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A System Level Design for a Bluetooth Front-end Receiver
Group #789
Supervisor
Angela LinShekar NethiShadi Tawfik
Jan H. Mikkelsen
January 9, 2004
AALBORG UNIVERSITY Department of Communication Technology
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Contents
Conclusion & Future Work
1/50
Unlicensed ISM band (2.4 - 2.4835 GHz)
Bit rate of 1Mbps
Frequency Hopping (1600 Hops/sec)
GFSK Modulation (BT = 0.5, h = 0.28 - 0.35)
Bluetooth is a wireless technology standard intended to be a cable replacement
Introduction to BluetoothDefinition
Short range (10 - 100 m)
Main radio specifications:
Introduction to BluetoothRadio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
2/50
Bluetooth was first originated by Ericsson in 1994, with the main targets being low cost, low power and low form factor
In 1998, the Bluetooth Special Interest Group (SIG) was formed
Currently, average price is around $25
High cost is the main problem delaying the widespread of Bluetooth
Introduction to BluetoothBackground
SIG’s initial target price of a Bluetooth solution $5
Radio part accounts for 80% of the total cost
Introduction to BluetoothRadio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
3/50
The Superheterodyne Receiver
- The Direct Conversion Receiver
Architectures can be classified according to IF used
I/Q Processing Receivers:
Radio Receivers ArchitecturesIntroduction
- The Low IF Receiver
All wireless front-end receivers employ downconversion to an Intermediate Frequency (IF)
Achieve higher Q components
Avoid high power consumption
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
4/50
avoids desensitization of the receiver
reduces linearity requirements for later blocks
Low Noise Amplifier (LNA)
Minimum noise added during amplification
Mixer
Downconverts RF signal to IF (usually IF = RF/10)
Radio Receivers ArchitecturesThe Superheterodyne Receiver – Operation (1)
RF Band select filter
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
5/50
RF image-band-reject filter
IF channel select filter
High Q filter for channel selection
Radio Receivers ArchitecturesThe Superheterodyne Receiver – Operation (2)
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
6/50
Low IF
High IF
Radio Receivers ArchitecturesThe Superheterodyne Receiver – Trade-offs
Razavi-RF Microelectronics
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
7/50
Razavi-RF Microelectronics
Bulky external components
Pros High sensitivity and selectivity successive downconversion
Cons
Radio Receivers ArchitecturesThe Superheterodyne Receiver – Pros & Cons
Cannot be integrated
Expensive
High power consumption
VLO1 VLO2
BPF1 BPF2 BPF3 BPF4
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
8/50
Traditional Downconversion
LO signal contains positive AND negative tones Image rejection before downconversion
Complex Downconversion
LO signal contains positive OR negative tones Image rejection after downconversion
Big Advantage
Introduction to BluetoothIQ Processing Receivers – Theory
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
9/50
Common disadvantage: IQ mismatches
1% gain and phase mismatch reduces IRR to 35dB
Introduction to BluetoothIQ Processing Receivers – Physical Realization
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
10/50
Q
I
Image rejection relaxed small IQ mismatches can be tolerated
Radio Receivers ArchitecturesDirect Conversion Receiver – Operation
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
11/50
DCR can be fully integrated
Radio Receivers ArchitecturesDirect Conversion Receiver – Problems (1)
DC offset
Imperfect isolation between different ports
Distortion of downconverted signal
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
12/50
Static and dynamic DC offsets
Radio Receivers ArchitecturesDirect Conversion Receiver – Problems (2)
Flicker noise major noise contributor in MOS devices
Even order non-linearities
LO leakage in-band interference for other receivers
Razavi-RF Microelectronics
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
13/50
Image rejection Polyphase filter
Radio Receivers ArchitecturesLow IF Receiver – Operation
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
14/50
IQ mismatches are a major concern
Pros Integrability
DC offsets, flicker noise and even order distortion can be easily removed
Combined advantages of Superheterodyne and DCR
Cons
Radio Receivers ArchitecturesLow IF Receiver – Pros & Cons
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
15/50
Performance CostPower
ConsumptionForm Factor
SuperheterodyneHigh High High High
Direct Conversion
Low DC offset
Flicker noise Even order distortion
LO leakage
Low Low Low
Low IFLow
IQ mismatches
Low Low Low
