A System Level Design for a Bluetooth Front-end Receiver Group #789 Supervisor Angela Lin Shekar Nethi Shadi 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 ( GHz)  Bit rate of 1Mbps  Frequency Hopping (1600 Hops/sec)  GFSK Modulation (BT = 0.5, h = )  Bluetooth is a wireless technology standard intended to be a cable replacement Introduction to Bluetooth Definition  Short range ( m)  Main radio specifications: Introduction to Bluetooth Radio 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 Bluetooth Background  SIG’s initial target price of a Bluetooth solution $5  Radio part accounts for 80% of the total cost Introduction to Bluetooth Radio 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 Architectures Introduction - 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 Architectures The 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 Architectures The 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 Architectures The 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 Architectures The Superheterodyne Receiver – Pros & Cons  Cannot be integrated  Expensive  High power consumption V LO1 V LO2 BPF1BPF2BPF3BPF4 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 Bluetooth IQ 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 Bluetooth IQ 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 Architectures Direct 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 Architectures Direct 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 Architectures Direct 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 Architectures Low 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 Architectures Low IF Receiver – Pros & Cons Introduction to Bluetooth Radio Receivers Architectures Bluetooth Receiver Design MATLAB Modeling Working Process Conculsion & Future Work 15/50

PerformanceCost Power Consumption Form Factor Superheterodyne High Direct Conversion Low  DC offset  Flicker noise  Even order distortion  LO leakage Low Low IF Low  IQ mismatches Low Off-chip Components Full Integration A low IF architecture is found suitable for a Bluetooth receiver Radio Receivers Architectures Summary Introduction to Bluetooth Radio Receivers Architectures Bluetooth Receiver Design MATLAB Modeling Working Process Conculsion & Future Work 16/50

Bluetooth Receiver Design Strategy 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 Design Overall Parameters – Total Noise Figure  Sensitivity (P MIN ) = -70 dBm  Bandwidth (B) = 1 MHz  From Bluetooth radio specifications NF TOT ≤ 33 dB  (BER) MAX =  Mapping for GFSK  (SNR o ) MAX = 21 dB  But, Carrier-to-Co-Channel interferenece (C/I CO-CH ) = 11 dB (SNR o ) 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, P INT1 = -39 dBm  GFSK modulated signal, P INT2 = -39 dBm IP 3i,TOT ≥ – 21dBm  Desired signal (C) = -70 dBm  IM test requirements  Carrier-to-Co-Channel interferenece (C/I CO-CH ) = 11 dB Bluetooth Receiver Design Overall Parameters – Linearity P INT = -39 dBm Introduction to Bluetooth Radio Receivers Architectures Bluetooth Receiver Design MATLAB Modeling Working Process Conculsion & Future Work 19/50

 Maximum interference power level (P INT,MAX )  Follows from definition of SFDR  Total noise figure (F TOT ) = 32 dB  Total 3rd order Intercept Point (IP 3iTOT ) = -20 dBm SFDR = 29.3 dB  Sensitivity level (P MIN ) = -70 dBm Bluetooth Receiver Design Overall Parameters – SFDR P INT,MAX = dBm Introduction to Bluetooth Radio Receivers Architectures Bluetooth Receiver Design MATLAB Modeling Working Process Conculsion & Future Work 20/50

 ADC full scale power (P FS,ADC )  ADC Full scale voltage (V FS,ADC ) = 0.8 V  ADC Input resistance (R in,ADC ) = 6 k  G TOT,MAX = dB G TOT,MIN = 7.27 dB Bluetooth Receiver Design Overall Parameters – AGC Range  Sensitivity level (P MIN ) = -70 dBm  Maximum signal level (P MAX ) = -20 dBm P FS,ADC = dBm Introduction to Bluetooth Radio Receivers Architectures Bluetooth Receiver Design MATLAB Modeling Working Process Conculsion & Future Work 21/50

Bluetooth Receiver Design Overall 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 Design Overall 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 Design Overall Parameters – Desensitization & Blocking (1)  Overall gain reduction is due to gain reduction in LNA only 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 Design Overall Parameters – Desensitization & Blocking (2)  Typical values for CMOS LNAs  NF LNA = 4 dB  G LNA = 15 dB   NF from test with minimum desired signal power (P SIGNAL )  IM test: P SIGNAL = - 64 dBm  Out-of-band blockers test: P SIGNAL = - 67 dBm  In-band blockers test: P SIGNAL = - 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 Design Overall Parameters – Desensitization & Blocking (3)   3 = 0.6 mV -2  Using a typical value for a CMOS LNA  IP 3i,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 Design Overall Parameters – Desensitization & Blocking (4) P BL,MAX = – 17.3 dBm  Referring to a 50  load B MAX = ±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 Design Block 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  IP 3i,RF = 30 dBm Introduction to Bluetooth Radio Receivers Architectures Bluetooth Receiver Design MATLAB Modeling Working Process Conculsion & Future Work 28/50

Bluetooth Receiver Design Block Level Design – Parameters Introduction to Bluetooth Radio Receivers Architectures Bluetooth Receiver Design MATLAB Modeling Working Process Conculsion & Future Work 29/50

Bluetooth Receiver Design Summary 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 Modeling Aim 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

f s ≥ 2f max MATLAB Modeling RF 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 Modeling Base-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 Modeling GFSK Signal Generation – Basic Principle g(  ) Introduction to Bluetooth Radio Receivers Architectures Bluetooth Receiver Design MATLAB Modeling Working Process Conculsion & Future Work 34/50

MATLAB Modeling GFSK Signal Generation - Waveforms PSD of GFSK signal Bipolar bits stream Gaussian shaped bits Introduction 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 Modeling RF Noise Model – Basic Principle Introduction to Bluetooth Radio Receivers Architectures Bluetooth Receiver Design MATLAB Modeling Working Process Conculsion & Future Work 36/50

MATLAB Modeling RF Noise Model – Algorithm Introduction to Bluetooth Radio Receivers Architectures Bluetooth Receiver Design MATLAB Modeling Working Process Conculsion & Future Work 37/50

MATLAB Modeling RF 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 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 Modeling RF Filter Model – Basic Principle (1)  General transfer function of any analog filter Introduction to Bluetooth Radio Receivers Architectures Bluetooth Receiver Design MATLAB Modeling Working Process Conculsion & Future Work 39/50

 For the RF band-pass signal MATLAB Modeling RF Filter Model – Basic Principle (2) Introduction to Bluetooth Radio 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 Modeling RF Filter Model – Basic Principle (3) Introduction to Bluetooth Radio Receivers Architectures Bluetooth Receiver Design MATLAB Modeling Working Process Conculsion & Future Work 41/50

MATLAB Modeling RF Filter Model – Results Introduction to Bluetooth Radio 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 Modeling LNA Model – Basic Principle Introduction to Bluetooth Radio Receivers Architectures Bluetooth Receiver Design MATLAB Modeling Working Process Conculsion & Future Work 43/50

MATLAB Modeling LNA 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 Modeling LNA Model – GFSK Signal Test Introduction to Bluetooth Radio Receivers Architectures Bluetooth Receiver Design MATLAB Modeling Working Process Conculsion & Future Work 45/50

MATLAB Modeling Polyphase 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 Modeling Polyphase 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 Process Time 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 Process Analysis 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

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