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Energy Efficient Wireless Transmitters: Polar and Direct-Digital Modulation Architectures Jason Thaine Stauth Seth R. Sanders Electrical Engineering and Computer Sciences University of California at Berkeley Technical Report No. UCB/EECS-2009-22 http://www.eecs.berkeley.edu/Pubs/TechRpts/2009/EECS-2009-22.html February 4, 2009

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Energy Efficient Wireless Transmitters: Polar andDirect-Digital Modulation Architectures

Jason Thaine StauthSeth R. Sanders

Electrical Engineering and Computer SciencesUniversity of California at Berkeley

Technical Report No. UCB/EECS-2009-22

http://www.eecs.berkeley.edu/Pubs/TechRpts/2009/EECS-2009-22.html

February 4, 2009

Copyright 2009, by the author(s).All rights reserved.

Permission to make digital or hard copies of all or part of this work forpersonal or classroom use is granted without fee provided that copies arenot made or distributed for profit or commercial advantage and that copiesbear this notice and the full citation on the first page. To copy otherwise, torepublish, to post on servers or to redistribute to lists, requires prior specificpermission.

Energy Efficient Wireless Transmitters: Polar and Direct-Digital Modulation Architectures

by

Jason Thaine Stauth

B.A. (Colby College) 1999 B.E. (Dartmouth College) 2000

M.S. (University of California, Berkeley) 2006

A dissertation submitted in partial satisfaction of the

requirements for the degree of

Doctor of Philosophy

in

Engineering – Electrical Engineering and Computer Sciences

in the

GRADUATE DIVISION

of the

UNIVERSITY OF CALIFORNIA, BERKELEY

Committee in Charge Professor Seth R. Sanders, Chair

Professor Ali M. Niknejad Professor Paul K. Wright

Fall 2008

The dissertation of Jason Thaine Stauth is approved:

Chair Date Date Date

University of California, Berkeley

Fall 2008

1

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Contents i

Contents

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Contents ii

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Contents iii

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List of Figures i

Figure 1. CMOS ft and fmax (performance analog/mixed signal devices), International

technology roadmap for semiconductors (ITRS) [1]. ................................................. 1 2''&* .......................................... 5 2<*,+,,A,* ......................... 6 Figure 4. Complex constellation diagram and trajectory for (a) constant envelope

modulation and (b) π/4DQPSK, which uses amplitude modulation for the same constellation points as (a)............................................................................................ 7

2=*&,+,&* .... 9 2C*?"* .............................. 10 Figure 7. Transmitter output spectrum showing spectral regrowth. ................................. 11 Figure 8. Direct-conversion Cartesian transmitter schematic diagram............................. 12 Figure 9. Effects of I/Q and quadrature LO gain and phase imbalance........................... 13 Figure 10. Kahn envelope elimination and restoration (EER) transmitter architecture

[19]............................................................................................................................ 14 Figure 11. General representation of the polar transmitter architecture. .........................15 Figure 12. Phase-path circuit architectures: representative techniques ........................... 17 Figure 13. Time- and frequency-domain waveform comparison: Cartesian and polar

systems. Baseband I/Q waveform with two-tone zero mean sinusoid..................... 18 Figure 14. Distortion mechanisms in polar systems: gain and phase vs supply voltage. 20 Figure 15. Common-source amplifier circuit showing mechanisms for AM-AM, AM-PM

distortion ................................................................................................................... 20 Figure 16. Representative probability distribution function (PDF) for CDMA

applications [31]........................................................................................................ 23 Figure 17. Power amplifier block diagram and schematic for a CMOS common-source

PA ............................................................................................................................. 24 Figure 18. Class-AB PA voltage and current waveforms................................................ 27 Figure 19. Switching PA schematic and time-domain waveforms.................................. 29 Figure 20. Class E PA schematic..................................................................................... 31 Figure 21. Power amplifier efficiency in power backoff overlaid with a representative

PDF ........................................................................................................................... 33 Figure 22. Efficiency versus output power: i.) conventional class B PA, ii.) class B PA

with dynamic supply regulation, iii.) class B PA, dynamic VDD with realistic loss mechanisms............................................................................................................... 38

Figure 23. Envelope tracking transmitter using traditional Cartesian architecture with a dynamic supply modulator to improve average efficiency....................................... 39

Figure 24. Time domain waveforms for VDS RF carrier waveform and power loss: fixed VDD and dynamic VDD. ............................................................................................. 40

Figure 25. Time domain envelope tracking waveforms .................................................. 40 Figure 26. Dynamic supply polar modulation system ..................................................... 42

List of Figures ii

Figure 27. Linear regulator topologies............................................................................. 45 Figure 28. Generic voltage-mode switching regulator block diagram ............................ 46 Figure 29. DC-DC conversion cells: buck, boost, and inverting buck-boost .................. 46 Figure 30. Typical battery discharge curve and power converter mode of operation ..... 46 Figure 31. Pulse-width-modulation (PWM) waveform................................................... 48 Figure 32. Fundamental and harmonics of pulse-width modulated waveform versus duty

cycle, normalized to fundamental peak. ................................................................... 48 Figure 33. Contour representation of average efficiency of the switching regulator vs

gate width.................................................................................................................. 51 Figure 34. Hybrid voltage regulator schematic: a.) Series hybrid, b.) Parallel hybrid .... 52 Figure 35. Effect of supply noise on RF amplifier output spectrum ............................... 55 Figure 36. Noise sources in RF systems .......................................................................... 59 Figure 37. Self-induced power supply noise from high supply impedance at the envelope

frequency................................................................................................................... 66 Figure 38. CMOS inductor-degenerated common source amplifier showing nonlinear

elements. ................................................................................................................... 68 Figure 39. MOSFET drain current versus gate-source and drain-source voltage.

Nonlinearities are extracted around the dc operating point highlighted in the figure.................................................................................................................................... 68

Figure 40. ! .................................................................. 77 Figure 41. D, ..................................................................................... 77 Figure 42. ,!,*

6*8G6*8*......................................................................................................... 78 Figure 43. ,

+ ........................................................................................................................ 79 Figure 44. ,,!,+

*....................................................................................................................... 80 Figure 45. Mea&+:"75 .................. 82 Figure 46. "&+*8975 .................... 83 Figure 47. ))&3'?!'+

,!&*............................................ 85 28 *!+,..................... 88 Figure 49. Model for parallel hybrid switching-linear regulator ..................................... 88 Figure 50. Two different time-domain envelope signals that share the same power

spectrum: one with peak-average power ratio (PAPR) of 10.1dB, and another with PAPR or 5.2dB.......................................................................................................... 92

2=6*,+ .................................................. 94 2=*&&#"! ...................... 97 2=<*&#"'5(

H6# ...................................................................................................... 98 2=8*&&!#"+'

+0=810=:1............................................................................................ 102 2==*&5&/!:= "#' 102

List of Figures iii

2=C*. ....................................................................................... 107 2=E*#&&+,!#"

.............................................................................................................. 108 2= *#&&&#"

*............................................................................................................. 108 2=:*+! .................. 110 2C*/!:= "#' *66D#F........................................ 110 2C6*;+05 DCSR ii /* 1&+

................................................................................................................................. 112 Figure 62. Hybrid regulator model including output capacitance ................................. 113 Figure 63. Hybrid regulator with load capacitance: efficiency versus normalized time

constant (simulation vs theory)............................................................................... 117 Figure 64. Conventional cellular phone block diagram: digital application processor,

DSP, Audio, Power management; Radio is still largely analog ............................. 119 Figure 65. Proposed digital polar architecture............................................................... 119 Figure 66. Traditional Cartesian transmitter architecture: lowpass data conversion

followed by upconversion mixers........................................................................... 121 Figure 67. π/4DQPSK and 8PSK constellation diagrams ............................................. 121 Figure 68. Input-output transfer characteristics for a 3-bit D-A converter.................... 123 Figure 69. Comparison of continuous and quantized signal levels showing error between

±½ LSB................................................................................................................... 124 Figure 70. Frequency-domain representation of discrete-time sampling process ......... 125 Figure 71. Time- and frequency-domain characteristics: zero order hold (ZOH)

reconstruction.......................................................................................................... 127 Figure 72. Signal and noise before and after sampling.................................................. 128 Figure 73. Quantization noise spectral density: a.) Nyquist-rate sampling, b.)