Off-chip Components
Full Integration
Full Integration
A low IF architecture is found suitable for a Bluetooth receiver
Radio Receivers ArchitecturesSummary
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
16/50
Bluetooth Receiver DesignStrategy
Overall Receiver Parameters Calculation
Verification
Block Level Design
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
17/50
Bluetooth Receiver DesignOverall Parameters – Total Noise Figure
Sensitivity (PMIN) = -70 dBm
Bandwidth (B) = 1 MHz
From Bluetooth radio specifications
NFTOT ≤ 33 dB
(BER)MAX = 10-3
Mapping for GFSK (SNRo)MAX = 21 dB
But, Carrier-to-Co-Channel interferenece (C/ICO-CH) = 11 dB
(SNRo)MAX = 11 dB
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
18/50
Two interferers
sine signal, PINT1 = -39 dBm
GFSK modulated signal, PINT2 = -39 dBm
IP3i,TOT ≥ – 21dBm
Desired signal (C) = -70 dBm
IM test requirements
Carrier-to-Co-Channel interferenece (C/ICO-CH) = 11 dB
Bluetooth Receiver DesignOverall Parameters – Linearity
PINT = -39 dBm
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
19/50
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
SFDR = 29.3 dB
Sensitivity level (PMIN) = -70 dBm
Bluetooth Receiver DesignOverall Parameters – SFDR
PINT,MAX = -40.6 dBm
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
20/50
ADC full scale power (PFS,ADC)
ADC Full scale voltage (VFS,ADC) = 0.8 V
ADC Input resistance (Rin,ADC) = 6 k
GTOT,MAX = 57.27 dB
GTOT,MIN = 7.27 dB
Bluetooth Receiver DesignOverall Parameters – AGC Range
Sensitivity level (PMIN) = -70 dBm
Maximum signal level (PMAX) = -20 dBm
PFS,ADC = -12.73 dBm
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
21/50
Bluetooth Receiver DesignOverall Parameters – In-band Filtering Requirements
In-band blockers test specifies a desired signal power level of - 60 dBm
In-band interferers power levels
Overall filtering requirements for in-band interferers
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
22/50
Bluetooth Receiver DesignOverall Parameters – Out-of-band Filtering Requirements
Out-of-band blockers test specifies a desired signal power level of - 67 dBm
Out-of-band interferers power levels
Overall filtering requirements for out-of-band interferers
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
23/50
Main Assumption
Bluetooth Receiver DesignOverall Parameters – Desensitization & Blocking (1)
Overall gain reduction is due to gain reduction in LNA only
FTOT = FLNA+FRx’ – 1
GLNA
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
24/50
Rx’
G’LNA ≥ 15.5 dB
Bluetooth Receiver DesignOverall Parameters – Desensitization & Blocking (2)
Typical values for CMOS LNAs
NFLNA = 4 dB
GLNA = 15 dB
NF from test with minimum desired signal power (PSIGNAL)
IM test: PSIGNAL = - 64 dBm
Out-of-band blockers test: PSIGNAL = - 67 dBm
In-band blockers test: PSIGNAL = - 60 dBm
NF = 3 dB
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
25/50
To obtain 3
Bluetooth Receiver DesignOverall Parameters – Desensitization & Blocking (3)
3 = 0.6 mV-2
Using a typical value for a CMOS LNA IP3i,LNA = - 9 dBm
| B | ≤ 1.37 mV
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
26/50
Referring to a 50 load
Bluetooth Receiver DesignOverall Parameters – Desensitization & Blocking (4)
PBL,MAX = – 17.3 dBm
Referring to a 50 load
BMAX = ±1.37 mV
8 dB attenuation required before LNA
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
27/50
Bluetooth specifications v1.1
Bluetooth Receiver DesignBlock Level Design – Assumptions
Assumptions for unavailable values
RF band select filter attenuation for f = 6 GHz continues constantly for higher frequencies
Polyphase channel select filter for adjacent channels (f ≥ 3 MHz) extracted from a LPF of the same order
RF band select filter is almost perfectly linear IP3i,RF = 30 dBm
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
28/50
Bluetooth Receiver DesignBlock Level Design – Parameters
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
29/50
Bluetooth Receiver DesignSummary and Conclusion
A low cost Bluetooth low IF receiver can be implemented in a standard CMOS process
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
30/50
Building the front-end receiver in a simulation environment is a further step towards more accurate evaluation of performance
MATLAB ModelingAim and Accomplishments
Previous calculations use approximate formulas
Polyphase filter
The group was able to build behavioral models in MATLAB for the following:
LNA (Mixer)
RF band select filter
RF noise
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
31/50
fs ≥ 2fmax
MATLAB ModelingRF Simulation Problem
A computer can only deal with discrete time signals
Sampling of input band-pass signal is required
Still bounded with Nyquist Sampling Theorem
