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LANforgeWiFiRFAttenuatorUserGuideOverview

1. Features

2. AccuracyandRFIsolation

3. UpgradeAttenuatorFirmware

4. Driverinstallation(Windows)

5. OpenSourcecodeandHardwareFiles

OverviewTheLANforge-AttenuatorisdesignedtoaddRFattenuationon2.4Ghzand5GhzWiFiconnections.Itsupports3attenuatormodules,eachcapableofaddingattenuationtooneconnection.Theattenuationrangeis0to95.5dB(seenotesonsignalstrengthbelow).Theattenuationmaybecontrolledbyknobsonthefrontofthesystem,andmayalsobeadjustedprogramaticallyoveraUSB-serialport.Currently,theserial-portoptionisonlyavailableonLinux.Eachattenuatonmodulemaybeconfiguredindependentlyoftheothers.

TheLANforgesoftwaresuitecanalsocontroltheattenuatorthroughitsGUIand/orCLIforintegratedtestingscenarios.Thisincludesbuilt-inscriptingtoautomaticallyadjustattenuationovertime.

1. Features

TheLANforge-AttenuatorusestheATS0760-95modulesfromEUBUS.Asummaryofthetechnicalspecificationsisbelow:

Type: ATS0760-95

Impedance: 50Ω

FrequencyRange: 0.7GHz–6.0GHz

AttenuationRange: 0–95.5dB

AttenuationSteps: 0.5dBincrements

AttenuationAccuracy: 1-15db:±1dB,16-95.5dB:±1.5dBor4%ref.toIns.Loss

NetworkTestingandEmulationSolutions

InsertionLoss: 8dBnominal,10dBmax

max.VSWR: 2:1

MaximumInputPower: +20dBm

OperatingTemperature: 0°Cto+70°C

TheLANforge-Attenuatorcontains3ofthesemodules,foratotalof6RP-SMAconnectorsonthefrontpanel.Eachpairofconnectorsprovidesoneattenuationpath.Amicro-controllerprovidesacontrolinterfaceoveraUSBplugthatappearsasaUSB-Serialadaptertotheoperatingsystem.Theattenuatordoesnotrequireanexternalcomputertofunction:Itcanbemanuallyadjustedwithtwoknobs,andhasasmallLCDscreentoprovideinformationtotheuser.

ThetopknobadjuststheLCDmenuitems.ThefirstmenuisInformation,thesecondistoadjustallattenuatormodulesinlock-step,andtherestofthemenusareforadjustingindividualattenuatormodules.

ThebottomknobadjuststheattenuationwhentheselectedmenuisAllorindividualattenuatormodules.Pressingtheknobdownactivatesabuttonthattogglesbetweeneachclickadjustingby5dBmorby0.5dBm.Enablingthex5modeenablesquickadjustmentsoverlargerranges,andthe0.5modeallowsfinetuning.

Thesystemmaybepoweredoffofa500maUSBplug,butmanycomputersonlyprovide100maUSBplugs,soitissuggestedthattheexternalDCpower-brick(9v1-Amp)beusedatalltimes.

TheLANforgesoftwarecanmanagetheattenuatorovertheUSB-Serialinterface.Itcanbescriptedinthe2544andHuntscriptsintheLANforgeGUI.TheLANforgeCLIcanalsocontroloneormoreattenuators.Hereisascreen-shotoftheAttenuatorcontrolscreenintheLANforge-GUI:

UsersmayalsoprefertodirectlyinterfacewiththeattenuatorovertheUSB-Serialinterfaceusingminicomorsomeotherserial-consoleapplication.Theserialportwillbenamedsomethinglike:/dev/ttyACM0,andthesettingsare:1152008N1.TheLANforge-Attenuatorprovidesatext-basedinterface,andsupportsthesecommands:

info

Displayinformationandcurrentsettings.

eepromread

DisplayEEPROMinformationandcurrentsettings.

attenget[index]

Displayattenuatorconfigurationforspecifiedmodule.

attenset[index][dBmtenths]

Setattenuatorconfigurationforspecifiedmodule.Theattenuationisintenth'sofadB,butthemodulessupport0.5dBsteps,soyoucoulduse'55'toset5.5dBm,butsettingitto'51'wouldrounddownto5.0dBm.

atteneepromset[key][val]

Setattenuatoreepromconfiguration.ThisshouldnormallynotbedoneexceptbyCandelaengineers.

acount[attenuator-count]:Setnumberofattenuatormodulesavailableinattenuator.

test[0|1]:Enable(1)orDisable(0)testmode.Testmodeisonlyusefulwhentheattenuatorconnectorcableshavebeenconnectedtoattenuator-4andoneoftheotherattenuatorconnectorsontheadapterboard.Thetestistoverifythecablesandshieldweremanufacturedproperly.