Oversampling.......................................................................................................... 129 Figure 74. Signal and quantization noise with noise shaping........................................ 130 Figure 75. Linear model of the noise-shaping process: quantization noise appears as a

disturbance .............................................................................................................. 131 Figure 76. Noise-shaping data conversion blocks: a.) Error-feedback structure, b.) first-

order sigma-delta modulator ................................................................................... 131 Figure 77. RF DAC: quantization of RF carrier amplitude ........................................... 135 Figure 78. Frequency-domain RF DAC with sampling images .................................... 135 Figure 79. RF DAC example implementation: binary weighted class-A amplifier stages

(current summing), as in [105]................................................................................ 136

Figure 80. Bandpass Σ∆ modulator with center frequency at 4

sf................................. 137

Figure 81. Direct digital modulation: transmitter operating as a D-A converter.......... 138 Figure 82. Cartesian RF data converter ......................................................................... 139 Figure 83. Polar RF data conversion: RF amplitude DAC with phase-modulated clock

signal ....................................................................................................................... 140 Figure 84. Upsampling to reduce spectral images, process in Pozsgay [106]............... 142

List of Figures iv

Figure 85. Digital polar modulation architecture........................................................... 144 Figure 86. Candidate polar architectures ....................................................................... 146 Figure 87. Time and frequency domain examples for full- and half-amplitude modulation

................................................................................................................................. 148 Figure 88. Pulse-density modulator block ..................................................................... 150 Figure 89. 1-Bit polarity feedforward to reduce power from rapid phase transitions... 152 Figure 90. Constellation diagram for 8DPSK with feedforward phase transition:

4

5

4

ππ → .................................................................................................................. 152

Figure 91. Polarity bit significantly reduces high frequency power in the RF clock signal waveform by smoothing phase transitions near origin ........................................... 153

Figure 92. Effect of polarity on amplitude quantization - ∆Σ process remains linear near zero.......................................................................................................................... 155

Figure 93. Error-feedback digital ∆Σ modulator ........................................................... 156 Figure 94. Example baseband 3rd order ∆Σ modulator spectrum with a notch at ±12MHz,

123 5.25.2)( −−− −+−= zzzzG ................................................................................. 157

Figure 95. ∆Σ Modulator: 1st, 2nd, 3rd order comparison, all zeros at 2.4GHz............... 158 Figure 96. Complementary class D PA schematic......................................................... 159 Figure 97. Schematic representation of class-D power amplifier with cascode output

stage ........................................................................................................................ 162 Figure 98. Current recycling scheme: excess current from PMOS drive stage used by

digital processing .................................................................................................... 163 Figure 99. Class-D PA output stage NMOS layout: gate and cascode share diffusion

region to reduce junction capacitance..................................................................... 163 Figure 100. Level shift and deadtime control ................................................................ 165 Figure 101. System-level implementation of Bluetooth transmitter.............................. 166 Figure 102. Die Photo of CMOS class D PA and RF pulse-density modulator circuits

................................................................................................................................. 166 Figure 103. Block diagram of the experimental setup................................................... 167 Figure 104. Time-domain waveforms at transmitter output .......................................... 168 Figure 105. Efficiency and output power vs supply voltage ......................................... 169 Figure 106. Efficiency and linearity&! ................................................... 169 Figure 107. Power of digital processing (pulse-density modulation, clock recovery,

sampling and synchronization) with and without current recycling scheme. Measured as power drawn from Vhalf regulator .................................................... 170

Figure 108. Measured constellation diagrams ............................................................... 172 Figure 109. Efficiency and output power vs supply voltage ......................................... 173

List of Tables i

Table I. Comparison of power amplifier performance .................................................... 32 Table II. Average efficiency calculations for the curves in Figure 21 *constant bias

current **variable bias current.................................................................................. 33 ,///*........................................................................................................................... 105 Table IV. COMPARISON OF FOMS OF VARIOUS AMPLIFIER CLASSES (DATA

FOR CLASS E, F-1, F2,3,4,5 FROM [34])............................................................ 161

1

Chapter 1 Introduction

Figure 1. CMOS ft and fmax (performance analog/mixed signal devices), International technology roadmap

for semiconductors (ITRS) [1].

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Chapter 2 Transmitter Fundamentals

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Transmitter Fundamentals 6

and Q(t) baseband signals and upconverted using quadrature local

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Transmitter Fundamentals 7

Figure 4. Complex constellation diagram and trajectory for (a) constant envelope modulation and (b)

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Transmitter Fundamentals 9

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Transmitter Fundamentals 10

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Transmitter Fundamentals 11

Figure 7. Transmitter output spectrum showing spectral regrowth.

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Transmitter Fundamentals 12

Figure 8. Direct-conversion Cartesian transmitter schematic diagram.

+ +

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Transmitter Fundamentals 13

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Transmitter Fundamentals 14

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Transmitter Fundamentals 15

Figure 11. General representation of the polar transmitter architecture.

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Transmitter Fundamentals 16

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Transmitter Fundamentals 17

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2.3.2 Issues in Polar Systems

Transmitter Fundamentals 18

Figure 13. Time- and frequency-domain waveform comparison: Cartesian and polar systems. Baseband

I/Q waveform with two-tone zero mean sinusoid.

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Transmitter Fundamentals 19

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Transmitter Fundamentals 20

Figure 14. Distortion mechanisms in polar systems: gain and phase vs supply voltage

Figure 15. Common-source amplifier circuit showing mechanisms for AM-AM, AM-PM distortion

#-*/'#

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Transmitter Fundamentals 21

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Transmitter Fundamentals 22

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2.4 Power and Energy Efficiency: Polar and Cartesian Architectures

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Transmitter Fundamentals 23

2.4.1 Typical Use Patterns: Probability Density Function (PDF) of Transmit Power

0

0.5

1

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2

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3

3.5

-50 -40 -30 -20 -10 0 10 20 30

Output Power (dBm)

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Transmitter Fundamentals 24

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+0#1&

)2*#

Transmitter Fundamentals 25

, + ,( * ;

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,+*

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+( '

Transmitter Fundamentals 26

'#3+.

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/ # &

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+( D! +(

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2.5.2 Linear Power Amplifiers: Class AB

Transmitter Fundamentals 27

Imax

Vdsat

VDS

IDS

180o<Φ<360o

V

DS (V

) ; I

DS

(A)

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+',

&&''+(

* #' #' ' + '

*

' ''2!

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#*

Figure 18+&+&##* &

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Figure 18*+(+

Transmitter Fundamentals 28

&.*'

&',+<C0#16 0 1* & + + &' DSDSloss VIP ⋅= *#+

ply

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P

sup

=η , 0:1

+% +& % ++ * +3&#',

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odrain V

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061

+Φ 26 ' ov

&&'η#I6J*###

* => # +0360=Φ DDo Vv =ˆ * . E *=> + 0180=Φ

Transmitter Fundamentals 29

DDo Vv =ˆ *061#*/'

'Φ '5'6>0'

+ 5 Φ 51* / ,

, ,

!& +& & &

*#'061'+

$+&'+

, * + & .

+*

Figure 19. Switching PA schematic and time-domain waveforms

2.5.3 Switching Power Amplifiers: Class E example

IDS

V

DS (V

) ; I

DS

(A)

VDS

VGATE VDD

a.) Switching PA schematic

b.) General VDS waveforms

c.) Class E VDS - IDS waveforms

Constrained by output network

VDS (V)

Constrained by switch

time

time

Transmitter Fundamentals 30

+ + &

,&&+*&&&

MLML

* &+&'+

&++6> * %

+#!#

&,&*

Figure 1901+";+#*&

#&'.&&

,+*+Figure 190,1'+&M'L

! & 5* & M'L !

& , +(*

+( 5 + , & & +&* /' &&+!& 5'

& 5 & + 0N?1* + ,

5+&&*

Transmitter Fundamentals 31

Figure 20. Class E PA schematic

# & , 5 & + !& $ *,

)2+' I='86'8J'+&' I86'8<J* +

Figure 1901'!&.5+&*

Figure 20+";#'I8J*&,&

, &* ! &&*

+('

+IE'6'86J*+(!

&+&-+

Figure 19 01* ! +(+ +

,&5+5&&

+*/,('I86J'

+.&+(

c

L

c

L

w

R

w

RL 1525.1

16

)4( 2

≈−= ππ, 0661

LcLc RwRwC

11836.0

1

)4(

821 ≈

+=

ππ, 061

L

DD

L

DDL R

V

R

VP

22

25768.0

4

8 ≈+

, 06<1

Transmitter Fundamentals 32

+ cw 3''' Figure 20' +&*

# +,( + ! & .

&, ,* / ' DDDS VV ⋅≈ 56.3max *

, , & , !& ,(+* / ";

. ,(+ , - &

&* ( & + , +

. + & &

&*

class A class B class E

Peak Efficiency 50% 78.50% 100%

Supply constrained output power (W) (VDD=1V, RL=1Ω) 500mW 500mW 577mW

Breakdown constrained output power (W) (VDSmax=2V, RL=1Ω) 500mW 500mW 182mW

Table I. Comparison of power amplifier performance

Table I*+##* 2

&' , +

#*7+&'&,(+&&'

+ + ' +* ,(+ , + & 5!

