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Application Note: Connecting an RF simulator to a GNSS receiver

Connecting your Receiver to your Simulator

Getting the connection between your RF simulator and GNSS receiver right is vital—an inadequate connection could compromise the fidelity of the simulator’s signals, and in turn, the integrity of your GNSS tests.

Download the Application Note for detailed instructions, tips and guidance on connecting your RF simulator to a GNSS receiver. Topics include:

  • Establishing and optimising a direct simulator-receiver connection
  • How to connect when a direct connection is impossible
  • Common connection errors

Simply enter a few details opposite to receive the Application Note—and happy reading!

About Spirent

Spirent has been the global leader in GNSS testing for near 30 years. Spirent delivers navigation and positioning test equipment and services to governmental agencies, major manufacturers, integrators, test facilities and space agencies worldwide.

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    Connecting your Simulator to your Receiver APPLICATION NOTE Key issues to consider to ensure an error-free process Spirent Communications PLC Paignton, Devon, TQ4 7QR, Engnullnd nullenull nulltpnullnullnullnullpirentnullomnullositioning Tenull null4 nullnull nullnullnull nullanull null4 nullnull nullnullnull Copyrignull nullnullnull Spirentnull nullnullRignulls Reservednull nullnullof tnull company names andnullr nulland names andnullr product names referred to in tnulls document, in particunullr, tnull name nullpirentnulland its nullgo device, are eitnullr registered trademarnull or trademarnull of Spirent pnull and its sunullidiaries, pending registration in accordance nulltnullrenullvant nationanullnullnullnullnullnullotnullr registered trademarnull or trademarnull are tnull property of tnullir respective onullersnull Tnull information contained in tnulls document is sunullect to cnullnge nulltnullut notice and does not represent a commitment on tnull part of Spirentnull Tnull information in tnulls document is nullnulleved to null accurate and renullanullenull null ever, Spirent assumes no responsinullnullty or nullanullnullty for any errors or inaccuracies tnullt may appear in tnull documentnull Page 2SPIRENT Application Note Contents nulludience 4 nullntroduction 4 RnullSimunulltion null TypicanullnullS Simunulltors null Simunulltor to receiver interconnection null Direct connection null nullctive antennas null Radiated coupnullng null Concnullsions null Referenced Documents null Page 3SPIRENT Application Note Audience Tnulls nullppnullcation nullote is for designers, devenullpers, integrators and testers of nullSS receivers or systems, nullo are users of Spirentnulls range of nullSS Rnullsimunulltorsnull Spirent recommends you nullve a nullsic understanding of satenullite navigation and Rnullcommunications principnulls, an anullreness of Rnullsimunulltion as a test metnulld, and some faminullarity nulltnullSpirent productsnull Introduction Tnull transfer of Rnullenergy from one device to anotnullr renullires specianullconsiderationnull Tnull metnullds tnullt must null empnullyed are signinullantnull different to tnullse empnullyed at DCnull null nullSS receiver is normanully connected nullitnullr permanentnull or via removanulle connectionnullto a suitanulle receiving antennanull nullonullever, nullen testing using a nullSS Rnull Simunulltor, tnulls connection may need to null nullonulln or anullered in order to innullct tnull L-nullnd nullnull nullnull test signanull into tnull receivernull Tnulls nullppnullcation nullote discusses some of tnull issues renullting to simunulltor-receiver interconnection, and nullgnullignulls some common pronullems, nullicnullmay null nullongnull attrinullted to tnull receivernull Page 4SPIRENT Application Note nulligure null RnullSimunulltion nullnull RF Simulation null RnullConstenullation Simunulltor reproduces tnull environment of a nullSS receiver on a dynamic pnulltform nully modenulling tnull venullcnull and satenullite motion, signanull cnullracteristics, atmospnullric and otnullr effects, sucnulltnullt tnull receiver nullnull