For RF signals, sampling frequency would be very high
Huge number of samples
Computationally inefficient
Therefore, use base-band representation of band-pass signals
Model built to deal with base-band form input
Model gives output in base-band form
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
32/50
is the complex envelope
MATLAB ModelingBase-Band Representation of Band-Pass Signals
Any band-pass (modulated) signal can be written as
Consequently, the band-pass signal can be written as
contains all transmitted information
is a base-band signal
Canonical forms of transmitters and receivers
I(t) and Q(t) are real signals
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
33/50
m(t)
MATLAB ModelingGFSK Signal Generation – Basic Principle
g()Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
34/50
MATLAB ModelingGFSK Signal Generation - Waveforms
PSD of GFSK signal
Bipolar bits stream Gaussian shaped bitsIntroduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
35/50
modulation index = 0.35
BT = 0.5
The PSD of white noise is infinite
Direct simulation of white noise is impossible
Usually, we have a limited bandwidth of interest
MATLAB ModelingRF Noise Model – Basic Principle
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
36/50
MATLAB ModelingRF Noise Model – Algorithm
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
37/50
MATLAB ModelingRF Noise Model – Results
Simulation parameters
Two sided PSD ≡ NF = 3dB
Center frequency = 200 MHz
Noise bandwidth = 100 MHz
Sampling frequency = 1 GHz
Brick wall filter ≈ 8th order Butterworth LPF
2/)1(2/' oTFkN
PSD of generated RF noise
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
38/50
Using partial fractions expansion:
MATLAB ModelingRF Filter Model – Basic Principle (1)
General transfer function of any analog filterIntroduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
39/50
For the RF band-pass signal
MATLAB ModelingRF Filter Model – Basic Principle (2)
Introduction to BluetoothRadio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
Output of RF band-pass filter
Carrier frequency >> bandwidth
Spectrum ≈ zero outside bandwidth
40/50
From previous analysis we can now write
MATLAB ModelingRF Filter Model – Basic Principle (3)
Introduction to BluetoothRadio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
41/50
MATLAB ModelingRF Filter Model – Results
Introduction to BluetoothRadio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
Center frequency = 200 MHz
Bandwidth = 10 MHz
Sampling frequency = 1 GHz
Direct Implementation
First order bandpass filter
Bandwidth = 5 MHz
Sampling frequency = 1 GHz
Low-pass equivalent
First order Butterworth LPF
42/50
Model non-linearity power series expansion
Considering only fundamental component at the output
MATLAB ModelingLNA Model – Basic Principle
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
43/50
MATLAB ModelingLNA Model – Sine Wave Test
0 = 2 = 3 = 0
Test signal: sine wave
Amplitude = 1 V
Perfectly linear LNA
Voltage gain (1) = 15 dBV
Frequency = 5 Hz
Test signal: sine wave
Amplitude = 1 V
Non-linear LNA
Voltage gain (1) = 15 dBV
Frequency = 5 Hz
0 , 2 , 3 ≠ 0
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
44/50
Perfectly linear LNA
Non-linear LNA
MATLAB ModelingLNA Model – GFSK Signal Test
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
45/50
MATLAB ModelingPolyphase Filter Model – Basic Principle
Polyphase filter deals with downconverted signal direct simulation
Basic Transformation
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
46/50
Polyphase filter
MATLAB ModelingPolyphase Filter Model – Results
Test signal: GFSK
Center frequency = 2 MHz Bandwidth = 1 MHz
Sampling frequency = 10 MHz
Bandwidth = 1 MHz
Center frequency = 2 MHz
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
47/50
Conclusion and Future Work
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
48/50
Conclusions:
A low IF receiver architecture is suitable for Bluetooth
The architecture can be implemented in a low cost standard CMOS process
Behavioral models for RF blocks can be implemented in MATLAB
Future work:
Building a complete low IF receiver in MATLAB to perform more accurate tests
Working ProcessTime Line
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
49/50
Problems arise from different expectations
Working ProcessAnalysis
Introduction to Bluetooth
Radio Receivers Architectures
Bluetooth Receiver Design
MATLAB Modeling
Working Process
Conculsion & Future Work
50/50
Expectations about working hours
Working style
Supervisor guidance
RF design field
Key points to a good project
Try to learn from each other
Being good listeners
Discussions
Be self motivated
THANK YOU
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