!* &(&

5 ' + &

Transmitter Fundamentals 33

( !< & "; IEJ*

7+&' , "; ! + ( &

3,'+,-!$&

+(&*

2.5.4 Efficiency in Power Backoff #*8*6'.+',

,- + 5 , ,,

*#&,

,3&+*

0%

1%

2%

3%

4%

5%

-60 -50 -40 -30 -20 -10 0dB(Pout) - dB(Pmax)

Pro

bab

ility

.

0%

20%

40%

60%

80%

100%

Eff

icie

ncy

PDF

class E

class B

class A

Figure 21. Power amplifier efficiency in power backoff overlaid with a representative PDF

18.21%14.46%0.78%* / 9.2%**

Average Efficiency:

Class EClass BClass APA Class:

18.21%14.46%0.78%* / 9.2%**

Average Efficiency:

Class EClass BClass APA Class:

Table II. Average efficiency calculations for the curves in Figure 21

*constant bias current **variable bias current

Transmitter Fundamentals 34

Figure 21 + #' '#

+*+5.+,

&* & + &

,&+&0$

. 1* # & 2

&+&*/.'+

,+(+* # + &'+

6>*

. 0 1 &', 2*

& & Figure 21 +

Table II* #& +( *

2'&&

(*2#+,'

*Table II+

*/',(&

,+*

++(,(&

3 + , & & *

'++!+ &

& + * + + &

Transmitter Fundamentals 35

( # ' & &

,* + & +( 8 = + ,

, * C+

, & & ,

+*

36

Chapter 3 Power Management for RF Transmitters and Polar Systems

+ +

* '+,-

I6'88J* 7

& * + &

,,,'3&,

* 7' + , &,

.+&

I8=' 8CJ* +

+ ' + 0#1'+ ,

'&*

+ &

+ 3* + , +

','+,

# &* + & '

+ ! &*

+'

Power Management for RF Transmitters and Polar Systems

37

+&+-,&'

.*

3.1 Motivation: Efficiency

#'++++

, 3 ,, *

&+&,,,+(+&'

, 2*

'+#+.&+&

,&&'&

,,(*3#

*/*<+,

+# 3

@)'+ Figure 10* 7+&', +

,&*

Power Management for RF Transmitters and Polar Systems

38

0%

1%

2%

3%

4%

-60 -50 -40 -30 -20 -10 0dB(Pmax) - dB(Pout)

Eff

icie

ncy

0%

10%

20%

30%

40%50%

60%

70%

80%

90%P

rob

abili

ty

PDF

ii.)

iii.) i.)

Figure 22. Efficiency versus output power: i.) conventional class B PA, ii.) class B PA with dynamic

supply regulation, iii.) class B PA, dynamic VDD with realistic loss mechanisms.

Figure 22 #+ +

*+0.!.15(+'+

#&.πA8'E *=>* #+ '

+&)2*&

+&'?'.*&+& #+

*/!&'+,

0**

πA8 4@ Figure 4' 4#"'#@'

@1' & +

&*

& *1 ,

$+,

Power Management for RF Transmitters and Polar Systems

39

* ;&'Figure 22+&

+'++'+#

(, 2*2&'&C*=>

68*8>&*8>&*

&,3&+

&*

3.1.1 Envelope Tracking System

22 QI +

Figure 23. Envelope tracking transmitter using traditional Cartesian architecture with a dynamic supply

modulator to improve average efficiency.

Power Management for RF Transmitters and Polar Systems

40

Figure 24. Time domain waveforms for VDS RF carrier waveform and power loss: fixed VDD and dynamic VDD.

Figure 25. Time domain envelope tracking waveforms

VDD

VDS

PLOSS

time (s)

VDD

VDS

PLOSS

time (s)

a.) Fixed VDD, low amplitude class B b.) Dynamic VDD, low amplitude class B

Power Management for RF Transmitters and Polar Systems

41

&( &&&& #' (

&' & * 3

+ + Figure 23*

&+&+&&

&*/&'+,&

&&+&$+'

+Figure 24*/&+*/

+ & !

&*/&-&&'

+ & & ( * ".+ &

&-&&

+ # * / . # & +(

' &

, I ' <J* , ,,'

&)2#I6J*

Figure 25+.+&&(

* Figure 25 01+)2&+&

. *<** . ? 6*?' + .' *= 6*=O* Figure 25 01 + . ?* 7'? )2&?5+#$&";&+

Power Management for RF Transmitters and Polar Systems

42

, * Figure 25 01 + )2?+&* )2 + +?' , , & . ,& ?&*++.?',+,&*.& ( +(7* I6J'

* IJ' * I8EJ I8 !=J* ;

. # & * / I J'

*&(;2 "+&,+

"75&,+6:>! >*

3.1.2 Dynamic Supply Polar Modulation

22 QI +

Figure 26. Dynamic supply polar modulation system

, + +

* # *<*6' +#& ,+

)2+&+

Power Management for RF Transmitters and Polar Systems

43

( ))(cos ttwVv cDDRFO φα +⋅=− ' 0681

+ RFOv − )2+&' )(tφ !&)2'

α ,+ *Mα L ',

#'&'IEJ*

+2C*

,,' ( @ 3

26*&!#*

& +

& * # *<*'

*/

#"!#" #"!" '

,+?"*&

,++&*

& & , #

#0,1* "

+(3+& 5+#'

,!&*+

-&#I6<'<'8J*

&&,*

Power Management for RF Transmitters and Polar Systems

44

#,&&+&

&* %( ' & 6> *

+ & , (

+ ,(' + & *1 2 * 7+&'

+ , ,

,+ * ,+ ,+

& + 3* F +

#I<J*

*

+ + & I6J I=6J'

&#+6<"75+&*

Power Management for RF Transmitters and Polar Systems

45

-

+ Av VDDLoad

Vin Vout -

+Av VDD

LoadVin Vout

a.) Generic linear regulator b.) CMOS linear regulator

Figure 27. Linear regulator topologies# & ' ' &

,* +Figure 27' &&

& .&* / ";. Figure 27 0,1'

";&&*

/ "; & .

.&* &

,+'+''

I=!=8J*&&

,+$,

*7+&'++'

DD

outLR V

V=η ' 06=1

Power Management for RF Transmitters and Polar Systems

46

+ LRη *(

& + & *

3.2.2 Switching Voltage Regulators

Figure 28. Generic voltage-mode switching regulator block diagram

Figure 29. DC-DC conversion cells: buck, boost, and inverting buck-boost

Figure 30. Typical battery discharge curve and power converter mode of operation

2

3

4

0 1 2 3 4 5

TIME (H)

CE

LL

VO

LT

AG

E (

V)

Li-ionbuck

boost

Li-ion

Vout

Power Management for RF Transmitters and Polar Systems

47

+,,+'

, 3 . & & *

+Figure 28+'&'

&& &*#

-+&&*

, + &

&!*.+Figure

29 + 0,(1' 0,1' + 0,(!,1

&* ;0,(1'

+ ! & I==!=EJ*

*(,(!,&

,* (&

+ +' ( ' , 6>

* (!, & , & &'

, ,++ &, &* +

Figure 30',&,&3&',(!+

& +* / ,& , &' ,! *

Power Management for RF Transmitters and Polar Systems

48

Figure 31. Pulse-width-modulation (PWM) waveform

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.2

0.4

0.6

0.8

1

Duty Cycle

No

rma

lize

d R

ipp

le

Ripple Fundamental

Second Harmonic

Third Harmonic

Small Ripple Approximation

Figure 32. Fundamental and harmonics of pulse-width modulated waveform versus duty cycle, normalized

to fundamental peak.

"- ,+ + '

&'+

* ! & ,

, * +

. +

I= '=:J'&(,+I<CJ*

+

+ 3* + & !+

0"1 &* +Figure 31'+

DT

T T/2

D=duty cycle

Power Management for RF Transmitters and Polar Systems

49

"' + +&

+&* "' + *

&+35

,& ! &* 7+&' +

+& &* 2!

"+&:

⋅⋅−⋅+= ∑∞

=1

)cos()sin()1(2)(

n

swn

in n

tnwDnDVtV

ππ

, (16)

+.&"' sww +3'

' ,*

&+2<*

,+ . , +

&* +,

,+,.+)2+

*+(+,&

0?;1'**6',I=J*

, +'+&!

$&+#*,

&.+,,8*

+

* 5

Power Management for RF Transmitters and Polar Systems

50

+ +

*9',&(,+

'+,&./A4,+I6<J*

' + 3

+* 9'+3+

+ & * ) I<CJI8=J,+

+ 5 + & 0+ .