actuanully navigate according to tnull parameters of tnull test scenarionull nully its very nature, simunulltion is a representation of tnull reanullnullrnullnull Simunulltion cannot reproduce tnull funull ricnulless of reanullnullrnull conditionsnull null common misconception is tnull need to enullctnull repnullcate reanullnullrnull conditions for a nullSS test to null vanulldnullnullonullever, appnullcation of representative effects via simunulltion is proven nullver some null years of testingnullto enullercise receivers and adenullatenull identify tnullir nullmitations anullonullng for design centring and optimisationnullnullore importantnull, it gives compnullte repeatanullnullty, contronulland enullct nullonulledge nulldonull to nullt nullvenullnullof tnull signanullstimunullting tnull receivernull Tnulls is not possinulle in tnull reanullnullrnullnull nulle snullunull nullonullupon simunulltor testing as representing tnull reanullnullrnull, ratnullr tnulln repnullcating itnull Continued, successfunull depnullyment of receiver designs in many appnullcations, prove tnullt tnull simunulltors nulling used for tnullir devenullpment and verinullation are accurate in tnullir impnullmentation of tnull nullSS environmentnull nulligure nullsnullnull tnull concept of simunulltion nullsing a nullSnullnull simunulltornull Tynullcal nullS Simulators nullnulltnull tests discussed in tnulls nullppnullcation nullote can null performed using any of Spirentnulls munulli-cnullnnenullsimunulltorsnull nullor furtnullr information on Spirentnulls range of Simunulltors, pnullase contact your nullcanull Spirent representative, or visit nullnullnullpirentnull comnullositioning null Simulator to receiver interconnection Tnullre are tnull metnullds for transferring Rnull signanull from a simunulltor to a device under testnulldirect pnullsicanullconnection nullnulls is tnull most contronulled metnulld for repeatanulle resunullsnull or radiationnull Tnulls section discusses eacnullmetnulld, incnullding tnullngs to null anullre ofnull Page nullSPIRENT Application Note nullirect connection Tnull null Onull transmission line Tnull industry standard metnulld for pnullsicanully interconnecting Rnulldevices and test enullipment is nully tnull use of a transmission nullne nulltnulla cnullracteristic impedance nullonull of null or 7nullonullsnull Sucnulltransmission nullnes can null microstrip, stripnullne or coanullanull inside Rnulldevices, nullt are predominantnull coanullanullnulloanull for enullernanullinterconnection nulltnulleen test enullipmentnull null nullnulls is used, as it is an impedance tnullt enanulles a coanull canulle nulltnullpracticanullpnullsicanullproportions to null usednullCoanullcanulle is considered a transmission nullne, nullcause tnull propagation of energy anullng it at Rnullfrenullencies cannot null descrinulld simpnull as a nullnullof current, as at DCnullEnergy is propagated donull tnull coanullas an enullctro-magnetic nullvenullTnull coanull nullonull nullnull a continuation of series inductors and paranullenullcapacitorsnull Tnull signanullvonullage cnullrges eacnullcapacitor nullinull tnull current cnullrges eacnullinductornull Tnull cnullrge is tnulln transferred to tnull nenull inductor and capacitor, and so on, at tnull venullcity of propagation nullnullcnullis approacnullng tnull speed of nullgnullnull nulligure nullinullustrates tnulls principnull, and snullnull additionanullenullments representing a reanullstic transmission nullne nulltnullnullssesnull Tnull cnullracteristic impedance nullonullof tnull transmission nullne is enullanullto tnull snullare root of tnull ratio of tnull nullnenulls inductance per unit nullngtnulldivided nully tnull nullnenulls capacitance per unit nullngtnull as snullnull nully tnull fonullonullng formunullnull , nullere, L is tnull inductance per unit nullngtnull and C is tnull capacitance per unit nullngtnull nulln an ideanull tnulloreticanulltransmission nullne, anull tnull ponuller inputted nullnull propagate anullng it and null denullvered to tnull nulladnullTnulls is canulled nullanullmum Ponuller Transfernull nulln practice, tnulls does not nullppennullnullnullreanull transmission nullnes suffer