

• Sampling frequency 1 GHz

• Brick wall filter 8th order Butterworth LPF

Conculsion Future Work
Working Process
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MATLAB ModelingRF Filter Model Basic Principle
(1)
Introduction to Bluetooth

• General transfer function of any analog filter

Radio Receivers Architectures
Bluetooth Receiver Design

• Using partial fractions expansion

MATLAB Modeling
Conculsion Future Work
Working Process
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MATLAB ModelingRF Filter Model Basic Principle
(2)
Introduction to Bluetooth

• Output of RF band-pass filter

Radio Receivers Architectures
Bluetooth Receiver Design

• For the RF band-pass signal

• Carrier frequency gtgt bandwidth

MATLAB Modeling

• Spectrum zero outside bandwidth

Conculsion Future Work
Working Process
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MATLAB ModelingRF Filter Model Basic Principle
(3)
Introduction to Bluetooth
From previous analysis we can now write
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Conculsion Future Work
Working Process
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MATLAB ModelingRF Filter Model Results
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Conculsion Future Work

• Direct Implementation

• Low-pass equivalent

• First order bandpass filter

• First order Butterworth LPF

Working Process

• Center frequency 200 MHz

• Bandwidth 5 MHz

• Bandwidth 10 MHz

• Sampling frequency 1 GHz

• Sampling frequency 1 GHz

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MATLAB ModelingLNA Model Basic Principle
Introduction to Bluetooth

• Model non-linearity ? power series expansion

Radio Receivers Architectures
Bluetooth Receiver Design

• Considering only fundamental component at the
  output

MATLAB Modeling
Conculsion Future Work
Working Process
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MATLAB ModelingLNA Model Sine Wave Test
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Conculsion Future Work

• Perfectly linear LNA

• Non-linear LNA

• Voltage gain (a1) 15 dBV

• Voltage gain (a1) 15 dBV

Working Process

• a0 a2 a3 0

• a0 , a2 , a3 ? 0

• Test signal sine wave

• Test signal sine wave

• Amplitude 1 V

• Amplitude 1 V

• Frequency 5 Hz

• Frequency 5 Hz

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MATLAB ModelingLNA Model GFSK Signal Test
Introduction to Bluetooth

• Perfectly linear LNA

Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling

• Non-linear LNA

Conculsion Future Work
Working Process
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MATLAB ModelingPolyphase Filter Model Basic
Principle
Introduction to Bluetooth

• Polyphase filter deals with downconverted signal
  ? direct simulation

• Basic Transformation

Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Conculsion Future Work
Working Process
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MATLAB ModelingPolyphase Filter Model Results
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Conculsion Future Work

• Test signal GFSK

• Polyphase filter

• Center frequency 2 MHz

• Center frequency 2 MHz

Working Process

• Bandwidth 1 MHz

• Bandwidth 1 MHz

• Sampling frequency 10 MHz

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Conclusion and Future Work
Introduction to Bluetooth

• Conclusions

• A low IF receiver architecture is suitable for
  Bluetooth

Radio Receivers Architectures

• The architecture can be implemented in a low
  cost standard CMOS process

Bluetooth Receiver Design

• Behavioral models for RF blocks can be
  implemented in MATLAB

MATLAB Modeling
Conculsion Future Work

• Future work

Working Process

• Building a complete low IF receiver in MATLAB to
  perform more accurate tests

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Working ProcessTime Line
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Conculsion Future Work
Working Process
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Working ProcessAnalysis
Introduction to Bluetooth

• Problems arise from different expectations

• Expectations about working hours

Radio Receivers Architectures

• Supervisor guidance

Bluetooth Receiver Design

• Working style

• RF design field

MATLAB Modeling

• Key points to a good project

Conculsion Future Work

• Discussions

Working Process

• Being good listeners

• Try to learn from each other

• Be self motivated

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THANK YOU ?