of Phase Noise Measurement

I
I
o
The "Arl" of
Phase Noise
f,lleasurement
DieterScherer
March1985
o
Rf & Mlcrowave
Measurement
Symposlum
ancl
txhlbltlon
ftE'HF$|IfJJ
o
O
o
o
INTRODUCTION
Measuring and specifying phase noise has become inereasingly important as phase
noise is the limiting facior in many RF and microwave systems,like Doppler radar and
space telemetry sy.te-. or communicationlinks. The complexity and subtleties of the
1nuurur.-unt have earned it the reputation of being more art than science.
This paper gives an introduction to phase noise measurementfocusing on the two most
and useful techniques,the "Two Source Phase Detector" and the "Delay Line
"o--o1
Frequenc;- Discriminator" methods. System limitations are pointed 9ut a-swell as the
potential ,our"". of erroneousdata when phase noise is measuredin a bench set up.
The lt72gc Carrier Noise Test Set is HP's latest contribution in this field, designed to
simplify and automate the complex task. A table of comparisons will show where the
ttTigC and the various other HP solutions are optimally employed.
O
Why MeasurePhaseNoise?
1.
Phasenoisecauses. . .
environment
in multi-signal
o Lowerreceiversensitivity
Transmiller
H
q-
DopplerSignal
DecorrelatedClutler Noise
J_
o Glutternoisein DopplerRadarSystems
r Phaseerrorsin digitalcommunicationsystems
in the presenceof a
phasenoiseimposesfundamentallimitations wherevera weak signal is processed
receiverlocal oscillatorare
.tiorrg interferini rij""r. In the aboveexample,phasenoisesidebandsof the
to thI Ifpioduct of the strong interfering sjsnll and cover up the weak wanted signal.
ti"".i"*"a
signal in this caseis
A similar situatio;exists with cohereit Dopplerradar. The strong interferring
unwanted return
of
this
p;;;;J
ty reflectionsfrom large stationarl' f5;".ts. Phasenoise side bands
signal'
weak
Doppler
lien"i"r. ,iecorrelateJbvdelav ind potentially coveras clutter noisethe
Phasenoise adds to
b,,r"n in the world of d-igitaliata tiansmission phasenoise is a limiting faetor.
the carrier or data clock
o*,"r^il system rroir. in.rJ"sing Bit Error Rate and may causea cycle slip in
recovery.
5
2.
of PhaseNoise
BasicRepresentation
2.1 In the Time Domain:
A ,0(t)
v(t): Signatwithrandomphasefluctuation
v(t): Vscos f?rtsl+ J O (t)l
DisPlaY
OscilloscoPe
V(t) = Vs cos 2rlsl
ar <> ao(t)
andPhasearerelatedbY
Frequency
f(r):##
In the time domain phase noise can be observedas phase jitter of the signal on an oscilloscopedisplal' or
a time interval counter may detect the instantaneous time fluctuations of the zero crossings.
phase or frequencyfluctuations are the same physical phenomena.One can be derivedfrom the other as
angular frequency is the first derivative of phase with respect to time.
6
o
O,,
In the FrequencyDomain:
FJd(t):Jd(f)
S4
SpectralDensityof PhaseFluctuations
SO(f)-Jd2rms(f)
f'3 F l i cke r FM
I d2rms
f' 2 Random W alk Phase
t-t FlickerPhase
fo White Phase
| -€
FourierFrequencY
s3
Fluctuations
spectralDensityof Frequency
: fzSO(f)
Sr t(f) = Jf2rms(f): l2J @2rms(l)
domain.Terms like
Spectraldensity distributions describefrequencyor phasenoisein the frequency
.,White,,',,Flicker,'and ..RandomWalk" refei to the slopeof f , f-t, and f-2 of thd densitydistribution.
time domain rrluiiipri."tion by the Fourier frequency- conespond.rlsto differentiation in the
noise.
converti the spectraldensity of phasl noiie to the spectraldensity offrequency
7
2.3 Relationof PhaseNoiseto CarrierSidebandNoise
offset
The modulari6n pf the signal phase manifests itself in modulation sidebandsto the carrier at
are
levels
sideband
The
rFourier
frequencyr.
rate
frequenciesu.hich ar" muliiples of the modulation
first
onl5'the
modulation,
For
small'angle
terms.
by
Bessel
relatedto the magnirucleof the phasedeviation
b1'
Besselterm is signrficanr and the relation betu'eenphasedeviation and sidebandlevel is approximated
Forsmallanglemodulalion
( I ar. < l radian)
?P
=
J d2rms
{-t d2rms(f)
A common,though indirect.representationof phasenoiseis,7{fr,the ratio of the single sidebandnoise
po$.er in a I Hz band*'ldth to the total carrier power specified at a given offset, f of the carrier'
produce
This representation is applicable only for very small phase deviations, sufficiently small to
negligible higher order sidebands.
Definitionol Y (t)
y(tt=ry
-+
fogl= |
+-fott
\
Refationbetween2,5 5, Sl f:
lor -\6<< lradian
st
8i
$rb
E!
