SVSWR—Site Voltaggge Standing Wave Ratio...until October , 2010 for emissions measurements above 1...

SSVSWRVSWR——Site Voltage Standing Wave RatioSite Voltage Standing Wave Ratiog gg g

Site evaluation above 1 GHzSite evaluation above 1 GHz

Validation of OATS and SemiValidation of OATS and Semi anechoic Chamberanechoic ChamberValidation of OATS and SemiValidation of OATS and Semi--anechoic Chamberanechoic Chamber

Peter BerquistPeter Berquist

Emissions Test Consulting, LLCEmissions Test Consulting, LLC1736 Stove Prairie Circle1736 Stove Prairie Circle

CCLoveland Colorado 80538Loveland Colorado 80538970970--667667--24512451

Presentation Outline Presentation Outline

IntroductionIntroductionSVSWR Measurement DefinitionSVSWR Measurement DefinitionSVSWR ProceduresSVSWR ProceduresResultsResultsPrecautionsPrecautionsSummarySummary

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SVSWRSVSWR--IntroductionIntroduction

SVSWR is CISPR’ method of validation of a test SVSWR is CISPR’ method of validation of a test site from 1 GHz to 18 GHz but limited to the site from 1 GHz to 18 GHz but limited to the maximum specified limit frequency.maximum specified limit frequency.maximum specified limit frequency.maximum specified limit frequency.The test environment is reflection freeThe test environment is reflection free——no no groundplanegroundplane——removed by absorbersremoved by absorbersCISPR 16CISPR 16--11--4:20074:2007--4 is the applicable standard4 is the applicable standardApplies to test sites for testing to CISPR 22:2005 Applies to test sites for testing to CISPR 22:2005 CISPR 22 2005 A d t 1 d fi th t tCISPR 22 2005 A d t 1 d fi th t tCISPR 22: 2005 Amendment 1 defines the test CISPR 22: 2005 Amendment 1 defines the test limits and frequency rangelimits and frequency range——11--6 GHz6 GHzThe FCC defines the measurement upper limit ofThe FCC defines the measurement upper limit ofThe FCC defines the measurement upper limit of The FCC defines the measurement upper limit of 5 times internal clock frequencies5 times internal clock frequencies——up to 40 GHzup to 40 GHz

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CISPR 22:2005 Amendment 1 Implementation CISPR 22:2005 Amendment 1 Implementation d td t O t b 1 2011O t b 1 2011datedate——October 1, 2011October 1, 2011VCCI Japan Implementation DateVCCI Japan Implementation Date——April 1, 2010April 1, 2010However members have the option of waitingHowever members have the option of waitingHowever, members have the option of waiting However, members have the option of waiting until October , 2010 for emissions measurements until October , 2010 for emissions measurements above 1 GHzabove 1 GHz

Note: VCCI will require telecommunication port Note: VCCI will require telecommunication port measurements as of April 1, 2010measurements as of April 1, 2010

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ANSI C63.4:2003 is the current site validation ANSI C63.4:2003 is the current site validation standard for > 1 GHz. The site is deemed standard for > 1 GHz. The site is deemed adequateadequate if it meetsif it meets NSANSA Some logic!!Some logic!!adequateadequate if it meets if it meets NSANSA. . Some logic!!Some logic!!However, Section 4.1.5.4However, Section 4.1.5.4--note specifies a note specifies a reflection freereflection free environment, environment, well indirectlywell indirectly--the the reflection is considered an ERRORreflection is considered an ERRORANSI C63.4:2009 is the optional requirement ANSI C63.4:2009 is the optional requirement calls for meeting CISPR 16calls for meeting CISPR 16--11--44--SVSWR to 18 GHzSVSWR to 18 GHzcalls for meeting CISPR 16calls for meeting CISPR 16--11--44--SVSWR to 18 GHzSVSWR to 18 GHzORORAlternatively covering a minimum area of 2.4 by Alternatively covering a minimum area of 2.4 by y g yy g y2.4 meters (for a 3 meter test distance) between 2.4 meters (for a 3 meter test distance) between the antenna and the EUT Using RF absorbing the antenna and the EUT Using RF absorbing materialmaterial

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material material The FCC accepts either standard The FCC accepts either standard


ANSI C63 Subcommittee 1 has been working on ANSI C63 Subcommittee 1 has been working on d ti th hd ti th h li d TDR th dli d TDR th dand promoting the much and promoting the much maligned TDR methodmaligned TDR method

for site validationfor site validationDoes not simulate the EUT environmentDoes not simulate the EUT environment

The The TDR methodTDR method, as proposed, is wrought with , as proposed, is wrought with enormousenormous errors and inadequacies errors and inadequacies

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SVSWR Measurement DefinitionSVSWR Measurement Definition

ForewordForewordSVSWR is a new method for site validation of a freeSVSWR is a new method for site validation of a free--space space

environment used to make radiated emissions environment used to make radiated emissions measurements from 1measurements from 1--18 GHz. 18 GHz.