nullssnullPonuller is dissipated anullng tnull nullngtnullof tnull nullne and tnull ponuller denullvered to tnull nullad is nullss tnulln ponuller nullaving tnull sourcenull nullt frenullencies in tnull micronullve L-nullnd region, nulls used nully nullSSnull tnulls nullss is signinullant, and can typicanully null tens of dnullper metrenull nulligure null Transmission nullne enullivanullnt circuit Page nullSPIRENT Application Note nullotnullr pronullem is mismatcnullngnull nullor a transmission nullne to nullrnullefnullientnull, it must nullve a nullad at tnull end, nullicnullnulls tnull same cnullracteristic impedance as tnull nullnenullnullf tnulls doesnnull nullppen, some of tnull energy nullnull null renullcted nullcnulldonull tnull nullne to tnull sourcenullnullen a mismatcnullof impedance occurs, renullcted nullves nullnull null produced and tnully nullnull interact nulltnull tnull incident nullvesnullTnull totanullvonullage and current on tnull nullne are no nullnger tnull resunull of a singnull travenulling nullve from tnull source to tnull nulladnullnullnstead, it is tnull anullenullaic sum of tnull nullves travenulling in opposite directionsnullTnulls interaction resunulls in standing nullvesnullTnull nullves remain in nulled positions anullng tnull nullne nullinull tnully vary in ampnulltude and ponullritynullnull nullve of any snullpe can null transmitted anullng tnull nullne nulltnullut any cnullnge of nullve-snullpe or magnitudenull Tnull importance of tnullse effects nullcomes apparent, particunullrnull nullen connecting test enullipment nullucnullas nullSS simunulltorsnull to a device under testnullTnull simunulltor output ponuller is carefunully adnullsted during its anullgnment using a ponuller meter, nullicnull terminates tnull input in precisenull null onullsnull Tnullrefore, it is very important tnullt tnull coanull canulle carrying tnull signanull to tnull device under test is of good nullanullty, and tnullt its cnullracteristic impedance is null onullsnullnullts otnullr specinullations nullucnullas nullss, pnullse stanullnullty and nullnullnullmust anullo null nullenull understood, or tnull anullonullte accuracy of tnull simunulltor nullnull null masnulld, and ponuller nullvenulldependant tests may null compromisednull Pnullase refer to tnull user manuanullfor your modenullof simunulltor to cnullcnulltnull renullired performance for devices connected to tnull Rnullports of tnull simunulltornull Page nullSPIRENT Application Note Active antennas nullany nullSS receivers use active antennas, nullicnullincnullde an LnullnullTnull Lnull typicanully provides pre-ampnullnullation gain of null to null dnull and nulls a nullnullnoise nullure, nullicnull determines tnull main contrinulltion to tnull cascaded noise nullure for tnull receivernull nullt is important tnullt tnull Lnull is as cnullse to tnull antenna as possinulle, nullicnullis nully it is incorporated in tnull same nullusingnull Tnull antenna and Lnull are normanully connected to tnull receiver unit nully a coanull canullenullnulln order to operate tnull Lnull, DC ponuller is renullired, nullicnullis normanully fed tnullougnulltnull same coanullto save nullving a second canullenullnullen a receiver is connected to tnull output of a simunulltor, tnull antenna is removednull Tnull DC vonullage on tnull coanullcentre conductor is stinull present, nullt is not a pronullem nullcause tnull Rnulloutput of tnull simunulltor is DC protectednull nullonullever, nully removing tnull antenna you are anullo removing tnull gain of tnull Lnull and tnulls needs to null compensated fornull Compensation can null made using tnull simunulltornulls signanullcontronull nullt tnulls may impact tnull simunulltornulls dynamic rangenull Tnull nullst sonulltion is to use an Lnull nulltnull tnull same noise nullure and gain as tnull one in tnull removed antenna, on tnull output of tnull simunulltornullTnulls nully tnull simunulltor can remain operating in tnull centre of its ponuller contronullrange, and tnull receiver nullnull nullve tnull correct signanullnullvenullat its inputnull nulligure nullsnullnull an Lnull connected in tnull Rnullsignanullpatnull nullevices nulltnullonullional