Whentesting,firstconnectattenuator1headertoattenuator4,pressthebottombuttontostartthetest.Eachtimeyouclickit,adifferentheaderwillbetested.So,whentestingattenuator3header,expect1and2tofail,but3shouldpass.Attenuator4headeristestedindirectlywhentestinganyoftheothers.

serrno[serial-number]:Settheserialnumber.

Themicro-controllerintheLANforgeAttenuatorisconfiguredtoresetitselfeachtimeanewserialconnectionismadetotheAttenuator.Itonlytakesasecondortwotoboot,butthiscouldcauseinterruptionoftestingifyourapplicationoftenopensandclosestheserialconnection.Ifyouarecontrollingtheattenuatorovertheserialconnection,itissuggestedthatyouprogramitinsuchawaythattheserialconnectionremainsupforthedurationofthetest.Pleasecontactsupportifyouhaveanyquestionsonthis.

2. AccuracyandRFIsolation

TheLANforgeAttenuatorhasbeendesignedwithRFIsolationandaccuracyinmind,butintestingwiththeLANforgeCT520WiFiretrafficgeneratorsystems,westillseeabitofsignalleakageevenwhenattenuationissetto95.5.WesuspectthattheCT520systemsleakabitofsignaloutoftheirNICsandcommunicatedirectly,bypassingtheattenuator.

Theinternalattenuatormodulesaretestedbytheirvendorandshouldhaveexcellentisolation.TheSMAcablesconnectingtheattenuatortothefaceplatearedouble-shieldedKSR-100with>90dBisolation.

TheLANforgeattenuatorcomeswith6cablestoconnecttheattenuatortosystemsundertest.ThesecablesuseLMR-195cablewhichalsohasisolationof>90dB.Ifyouuseyourowncables,besuretheyareofhighqualityforoptimalperformance.Ourtestingindicatesthateventhesedouble-shieldedLMR-195cablesmaybeleakingmorethatwehoped,sowewillcontinuetoinvestigatedifferentcabletypes.

Ourprimarytestsetupisone3-antennaAPconnectedtoanother3-antennaStationsystem(3x3MIMOAtheros/Qualcomradio).TheAPandStationsystemareabout3feetapart,andtheattenuatorsystemsitsbetweenthem.Themaximumattenuationgivesasignallevelofabout-84dB,andnoisefloorofabout-92.Thisisrightatthecut-offpointfortheAPandStationtocommunicateandtheymaylooseassociationfromtimetotime.Hereisagraphofsignallevelv/sattenuationsettingsforthisconfiguration.Inthiscase,thesignalwenttoabout-86andthenlostconnection(andsoreportedsignalas0).

Thegraphbelowshowstheattenuationv/srx-rate.Theconnectionwaslostatmaxattenuationandreportedazerosignal.Thatmakestheright-handsideofthegraphabitweird.

3. UpgradeAttenuatorFirmware

TheLANforge-AttenuatorusesanArduino-Megaasthecontroller.Thefirmwareisstoredonflashinthecontrollerandmaybeupdatedusingthe'avrdude'programonaLinuxmachine.ThefirmwarecanbedownloadedfromtheDownloadspage.Itwillbenamedsomethinglike:attenuator-1.0.hex .

Toupgrade,dothefollowingsteps.Dotheconsolecommandsastherootuser.