E:
1_
11
Y (t)= iS o(t)=i -t, srf (t)
€i
E.b
.E'E
*l1 HzL
69
o
o
3 PhaseNoiseMeasurementTechniques
o DirectSpectrumAnalysis
) o Two Sourcesand PhaseDetector
o FrequencyDiscriminator
) o DelayLine FrequencyDiscriminator
o CarrierSuppression
(OndriaBridge)
o Heterodyne
PeriodGounter
From the multitude of techniquesto measurephaseorfrequency noisetwobasicmethods are singled out
and explained in somedetail onthe following pages:the "Two Sourcesand Phase Detector" technique and
the "Dela5' Line Frequency Discriminator" technique'
Both methods are ielatively simple to implement and are broadband solutions.They also compliment
each other well. The first method rnl.rur"s phase noise;high sensitivity is obtainable and two sourcesare
needed. The second method measures frequency noise, has inherently lower sensitivity close in but no
secondsourceis required.
3.1Two Sourcesand PhaseDetectorTechnique
Source
UnderTest
lsolationAmPl.
lv'
PhaseDetector
(DoubleBalancedMixer)
lsolationAmPl.
Calibration
Allenuator
t_
tl
Low PassFiller
^Al
i+
I
Low Noise
Amplifier
, 1! F = F
v
L--
NarrowBand
PhaseLock LooP
sd (t)
y (t)
sd (t)=Jdimsltl=1/z
Hz)
JV273ns(1
(forJd<<lrad.
V2grms
forld<<1rad.
=
9 $ l = 1 1 2s 6 ( l l 1 / q
J V2rms(1 Hz)
vzBrms
generatesa signal
With the LO and RF input in phasequadraturesteadystatewise,the mixer IF output
phase
detectorcoxstant
the
operation
In
linear
sources.
two
tl"
of
phase
difference
oroportional to the
is
frequen-cv-offset.
produced
when
Bource
either
signal
beat
sinusoidal
the
of
;;;i;;;;;rr.
phaselock
"orftg"
Most sourc", ,nould-6riftout of quadratureover the periodof measurement.A narrow band
ioicesthetwo signalsinto phasequadrature.Atrates lessthan theloopbandwidth the
l";;;;t;atically
phase fluctuations are
,ou-r.", now track each other; at rates higher than the loop bandwidt\ t-he
unaffected.The two isolation amplifiers shouldpreventinjection locking of the Bources.
phase noisemeasuredon the IF port representsthe nns-sumof the noisecontributionsof eachsource.
Eoureeshould be either
For definite data on the sourceut d"r ttst, the phase noise of the reference
well characterized.In the absenceof any information on both sources,onecan at least state
", sourcenoise is worse than the measureddata. If 3 unknown sourcesare available, 3
""gfigiUi.
that neither
accuratelyeach
i""rui"rn"nts with B different sourcecombinationsyield sufficient data to calculate
individual noiselevel.
10
o
O 311 The Mixeras PhaseDetector
Vg cos t,,11
Vs cos(-nt - 6(l))
v (t)=
15
cos(t,n - ,L) t. O(t)) +
ffi. oiL)t * o(r))+...
vB peak
V (t) = VBpeakcos({rn - col1t. O(t))
KL = ConversionLoss
VB peak= PeakVoltageof
BeatSignal
for c,rL= <,.,8 and d(t) = (k +1) 90" - Jd(t)
JV (t) = (t) VB peaksin Jd(l)
for ld<<l radian
Jv (t) = (t) K6 -\d(t)
I VoltsI
K6=vBpeak L ,d J
basedon one signal gating the
The frequencyconversionof signals applied.toa.mixer |f qhvsically
a multiplying process.
represents
case
Either
diodes.
other or on the nonlinear conductanceoriite mixer
frequencyof the input
difference
in
the
product
resulting
generates
a
Among many terms,ih" mixer also
signals.
(linearrelationbetweenRF and IF
with a sinusoidalinput at the RF port and assuminglinearoperation
VB
peak
voltage
a
with
peak'The phaseslopeof this beat
voltage),the beat sigrial is also ,it" wave
"
signal at zerocrossingsequals= VB peak-'
t; trreiaf;6 hequencyand at a.phaseoffset of 90ophasefluctuationsJdrt)
setting both inpui ft;;ir
related.The mixer actsas
resultin voltagefluclua"tionsJv(t rwhich for smalllhase devjationsarelinearly
VB
to
equal
K6
of
peak'
constant
a phasedeteciorwith a phasedetector
11
3 . 1. 2
Ko = vB peak
: fvg 76s
Jv(f) =Kd r O(f)
J d76s(f):;;
1
.
JV 765(f)-
S O(t): J d2rms(f)= 172
forJ 6<<1
g (t')
o
Calibrationwith BeatSignal
1
ffi-,
-JV rms(f)
JV2rms (1 Hz)
v2Brms
JV2 rms(l Hz)
-:
1
/
4
e (l 1/2so(f)
v'B ,r,
J V 2 r m s ld B m
Phasenoisespectrumin dBm
correcledfor bandwidthand
analyzer characteristics.
-V2BrmsldBm
Beatsignalin dBm.
-Kel dBm
-6 dB
Atlenuation(if beatsignalwas
attenuatedin calibration).