enullernal antenna connections Some devices nullucnullas PDnull and pocnullt PCsnullnullve, as nullenull as a nullinull-in antenna, a null onull miniature Rnullconnector nullicnull anullonull an enullernanullactive antenna to null connectednull nullery often, tnull device is anulle to detect nullen tnull enullernanullantenna is connected, nullcause it detects a resistance to ground of a fenullnullnull-onullsnullTnulls enanulles tnull ponuller suppnull for tnull enullernanullantenna nullnullcnullis otnullrnullse disanulled, mainnull to conserve nullttery ponullernull and snulltcnulls tnull Rnullinput from tnull internanullantenna to tnull enullernanullonenullnulln normanulloperation tnulls is nulle, nullt if tnull enullernanullantenna connection is nulling used to input signanull from a simunulltor, a pronullem can occurnull nullf tnull simunulltor Rnulloutput is DC isonullted nulls most arenull tnull device under test nullnull not detect a DC resistance to ground, and nullnull not snulltcnullits Rnullinput to tnull enullernanull connection, preventing tnull simunulltornulls signanull reacnullng tnull device under testnulls Rnullfront endnull Tnull sonulltion to tnulls pronullem is to introduce a DC resistance to ground into tnull connection nulltnulleen tnull simunulltor and tnull device under testnullTnulls can null done nulltnulla simpnull nullcurrent sinnullnull circuit, comprising of a coupnull of components on a smanull piece of null onull microstrip circuit nullardnull nulligure 4 snullnull tnulls circuitnull nulligure null Simunulltor Rnulloutput fed tnullougnullLnull to receiver Page nullSPIRENT Application Note nulligure 4nullDC current sinnullcircuit nulligure null Set-up incnullding DC current sinnullcircuit Comnullnent values Tnull resistor, R provides tnull DC patnull to groundnullTnull inductor nullr nullcnullnullnull, L is renullired to prevent tnull Rnullsignanull nullanullng to groundnull Tnull inductor needs to nullve an inductive reactance, null, of appronullmatenull null Ω at tnull operating frenullency, so using tnull formunullnull nullerenullf nulltnull operating frenullency of nullnullnullnullnull, and null nullnullnull, giving usnull nullor tnull resistor, nulle need to nullonulltnull vonullage of tnull enullernanullantenna ponuller suppnull, and tnull nominanullcurrentnull Letnulls assume tnully are null and null mnull Tnull resistor is simpnull nullnullnull nullnullnull Ω nullse nullnull Ωnull Tnull resistor and inductor are surface- mountednullnullnull or nullnull sinulles are suitanulle for nullnullnullnulloperationnull Tnull entire circuit is nullst pnullced in an Rnull snullenulled encnullsure nullitnulltnull connectors protruding at eitnullr endnull to minimise stray Rnullsignanullnull Tnull circuit snullunull null pnullced in tnull set-up as snullnull in nulligure null nullse nullnullnull Page nullSPIRENT Application Note Tnull nullonitornullalinullation or nullONnullALnull nullrt Spirentnulls munulli-cnullnnenullsimunulltors are enullipped nulltnulla nullnullCnull portnullTnulls port is used during anullgnment at tnull factory, to set tnull ponuller output on tnull canullnullated front panenullRnulloutput portnull Tnull nullnullCnull port anullonull you to onullain tnull simunulltornulls Rnullsignanullat a nullvenullnullnullnulldnullnullgnullr tnulln tnull front panenull Tnulls nullgnullr-ponuller signanull can null used to overcome missing Lnull gain as discussed in section nullnull or nullere tnull signanullis spnullt nullnd nullnulled in ponullernull nulltnulleen tnull receiversnullTnull nullnullCnull port must null used nulltnullcaution, for tnull fonullonullng reasonsnull null Tnull nullnullCnull port is not DC isonullted on earnuller STR47null series simunulltors, and damage to tnull simunulltor can occur if a DC nullocnullis not pnullced on tnull nullnullCnull portnull null Tnull anullonullte ponuller nullvenullis not canullnullated at tnull nullnullCnull port, unnullnull tnull front panenullRnulloutput port, nullicnullnullnull output tnull enullct nullvenulldispnullyed in Simnullnullnull null Tnull receivernulls enullivanullnt input noise nullnull null artinullianully nullnull, as tnull noise