1+

fswERIP GOrms ⋅⋅≈ 2min 2 ' 06E1

+ rmsI swf +3*7' GE

&+'O

O GR

1=

& +* 2 "; + &

3,+

)(1

minondsTDDO VVVCox

lG −−−= µ , (18)

2min DDG CoxVlE = , and (19)

swG

Ormsopt fE

RIW

⋅⋅

=2

(20)

+ minl '&' µ ,'Cox .' DDV

Power Management for RF Transmitters and Polar Systems

51

&' ondsV − &!&+*/(20)'

optW +&+*/+

' . &

&*

5455

5556

56

56

57

57

57

57

57

58

58

58

58

58

59

59

59

59

59

60

60

606061

NMOS Width (mm)

PM

OS

Wid

th (m

m)

1 2 3 4 51

2

3

4

5

Power Converter Average Efficiency Contours

Figure 33. Contour representation of average efficiency of the switching regulator vs gate width

3 06E1(20)&,5+

'+ rmsI * / '&

*/' 2,

5+*)I<CJ,+&

5 + .& *

Power Management for RF Transmitters and Polar Systems

52

5 + Figure 33 ="75 ( ,+

6* . + *6 ";* 7' & +

+&F";";+&*

2#&5&.

&* #& + +&C>&

& ++ ,+ ( +* & 5

,0";&15

(+ &* . , ,

'(*

3.2.3 Hybrid Voltage Regulators: Introduction

Figure 34. Hybrid voltage regulator schematic: a.) Series hybrid, b.) Parallel hybrid

#',&,+

* 7, &,, +

'' +'*

Power Management for RF Transmitters and Polar Systems

53

+!,

!,'+Figure 34*

, + & +! 0D ;1

'+&*+-

&+ & $

++!*"5

&&++D ;*/

' +!!-! 0))1

+*

'&&&*

,+,,(&

&,&&*#

,+'&#&*/

'#&,'

+(!!&+0#)1'ICJ*

!,&++

*/.'&+'&

&*+'

&'*

/ ' + 0& 1

+ 0 1* &

Power Management for RF Transmitters and Polar Systems

54

,-&' + * /

.'+ &

I 'C6'CJ*&,

* +

30 1*/.3

+!ICJ*/='

+,5!

,,!*)+,

! & +-,

&'&' &IC<'C8J*/

' ( = +

*;+'+++

&(*

55

Chapter 4 Power Supply Noise Analysis for RF Amplifiers

Figure 35. Effect of supply noise on RF amplifier output spectrum

/'++-)2

* & +3

,)2*#&'(

+ (+ , +

* ?! 0?;1 &

, & 3! 0&1

, & & I=J* ++

+ * 2 0681' # &

,++)2*

P(dB) P(dB)P(dB)

Power Supply Noise Analysis for RF Amplifiers 56

# ' . , + ?; # ,

+ & &!&

*

7+,-

)2* D# &&'

* 7+&'

& *

"++.+)2

*.,&(

3 * 2<= +

3.+)2$)2

,'!,')2-

,I:J*

+(I:JI<J-

+(";!'+,";

#'#'#*+(&

('(++,

&* ? +

. * . !

, ! & 3

*',

Power Supply Noise Analysis for RF Amplifiers 57

IC=J'5ICCJ',,,3I6=J*

,. /"<&<', .

*

+ , ";

+0#1*

8*<!+

* & ? &+

.!)2+* 8*8

, , 5

"; * 8*= ?

,* 8*C

. * + ! 9

:"75,+*8975*

/.&'? +

&*7,071

3 , ,' +

##& 0# 1!!01

ICEJ*,3&

+&.'&,

Power Supply Noise Analysis for RF Amplifiers 58

3 3 (+ * 7'

+ , * ( ,

,,+

- + 0#)1' + + !

+&* / ' ? 0?1 &

&

• ? , +(+ 0& +(1*

• ? ( & . 3 ,& & '+&*

• &0+,+!+&1

• ?+!,,,&' IC J' + 3 +*

Power Supply Noise Analysis for RF Amplifiers 59

RF OutputDigital Block

on/off chip magnetic coupling

noise currentdigital current noise

RF AmplifierVDDBandgap reference+PWMVoltage Regulatorsupply ripple

+thermal noise on/off chip electrostatic coupling woP(dB)

Power Supply Noise

RF BlockInterconnect

Figure 36. Noise sources in RF systems

? & . ,

! & * + Figure

36',++

' ,+ , '

,(

+ IC:J* , - ,

&I6'8E'=6J*/6>

6> & &* '

+(!*/'?

& + )2

*

/ +

Power Supply Noise Analysis for RF Amplifiers 60

3&)2*,

+3', &* +3'

. ,, !,!,

3* /'?,

& + 0#1 +

- 0))1* , .5

+&&'+

?"#)3*

!

+.+)2,&,

* +

&

*#3,+(

,* /, +3

5 * D+ 3

, , ,

,*

# ! ,

* / )2 &'

,5+++

Power Supply Noise Analysis for RF Amplifiers 61

I6'EJ*,&

' , ,+ & &

& * , +

+,&*/'

, 5 &

+*5,

'',++'...

...

...),(

303

20201

212

22111

330

22010

++++

++++

++=

vddvddvdd

vddinvddinvddin

inininvddinout

SaSaSa

SSaSSaSSa

SaSaSaSSS

' 061

++-+ # & P ' ' *7', + ' , + ' , ,+ */+ )cos( 0tvS iin ω= '

+ )cos( tvS Ssvdd ω= '

,+, Sωω ±0 ''

.2

1)( 110 SiSout vvav =± ωω 01

/',

,!,+01* # 01'3 &,

Power Supply Noise Analysis for RF Amplifiers 62

,

* / ,

+! ' + &

+(+'.*,

+,'3

.,' ⋅=sva

adBdBcSideband

12)(

11

10 * 0<1

.' + .

',,0<1*/

, !

* ' ,

,,!!'+-0))1I8J*

/+(++)))2

=11

102)(

a

adBdBVPSRR * 081

11

102

a

a &,.0<1,,

* & 081 *

081

*/,061!081

Power Supply Noise Analysis for RF Amplifiers 63

+! * F. + + , +

+3*

? , 5 ,& +

*#+('+

* ?

' !&

' ',+

∑∞=

=0

))(()(n

n txFty ' 0=1

+

...)()...(),...,(...))(( 111 nnnnn ddtxtxhtxF ττττττ −−= ∫∫ ∞

∞−

∞−

* 0C1

/0C1' ),( 1 nnh ττ L (+?(*!'+&0C1'(+? ? ICCJ* 2 & 0=1 0C1' ?

5 & *

?(,3??

I6=' C=' CC' E6J* /

? 3 ' ),...,,( 21 nn jjjH ωωω '

Power Supply Noise Analysis for RF Amplifiers 64

&

3 ICCJ* " , ?!

..!3I6='

6C'C='CC'C 'E6!ECJ*

. ! ? ! , ,

. & 0C1 *

,,+'!

,*#061'

, ,. ,+ )2 *

!?',

,' & ,

.*

∑∑∞

=

=

=0 0

21 ))(),(()(m n

mnout tvtvFtv 0E1

...)-()...-()-()...-(),...,())(),(( 1212111121 nmnmmmnmmnmn ddtvtvtvtvhtvtvF +++

∞−+

∞−∫∫= ττττττττL 0 1

Looo Looo Looo++++

++++

+++=

221122

21212111

3203

2202201

3130

2120110

),,(),,(),(

),,(),()(

),,(),()(

SSjjjASSjjjASSjjA

SjjjASjjASjA

SjjjASjjASjAS

cbacbaba

cbabaa

cbabaaout

ωωωωωωωωωωωωωω

ωωωωωω 0:1

? +

Power Supply Noise Analysis for RF Amplifiers 65

, + 0E1' + 0 1 !

&0C1*/0 1'?(' + ' ? * / 3 ? ,+ 0:1*

7?'-*ω3&,& 3 * QR

3

3 * 0:1

,+IE8J* /0:1'01?+*,* , * / , ? 0:1 061*

0:13

+(*

Power Supply Noise Analysis for RF Amplifiers 66

Figure 37. Self-induced power supply noise from high supply impedance at the envelope frequency

#,,#*#+

2 <E' + )2

&*/'&+*

,++*

&!?+,

+! 20A ' 30A '*!,

,',&+

,&3*/+

3+#*/+(

+ *

11A * / , ,

'!,5

* / ' 11A

Power Supply Noise Analysis for RF Amplifiers 67

,,*

/+('+F!,(,.+0

*2<=<!

+&*

, '+

*/++ω'++ω'+ , ω ω' + ,ω ω ω ω*))+

),(

)(2

011

010

SjjA

jAdBPSRR

ωωω

= ' 0<1

+ , & ( .

* / , '

' ),(),( 12112111 ωωωω jjAjjA ≠ * /&' , +

' 3

,* # ?

, +3 IE6J* #

+&',

&.*

Power Supply Noise Analysis for RF Amplifiers 68

Figure 38. CMOS inductor-degenerated common source amplifier showing nonlinear elements.

