optimizing wideband software radio performance · optimizing wideband software radio performance...
TRANSCRIPT
Optimizing Wideband SoftwareRadio Performance
1998 INTERNATIONAL SYMPOSIUM ONADVANCED RADIO TECHNOLOGIES
Boulder, Colorado
9-11 September 1998
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
2
Optimizing Wideband SoftwareRadio Performance
Dr. Donald H. SteinbrecherSubmarine Electromagnetic Systems Department
Bldg.1319, Room 356, Code 34111176 Howell Street
Newport, RI [email protected]
Tel:401.832.5656 Fax:401.832.7345 DSN: 920.5656
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
3
Wide-band RF DigitalConversion
• Essential to a seamless air-glass interface
• High Spurious-free Dynamic Range is Key
• Frequency Translator and A/D Converter
are the Cornerstones of Performance
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
4
Wide-band RF/Digital Conversion Is Essentialto a seamless air-glass interface
• Air-Side Signals are modulated on to analogRF carriers (eg 900 MHz)
• Glass-side signals are digital and are
modulated onto digital carriers(ATM over
SONET)
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
5
High Spurious-free Dynamic Rangeis Key
• A typical 12-MHz Cellular Band Needs 70-dB for Signal Dynamic Range plus 30-dBfor A/D Converter Headroom
• 70+30 = 100-dB SFDR for continuous full-band operation. (about 16-bits/sample)
• …Unless, of course, you power control
48-Tone Test, 10-MHz Band
99-dBSFDR
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
7
Intercepts
PowerOut
PowerIn
fundam
enta
l
dist
ortio
n
Intercept
Gain
0input
intercept
outputintercept
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
8
Third-Order Intercept
Noise Level
Two-Tone Level
Dynamic Range
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
9
Third-Order Intercept
Noise Level
Two-Tone Level
Inter-ModulationRatio(Db)
Third-Order InterceptIMR/2
IMR
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
10
Spurious-Free Dynamic Range
• SFDR is defined as a power ratio...
• The numerator is the power in each tone of a two-tone.....
• The denominator is the noise power in a specifiedbandwidth, usually one Hertz...
• The ratio is taken when the power of the largestdistortion product produced by system non linearity isjust equal to the noise power in the specified band.
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
11
Spurious-Free Dynamic Range
PP
IkT Fthird
tt
third
= =3
2 0
SFDR
P(two tone)
kT0F
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
12
Spurious-Free Dynamic Range
SFDR
P(two tone)
kT0F
( )SFDR =
P
kTtt
0 F
kT F I
kT Fthird= 0
1 3 2 3
0
/ /
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
13
Spurious-Free Dynamic Range
SFDR
P(two tone)
kT0F
SFDR =I
kTinputthird
0 F
2 3/
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
14
Spurious-Free Signals,30-KHz Band
100-dBSFDR
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
15
The A/D Aperture Constraint
fNyquist fsample
Full Scale Input to theA/D Converter
S(t)
S t f tNNyquist( ) sin( )= −2 21 π
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
16
The A/D Aperture ConstraintS(t)
1 2 21= −NNyquist aperturef tsin( )π
1
taperture
ω πt N= 2
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
17
The A/D Aperture ConstraintS(t)
1 2= NNyquist aperturef tπ
1
taperture
ω πt N= 2
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
18
The A/D Aperture Constraint
( )N N Log fA Nyquist= − 2
Nt
A N
apertureeff
=1
2 π
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
19
The A/D Aperture Constraint
( )N N Log fA Nyquist= − 2
Nt
A N
apertureeff
=1
2 π
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
20
Optimum Design
Log2(fNyquist)
Neff
Aperture Constraint
NA
Slope = -1
( )N N Log fA Nyquist= − 2
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
21
1-LSB Occurs in1-LSB Occurs in
3.24 x103.24 x10-13-13 Second Second
The Speed of Light...The Speed of Light...
Light Travels AboutLight Travels About
100 microns100 microns
16-Bit Quantizer, 15-MHz Sinusoid
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
22
RF TranslatorRF Translator
Intermediate-Frequency
Analog Processor
Intermediate-Frequency
Analog Processor
AntennaElement
AntennaElement
Analog-to-Digital
Converter
Analog-to-Digital
ConverterDigital Object
FormatterDigital Object
Formatter
Atmosphere
Network Fibersphere
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
23
Atmosphere FibersphereAnalog RF A/D ConversionR
elat
ive
Ban
dwid
th
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
24
Atmosphere FibersphereAnalog RF A/D ConversionR
elat
ive
SFD
R
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
25
Wide-Band Software RadioDesign is Driven by the
Properties of the Chosen A/DConverter
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
26
f=0
f=fNyquist
N02 N01N03N04NikFrequency AxisIncreasing
Nyquist zones of a periodically driven A/Dconverter. The zone most often used as the
signal band is N01
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
27
Intermediate-Freq.
Processor
Frequency
Translator
A/D
Converter
Translation
ImageAlias
Frequency Axis
f=0
f=fN/2
The basic analog elements of asoftware radio.
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
28
Translation
ImageAlias
SFDR
Anti-aliasFilter
Requirement
Signal Band
Frequency Axis
f=fN/2
f=0
f=fIF
Alias Band Image Band
Nyquist Band
Figure 3. The anti-aliasing filer requirement isdetermined by the properties of the A/D converter.
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
29
SFDR
Signal BandAlias Band Image Band
Nyquist Band
RippleBand
Anti-aliasFilter
Requirement
The anti-aliasing filer requirement is determined bythe properties of the A/D converter.
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
30
Partition Band
SFDR
Transition BandTransition Band
Signal BandSignal Band
The digital filter characteristics of the signal bandpartitioner.
Frequency Axis
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
31
A/D
Converter
Digital
Filter
Digital
Filter
Digital
Filter
Digital
FilterCommutator
CH 01
CH 02
CH 03
CH nn
A digital partitioner separates the Nyquist band intonn equal sub bands.
Dis
cret
e or
der-
nn F
ouri
er T
rans
form
01
02
03
nn
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
32
ATM PacketFormatter
ATM PacketFormatter
CH ik
Network Fibersphere
Address ControlAddress Control
8/7/98 15:04 Copyright 1998 Donald H. SteinbrecherAll rights reserved.
33
Summary
• A/D Converter drives design of SoftwareRadio.
• Opportunity for developing a core radiocomponent suitable for all software radiosusing a particular A/D Converter.
• Opportunity for developing a networkinterface device suitable for a wide varietyof software radio applications.