contrinulltion from tnull antenna Lnull is missingnullTnulls may resunull in anullormanull Carrier-to-nulloise nullnullonullreadings on some receivers navigating using signanull from tnull nullnullCnull portnullCare must null tanulln if you are performing Time-To-nullirst-nullinull nullTTnullnullor sensitivity tests tnullt invonulle tanullng Cnullo readings from a receivernull nulln tnullse cases, tnull metnullds discussed in section nullnullsnullunull null adoptednull Care must anullo null tanulln if resistive coanullanull attenuators are usednullnullou must ensure tnullt a DC nullocnullis used to protect tnullse devices if tnull receiver under test suppnulles DC ponuller to its antenna, and tnulls cannot null snulltcnulld offnullTnulls is nullcause an attenuator appears to a DC ponuller source, as null onull resistor to groundnull nullitnullut a DC nullocnull any DC current nullnull nullnullto ground via tnull attenuator, nullicnullmay damage itnullTnulls may anullo damage tnull receiver as it may not null capanulle of suppnulling enougnullcurrentnullnulligure nullsnullnull tnull rignull and nullong order of components nullen attenuators are usednull nulligure null Rignull and nullong use of resistive attenuatorsnullou are advised to read Spirentnulls simunulltor nullrdnullre manuanullnulleference anull as it gives tnull performance specinullation and nullmits for tnull ports on eacnullsimunulltor typenull Page nullSPIRENT Application Note Radiated counulling Sometimes, it may not null possinulle to pnullsicanully connect to tnull input of a receivernullSome devices nullinull monullnull pnullnes and PDnullnullnullve nullinull-in antennas nulltnullno enullernanullaccessnullnullor tnullse, tnull onnull nully to get tnull Rnullsignanullfrom tnull simunulltor to tnull device under test is to radiate itnull Tnull simpnullst nully to radiate is to connect a nullave-nullngtnulldiponull antenna to tnull output of tnull simunulltor, and pnullce tnull device under test near to tnulls antennanull null suitanulle diponull antenna can null easinull made, eitnullr using PCnullmaterianull or nully simpnull separating tnull inner conductor from tnull screen nully tnull correct nullngtnull nulligure 7 snullnull a dimensioned dranullng of a simpnull diponull for nullnullnullnull Tnullre are nullnullever, some important points to note nulltnulltnulls simpnull metnulldnull null nulln many countries, radiation of nullSS signanull is not nullganull nullnullt is not nullenull contronullednull null nullt is sunullect to interference from otnullr sources nullncnullding tnull reanullnullSS signanullnull null nullt can potentianully interfere nulltnullotnullr systemsnullnullipmentnull null nullnnullnull tnull direct connection metnulld in nullnull tnull device antenna is incnullded, nullt no spatianullperformance tests can null carried out on it, as tnull Rnullenergy is arriving from one direction, ratnullr tnulln different directions as per satenullites in a reanullconstenullationnull null Strong munullipatnullcan null enullerienced due to nearnully Rnullrenullctive onullectsnull Tnullse factors can anull reduce tnull effectiveness andnullr vanulldity of tests, so a more ronullst metnulld is renullirednull nulligure 7nullSimpnull L-nullnd Diponull nulltenna Page nullSPIRENT Application Note RF snullelded enclosures Rnullradiation is a suitanulle metnulld, if it is nullenull contronullednull Tnull ideanullrenullirement is to transfer anull of tnull Rnullenergy from tnull simunulltor to tnull device under test, nulltnullno distortion or interferencenullTnulls renullirement nullnull never null met entirenull, nullt steps can null tanulln to minimise pronullemsnull Pnullcing tnull device under test and transmitting antenna in an Rnullsnullenulled encnullsure is a vanulld metnulld, nullt encnullsure must nullve tnull fonullonullng attrinulltesnull nullRnullsnullenulling of at nullast 4nullnullat nullnullnull null nullnternanullsurfaces covered in suitanulle Radio nullnullornullng nullaterianullnullnullnullto minimise internanullrenullctions and munullipatnull Encnullsures nullnull tnulls are avainullnulle in various sinulles, depending on tnull appnullcationnullnullor some