link impairments a few - ucsb€¦ · oscillator am and pm sidebands (skip): cosinusoidal phase...
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Copyright Mark Rodwell, 2016
Link Impairments
A few
Mark Rodwell, University of California, Santa Barbara
ece145c lecture notes
Copyright Mark Rodwell, 2016
Reminder: Multipath Propagation
n"propagatiopath -multi" :paths signalMany
pattern. beam antennain objectsMany
antennas)y directivit-(lowbeamwidth angular largeGiven
reflection ofStrenght
antennas ofy Directivit
strenght signaldifferent haspath Each
shift. phase possible :conditionboundary surface Reflecting
delay.different length,different haspath Each
Copyright Mark Rodwell, 2016
Fading vs Intersymbol interference
periods symbollonger :ODFM useor
receiverin equalizer adapitive need
another with interfers periodbit One
ceinterferen lIntersymboperiod) Symbol spread(Delay
separation eappropriatat antennas receiving two:fix
signalery weak possibly vceinterferenphase ofout are Carriers
aligned~ periods symbol with arrive signals NLOS and LOS
Fadingperiod) Symbol spread(Delay
Copyright Mark Rodwell, 2016
Interference by Intermodulation (1)
ce.interferen cause also will tonesdistortion These
. )2( and )2( sfrequencieat tonesdistortion
generate will and sfrequencieat signalsinput strong
, *distortionorder -odd*Given
1221
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Copyright Mark Rodwell, 2016
Interference by Intermodulation (2)
signal. desired with theinterfere willand passband,filter IF e within thliemay
)2(or )2(either yet passband,filter IF theoutside sfrequencie to
d translatebemay ) , ( tonesginterferin original themixer, After the
mixer. and stage RF
by the produced be will)2( and )2(at then tones
passband, filter the RF e within thlie and at tones theIf
ce.interferen nosuffer illreceiver w theand rejected, be they will
filter, RF theof passband theoutside lie and at tones theIf
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Copyright Mark Rodwell, 2016
Interference by Intermodulation (3)
it. outside lie es themselevsignals ginterferin even the passband,
sfilter' baseband e within thliemay productsation intermodul The
occur.may ation intermodul strong that stages IF
in the isit case, in this gain;high very have amplifiers IF The
filters. IF *and*
RF both the of passbands theinside liemay and at
sinterferer strong thereceiver, conversion-dual aIn
21 ff
Copyright Mark Rodwell, 2016
Interference by LO Phase Noise
y.sensitivitreceiver thedegrade willThis
overlap. willsignals variousof spectra converted-down The
spectrum. oscillator thebroadens This
ns.fluctuatio timinghave sOscillator Real
Copyright Mark Rodwell, 2016
Oscillator phase modulation
)exp()()exp(
))(1)(exp()(
(radian) 1)( :ionapproximat angle-Small
))(exp()exp()(
)()( nsfluctuatio phase have We
))(exp()exp(
))((exp()(
:)( nsfluctuatio timingAdd
)exp()(
:nOscillatio
0,0,
0,
0,
0,
0,
0,
tjVtjtjV
tjtjVtV
t
tjtjVtV
tTt
tTjtjV
tTtjVtV
tT
tjVtV
LOLOLOLOLO
LOLOLOLO
LO
LOLOLOLO
LOLO
LOLOLO
LOLOLO
LOLOLO
Copyright Mark Rodwell, 2016
Oscillator phase modulation
))(exp()2/())(exp()2/(
)exp( )(
)exp()exp()2/(
)exp()exp()2/()exp( )(