Accounls lor rms valueof beat
signal(3 dB) and conversionof
s 6(f)roS (f) (3 dB).
+2.5dB
Accountsfor log amPlifierand
of noise
videoliltering(averaging)
(if analogspectrumanalYzerls
used).
Assuming VR ,.ooL as the phasedetectorconstantdictateslinear operationof the mixer. The calibra'
for iz tf ror Sl6rfrcan then be read from the aboveequations.
ti""lilr,"."p"."trtifln"lyzer
PM or FM
Othercalibration methodsare basedon thllharacterization of the phaseslope,on calibrated
signal.
spurious
sidebandson one of the two sourcesor on the injection of a calibrated
12
O
313
SystemNoiseFloor
lVn MtX
Jvn t.t.tr
Low NoiseAmplifier
t
=
system(f)
JV2ntlttx +JV2nLNe
v2g rms
The noise floor of the measurement system is establishedby the equivalent amplifier and mixer noise
tshot noise, flicher noiser at the IF port redueed by the phase detector gain K6 (VB peak for linear
operation r.System sensitivity is therefore maximized by using a high level mixer, selecting a mixer u'ith
low flicker noise and follou'ing the mixer with a low noise amplifier.
-80
dB c
5 MHz- 1.6GHz
Example:3047AMixer-Amplifer
- SyslemNoisewlth High LevelDoubleBalanced
Mixerand Low NoiseAmplifier
.rN
ob -100
F@
urg
9
- ^Y
et
-120
=\
urO
O-
gE
-140
ACE
-tr
6g
\
U'E
E
-160
\
\
o
-180
lHz
-
1 0H z
1 00Hz
1 kHz
10kHz
100kHz
l MHz
f [HzJ
t3
31.4 PotentialError Sources
o Suppression
or peakingol noisenearor belowthe phase
lock loop bandwidth.
o Inieclionlocking
r Deviationfrom phasequadrature(resultingin an
effectivelylowerK6)
o Non-linearoperalionof mixer(if linearitywasassumed
in calibration)
o Distortionof RF-Signal(resultingin a deviationol K6
from VB peaf)
o Saturationof the preamplilieror spectrumanalyzerin
calibrationor by high spurioussignals(e.9.line
spurious)
o Changeof impedanceinterfacewhile going lrom
calibrationto measurement
e lnsuflicientcancelationof commonsourcenoisein a
residualnoisetest
r AM-noise(in particularAM noiseof the common
sourcein a residualnoisetesl)
o Closelyspacedspurious(e.9.line multiples)
as Phasenoise
misinterpreted
o Noiseinjectedby peripheralcircuitry (powersupply,
phaselock looP)
(€.9.,
o Noiseinjectedby peripheralinstrumentatioh
DVM)
oscilloscope,
o Microphonicnoise.
o
Technique
Os: DelayLine FrequencyDiscriminator
Source
underTesl
PowerAmPlifier
Delay Line ( r)
Srt(t) = lf2r|nr{f)
tort=fi2JVrms = K62tr
Jf *.
Jvtrms (t Hz)
O
srt(f)
Srt(l)
7 (f) derivedfrom Srt(f)
:I (tl=*irs-rtt
n =i +
rorro<<1
JV"r. (1 Hz)
6"t-
A delay line and a mixer operating as a phase detectorhave the combinedeffect of a frequency
discriminator.The delayline transformsany frequencyfluctuationinto a phasefluctuationand the mixer
with the L and R inputs at g0ooffsetlinearly convertsthe phasefluctuationsinto voltagefluctuationsat
the IF port. As derivedon the next page,the equivalentfrequencydiscriminatorconstantKp is proportional to r and K6.
=
The frequen"yio phaseconversionhas a sin x/x characteristicwith a null at f 1/r. Measurementsare
thereforelimited to f < L/Zt twith correctionl.
The systemcan becalibratedby characterizingthe frequencyslopegt KOand ", or moreconvenientlyb5'
.aaing fftl sidebandsto the sourc€under test ror a substitute)and determiningtheir level as reference
level with an RF spectrumanalyzer.