DC operating point

Typical operating

region

Figure 39. MOSFET drain current versus gate-source and drain-source voltage. Nonlinearities are

extracted around the dc operating point highlighted in the figure.

/ ! - ' +

, ";+ 6 * 2 < + ,

,+)2(*!,

)2 , #' +!

Power Supply Noise Analysis for RF Amplifiers 69

* 2 < + - ";

* / .'

01' 0 !,( -

01*;,,!

'&&*

F 2< +. /"<&<

*2<:+

& ! ! &*

+

gsv dsv */' dsgs vv × *

. ,+

*2<:

& /!? * +

' , & /!? , '

& ' & * ? .

& 01,+&&&*

++

!3I6='6C'ECJ*.

& - ,

Power Supply Noise Analysis for RF Amplifiers 70

LL LLL++++

++++

++⋅+⋅+

−−−−

+++=

33221

33

221

221

21211

33

221

33

221

32vdb

dt

dCvdb

dt

dCvdb

dt

dC

vdsgovdsgovdsgo

vgsvdsgmovgsvdsgmovgsvdsgmo

vsbgmbvsbgmbvsbgmb

vgsgmvgsgmvgsgmid

*0<61

/ 0<61' + ' ,

'! - ' ' *

502< 1*.!&'I6='

CCJ'6A6A<<+*

&?0:1'3+

&3.0<61',+

*+,I6='CC'E8J*#3?

+ '

+'.',&*

! , + +

* 2 ! 2 < ' +

&'

Power Supply Noise Analysis for RF Amplifiers 71

&',(3*

%'?0:1,+

∑∑∞

=

=

=0 0

21),...,(i j

jika

nijn SSjjAS oωω ' 0<1

+ nijA

*2' &+

* / ,

& * & ,

''

* ' & 3

'.,&I6='CC'E8J*

/' 1ijA +,

'+ 2ijA + , &

&*2< &

)()()(

0

1110

aaSa jK

gmjyjA

ωωω −= '+ 0<<1

)()()()( 11110 LXSLXa yyyyyyygmbgmjK ++⋅++⋅++=ω * 0<81

+ * 3 &, 3 ICC'E8J*

2 & ' ( ) 1)( −= SaaS Ljjy ωω * !

Power Supply Noise Analysis for RF Amplifiers 72

' & ω* / 0<81111 )( Cjgojy aa ωω += ! ,

'1go ' ' 1C 0<61* !

1)()( −= Caax Ljjy ωω +

( 'CL *

1)( −= LL Ry * / 0<81 )( ai jy ω ,

iy .',,

ω* 2++. 3ω.*+

0

1101

)()(

K

yygmjA LX

a

+=ω ' 0<=1

0

111210

)()(

K

ygmbygmyjA SX

a

+++=ω ' 0<C1

0

201 )(

K

yyjA LX

a =ω * 0<E1

/0<=1!0<E1'.''0<81'&3'ω'*20<=1 0<E1 3&,ω+ 3 ' ω' + 0<C1' ω 3 )2 ' ω* . 5 ,& ,+

Power Supply Noise Analysis for RF Amplifiers 73

*

? 5 . ,+

, 111A */' 1

11A ,)2

[ ])(),(),()( 00111 SSSoout VsVijjAv ωωωωωω o=± ' 0< 1

+ ω ω 3 )2 '&* # & ' 1

11A

, )2 + ,

*

111A &,?0:1*

+0<:1*7' 111A 5,

&0+ */0<:1' 222 )( Cjgoy ba ωω ++=

! ' 1))(( −+= SbaS Ljy ωω

'&ωω*'''' 3 * + 081!08<1* 7' 3 )2

,ω3,ω*0

423222111111

222),(

K

KgmbKgmKyKgmoyjjA Sba

−++=ωω ' 0<:1

Power Supply Noise Analysis for RF Amplifiers 74

+

[ ] [ ])(1)()(2)(1)(),( 210

101

210

110

2011 abaabba jAjAjAjAjAjjK ωωωωωωω −−−+= ' 081

[ ] [ ])()()()()()(),( 110

210

101

210

110

2012 aabaabba jAjAjAjAjAjAjjK ωωωωωωωω −+−= ' 0861

[ ])(1)(),( 110

2013 abba jAjAjjK ωωωω −= ' 081

)()(),( 201

2104 baba jAjAjjK ωωωω = * 08<1

#0<:1'&

& & * "- , &

' ' * & .*

7+&'&,

* , & &*'

!&*

2+&0810<1' ,+111

1102

A

AdBPSRR = '

+0<<10<:1*.

Power Supply Noise Analysis for RF Amplifiers 75

";+

423222111

1

222 KgmbKgmKyKgmo

gmdBPSRR

−++= * 0881

/0881'. 110A 1

11A *#'

* & +

&,' & ' 3* 3' ))

,,

-&*

)) 0881 +( ,

* ( * 7+

- & , & &,' +

+ * ' .5

))',&*&))'(+

• /&+• ) & 01 '+!&*

• )-01• )01,

Power Supply Noise Analysis for RF Amplifiers 76

/,&&))

& &*

&, + 3'+&' +

&-''*

#!!#A#++,6

";&+,+

* .&F";&+

+3,,- ,*

+5&.+6=+&=K*

& ( + , . 6

*8975+=K<7&

,+,*#!,+(+!

3*

Power Supply Noise Analysis for RF Amplifiers 77

Figure 40.

Lx

50Vin VoRin Vdd VripplePin

VddMatchingRF Source

Supply + Noise SourceSpectrum AnalyzerAmp

Figure 41. 2 8 + , +(*

+ ,+ !!,

* F +,(,

,&*286+,*&

,'&,)2',+&

-+'5

*5,+'+,

Power Supply Noise Analysis for RF Amplifiers 78

,* # / , , + 2 8* &

+, + 5 *

,++!,++(5*/

!+!87*/,+

+!,+!

+,<7+,*

ground

downbonds

RF-in

RF-out

BiasVdd

Figure 42.

)2+++,+!<63

*8975*+-36"75+=?

+ ! &* 2 8<

* # , ?

' ,& + +* #

Power Supply Noise Analysis for RF Amplifiers 79

+ +' ,

+ 6! * # + .

&*)),

&";&+*/

'?

*

-80

-70-60

-50-40

-30

-20-10

010

20

-30 -20 -10 0 10Pin (dBm)

Po

ut (

dB

m)

Measured

Volterra

Vo @ 2.4GHz

Vo @ 2.4GHz + 1MHz

Figure 43.

Power Supply Noise Analysis for RF Amplifiers 80

16.0

18.0

20.0

22.0

24.0

26.0

28.0

30.0

-30 -20 -10 0 10Pin (dBm)

PS

RR

(dB

)PSRR (meas)

PSRR (calc)

PSRR (Spectre-BSIM)

Figure 44.

2 88 + )) & +* 2 0<1' ))

,01

)()()( dBVeSupplyNoisdBcSidebanddBVPSRR += 08=1

/,&

&*#,8*<*'

+,0

,,+ ! 1 + !& 05!?1

* /288' 0881?

++/"<&<*,+

+6!+*2

8<' ,+

* )) ,

(Volterra)

Power Supply Noise Analysis for RF Amplifiers 81

,+* ++

++',&*

+6!<.+*&.,

& !, & &

* / 2 8< 2 88' ? ,

& < +* / . +

,+!<,+

+(*

, / 4 + !@ 9 + ,

E(75*,,+&<,&

68 !,! * % 3, IC J' ,,

+&?3

*

,' +

*++,

+IC 'EJ.*

/ 4 + & ";

,F/G/!=86A=C)2*&

3' 9+

Power Supply Noise Analysis for RF Amplifiers 82

:"75 ' *8975* +

?*

Figure 45. Mea !!"#$

Power Supply Noise Analysis for RF Amplifiers 83

Figure 46. " %&#$

28=+&+

+ ! ?! * 9 +

:"75* -6"75',

::"75:6"75* , 9&

( = ,+ ,*

+ 6!< 3 '

!?:"75*28C+

+*8975S6"75*/?'

,,*+

Power Supply Noise Analysis for RF Amplifiers 84

!: 0 G/

+&1' , ,

+6!<* !"#$%

/' ? & &!&

* , !&

,,(+'+28E*7'))+

& +

,!01'01'-01*/28E'+&

+ , &* /

,+&'))

*'))28E*

Power Supply Noise Analysis for RF Amplifiers 85

0

10

20

30

40

50

60

70

1.E+06 4.E+06 1.E+07 5.E+07 2.E+08 7.E+08 3.E+09 1.E+10Frequency (Hz)

PS

RR

(dB

V)

gmo11gmo11+go2gmo11+go2+C2

go2*

gmo11*

C2*

Total PSRR value

Figure 47. '(()*+*

* Change in PSRR when effect of parameter is included (i.e. gmo11 is shown to reduce PSRR from infinite to the edge of the shaded region indicated in the legend).