A freeA free--space environment is radio frequency reflectionspace environment is radio frequency reflection--free free environment, as found in space. environment, as found in space.

This may be a little impractical here on Mother EarthThis may be a little impractical here on Mother Earth

SVSWRSVSWR--What is it?What is it?SVSWRSVSWR--What is it?What is it?The term The term VSWR comes from analogous term used in VSWR comes from analogous term used in transmission line theory. transmission line theory. VSWRVSWR--is an acronymis an acronym--Voltage Standing Wave RatioVoltage Standing Wave Ratio

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VSWRVSWR is an acronymis an acronym Voltage Standing Wave RatioVoltage Standing Wave Ratio


VSWR W i l iF:\VSWR\Reflection_file\reflection.htm

G:\Applets Physics\ph14e\stwaverefl.htm

VSWR Wave simulation

G:\Applets Physics\ph14e\stwaverefl.htm

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When a transmission line is terminated with an When a transmission line is terminated with an impedance, Z , that is not equal to theimpedance, Z , that is not equal to theimpedance, Z , that is not equal to the impedance, Z , that is not equal to the characteristic impedance of the transmission characteristic impedance of the transmission line, not all of the incident power is absorbed by line, not all of the incident power is absorbed by the termination. Part of the power is reflected the termination. Part of the power is reflected back so that phase addition and subtraction ofback so that phase addition and subtraction ofback so that phase addition and subtraction of back so that phase addition and subtraction of the incident and reflected waves creates a the incident and reflected waves creates a voltage standing wave pattern on the voltage standing wave pattern on the transmission line. The ratio of the maximum to transmission line. The ratio of the maximum to minimum voltage is known as the Voltage minimum voltage is known as the Voltage Standing Wave Ratio (VSWR).Standing Wave Ratio (VSWR).

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Instead of the reflection of a mismatch source and Instead of the reflection of a mismatch source and l d f bl th fl ti i f bj tl d f bl th fl ti i f bj tload of a cable, the reflection is from an object on load of a cable, the reflection is from an object on a measurement site. a measurement site.

Some of those objects might be:Some of those objects might be:Some of those objects might be:Some of those objects might be:GroundplaneGroundplaneExposed Ferrite TileExposed Ferrite TileAntenna mastAntenna mastAntenna feedlinesAntenna feedlinesChamber WallsChamber WallsAbsorbersAbsorbers——in some casesin some cases

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SVSWR Measurement DefinitionSVSWR Measurement DefinitionReflections on the site cause the addition and subtraction of Reflections on the site cause the addition and subtraction of

waves at the observation point (receive antenna). waves at the observation point (receive antenna).

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As the frequency increases, the wavelengths decrease.

The two differing path lengths cause a in-phase or out-of-phase condition adding and subtracting from the direct path propagation

Reflections from Groundplane on OATSTwo EMCO 3115 Horn Antennas

condition—adding and subtracting from the direct path propagation

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Horizontal-No Absorbers Horizontal--Absorbers


This addition or subtraction to the direct path This addition or subtraction to the direct path ti b ltiti b lti th ti bth ti bpropagation by multipropagation by multi--path propagation can be path propagation can be

responsible for:responsible for:Adding 6 dB Adding 6 dB ggOR completely canceling the direct path propagationOR completely canceling the direct path propagationOR somewhere in between the above conditionsOR somewhere in between the above conditions

The magnitude of the interference depends on:The magnitude of the interference depends on:The magnitude of the interference depends on:The magnitude of the interference depends on:The path length of the unwanted reflection with respect The path length of the unwanted reflection with respect to the direct path (wanted)to the direct path (wanted)The quality of the reflectorThe quality of the reflector——size, material, etc.size, material, etc.

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OmniOmni--directional source antenna (used to simulate the directional source antenna (used to simulate the EUT) is used to illuminate all objects for 360EUT) is used to illuminate all objects for 360°°..The normal measurement antenna is used to receive.The normal measurement antenna is used to receive.