15
s.2.1 Theoryof DelayLine FrequencyDiscriminator
rd(r)(
v(r)=Kd rd(r)
Delay time r
t(t) = lo +Jt sin 2;ft
V(t) = Ve cos (2;fst - f .ot 2nltl
FM
Carrierwithsinusoidal
fs = CarrierfrequencY
| = FM rate
Jf = FM deviation
on PhaseDetectorJO(t)
PhaseDifference
2rrl(r-r) - 2ilsl-f
Jd(t) = Zrts(t - r)..*"ot
Jd(t) = -2rrls' .,+ (cos 2rrl(t - rl - cos 2iltl
"ot
2trlt
JO(t)=- 2nlsr * 2f sinzrfr sinp'r 1t- 7\
=
PhaseDetectorOutput:V(t) K6 -\@(t)
= (2k+1)?(PhaseQuadrature):
lor 21116r
V(f) = KO2f sin z:'lrsin 2trt(r -il
TransferFunction:
Jv = Ko2{sin nlr= K62,..rlt #
forr=fi:
sin-zrfz = |
tlr
JV = K6 2nr Jl
r_-
Kp t#l
= FrequencyDiscriminator
Constant= K62nr
o
()szz
SystemNoiseFloor
lVn urx
JVn lxa
L o w N o i s eA m p l i f i e r
Srt(f ) system
DelayLine
!'r
t'
Psz
(if used):
Jdnr =
ol RFAmplitier
Noise
Phase
ffi
1t * f t
Kd = VB peak= fiffiott
Ko (in linearoperation):
with L = ConversionLoss(Power)of Mixer
noise.This also
Mixer noiseand basebandamplifier noiseare interpretedby the systgmas frequency
uv un nr amplifier.The amplifiermight have beenaddedto boostthe
holdsfor phase
"oir.l"tioJu."a
signal level lowered b1'the lossy deial'line'
':{:l;#-
JV2n..nl
(X5Z--1'
srt(t)
1(tt=++
sYstem
,
(#l' ('*f
,lJ.t
Jr-l2pp
(2;rl2
for J6<<1
- *f
- rr+23r1
closein and
Mixer, basebandamplifier and RF amplifiernoiseall have a flicker noisecharacteristic
Ko u'hich
reduced
showwhite noisefarther out.The contribution. of mixer and basebandamplifier are
!v
emplol' a
is
to
though'
p"i"t. out the benefit of the RF amplifier as it maximizesKg'"A bet*:8:Itllon,
il
Jon-r"
and
Yith
amplifier u.r*.-itr. signal split and eliminatethe needfor an RF amplifier
;;;;;
'
f-2 and f-3 towards the
with
characteristic,
noise
L(f)increases
white
rndth"r,
flicker
S;;;;a:fn",
but poor sensitivity as
"
carrier. This means
sood sensitiyity far out (limited by the sinx/x response)
comparedwith the phasedetectormethodclosein'
N
{(,
6
!{ -3
=\
ApproximaleSyslemNoise
Floor of the DelaYLine
DiscrlminalorTechnique
2Z'.
uJ=
.h
l-
ICE
Ag
cg
Y!
- r e G,
o
o
t!t,**;"""G
F
1 Hz 10 Hz 100Hz 1 kHz 10 kHz
17
is to lump
A different*.a5.ofesrimatingthe s)'stemnoisefloor of the delal'line discriminatortechnique
line
delal'
The
perturbation
J02r-tor
"rrr'
phase
noise
all noise contributions into an equivalent
of
a
factor
phase
by
noise
equivalent
this
enhancei
discriminator.interpreting Jc) as frequency rrbi.u
| /2;f ;.
Example:
= -160 dBc/Hz'
Phase noise of the mixer at i kHz ! t 't kHz'
noise floor is
system
with a 100 nsec dela5'time the resulting
J2=!t
l| i l' ' .
2rf;
'Hz
= -160 dBc + 61 dB = -96 dBc
-100
-90
-80
-70
-60
9 rttl
e, tn -50
Losl *40
-30
Enhancemenlof
equivalentPhasenoise
perturbationbYdelaY
-20
t,tll=gxl=rl
l " r ?( r )g r ( t ) \ 2 ; f
I
rti
;r
+10
0
100Hz
18
O
with Resonator
s.2.3 FrequencyDiscriminator
Low Noise
plifier
t-r[rro,r'h
56(l) for t '*
CavityResonalor
CrystalFiller
Bandwidth
InsideResonator
1t. $ I'
o
ddl
E q u i va l e nDt e l a yT i me r =Eilfo=r[
KD= K52;r =*ri}
,?a
Jvrms(f)= Kdfi rttmsltl
Although not a broadbandsolution,it can be advantageousto replacethe delay line with a cavity
resonatoior crystal filter. Groupdelay td6/du\ producesan equivalentr of Q/ rfo for Fourierfrequencies
less than half the bandwidth. Inside fo/zq, the systemthereforemeasuresthe spectraldensity of
frequencynoise*'ith a discriminatorconstantof K6 2Q'/fo.
Bandwidth
OutsideResonator
1f' $ t,
Jvrms(Q= Kd Jdrms(f)
Outside fot}Q,the system ma]' be vieg'ed as 2 signals applied to a phase ddtector u'ith the sideband
noise of one"signalstripped off by the cavity resonator.The system then measuresJd216s with a phase
detectorconstant K6.
19
Solutions
4 HP PhaseNoiseMeasurement
o HP 11729C/8662A
PhaseNoiseTestSystem
(phasedetectormode)
o HP 11729CCarrierNoiseTestSet
(delayline discriminatormode)
o HP 3047APhaseNoiseMeasurement
System
o HP 11740AMicrowavePhaseNoise
System
Measurement
Following is a comparisonof HP phase noise measurementsolutions with particular focus on the
Carrier NoiseTest Set,HP's most recentcontributionto phasenoisemeasurement.