# + 3 & ( (

01 01* '

+ , ! 0**0<611* +,!'* ' )) 3*!01, 3+ && ,

(*-0

Power Supply Noise Analysis for RF Amplifiers 86

13+

&*())&

( * # 3' )) ,

& * 7+&'

, -'* # +3')) + ( , +

*,+&*,'' .<7&*#!

*

& *2+3' , ,*0<:1!0881',,,

?*

# 2 8E' ? & + .

,+*/

! .' )) ,*

+ ' &

&?*&

'' *;&',&*

Power Supply Noise Analysis for RF Amplifiers 87

#++)2+

* & +

.!+

)2*)&,+++6!

* + 9

& :"75 *8975 + + + 6!<* "!

?+,&,&

&3 +*

' IC J' , & !

+, 3 . !3

* & )2 &

& + -' , !! 0;1

'&&(01

+*

88

Chapter 5 Optimum Operating Strategies for Hybrid Voltage Regulators

,

Figure 49. Model for parallel hybrid switching-linear regulator

#<'&&

&+&(*

&,,'++

Optimum Operating Strategies for Hybrid Voltage Regulators 89

0#1.+*7,&'

+ 2 8 ' &

* . &, ,

+&*

28 +,&<**<*

&+'#&*

+'

'&*#

+Figure 49*/,

' + &

IEE!E:J*

, & & ,

,&&&*

/,' ! &+&

*,(&&

+ * 7+&' +

&',*

& & + &

&0";&1*

,+ A + ! &' , 3

+ 3' +* #

Optimum Operating Strategies for Hybrid Voltage Regulators 90

, ' , + *

,+,&&

' + + +' , +

*

/ , ' !,+ &

& + I6<' =' =8J' +

+ & &

I ' 6J*,,',

&,,IC6'C' J'

! I <' 8J* / ' +

,+ ( , & +

0! 1 '+ & , + &

. I =! EJ* 7+&' ' &

,+( ! & +

+ 3 I<C' 8=' 8E' =J* / ' ,

, ' ,+'

IC6'CJ*

2 + 2 8 ' & & ,

, + ,(*

+ , &

Optimum Operating Strategies for Hybrid Voltage Regulators 91

& * D ,(

&*,+

, !,+ +,

"75 I=' =8J* /

+,+',

+ ! & I <' 8J'

+ & * ' &

'

+*/+('+

& 5 +

0!1'IC6J''I J*+

&!5,++*#

,+ +

ICJ*

Overview ,.&

)2 + * . +( IC6' C' ! 8J +

,* /+

+ 3! *

&&3

Optimum Operating Strategies for Hybrid Voltage Regulators 92

,++*+(

+ & " * / +

5,+3!*/

',++3!'+

,53*

0 1 2 30

5

10

15

Sig

na

l A (

V)

0 1 2 30

5

10

15

Sig

na

l B (

V)

time (s)0 5 10 15 20 25

-100

-80

-60

-40

-20

0

20

frequency (Hz)

Po

wer

Sp

ect

rum

(dB

/Hz)

PAPR=5.2 dB

PAPR=10.1 dB

Figure 50. Two different time-domain envelope signals that share the same power spectrum: one with

peak-average power ratio (PAPR) of 10.1dB, and another with PAPR or 5.2dB.

, 3

ICJ*23!,

& + * # . +

Figure 50* 7'+&+&+

*(!&+0#)16*6'

+#)=** / 5

,*,!

Optimum Operating Strategies for Hybrid Voltage Regulators 93

+ 5,++

!*

/'+&.+

&' & &'

& * 5 ,

* / +

' +

&++*&IC6'C' J'

,+ , &&

&,+* /'++.

'3!+,

*&+

,3!,&+

/!:= "#/ *66A*

& ' +

A , 5

+3I8='==J*D''&

!,+ ' , & + + '

+ & * ,

Optimum Operating Strategies for Hybrid Voltage Regulators 94

& ' + +

+*

7+3!+&

&'',+ +*

#+ 2=6' +

5 ,+ & ++* &

&,5',

&&&

dd

out

V

Vd = ' 08C1

+ outV & & & ++ bta ≤≤ '

∫−=

b

a

dttfab

tf )(1

)( *2+#',(#

$#&&*

'+!!!

*/,&

Optimum Operating Strategies for Hybrid Voltage Regulators 95

I8J* !'

'+ (* 2

+&'+,

+ *

,+,(

*+ &*

+ + ,+!<C

* ,&,&

'

S

L

P

P=η ' 08E1

+ LP &+ SP &+

*#2=6'&+

+

[ ]diiVP SRLRDDS ⋅+⋅= ' 08 1+ LRi ' SRi +&'

' DDV , &* &

&& ' LRi SRi * 2

&+&'#"+!)2'.

08E1 08 1 , & . ,

& , &* / , +

Optimum Operating Strategies for Hybrid Voltage Regulators 96

08 1 ' .

+*#'

=*8' ,

&* ) + , &*

&',

5* . !#" +!

. , 3!

,* 2 + ' "#' %"

*66'!

& +&* 7+&' LRi SRi , '

, , ' + , =*C*

' . & +&

+ ' & 5

&,*

& . )2 +

, .* 2

)2 ' & & +& ,

+

Optimum Operating Strategies for Hybrid Voltage Regulators 97

)cos()( wtvvtv aDCo ⋅+= '

)cos()( wtiiti aDCo ⋅+= *08:1

7'&&'&' &*/08:1'+(' , & &

,*

0

0.2

0.4

0.6

0.8

1

0 2 4 6 8angle (radians)

En

velo

pe

volta

ge

(no

rmal

ized

)

Sinusoidal AM Two-Tone

2 = + 5 & & !#"

+! * / !#"

DCa vv = * & + & '

'

.2

)()(1

0

aaDCDC

T

ooL

ivivdttitv

TP

⋅+⋅=⋅= ∫ 0=1

&.&++'08 1'

& LRi & , SRi

Optimum Operating Strategies for Hybrid Voltage Regulators 98

& ' ' T'

*

0

0.2

0.4

0.6

0.8

1

curr

ent

(A)

-Φ +Φ

iSR

iDC

<iLR>2Φ

iLoad

2=<+ +& ,* /

+ '

. 6 * + ! ' & * 7+&' .

+2=<'+

TU6 * &,+*2+&08:1'Φ ,&

=Φ −

a

DCSR

i

ii1cos * 0=61 0=61' & ,+

Optimum Operating Strategies for Hybrid Voltage Regulators 99

( )

[ ].cossin

)cos(2

1

ΦΦ−Φ=

−⋅+= ∫ΦΦ−

π

φφπ

a

SRaDCLR

i

diiii 0=1

7'&

+*&'

2=6',+&+&

08C1' 08 1' 0=1' + +

,&'*/,0=1

+ + * #& #"

&+

[ ]ΦΦ−Φ+⋅

⋅+⋅

=cossin

2

π

ηa

ddDCSR

aaDCDC

iVvi

iviv

* 0=<1

/ 0=<1' & + &

+&' &' ' T' *

, 0=61 0=<1'& .

,+' SRi *%',5

, + & . &

* 0=SRdi

d η ',

⋅+=

dd

DCaDCSR V

viii πcos* ' 0=81

Optimum Operating Strategies for Hybrid Voltage Regulators 100

+ *SRi 3! + * .

&' *η '& *SRi .

( )*

*

sin

2

Φ+⋅

⋅+⋅

=

π

ηa

ddDCDC

aaDCDC

iViv

iviv

' 0==1

+ *Φ ',+

dd

DC

V

vπ=Φ* * 0=C1# 0=81' , +

3 ',

&+&*

IC6' J' +

+ *

+! ' . .

, ,* 2

)2 + 3' 2w 1w ' , 3

' ' & !+& + ( &

va×2 'ICJ'

−⋅= t

wwvv aenv 2

cos2 12 * 0=E1/'+

Optimum Operating Strategies for Hybrid Voltage Regulators 101

=Φ −

a

SR

i

i

2cos 1 ' 0= 1

+load

aa R

vi = ++*

2+ & ' 3!

+,+!

⋅⋅=dd

aaSR V

vii 2cos2* ' 0=:1

+ ddV , &* .&

+!&&

[ ])cos()sin(2*

ΦΦ−Φ⋅⋅+⋅⋅

=addSRa

aa

iViv

ivπη * 0C12 +!' ,,+:<*<> !