1. StopLANforgecd/home/lanforge;./serverctl.bashstop

2. Un-plugtheUSBcable,thenpowercable,andplugpowerandUSBbackinagain.

CheckthekernelmessagestofigureoutwhatserialporttheAttenuatorisusing:

[root@lec2010-ath9k-1lanforge]#tail-10/var/log/messagesOct1911:25:17localhostdhclient[25360]:DHCPRELEASEonrddVR15to99.88.77.2port67Oct1911:25:34localhostkernel:[1276937.250169]usb2-2:>USBdisconnect,devicenumber23Oct1911:25:39localhostkernel:[1276941.370134]usb2-2:>newfull-speedUSBdevicenumber24usinguhci_hcdOct1911:25:39localhostkernel:[1276941.571176]usb2-2:>NewUSBdevicefound,idVendor=2341,idProduct=0042Oct1911:25:39localhostkernel:[1276941.584803]usb2-2:>NewUSBdevicestrings:Mfr=1,Product=2,SerialNumber=220Oct1911:25:39localhostkernel:[1276941.599345]usb2-2:>Manufacturer:Arduino(www.arduino.cc)Oct1911:25:39localhostkernel:[1276941.608628]usb2-2:>SerialNumber:74934303030351118071Oct1911:25:39localhostkernel:[1276941.620586]cdc_acm2-2:1.0:>ttyACM0:USBACMdeviceOct1911:25:39localhostmtp-probe:checkingbus2,device24:"/sys/devices/pci0000:00/0000:00:1d.0/usb2/2-2"Oct1911:25:39localhostmtp-probe:bus:2,device:24wasnotanMTPdevice

Inthiscase,itisusing/dev/ttyACM0

3. Uploadthenewimageusingavrdude(usetheserialdevicethatmatchesyoursystem)

avrdude-patmega2560-cstk500v2-P/dev/ttyACM0-b115200-D-Uflash:w:attenuator-1.0.hex:i

4. YoumaynowrestartLANforge,orusesomeothermeansofaccessingtheserialporttocontroltheAttenuator.

4. InstallDrivers(WindowsOnly)

WhenusingtheLANforge-AttenuatoronWindows,adrivermustbeinstalledbeforetheattenuatorcanbeaccessedovertheUSB-Serialport.ThereisnoneedtoinstallanydriversonLinux.

First,installtheLANforge-ServerpackageforWindows(version5.2.8orhigher).Ithastheneededdriver,andwillbeusedtomanagetheLANforge-Attenuator.

InstallDriversonWindows7andlater

InstallDriversonWindowsXP

1. ConnectUSBcablefromAttenuatortoPC.

2. ClickStart→ControlPanelandchoosethe'AddHardware'option.

3. ItshouldfindanewUSBdeviceinthePorts(COM&LPT)section.Ifnot,continueontothenextstepanyway,perhapsitwasalreadydiscoveredautomatically.

4. Right-Clickon'MyComputer'inthestartmenu,andchoose'Properties'

5. SelecttheHardwareTab.

6. ClickDeviceManager

7. LookforaneworunknownUSBdeviceinthePorts(COM&LPT)section.

8. Right-ClickonthisdeviceandchooseUpdateDriver.

9. Selectthe'Installfromalistorspecificlocation'optionandclick'Next'.

10. Selectthe'Includethislocationinthesearch'checkboxandchoosetheLANforge-Serverdirectory(C:\ProgramFiles\LANforge-Serverbydefault).

11. Click'Next'.Itshouldfindthe"LANforgeAttenuator(ArduinoMega2560R3)driver.Thisdriverisnotsigned,soclickthe'ContinueAnyway'optioninthewarningdialog.

12. ClickFinish.

13. Start(orre-start)theLANforgeManagerand/orLANforgeResourceprocessesthatwerepreviouslyinstalled.ConnecttheLANforge-GUItotheLANforgeManagerandselectthe'Attenuators'tab.YoushouldseetheAttenuatorlistedinthetable.

5. OpenSourcecodeandHardwareFiles

TheLANforgeAttenuatorcontrollogicisbasedontheArduinoMegamicrocontroller.CandelaTechnologiesreleasestheArduinosourcecodeusedtoprogramtheArduinoMegaaswellastheEaglePCBlayoutandroutingfiles.ThesourcecodeisreleasedundertheGPL(GNUPublicLicense),andtheEaglehardwarefilesarereleasedundertheCreativeCommonsAttribution-ShareAlikelicense.YoumaydownloadthecodeandEaglefilesontheDownloadspageaftercreatinganaccountonourwebsite.

CandelaTechnologies,Inc.,2417MainStreet,Suite201,Ferndale,WA98248,USAwww.candelatech.com|[email protected]|+1.360.380.1618