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The EUT source could exist anywhere within the test The EUT source could exist anywhere within the test volume and radiate in any direction volume and radiate in any direction

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The receive antenna beamwidth must be sufficient to The receive antenna beamwidth must be sufficient to encompass the test volumeencompass the test volume

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SVSWR Measurement DefinitionSVSWR Measurement DefinitionDualDual ridge Horn and Standard Gain antennas don’t complyridge Horn and Standard Gain antennas don’t complyDualDual--ridge Horn and Standard Gain antennas don t complyridge Horn and Standard Gain antennas don t complyANSI C63.4ANSI C63.4--2009 Specifies Only Horn Antennas for measurements 2009 Specifies Only Horn Antennas for measurements

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SVSWR Measurement DefinitionSVSWR Measurement DefinitionLogLog--periodic antennas comply across the band but sacrifice some periodic antennas comply across the band but sacrifice some sensitivitysensitivitySchwarzbeckSchwarzbeck ESLP 9145 is an exampleESLP 9145 is an example

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Sensitivity sacrifice in additional antenna factor for LSensitivity sacrifice in additional antenna factor for L--PP

Dual-ridge Horn Schwarzbeck Log-periodic

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OmniOmni--directional source antenna defineddirectional source antenna definedHH--Plane requirements shownPlane requirements shown

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SVSWR Measurement DefinitionSVSWR Measurement DefinitionBi i l HBi i l H f ibl f Hf ibl f H PlPlBiconical HornBiconical Horn--performance possible for Hperformance possible for H--PlanePlaneThe POD approaches perfectionThe POD approaches perfectionSchwarzbeck 9112 conforms but approaches directionalSchwarzbeck 9112 conforms but approaches directional

POD Schwarzbeck 9112

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SVSWR Measurement DefinitionSVSWR Measurement DefinitionEE--Plane RequirementsPlane Requirements--dipole in naturedipole in nature

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EE--Plane patternsPlane patterns

POD Schwarzbeck 9112

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SVSWR Measurement DefinitionSVSWR Measurement DefinitionETSETS--Lindgren 3183 Source AntennaLindgren 3183 Source Antenna

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A series of measurements A series of measurements are made at different are made at different distances from the reference distances from the reference pointpointThese measurements will These measurements will define the test volume in two define the test volume in two dimensionsdimensions——the area andthe area anddimensionsdimensions——the area and the area and height height Any reflecting objects that Any reflecting objects that are illuminated by the source are illuminated by the source antenna will cause the phase antenna will cause the phase ppaddition and subtraction of addition and subtraction of the wave at the receive the wave at the receive antenna. antenna. Changing the path length, Changing the path length,

ill th t dditi dill th t dditi dwill cause that addition and will cause that addition and subtraction to change.subtraction to change.

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Side SVSWR is influenced by Rx antenna patternSide SVSWR is influenced by Rx antenna patternThe pattern is changing not the SVSWRThe pattern is changing not the SVSWR--Typically 3 dBTypically 3 dB

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From the previous slideFrom the previous slide--it can be seen that it can be seen that The environment near the source antenna The environment near the source antenna matters more than the environment behind the Rx matters more than the environment behind the Rx antennaantennaantennaantenna

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SVSWR Measurement DefinitionSVSWR Measurement DefinitionWith th dditi f d ti th fWith th dditi f d ti th fWith the addition of a second propagation path from a With the addition of a second propagation path from a reflector the response will add and subtract depending reflector the response will add and subtract depending upon path length.upon path length.

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FreeFree--space conditions with the only propagation path is the direct space conditions with the only propagation path is the direct pathpathAs the source moves away from the receive antenna, the response As the source moves away from the receive antenna, the response change is 20*LOG(D1/D2)change is 20*LOG(D1/D2)change is 20 LOG(D1/D2)change is 20 LOG(D1/D2)

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SVSWR Measurement DefinitionSVSWR Measurement DefinitionTh fl ti th l th h d th hTh fl ti th l th h d th hThe reflecting path length changes as does the phase The reflecting path length changes as does the phase addition and subtractionaddition and subtraction

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By varying the distance of the source, the path to any By varying the distance of the source, the path to any reflecting object changes and thus changes the standingreflecting object changes and thus changes the standingreflecting object changes and thus changes the standing reflecting object changes and thus changes the standing wave.wave.All the measurements at different distances are corrected to All the measurements at different distances are corrected to the first reference distance by the freethe first reference distance by the free--space propagation space propagation formulaformulaIf the test environment simulates freeIf the test environment simulates free--space, the corrected space, the corrected readings will be very close to the reference reading at each readings will be very close to the reference reading at each position on the test volumeposition on the test volumeposition on the test volume. position on the test volume.

At each frequency, the maximum and minimum are found for At each frequency, the maximum and minimum are found for each of the six positions. each of the six positions. The difference is found This is the SVSWRThe difference is found This is the SVSWRThe difference is found. This is the SVSWRThe difference is found. This is the SVSWR

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SVSWR ProceduresSVSWR Procedures

SVSWR Positions are conditional depending upon test volumeSVSWR Positions are conditional depending upon test volume

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SVSWR ProceduresSVSWR ProceduresVSWRSVSWRSVSWRS

Procedures are detailed in CISPR 16Procedures are detailed in CISPR 16--11--44Th f i ifi d t 1Th f i ifi d t 1 18 GH18 GHThe frequency range is specified at 1The frequency range is specified at 1--18 GHz18 GHzHoweverHowever--CISPR 22:2005 upper limit of test is 6 GHzCISPR 22:2005 upper limit of test is 6 GHzThe acceptance criteria for SVSWR is 6 dBThe acceptance criteria for SVSWR is 6 dB