'E *=>0πA81 0→av * / +

'+,,,:*E>>* +

E>+!&ICJ*

Optimum Operating Strategies for Hybrid Voltage Regulators 102

00.10.20.30.40.50.60.70.80.9

1

0 0.1 0.2 0.3 0.4 0.5Modulation Amplitude, Normalized (V)

Effi

cien

cySin-AM isr=isr*Sin-AM isr=idc2-tone isr=isr*2-tone isr=idc

00.10.20.30.40.50.60.70.80.9

1

0.0 5.0 10.0 15.0 20.0 25.0Average Output Power (dBm)

Effi

cien

cy

isr = idcisr = isr*

! "#$%&'

2 =8 + & !#" +!

*&

5 6?' + !! +

5*2#"'

DCa vv = *+!+3+

' ' 0=E1* / + ,

Optimum Operating Strategies for Hybrid Voltage Regulators 103

' & > *

7+&'+' *SRi '&0=81

0=:1'&,('

+0==10C1*'

+& &*/&'

,.,

• #+&'+ */

' 0180 !&*&2=8&*

• #+++ '

'!#"' aDCSRia

iii +=→0

lim */+'

!+

0180 *#&'+!#'++*

+ 2 =8 ,& +

* 2 == + & + &+&

/!:= !& ! 0 "#1* /

&+& +,-

3 * ' 2 ==' & +

Optimum Operating Strategies for Hybrid Voltage Regulators 104

,& * ; *SRi &

* "# +&

&2=8*,!#"'+! "#+&

&(!!&+0#)1*#)

3 ,+

. & & & & & I6' <' J*

9'#)&++*,

& & & &

*

&,++ *SRSR ii = '

+ DCSR ii = ,++

,(* /+ DCSR ii = '&5

+ & * 7+&' ' ,

+ &'min

η * 2

2 =8'min

η ,+ E! >* & "# '

minη HC >*'+.+,('+,

& & 3, #' , , &* F. + + & + ,( I :J* / ' !,+ + & + ,+ ! ,

Optimum Operating Strategies for Hybrid Voltage Regulators 105

& I88J* + + &+ ,* (###)! !

*SRi ( )*cosΦ⋅+ aDC ii ( )*cos2 Φ⋅⋅ ai

*Φ dd

DC

V

vπ dd

a

V

v2

*η ( )*sin

2

Φ+⋅

⋅+⋅

πa

ddDCDC

aaDCDC

iViv

iviv ( )*sin2 Φdd

a

V

vπ max

η %7.9142

3 =+ππ %3.93

)1sin(4=

⋅π

minη %75

4

3 = %5.784

=π DCa vv =

!"## $

%

% *SRi % &

$'(%

%

Optimum Operating Strategies for Hybrid Voltage Regulators 106

% *SRi %)'(*

*SRSR ii =

% DCSR ii =

% +

)''* ),!*

% &

-' ... !"##

Optimum Operating Strategies for Hybrid Voltage Regulators 107

)/0#0#* 1

)&& !'!2 ''!*

%

% 3

&

4''%'-%-!5

% )''* ),!*%

%

% %)(,*%

/

%,

$',% 6

7 2 #!!&2

/

"!89 % &-' !"##:/7

Optimum Operating Strategies for Hybrid Voltage Regulators 108

6

%

; Ω10

+

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 50 100 150 200switching regulator current (ma)

Eff

icie

ncy

measuredtheorymeasuredtheory

Vdd=3V; Vo=1+1*sin(wt)

Vo=0.5+0.5*sin(wt)

Supply Voltage= 2V; Signal=va+vaSin(wt)

00.10.20.30.40.50.60.70.80.9

1

0 0.2 0.4 0.6 0.8 1Normalized Voltage Amplitude (V)

Eff

icie

ncy

theorytheorymeasuredmeasured

isr=isr*

isr=idc

Optimum Operating Strategies for Hybrid Voltage Regulators 109

$'0

"

)'(*<=

% , )/0#0#*

'!!= #=% #( 1 1

.

$ % +

!>%"> )''*

& #2"!

$ '

$'

*SRSR ii = % DCSR ii = $

%

%

1

Optimum Operating Strategies for Hybrid Voltage Regulators 110

Supply Voltage= 2V; Signal=2*va*abs(Sin(wt/2))

00.10.20.30.40.50.60.70.80.9

1

0 0.2 0.4 0.6 0.8 1Normalized Voltage Amplitude (V)

Eff

icie

ncy

isr=isr*isr=idcisr=isr*isr=idc

isr=isr*

isr=idc

!

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

-5 0 5 10 15 20 25Average Output Power (dBm)

Eff

icie

ncy

isr=isr*isr=idcisr=isr*isr=idc

CDMA

802.11a

"#$%&'() **+,-$ '-

9 '( 9

%

-!,> -<<>

Optimum Operating Strategies for Hybrid Voltage Regulators 111

$,! ... !"##

)&*

/ 7'("#%

$', #!Ω

6

"! 1 !"## '(12%

#' 1+);;?*

!"## );;?@#! 1*

;;? !"##

% $ ,!

$''

<<=

#:

Optimum Operating Strategies for Hybrid Voltage Regulators 112

0

0.5

1

1.5

2

2.5

-5.00 0.00 5.00 10.00 15.00 20.00 25.00Average Output Power (dBm)

isr*

/idc

CDMAWLANSinAM

. /0 DCSR ii /* 1 $,#

DCSR ii /*

&

:/7

;;? %

*SRi DCi⋅2 % )'(*

& *SRi

DCi DCSR ii /*

?% %*SRi 9% SRi ++

+ %

Optimum Operating Strategies for Hybrid Voltage Regulators 113

*SRi $%

%63

% $ '-,#

% *SRi %

%

%

% *SRi

8% + *SRi

+ % 4 !5

9 $'-,#%

Figure 62. Hybrid regulator model including output capacitance

Optimum Operating Strategies for Hybrid Voltage Regulators 114

%

Figure 62

%

6 %

% RC=τ %+3

%

6

)cos()( twvvtv aaDCo ⋅+= % ),#* DCv % av %

aw 3

[ ]

+⋅⋅+=R

Cjwtwvvti aaaDCo

1)cos()( % ),"*

R

Cjwa

1+ is the admittance of the load network at the frequency of the AM tone.

Optimum Operating Strategies for Hybrid Voltage Regulators 115

The current supplied to the load by the linear regulator, following the development of

section 5.4 follows as

[ ] )(1

)cos()( tiR

Cjwtwvvti SRaaaDCLR −

+⋅⋅+= % ),<*

⋅+

−=Φ −

aaa

DCSR

VCjwi

ii1cos ),(*

),(*% %3

3%

+

−=Φ −

RCjwi

ii

aa

DCSR

1

1cos 1 ),'*

( ) φφπ

dRCjwViii aaSRDCLR ∫Φ

Φ−

+⋅+−= /1)cos(2

1 ),,*

),,*

[ ].cossin~

ΦΦ−Φ=πa

LR

ii %

RCjwii aaa += 1~

),0*

%

),0* A 9

Optimum Operating Strategies for Hybrid Voltage Regulators 116

% %

0=SRdi

d η

DD

DC

V

Vπ=Φ* % ), *

** cos~ Φ+= aDCSR iii % ),-*

*

*

sin~

2

Φ+

+=

π

ηa

DDDCDC

aaDCDC

iViV

iViV

)0!*

8%), *)0!*)'(*)',*%

3

3 3

8%3

%

00.10.20.30.40.50.60.70.80.9

1

0 0.1 0.2 0.3 0.4 0.5Normalized time constant (wRC)

Effi

cien

cy

Vo=0.5+0.5Cos(wt) --Calc

Vo=0.5+0.5Cos(wt) --Sim

Vo=0.25+0.25Cos(wt) --Calc

Vo=0.25+0.25Cos(wt) --Sim

Optimum Operating Strategies for Hybrid Voltage Regulators 117

Figure 63. Hybrid regulator with load capacitance: efficiency versus normalized time constant (simulation vs theory)

Figure 63 ?

% Figure 629 3

3

3 )0!*

& 8%

), *)0!*

Figure 63 3

#2#!%

8% 3

3% 3B

3%

3

$

$%

%3%

Optimum Operating Strategies for Hybrid Voltage Regulators 118

Parallel hybrid voltage regulators are highly practical for dynamic supply transmitter

applications. These topologies can provide fast dynamic regulation with low noise and

high efficiency. If the operating conditions are carefully considered, power efficiency

can be comparable to a pure switching regulator solution. The key is to consider the

time-domain operation of the switching and linear regulator portions as many waveforms

can have the same power spectrum. In many cases, the switching regulator should supply

more than the average load current, with the linear regulator sinking more current to

ground in a push-pull output stage. There are many conceivable circuit architectures that

could optimize the bias conditions of the hybrid regulator through online sensing and

slow adaptive feedback. A final practical consideration includes the dynamics of the load

network. From an efficiency perspective, it is best to have any poles at the output be

substantially higher frequency than the modulation signal to avoid reactive losses. This

implies that the linear regulator may be best optimized with internal compensation rather

than using a dominant pole at the output.