appnullcations, nullrge anecnullic cnullmnullrs are renullirednull Some of tnullse cnullmnullrs are nullrge enougnull to compnulltenull encnullse rainullay nullcomotives or aircraft, and cost minullions of poundsnull nulltnullr encnullsures are mucnullsmanuller, and null on a nullncnullin a nullnullratorynull Tnull smanuller encnullsures are typicanully referred to as TEnullcenullsnullTEnullmeans nullTransverse Enullctric nullodenull and refers to tnull mode of coupnullng nulltnulln tnull encnullsurenull nullt is not possinulle to estanullisnulla far-nullnull mode of propagation in smanuller encnullsuresnull nullSS typicanully uses Rignull-nulland Circunullr Propagation nullCnullnullnullt tnulls can onnull null estanullisnulld in nullrger anecnullic cnullmnullrsnull nullor tnulls reason, tnull spatianullproperties of a devicenulls antenna cannot null tested in a TEnull cenull encnullsurenull null certain amount of cnullracterisation is renullired nullen using an encnullsurenull Pnullcement of tnull device under test in snullgnullnull different positions nulltnulln tnull encnullsure nullnull affect tnull coupnullng nullss, even in a TEnullcenull, nullicnullis designed to give a consistent TEnullnullnull nulltnulln tnull encnullsurenull nullonullever, tnulls inconvenience is smanull compared nulltnulltnull pronullems associated nulltnullan open radiated test set-upnull null typicanullmid-sinulled nullm nullngnullTEnullcenull encnullsure is snullnull in nulligure null nulligure null TEnullcenull encnullsure nullmage courtesy of nullccenullninullLtdnull Page nullSPIRENT Application Note Conclusions nulln tnulls nullppnullcation nullote, nulle nullve discussed tnull different metnullds of transferring tnull simunulltornulls Rnullsignanull to tnull device under test, and tnull pronullems tnullt need to null addressednull Direct connection is anullays tnull preferred metnulld, nullcause it is nullenull contronulled and protected against enullernanullinnullencesnull Radiated coupnullng is nullss contronulled, nullt is tnull onnull metnulld avainullnulle for devices nulltnullno enullernanullcoanullanullconnectionnull Radiated coupnullng can null a renullanulle metnulld, if it is carried out in an Rnull snullenulled encnullsure, and nullenull contronullednull null good understanding of tnullse metnullds, and tnull potentianullpronullems, nullnull add integrity to your testing, and nullnull to preserve tnull nullgnullnullenullty innullrent in tnull signanull of a precision Rnullsimunulltornull Renullrenced nullocuments anull Dnullnull7nullnullnull nulltest issue, Signanull nullenerator nullardnullre nullser nullanuanull nulllossary onullTerms dnull Decinullnull is a nullgaritnullic unit of measurement tnullt enullresses tnull magnitude of a pnullsicanullnullantity nullsuanully ponuller or intensitynullrenulltive to a specinulld or impnulled reference nullvenull DC Direct Current nullSS nullnullnullnullnullavigation Satenullite System Lnull Lonullnulloise nullpnullnullr PCnull Printed Circuit nullard PDnull PersonanullDigitanullnullsistant nullnull nullonullage Standing nullave Ratio Page nullSPIRENT Application Note CONTACT null Snullrent Communications null4 nullnull nullnullnull gnullnullnullanullsnullpirentnullom nullnullnullpirentnullomnullositioning Snullrent Federal Systems null 7null nullnullnullnull infonullpirentfederanullcom nullnullnullpirentfederanullcom nullot a smartnullonenull If you have a smartphone download a QR Code reader and then point your phone camera at the QR Code to read the graphic. DnullnullnullnullSnull nullnull nullacenullonull Linnulldnulln Tnulltter Tecnullorati nulloognull nullunull Digg Denullcious Reddit Stumnulleupon nully not snullre tnulls documentnull nulle are adding nenullcontent to our nullenullite on a regular nullsisnull nullonullarnulltnulls linnull nullnullnullpirentnullomnullositioning nullisit tnull Snullrent nullSS nullognulltnullre are currently over null nullsts nulltnull2 to 3 nenullnullsts added eacnullnulleenull Catcnullunullon nullatnulls nenullnull nullnullnullpirentnullomnullnullgnullositioningnullspnull Need more innullrmationnull gnss-sonulltionsnullpirentnullom RevnullnullnullSept nullnull