Then
)exp()2/()exp()2/()cos()(
:assume Now
)exp()()exp( )(
:nOscillatio
0,0,
0,
0,
0,0,
0,0,
tjVjtjVj
tjVtV
tjVtjj
tjVtjjtjVtV
tjtjtt
tjVtjtjVtV
mLOLOcmLOLOc
LOLOLO
LOLOmc
LOLOmcLOLOLO
mcmcmcLO
LOLOLOLOLOLO
deviation phase Squared-Mean2powercarrier
power sideband total
2/ :amplitude Sideband
:at Sidebands
2
c
c
mLO
j
Copyright Mark Rodwell, 2016
Oscillator phase: sinusoidal modulation
))(exp()2/())(exp()2/(
)exp( )(
Then
)exp()2/()exp()2/()sin()(
:assume Instead
)exp()()exp( )(
:nsfluctuatio phasen with Oscillatio
0,0,
0,
0,0,
tjVjtjVj
tjVtV
tjjtjjtt
tjVtjtjVtV
mLOLOSmLOLOS
LOLOLO
mSmSmSLO
LOLOLOLOLOLO
deviation phase Squared-Mean2powercarrier
power sideband total
2/ :amplitudes Sideband
:at Sidebands
2
S
S
mLO
Copyright Mark Rodwell, 2016
Oscillator AM and PM sidebands (skip)
.modulation phase sinusoidal : .modulation phase alcosinusoid :
.modulation amplitude sinusoidal : .modulation amplitude alcosinusoid :
))sincos(exp()sincos1()( :Signal /
sc
sc
msmcLOmsmcpmam
NN
tttjtNtNtv
2/2/sideband modulation phase
2/2/sideband modulation amplitude
where
:sidebandlower :sidebandupper
)()()(2)(
:SpectrumFourier
**
CSp
sca
paupau
mLOumLOuLO
jC
jNNC
CCCCCC
CCjV
Copyright Mark Rodwell, 2016
Oscillator AM and PM sidebands (skip)
PMn larger tha bemight AM :sources Optical
AM PMusually :soscillatortor in transis /clippingSaturation
sidebands. PM and AM ofconsist sidebands Total
Copyright Mark Rodwell, 2016
Oscillator phase noise
)() (4)()()(
) () (2)(
) (
) (2)(2
1)exp()(
) ()exp(
:ansformsFourier tr
)()()(density spectral random, is )( :Assume
)exp()()exp( )(
:nsfluctuatio phasen with Oscillatio
2*
0,
*
0,0,
LOLOLOLOVV
LOLOLOLO
LOLO
LOLOLOLOLO
LOLO
LOLOLO
LOLOLOLOLOLO
SjVjVjS
jjV
djtjVtF
tjF
jjjSt
tjVtjtjVtV
)() (2)(
correctjust will.Isomewhere.error 2 a up picked veI'
LOLOVV SjS
Copyright Mark Rodwell, 2016
Oscillator phase noise
)() (2
)() (2)(
LOLO
LOLOVV
L
SjS
)( sidebands plus line,n oscillatio central
:oscillator of spectrumPower
)( : nsfluctuatio phase of spectrumPower
LOS
S
deviation phase Squared-Mean2powercarrier
power sideband total 2
S
offset 100Hzat
radians/Hz 10 of magnitude a has means
" dBc(1Hz)100)Hz100("
bandwidth 1Hz ain carrier torelative dB as )(
as expressedusually noise Phase
1/25-
S
fL
fL
Copyright Mark Rodwell, 2016
Signal interference from LO phase noise
ysensitivitreceiver thedegradegreatly willand , above 43dB is This
dBm(1Hz)130dBc(1Hz)10030dBm
dBc(1Hz)100)MHz1( power, received 30dBm , from MHz 1offset
:Example
(dB/Hz) )(dB)(
unitslinear )(
:at density SpectralPower Noise Equivalent
referred-input ifeasiest are nsCalculatio
signals.both tosidebands add willnoise phase LO IF, At the
power frequency :signal gInterferin
power frequency :signal Received
1
11
11
11
kT
S
Lff
ffLP
ffLPS
f
Pf
Pf
noise
RF
RF
RFnoise
RF
rfRF
Copyright Mark Rodwell, 2016
Constellation rotation from phase noise
ionconstellat in the
pointsdecision themove also will
corrected,not if
phase, LO theof nsFluctuatio
impairment iscorrect th also
can processing digital ADC-Post
ns.fluctuatio phase se track theattempt to
willPLL LOreceiver The
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