119

Chapter 6 Direct Digital Modulation: A New Approach to Polar Systems

Figure 64. Conventional cellular phone block diagram: digital application processor, DSP, Audio, Power

management; Radio is still largely analog

Figure 65. Proposed digital polar architecture

& Figure 64%

% &;%%

8%

% %

'! 4#!5

Direct Digital Modulation: A New Approach to Polar Systems 120

C& :

$

-!C& 1

"#D.? <12

Figure 65

% + ?$

%

?$

% 39 #

?$

3

Σ∆ 4-#5 . Σ∆ ?$

E4-"5 :4-<5

+ E 4-(5 1 4-'5 C

4-,- 5

+

Figure 65 ?

% Σ∆

1

%

Direct Digital Modulation: A New Approach to Polar Systems 121

3

':6+;

%

.=>"!+

6.1 Transmitter concepts revisited

Figure 66. Traditional Cartesian transmitter architecture: lowpass data conversion followed by upconversion mixers

Figure 67. π/4DQPSK and 8PSK constellation diagrams

"% ?$

C% ?$

Direct Digital Modulation: A New Approach to Polar Systems 122

1 %

% + + % ?$

?$ 6 3

).=*% "#" &

+ 6 );?*

6 π2(F;&G ;&G )

* Figure 67

1"#D.?

"12 <12 4-5

3

%

Figure 66% ?$

?$ 6 8%

3H 3 ?$ ;

1 ;

%

/C%%

Direct Digital Modulation: A New Approach to Polar Systems 123

?$ :

%

% 39

6.2 Data conversion principles

000 001 010 011 100 101 110 11100.1250.2500.3750.5000.6250.7500.8751.00FS

out

V

V

Binary Input 1000

VFS∆=LSBV

Figure 68. Input-output transfer characteristics for a 3-bit D-A converter

3 Figure 68

<8% 9.

N

VFS % FSV

3

Direct Digital Modulation: A New Approach to Polar Systems 124

)/&1* LSBFS VV − $

4--5%% FSV % ( )N

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Direct Digital Modulation: A New Approach to Polar Systems 125

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Direct Digital Modulation: A New Approach to Polar Systems 126

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Direct Digital Modulation: A New Approach to Polar Systems 127

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Direct Digital Modulation: A New Approach to Polar Systems 128

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Direct Digital Modulation: A New Approach to Polar Systems 129

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Direct Digital Modulation: A New Approach to Polar Systems 130

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Direct Digital Modulation: A New Approach to Polar Systems 131

Figure 75. Linear model of the noise-shaping process: quantization noise appears as a disturbance

Quantizeru[n] y[n]

e[n] +-G(z)-1x[n] Quantizeru[n] y[n]+- z-1++

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Direct Digital Modulation: A New Approach to Polar Systems 135

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Direct Digital Modulation: A New Approach to Polar Systems 136

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Direct Digital Modulation: A New Approach to Polar Systems 137

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Direct Digital Modulation: A New Approach to Polar Systems 138

6.4 Direct-digital modulation for RF transmitters

Figure 81. Direct digital modulation: transmitter operating as a D-A converter

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Direct Digital Modulation: A New Approach to Polar Systems 139

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Direct Digital Modulation: A New Approach to Polar Systems 140

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Direct Digital Modulation: A New Approach to Polar Systems 141

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6.5 A 2.4GHz RF Polar Transmitter for Bluetooth 2.1+EDR

Polar Digital BasebandAmplitude Path

Phase PathDigital Phase ControlRF DAC

Class-D1-bit PARF Pulse-Density Modulator(@ 2.4GHz)Baseband Modulator(@100MHz) A Matching+BPF2 V

RFclk(Φ)BBclk

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6.5.2 Architecture

a.) Polar system with PWM supply regulation

RF Φ

Reactive BPF

Phase Path

Power Amplifier

Pulse-Density-Modulation

Amplitude Path

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Direct Digital Modulation: A New Approach to Polar Systems 147

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Direct Digital Modulation: A New Approach to Polar Systems 148

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Direct Digital Modulation: A New Approach to Polar Systems 150

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Direct Digital Modulation: A New Approach to Polar Systems 151

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Direct Digital Modulation: A New Approach to Polar Systems 152

Figure 89. 1-Bit polarity feedforward to reduce power from rapid phase transitions

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5

4

ππ →

Direct Digital Modulation: A New Approach to Polar Systems 153

Figure 91. Polarity bit significantly reduces high frequency power in the RF clock signal waveform by

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Direct Digital Modulation: A New Approach to Polar Systems 154

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Direct Digital Modulation: A New Approach to Polar Systems 155

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Direct Digital Modulation: A New Approach to Polar Systems 156

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Direct Digital Modulation: A New Approach to Polar Systems 157

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Direct Digital Modulation: A New Approach to Polar Systems 158

Figure 95. ∆Σ Modulator: 1st, 2nd, 3rd order comparison, all zeros at 2.4GHz

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Direct Digital Modulation: A New Approach to Polar Systems 159

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Direct Digital Modulation: A New Approach to Polar Systems 160

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Direct Digital Modulation: A New Approach to Polar Systems 161

Table IV. COMPARISON: FV-FI FIGURE OF MERIT FOR VARIOUS AMPLIFIER CLASSES

(DATA FOR CLASS E, F-1, F2,3,4,5 FROM [34])

Amplifier Class FV FI

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Direct Digital Modulation: A New Approach to Polar Systems 162

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Figure 97. Schematic representation of class-D power amplifier with cascode output stage

Direct Digital Modulation: A New Approach to Polar Systems 163

Figure 98. Current recycling scheme: excess current from PMOS drive stage used by digital processing

Figure 99. Class-D PA output stage NMOS layout: gate and cascode share diffusion region to reduce

junction capacitance

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Direct Digital Modulation: A New Approach to Polar Systems 164

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Direct Digital Modulation: A New Approach to Polar Systems 165

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Direct Digital Modulation: A New Approach to Polar Systems 166

6.5.8 System Implementation

Figure 101. System-level implementation of Bluetooth transmitter

Figure 102. Die Photo of CMOS class D PA and RF pulse-density modulator circuits

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Amplitude (A)On-Chip FPGA

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Direct Digital Modulation: A New Approach to Polar Systems 167

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Class-D1-bit PARF Pulse-Density Modulator(@ 2.4GHz) 2 VRFclk(φ)

Figure 103. Block diagram of the experimental setup

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Direct Digital Modulation: A New Approach to Polar Systems 168

?$ + 6 .=

a.) PA output with 200MHz clock signal

b.) Downconverted transmitter output with 2.4GHz clock, linear ramp signal programmed into amplitude

path

Figure 104. Time-domain waveforms at transmitter output

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Direct Digital Modulation: A New Approach to Polar Systems 169

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VHV=2.0V, Vhalf=1.0V, fo=2.4GHz, Tamb=27oC

0%

10%

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Direct Digital Modulation: A New Approach to Polar Systems 170

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regulator

Direct Digital Modulation: A New Approach to Polar Systems 171

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Direct Digital Modulation: A New Approach to Polar Systems 172

a.) π/4DQPSK (2MBPS)

b.) 8DPSK (3MBPS)

Figure 108. Measured constellation diagrams

Direct Digital Modulation: A New Approach to Polar Systems 173

Figure 109. Efficiency and output power vs supply voltage

Figure 108 π2(F;&G ;&G

31"#D.?

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Direct Digital Modulation: A New Approach to Polar Systems 174

3

;;?

Quantization noise of the digital modulator is a limiting factor for spectral performance.

Figure 109 a-d.) shows that the nearband spectral requirements for Bluetooth 2.1+EDR

are satisfied for both π/4DQPSK and 8DPSK test signals. Average power levels at the

spectrum analyzer are between 11-14dBm. The wideband spectral mask is satisfied due

to the addition of the bandpass filter at the output. However, it should be noted that in

peak-hold mode, which is required for the Bluetooth standard, there is little margin for

the -40dBm power limit (100kHz RBW). Shown in Figure 109 c.), the lowest margin

occurs near peaks in the quantization noise spectrum 50MHz from the center frequency.

Low margin in the spectral mask could make the system susceptible to load pull, power

supply variation, or other scenarios which cause wideband noise levels to increase. This

can be improved by operating the ∆Σ process at higher clock frequencies, or reducing

transmitter power level. In a fully-integrated version, it may be practical to operate the

∆Σ modulator at 250MHz or more, reducing the peak noise by 3-10dB. Due to limited

margin in meeting the spectral-mask, we do not present this as a fully-functional

Bluetooth transmitter, but rather a demonstration of a new and interesting topology

worthy of further investigation. The high efficiency and excellent linearity show that this

is a promising alternative to traditional Cartesian and polar transmitters.

175

Chapter 7 Conclusion and Future Work

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