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SVSWR ResultsSVSWR Results

SVSWR-Semi-ancechoic ChamberFront-Vertical-1.5 Meter

8-22-2007

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10

4567

dB

0123

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

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SVSWR Precautions SVSWR Precautions

OmniOmni--directional directional antenna mastantenna mast is critical to is critical to successsuccessReRe--radiation off the radiation off the feedlinefeedline or or antenna mastantenna mastshould be avoidedshould be avoidedshould be avoidedshould be avoidedExposed ferriteExposed ferrite tile are reflectors at these tile are reflectors at these frequenciesfrequenciesFoam absorbers tipsFoam absorbers tips are reflectors at low angles are reflectors at low angles of incidenceof incidenceAny medium other that air is a reflector at lowAny medium other that air is a reflector at lowAny medium, other that air is a reflector at low Any medium, other that air is a reflector at low angles of incidence at these frequencies angles of incidence at these frequencies

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SVSWR PrecautionsSVSWR Precautions

With large test volumes, With large test volumes, absorbersabsorbers may have to may have to be placed upon thebe placed upon the turntableturntablebe placed upon the be placed upon the turntableturntableCumingsCumings EVAEVA--12 works great for continuous 12 works great for continuous handlinghandling——flexible and clean from flexible and clean from PanashieldPanashieldReceive antenna’s Receive antenna’s beamwidthbeamwidth must must generouslygenerouslyencompass the test volumeencompass the test volume——antenna must be antenna must be the same used during emissions measurementsthe same used during emissions measurementsggAntennas are Antennas are not aimednot aimed at each other as in NSAat each other as in NSAETS 3115ETS 3115 is much better than ETS 3117 for a 2 is much better than ETS 3117 for a 2 meter test volumemeter test volume my experiencemy experiencemeter test volumemeter test volume——my experience my experience A A loglog--periodic antennaperiodic antenna may be required for large may be required for large test volumestest volumes---- > 2 meters (> 2 meters (for ANSI)for ANSI)

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SVSWR PrecautionsSVSWR Precautions

Measurement Instrumentation may have to be Measurement Instrumentation may have to be l dl d th tth t iti ititi itplaced placed nearnear the antennasthe antennas--sensitivitysensitivity

A A preamplifierpreamplifier should be used on Port 2 of the should be used on Port 2 of the network analyzernetwork analyzer——20 dB of head20 dB of head--room requiredroom requirednetwork analyzernetwork analyzer 20 dB of head20 dB of head room requiredroom requiredThe The noise floornoise floor should be checkedshould be checkedProblematic SVSWR is an indication that there Problematic SVSWR is an indication that there are reflection problems below 1 GHz. Those are reflection problems below 1 GHz. Those reflections will reflections will notnot necessarily be found by NSAnecessarily be found by NSA

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SVSWR SummarySVSWR Summary

SVSWR Technique was reviewed.SVSWR Technique was reviewed.Thi it lid ti ill b i d f CISPRThi it lid ti ill b i d f CISPRThis site validation will be required for CISPR This site validation will be required for CISPR measurements over 1 GHz. measurements over 1 GHz. The The ANSI C63.4:2003 ANSI C63.4:2003 only requires site validation below 1 only requires site validation below 1 GH t it iGH t it iGHz as an acceptance criteriaGHz as an acceptance criteriaThe The ANSI C63.4:2009 ANSI C63.4:2009 calls for meeting CISPR calls for meeting CISPR 1616--11--44--SVSWRSVSWRORORAlternatively covering a minimum area of 2.4 by 2.4 Alternatively covering a minimum area of 2.4 by 2.4 meters (for a 3 meter test distance) between the antenna meters (for a 3 meter test distance) between the antenna ( )( )and the EUT Using RF absorbing material and the EUT Using RF absorbing material

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SVSWR SummarySVSWR Summary

The SVSWR validation provides a method to The SVSWR validation provides a method to d t i fl tid t i fl ti t t itt t itdetermine reflectionsdetermine reflections on a test siteon a test siteWhile it detects the problems, there is no While it detects the problems, there is no indication of theindication of the source locationsource location of the problemof the problemindication of the indication of the source locationsource location of the problemof the problemThe The reflection locationreflection location can be found via TDR with can be found via TDR with two directional antennastwo directional antennas——another presentationanother presentationSVSWR does not detect anomalies in SVSWR does not detect anomalies in propagation propagation pathpath lossloss——only the presence of reflectionsonly the presence of reflections

Thank youThank you——Questions or comments?Questions or comments?

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SVSWR—Site Voltaggge Standing Wave Ratio...until October , 2010 for emissions measurements above 1...

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