rfid antenna measurement

This example demonstrates the basic measurement technique and utilizes most (but not all) of the DAMS Software capabilities.

This example will determine:

- Gain (Phi and Theta) - Match -Efficiency - 10dB spherical compliance -Antennarange(assuming10WattsTx,RFIDRetransmitefficiency=.001%920MHz)

RFID Antenna Measurement

http://www.DiamondEng.net · [email protected]. Box 2037 Diamond Springs, CA 95619 · 530-626-3857

Application Note #0421February2010Revised:January2011

2RFID - Application Notes Diamond Engineering

Absorberoverrotaryjoint ; NOTE: Be sure to switch the Azimuth and Elevation cables when using the FSM attachment.

Test System Specifications

System: DAMS6000 with FSM-5

Frequencies: 800MHzto1GHzwith101points

Azimuth: 0 to 360 (Step 5)

Elevation: -90to+90(Step10)

Method: Gain Transfer calibrated Yagi Ref.

ApplySampling8thordertocorrecterrorsIgnoretheabsenceoftheBalunchokenormallysuppliedbytheRFIDchip.

3Diamond Engineering Application Notes - RFID

System Calibration

❶EnsurethepictureinConfiguredPositionerisyourplatform.

❷Selectyourtestequipment.

❸PerformaVNAcalibrationfromthereferencetotheDAMsrotaryjoint.(DAMSprovidesscalar calfornon-vectormeasurements.)InsettingsmenucheckAdditionalParameterS11orS22.

❹ConfiguretheAz-ELmovement

❺ Set the default monitor plot items

❻MakesuretheAUTisproperlypositioned.UsethejogandZeroPositioner.

❼InitiateSCANAz/Elandbeginthemeasurement.Buttonwillturngreyuntilfinished.

/ TIP:Youcanmakemultiplemeasurementsforaveraging and min/max delete.

Measurement time remaining will update here.

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Monitor Plots

❶ After the measurement is complete proceed to Data Processing to save the data. (See next page)

❷ReturnandrotateReferenceAntenna90degrees.Repeatmeasurementandsave data. (See next page)

❸Themonitorplotsdisplaythelinkdatabydefault.Theycanalsobesettogain dataintheMonitorPlotsmenu.Additionally,realtimegaincanbeinvoked for pre-test or experimentation.

/ TIP:Whenutilizingthereal-timegainplot,youcanjogorzerotheposition.

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Where? How?


Saving Your Data

TosaveyourdatatoaREGandthensaveREGstoyourdrive:

❶Saveeachdatasettoaregister(REG1&2).LabeltheRegisters

❷LoadtheAlternateParameter(Sxxmatch)tothedisplayRegister.

❸ Save Alternative Parameter to unused Reg4.

❹Savethedatatothedisk

❺IntheeventofdatalossgotoRECOVERYintheRegisterUtilities

The data is now secure. Next the data can be processed into Gain data. While the math can be done inthearraycalculatortheGainTransferissetupforthis.Itrequiresknowledgeofthepathandthereference antenna.

/ TIP:RegisterUtilitiescanbeusedtoloadmultiplefiles.See“LoadsingleRegister”.

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Path Loss Generator

❶ Enter the Separation Distance and select the appropriate unit of measurement andclick“Continue”.

❷ Additionally,besidesTxRxseparation,youcanusethegroupdelay,specifyafixed pathloss,orusetheLaserBorsitetooltodeterminedistance,pointingangleand path loss.

❸Leftscale(yellow)ispathloss.Rightscaleispathlosssensitivitytolength(dB/in)

❹InvokeGeneratePathLoss.Oncedone,buttonwillturngreen.

(Continues next page...)

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(Continues next page...) [?]

❶InvokeReferenceAntenna.Oncedone,buttonwillturnGreen

❷ Followinstructionstocreatereferenceantennafile.PressContinuewhendone.

❸ YoucanimportarbitrarylossesbyaddingthemtotheRefHornfile.

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(Data in REG1 is used for Gain Transfer. REG1 was EQ.)


❶ InvokeGainXferforREG1(EQ)andREG2(EF)

❷CalculateABSAUTGain=REG4&0“TotalPowerFactor”

❸ Re-save ABSgain to REG3 so REG4 can be used for other things

❹ “CalculateTotalPowerfactor”willconvertREG1andREG2toGainandcalculate the ABS gain and store to REG4&0

/ TIP: You can perform circular, 3-point or substitution measurements in the Data Transfer window.

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(REG0 is the display REG used for plotting)After step 4 we have:

Click Gain Xfer again?


Compare the PeakEQ,EF Gains to Absolute Gain

❶ Enter Polar & Amplitude Plot, then recall REG3(ABS(G))

❷ CheckdBand3dB/divwith 20 Log (?)

❸ ClickGotoMaxSignal

❹ Readpeakgainand associatedF,Az-ELpositions,andnoteall three sets of[?] parameters

❺ Click“Normalize”

❻ CheckHold

❼ SwitchtoPen2

❽ RecallREG2andrepeatsteps3-7

❾ RecallREG1andrepeatsteps3-7

/ TIPS:-Youcansetthelinetype,pointtypeandlabelbyclickingon“NoDesc” -YoucanexportanycontourtoExcel.

(Color shading shown is for illustrative purposes only.)

...as indicated in img?

...as indicated in img?