LLTZ1C
20
o
4.1
PhaseNoiseTestSystem
HP 11729C/8662A
Principleol Operation
(PhaseDetectorMethod)
H P 11729CCarrierNoiseTesl Set
r
I
ill*Li
640 MHz
Low Noise
Reference
Signal
Microwave
Source
UnderTest
5- 1280M Hz I
Generation Selection
.01-18 GHz
al
lF-Amp
I
HP 8662A
Synthesized
SignalGenerator
Opl.003
x0
DC
FM
EFC
Inpul Inpul
Low Noise
I
Amp
Speclrum
Analyzer
5-1280 MHz
R
1 0H z 1 0M H z
I
I
I
I
I
r
I
I
,l
l l Conlroller
I
I
.J
L
J
astateof'theartlownoieereferenesignalat640MHz
The HP 86624Synthesizedsignal Generatorprovides
is
applied
to a steprecoverydiodemultiplier which gensignal
to the Hp 11Z2gCCarrier NoiseTest Set.This
18
GHz.
A switchedin filter selectsan_appropriate
beyond
ranging
MHz
eratesa combof signals spacedby 640
an lFrange of 5
themicrowavesourceutdertestinto
converts
down
combline.This microwavireferencesignal
to 1280MHz.
The doublebalancedmixer phasecomparesthe IF signalwith the outputsignal o{the HP 8662A(.01to 1280
MHz). phase quadratureis enforcedby phaselocking the HP 8662Ato the signal rurdertest either thru the
limited electroniccontrol of the HP 8662A's10 MHz crystal oseillator or thnr its DGFM port. The loop band'
widths can be set over a 4 decaderange.
A firstorder phaselock loopis enabledbythecapturefeaturemakinglock acquisitioneasy.Then thesecond
To enablephasenoise
orderphaselock loop (with very high dc gain) maintains lock and phasequadr-ature.
via the looptest
be
characterized
phase
can
noise
suppression
the
Larrd*idth,
within the loop
-"".u".-.nts
ports.
21
N
N
HP 11729CCarrierNoiseTest Sel
I
1
r
I
r+_
-
r--1
i o<---o_n=
^,n*:JOLi
2{-
^"-ilAfj
r lI
I
-
--'l
'
't
I----1---T--0ri_i8GHr
Microwavc Sortrco
Undor Tesl
Hi'I"'Tti i
IHIHH
tfgl^::;-;;;
combGenerator
r---1
(@:
! i , u L - - + - J :I- f I lt+-t llII":::
ltooi."ii
cED
(w!E
PowerAmP
rr-amoV
L -l-
J
l*i
I
I
I
6a0 mHt SAtt lillcr
I
I
640 MH2
Inpul
5-1280 MHz
I
40 dB
LNA
I
I
lo"p I
resl I
'1.5MHr
I
l0 Hr-l
l0 MHzl
HP 3582A/356t4
Low Frequency
Speclrum Analyrer
Loop Conlrol
Loop Conlrol Oulpul DC'FM
Aur. OulPul
HP 98364
DG3kTop Compuler
40 MHz Xlal
lo MHz Slal osc'
I I
160 MHz sral
640 MHz Low Noise
Relerence Signal
I
I
I
I
I
L-
o
0ll0 - 20 MHz
I Hz Sleps
1 2 8 0M H z O r r l P t t l'
| .l Hr SlePs
J
o
0 dBm
04
PhaseNoiseTestSystem
11 NoiseFloorof HP 11729C/8662A
(PhaseDetectorMethod)
N
I
o
o
-24
E
-40
I
F
-60
\
tr
tr,
g
E
tr
o
o
F
llJ
L
o
z
\
\
I
\
-80
;2in DC FM
\-86!
\
\
\
I
-100
\
\
12A
\
640 MHz ReferenceSignal '
from
HP 8662A
tl
-140
$ytt"m Noise@ 10 GHz
\
ll\-
t-.a
\
\
\
\
ltJ
o
rlpicalHpr'rz2eclaeize
\
\
-,---\_,r
-160
--
---
I
o.
o -180
o
@
Hz
1 0H z
1 0 0H z 1 k H z
10 kHz 100kHz
Oflsetfrom Carrier | [Hz]
ts
Js
J1
/ s y s t e m= 1 0 l o g ( N zr ' l Q r o- 1 0 1 0- 1 0 1 0 )
N = Multiplicalionnumber of the 640 MHz signal
/ r = Absolule SSB PhaseNoise of lhe 640 MHz
reference signal (dBclHz).
? a = AbsoluteSSB PhaseNoise of lhe 5 lo 640
(1280)MH: lunable signal (dBc/Hz).
,lg = Two-porl noise of HP 11729C(dBc/Hr).
Ollset
flom
carrier
Typical
640llHz
low
noise
oulput
lHz
10Hz
100H2
1 kHz
10 kHz
100 kHz
1 IlHz
-54 dBc
-94 dBc
-114 rlBc
-126 dBc
-149 dBc
-159 dBc
-159 dBc
MHz
1 0M H z
Typical
Typical
Typical
320-640 Two-porl Two-porl
llHz tunnolseof
noise ol
ableE662A HP 11729CH P 1 1 7 2 9 C
oulput
@ 5 G H z @ 10 GHz
-64 dBc
-99 dBc - 9 3 d B c
-94 dBc -112 dBc -106 dBc
-1ltf dBc -125 dBc - 1 1 9 d B c
-125 dBc -132 dBc - 1 2 6 d B c
-136 d8c -137 dBc - 1 3 1 d B c
-136 rlBc -1t18rlBc - 1 4 2 d B c
-146 dBc -153 dBc -147 dBc
For most microwaveapplications,11, the SSB phase noise of the 640 MHz referencesignal, is the
dominatingfactorin settingthe noisefloorof the systemas its phasenoiseis multipliedup to microwave
frequencies.