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(EQ)peakREG1(EF)peakREG2ABS(E)peakREG3

۞۞۞۞۞۞۞۞۞۞


Plot Peak Abs(E) Gain and Associated Ef,Eq Gains

❶ Recall ABS(E) REG3

❷ClickGotoMaxSignal

❸NotetheAz,EL,fontopofsliders

❹Click“Normalize”

❺CheckHold

❻SwitchtoPen2

/ TIP: Youcansetthelinetype,pointtypeandlabelbyclickingon“NoDesc”

7. RecallREG2(See❶)

8. Reset sliders (See ❸)

9. CheckHold(See❺)

10. Switch to Pen3 (See ❻)

11. Recall REG1 (See ❻)

12. Resetsliders(See❸)

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(Color shading shown is for illustrative purposes only.)Need color code key like on page 9...?


Plot the AUT Reflection Coeficient

❶RecallthepreviouslyloadedS11dataREG4

❷InvoketheSmithchart

❸InvoketheAmplitudeplot

ThisenablestheAUTmatchamplitudeandphasetobeplot.

MarkerreadsoutAUTimpedance

Markersreadoutamplitude

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Full Elevation for Full-Circle Azimuth Cuts

❶ Move Azimuth slider to see elevation cuts

❷ Move Elevation slider to see azimuth cuts

❸ The“Frequency”buttoncanbeusedtoenterfrequency. (M,G and k are valid multipliers.)

❹ Checkforfull360degElevationcut.Onlyvalidforfullscandata

/ TIP: You can export this data to Excel.

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23Indicates elevation cut


GNU Plotting

GNUplottingprovidesmoremarketableplots.ToutilizeGNU,followthesesteps:

❶Click“PlotwithGNUPlot”.

❷Clickheretorevealmoreoptions

❸ Move the polar plot aside. It’s best to have DAMS full screen so more plots can be runsimultaneously.

/ TIP: Theamplitudeplotmayalsobeusedto plotwithGNU.

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Plotting Peak Spherical Gain

❶Invokethespherical3-dAz/EL

❷Setthefrequencyslidertopeakgainbyinvoking“SetFromPolarPlot”

❸ CheckUse20Log(S21)

❹ InvokePlotAz-EL,which opens the 3D rendition as seen below[?]

/ TIP: Generallythepolarplotisusedtoidentifyadesired(Az,EL,f)contour.TheSphericalfrequencycanbeset“2”fromthepolarfrequencysliderin another window[?].

Where is said slider? Isn’t the

visible blue slider for the “VNA

Freq #” as it says below it?

/ TIP: Processing toolbar offers a host of plot tools.

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Spherical Plot of Gains (EQ),(EF),ABS(E)

m IMPORTANT: See note in spherical regarding multiple dB spherical plotting for exceptions.

1.BesuretheREGsareasfollows(fromGainXferTotalPower)

(Ef)

(Eq)

ABS(E)

N/A

Where is this?

Where?2.InthePolarPlotrecallABS(E)andinvoke“GoToMax”tosetthefrequencyslidertothefrequencyassociatedwithmaxABS(E)

❶ Set the freq slider to polar plot (max)

❷ CheckMultipalPlots

❸ Check20Log(S21)

(Continues next page...) [?]

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1. Recall REG1, Plot (EF)2.RecallREG2,Plot(EQ)3. Recall REG3, Plot ABS(E)

/ TIP: Plotscanalsobeoverlaidbychecking“Hold”.“Wire”canbeusedto delineate plots.

/ TIP: Byclickingwireornowiremultipleplotscanbemademorevisible.

What is this entire page?????


Determine Spherical Areas Less Than 10db Down From Peak

❶ SphericalplottingdisplaystheMaxintheisotropicdBvalue.Subtract10and enter into window.

❷ Depress“AddIsosphere”

❸ Click“PlotAz-EL”

❹ Userotationtoviewdata

❺ Byclickingwireornowiremultipleplotscanbemademorevisible

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Determine the Equivalent Number of Dipoles

❶ Depress“Add1/2wDipole”

❷ CheckS21^2

❸ Increase multiplier until dipole gain ~ ABS(Gmax)

❹ Select 3/4 dipole (with no wireframe)

❺ Click“PlotAz-El”

/ TIP: Byclickingwireornowiremultipleplotscanbemademorevisible

Two ideal Dipoles

RFID Peak Gain

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Determine the ABS(E)-3dB Compliance at 830MHz

1. Recall the ABS(E) data REG3

❷ Check“Use20Log(s21)

❸ Check“MultiplePlots”

❹ Setsliderto830MHz

❺ Click“PlotAz-El”toplotspherical.(Peakgain shouldappearinthe“AddIsosphere”window, as shown to right.[?])

❻ Press“AddIsosphere”

7. Subtract3frompeakgain.Maybeperformedin Add Isophere window, (see ❺)

8. Click“PlotAz-El”(see❺)

/ TIP: EverysphericalmaxissetinIsospherewindow

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What?? Wrong number???

How?

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Overlay G(theta) and G(phi) AzEL Gain at 930MHz

1. RecalltheGQdatafromREG1

2. InvoketheAzEL3dplot

❸ Click“TodB(20Log)”

❹ Select“Az-EL”

❺ Setfrequencyto930MHz

❻ Check“WireFrame”

❼ Check“HoldPlot”

❽ Plot the data

9. RecalltheGFdata(REG2)

10 Uncheck“WireFrame”andplotthe data once again, (see ❽).

/ TIP: Youcanuse“AddIsoplane”todeterminespeclimitsandbeamwidths

How?

How?

How?

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Color Plot of Az vs EL at 930MHz

1.MakeacolorgraphoftheAzELplane.

2.SelectAz-EL

3. With the previous plot present, change the ViewpointangletoAz=90EL=90

4. Re-plot the data

5.Usethedatareadertoclickondatavalues

/ TIP: The slider will change depending on which plot is selected.

How?

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rfid antenna measurement

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