23
o
Mode
HP 11729COperatingin Discriminator
4.1.2
--l
-I
I
Calibration
source
f-
I
t Signalal Carrierlreq. or lF wilh
I CalibratedFM Sidebands
I
I
I
L-
H P 1 1 7 2 9 CC a r r i e rN o t s eT e s l S e t
fcalibration
,
CombLine
Comb
Generalion Section
Calibralion
b
-6'rl
MicrowaveSource
u n d e rT e s t
i
I o.o1to 18GHz
lF-Amp
ExternalDelay Line
5 l o 1 2 8 0M H z
Baseband
Spectrum
Analyzer
iox.toI
'i"l
I
t_
a
a
o
o
Low noisedown convercionof microwavesignalunderlest
Delaylineoperatingat lF (5-1500 MHz)
Calibrationsignalprovidedby HP 8662A
PhasequadratureIndication.
The HP LL729Cmay also be usedin a delay line discriminator mode.The microwave referencesignal
generatedby the 640MHz signal down convertsthe Bourceunder test into the IF range.The powersplitter
ind auxiliaiy IF output allows one to simply ineert an appropriate delay line ext*nally.
Delayingt-hesignal at IF meanslower delayline lossesand alsoa wider choiceof delaydevices,like e.g.
SAW d;lav line. Any signal generator with FM sidebandsat IF or RF can Eenleas a calibration tool.
24
4.1.3
of HP 11729C
Sensitivity
Mode)
Discriminator
(DelayLineFrequency
-20
o
o
!
-40
1OOns
t Delay
o
G
cg
-60
\
C)
(!
o
o
o
,9
o
z
o
o
G
3
r
@
o
o
-'*r
"^J./
-,..11Hz
\..'
usclllalor
-trof
-ruoL
TypicalFree'Running
- -y'Source at 10 GHz I
10Hz
at 10GHz
I
\
\.\
\\\
\.-
tOOHz
1 kHz
1OkHz
lOOkHz
Offset From Carrier(Hz)
L.-..-.
1 MHz
10MHz
PhaseNoiseMeasurement
on PulsedRFSignals
4.2.1
P u l s e dR F S o u r c e( D U T )
I
I
I
Anti-aliasingFiller
J
t-
A
PulseDrive
NarrowBand
PhaseLock LooP
The basebandsignal ofa pulsedRF signal phaselockedto a referencesourceequalsthe basebandsignal
(0 is
of a. ut pulsedRf signal jated by the pulseenvelope(seeFig. A, B, C). The CW noisespectrumJ
multiplied by the envelopefunction of the pulse,
h(t)=
+**3,
(-t)n
n
n nt
Sln -It
n2'rt
cos -T\
Observedin the frequencydomain,this gating processmeansconvolvingthe two spectrato obtain the
pulsedbasebandsp""tto- (seeFig. C). The resulting spectrumhas J (f) folded around multiples of the
part of this spectrumis yieldedby the DC tcrm of the pulse
iuise repetitionfrequency(PRF).The relevant
it"t.ttshowsthattheleveloftheunpulsedphasenoisespectrum.c(0isreducedbythe
enrrelopefunction,
unPursrd
rqu"r.'J
the duty cycle.
J $1,*o= (+)'
Jl3por""a
A lowpass filter, the antialiasing filter, with a corner frequency of <PRF/2 needsto be employedto
eliminaie all the aliasing products (SeeFig. D). It also sen'eeto filter any phaeetransients associated
;th lh; pulse modulatoi which otherwise would limit the low noiee amplifier.
ftr. ,vrt"- sensitivity decreaseswith decreasingduty cycle.A sampleand hold circuit in the baseband
iri"en by the puisesignal,wouldimprovetheeystemaensitivityforlowduty cvcle!.Aeimplerway
"ir.uit,
to reducesystemnoisein the pulse off period is to gate either the LO or the R drive of the mixer'phase
deteetor.
A side effect of phaselocking to a pulsedRF signal is the reduction of the effectiveloop bandwidth
it becomesincreasingly important to have a well balancedmixer-phase
by t/T, For duty cycles <.:|ttu,
detector.
26
o
F r e q u e n c yD o m a i n
Time Domain
-+l
PRF
F i g A : P u l s eE n v e l o p e
zPar
Speclrumof PulseEnveloPe
t
c
A
c
G
s
F i g B : U n p u l s e dB a s e b a n dS i g n a l
( U n P u l s e dP h a s eN o i s e )
UnpulsedPhaseNoiseSpectrum
t
G
g
A
!
g
G
G
o
!ut
pulsed
l\/l\
-\ ,\
-2
Fig C: PulsedBasebandSignal
beforeLow Pass
\
PulsedPhaseNoiseSpeclrum
belore Low Pass
t
G
o
A
E
3
G
a
o
G
a
Fig D: PulsedBasebandSignal
afler Low Pass
PulsedPhaseNoiseSpectrum
aller Low Pass
4.2.2. PulsedPhaseNoiseMeasurements
(PhaseDetectorMode)
withthe HP 11729C
LPF
ffi
HP 11729C
Noise
Spectrum
Output
640
Input
5 to 1280
lnput
PLL Gontrol
Voltage
Output
Selectingpulse mode (phasenoise) on the HP 11729Capplies an error cunent to the mixer/phase
detector and switches in a user-suppliedlow pass filter to remove the pulse repetition frequency
feedthrough.
l
4.3
System
HP 3047APhaseNoiseMeasurement
ExamPle:
Apptication
on lrequencydivider
phasenoisemeasurement
Two-por4
HP 3047A Phase Noise llelcurement Syrlem
HP 98il6A or9816A
Derk Top ComPuter
125 Mllz
1 2 5M H z
t_
Comparison
Device
representsa high sensitivity phasedetectorsystem
The Hp 304?4.phase NoiseMeasurementsystem
automatesthe calibration and measurement
with controllableprr"". r""r, circuits. Extensive softwlre
procedures
ri--!r^-^ i^ ^- example
o -acidrrql
meas
phasenoise
noise measureresidual nhecp
of a
is.an ^oax-l^ ^f
Determining the phasenoise of frequencydividers
sum of
rms
the
will
measure
svstem
the
and
ment. Here,the phasenoiseof the 8662;. i;t;;i;;".J"a
noiseof both dividers.
LrI i lLrL
Eri
F[rt]F
r P L E S ! , i i 5 E t 0l H Z
+tstshr
-3S
-.ig
-59
- E gF
-i6
-BU
-so t- .
- r8g
- ilBF.
-ra6
-t30
-r{8
- l5Ei
-r661-.
-r79
lH=
29
4.4
MicrowavePhaseNoise
HP 11740A
System
Measurement
HP 11729CCarrierNoise
Tesl Sel
Deviceunder Test
' 1 0 . 4G H z
G u n nV C O a l
HP 3(X7A Spectrum AnalYzerSYslem
HP 9836A or 9815A
Desk Top GomPuler
800 MHz
540 MHz
RelerenceSignal
providesa broadbandand
In the Hp 11?40AMicrowaveNcise MeasurementSystem,the HP ll7290
source'
comparable
-- noisemicro*'avereferencesignal eliminating the needfor a eecond
lo*,
with either the
11729C
HP
of
the
The Hp gOaZephasedetectorsystemthen comparesthe IF output
IF
eource.
b-12g0 MHz outfut of the HP 8662A or any other suitable and tunable
-\
---T
--T
\l-
-\
''i".
:?
30
''rl
. (. )
lek
.dBc./P.z r
tez<
v's { !:12-l
Ir'!
reY
?er.
Comparisonof SystemSensitivities
Iou
-20
-40
l tP 11729C
N
E
(,
tr
;AW@\
C
-60
t,nz
00ns
elay
a\
l,
\
o
G
E
L
o
L
L-
-100
G
o
\
o
o
-120
I
0
2
o
o
G
a -140
o,
\
\\
-HP 117:
l9c/8662A
@ 1 0 cHz
t.\
\
'a
F.
\
t
\
o
o
o
=
\
*
l--i
\
-rHP 3047A@ 10 GHz*
\
-:a;=
-160
-180
iT;
1 0H z
100Hz
1
z
10 kHz
100kHz
1 MHz
10 M H z
Otfsetfrom Carrier(Hz)
.Performanceshownrequiresa second,usersuppliedsource
of comparablePhasenoise.
31
SystemsComparison
46 PhaseNoiseMeasurement
l-
-
;;;^- I
H P 8 5 6 6 AE
HP 35854
HP3582A
S p e c t r u mA n a l Y z e r
HP 11729C
C a r r i e rN o i s e
TestSel
HP 35854
Speclrum Analyzer
HP 3585A
Spectrum AnalYzer
HP 3582A
Spectrum Analyzer
HP 3582A
Speclrum AnalYzer
HP 35601A
S.A. lnlerface
HP 35601A
S.A. Inlerface
-
J--;,;;; I
I
HP 8562A
Synlhesized
Sig Gen
Reference
HP 8662A
xp seesa
I
HP 8340A
]
xe aozza
i_ _:':3:
i--I"r''Gl:l t
Principle ol
Operalion
SourceUnderTesl
/a\./
@-'
_
iI
Low Noise Microwave
Relerence Signal
sigGen
HPrs36A-1816A
l ,836 -rst6^ I
l-rP
SourceUnclerTest
HP 8556A/8
HP 8568A'B
HP 3561A
Spectrum Analyzer
li
.l
f "*'"-' I
Source Under Tesl
Reference
Relerence
1 0M H z- 1 8 G H z
5 M H z- 1 8 G H z
5 llHz -'18 GHz
10 MHa - 18 GHz
yes
no
yes
yes
- 123dBc at 10kHz
- 145dBc noisefloot
(withHP 1r729C)
-1't2 dBc al 10 kHz
- 145 dBc noise floor
123dBc al 10 kHz
145 dBc noise lloor
- 170dBc al 10 kHz'
- 170 ctBcnoise floor
Ollsel FrequencY
: 1 0M H z
<40 MHz
<10 llHr (<40 MHz)
<10 MHz
no
yes
yes
no
Aftl-Noise (Miuowave)
yes
w/erlemal deleclor
yes
yes
Manual Operation
yes
no
yG8
yes
Aulomalic Op€relion
yes
yes
te8
yes
user provided
€xlensive
crlemive
ur€r piovided
(HP-rB)
.Specification shown reguires a second. user suPplied source of comparable phas€ noise.
i
i
I
i
Two-pod Notse
32
ti
I
Typical Syslem
Noiie al 10 GHr
Sotlware
I
%G
\r;
6_
Reference
Frequency Range
HP11729C
CarrreN
r oise
T e s lS e l
t-'- - - - - -'
f .*..r^
"*t.*l I
Synthesized
I I
_l I
Source Under Test
(trequencY
discriminalofmodej
HP 11729C
Canler Noise
Tesl Set
I
I
HP11729C
CarrierNoise
Tesl Set
HP 11740A
Microwave
P h a s eN o i s e
Measuremenl
Syslem
H P 1 1 7 2 9 C / 8 6 6 2 A HP 3047A
PhaseNoise
PhaseNoise
Measurement
Tesl System
System
t F h a ! ' d € l e c t o rm o o ( )
GLOSSARYOF SYMBOLS
Availablenoisepowerin bandwidthB
CarrierlrequencY
CornerlrequencYof flickernoise
Fourierfrequency(sideband-,olfset-,modulation'
requency)
baseband-f
f(t)
IHzJ InstantaneouslreguencY
frequencylluctuation
Instantaneous
rf(t)
IHzl
K6
Ivolt/radJPhasedetectorconstant
Kp
lvolVHzl Frequencydiscriminatorconstant
[dBc/HzJ Ratioof singlesidebandphasenoiseto total signal
9ttt
powerin a 1 Hz bandwidthI Hertzfrom the carrier
Signalpower
Pg
lmwl
Powerof singlesideband
Pssb
lmwl
Qualityfactorof resonator
o
srt(f)
tllzzttlz! Spectraldensityof lrequencyfluctuations
s6(f)
lrad2lHzl Speclraldensityof phasefluctuations
t
Isec] Time
voltage
Instantaneous
Y(t)
Ivoltl
vB peak IvoltJ Peakvoltageof sinusoldalbeatsignal
Inslantaneous
Phasefluctuation
a0(r)
lradl
InstantaneousPhasePerlurbance
Ao(t)
lradl
Delaytime
T
lsecl
FKTB
fe
fs
I
lmwl
IHz]
lHzl
lHzl
REFERENCES
1r
Transmilters."IEEE Transactiorts
of Noisein Microu'ave
ctn
Ashler'.J.R..et al. "The l\leasurement
pp.
MTT-25,
29a'318,
Technigues,
Vol.
No.
4,
tApril, 19ii t.
Mierouat'cTheorl'and
0r
for MeasuringSpectralPurity", Microu'aves,
Vol. 16.
Fischer.M.."An Overvieu'of ModernTechniques
No. 7, pp.66-75,
July 1979.
J}
Hewlett-Packardstaff. "Understandingand MeasuringPhaseNoise in the FrequencyDomain,"
ApplicationNote207,October1976.
staff,"MeasuringPhaseNoisewith the HP 35854SpectrumAnalyzer",Application
4 ) Hewlett-Packard
IMay1981.
Note246-2,
D)
of Low PhaseNoiseSignalsUsing the8662A
staff,"Applicationsand Measurements
Hewlett-Packard
SignalGenerator",ApplicationNote 283'1,November1981.
Synthesized
A Tutorial Introduction",NBS Technical
6 t Howe,D.A.,"Frequenc]'DomainStability Measurements:
Note679,March 1976.
1t
Lance,A.L., Seal,\\'.D.,Hudson,N.W.,Mendoza,F.G.,and Donald Halford."PhaseNoiseMeasureAnalysis," Conferenceon PrecisionElectromagneticMeasurements.
ments Using Cross-Spectrum
Ottawa,Canada,June 1978.
8 t Ondria F.G.,"A lMicrowaveSystemfor Measurementsof AM and FM NoiseSpectra",IEEE TransacVol. MTT-16,pp.767-781,
September1968.
tionson Microu'aueTheorl'and Techniques,
9 t Scherer,Dieter,"Design Principlesand Test Methodsfor l,ow PhaseNoiseRF and MicrowaveSour-
ces",Hewlett-PackardRF and Microu'aveMeasurementSymposium,October1978.(Also editedverApril
sion in Microwaves,"Today'sLesson- Learn aboutLow-NoiseDesign",part 1, pp. 116-122,
May 1979r.
1979,part 2,pp.72-77,
l 0 ) Shoal J.H., Halford, D., Risley,A.S., "FrequencyStability Specificationand Measurement:High
Frequencyand MicrowaveSignals", NBS TechnicalNote 632,January 1973.
Technique- Conceptsand Implementation",
l l t Temple,R., "Choosinga PhaseNoiseMeasurement
Hewlett-PackardRF and MicrowaveMeasurementSymposium,February 1983.
34
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