AN2631 Application note - ABCelectronique

October 2007 Rev 1 1/25

AN2631Application noteXRAG2 UHF antenna

reference design

PurposeThe aim of this application note is to present a 90 × 10 mm reference antenna design for the XRAG2 UHF RFID memory chip.This document presents the antenna dimensions and tuning variables. It also explains the antenna development methodology, based on XRAG2 conjugate impedance matching and measurements of frequency detuning caused by antenna materials and assembly parasitic capacitance.

The provided antenna design matrix covers the 860-960 MHz UHF RFID frequency range in free space and various support materials.

This application note comes with two DXF archives that can be used to start evaluation sample prototyping with the XRAG2 using either E-Strap or flip-chip assembly.

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Contents AN2631

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Contents

1 Antenna design presentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.1 Antenna design and tuning parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.2 Flip-chip and strap footprints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2 Antenna simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.1 Antenna impedance criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.2 Antenna design tuning variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.2.1 Dipole strand length ∆ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.2.2 Dipole internal strand shrinkage a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.2.3 Internal S stub height h1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.2.4 Internal S stub position ∆1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3 Preliminary evaluation at STMicroelectronics RFID laboratory . . . . . 10

3.1 Anechoic chamber testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.2 Read range evaluation in front of UHF reader . . . . . . . . . . . . . . . . . . . . . 11

4 Antenna performance characterization according to ISO 18046-3 performance test methods 12

5 Antenna matrix generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5.1 Antenna tuning and material effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5.2 E-strap antenna matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5.2.1 XRAG2 flip-chip antenna matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

6 Antenna matrix application example . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

AN2631 List of tables

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List of tables

Table 1. Material parameters of the antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Table 2. Tuning parameters of the antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Table 3. Antenna tuning shift between simulation and material . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Table 4. E-strap matrix antena design characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Table 5. Flip-chip antenna design characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Table 6. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

List of figures AN2631

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List of figures

Figure 1. Antenna design example with E-strap footprint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Figure 2. XRAG2 E-strap dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Figure 3. Antenna E-strap footprint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Figure 4. XRAG2 die brief description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Figure 5. Antenna flip-chip footprint dimension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Figure 6. STMicroelectronics UHF test bench . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Figure 7. Evaluation result of XRAG2 tag mounted with strap. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Figure 8. Tag’s minimum electric field threshold (ISO 18046-3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Figure 9. Tag activation range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Figure 10. XRAG2 E-strap antenna matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Figure 11. Simulated port impedance Z11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Figure 12. E-strap antenna matrix simulation results Im(Z11) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Figure 13. E-strap antenna matrix simulation results Re(Z11). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Figure 14. XRAG2 flip-chip antenna matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Figure 15. XRAG2 flip-chip antenna matrix simulation results Im(Z11) . . . . . . . . . . . . . . . . . . . . . . . . 19Figure 16. XRAG2 flip-chip antenna matrix simulation results Re(Z11) . . . . . . . . . . . . . . . . . . . . . . . . 19Figure 17. Tag's minimum electric field threshold (ISO 18043-3) for 920 MHz . . . . . . . . . . . . . . . . . . 22Figure 18. Tag's minimum electric field threshold (ISO 18043-3) for 970 MHz . . . . . . . . . . . . . . . . . . 22Figure 19. Tag's minimum electric field threshold (ISO 18043-3) for 1020 MHz . . . . . . . . . . . . . . . . . 23

AN2631 Antenna design presentation

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1 Antenna design presentation

1.1 Antenna design and tuning parametersFigure 1 shows an antenna design example with E-strap footprint. Table 1 and Table 2 summarize the material and tuning parameters of the antenna, respectively.

Figure 1. Antenna design example with E-strap footprint

The material parameters of this antenna are the following:

As shown in the next section, ∆ is the main frequency tuning parameter while a is a fine tuning parameter of the antenna geometry.

Table 1. Material parameters of the antenna

Parameter Value

PET substrate length 90 mm

PET substrate width 10 mm

PET substrate thickness 50 µm

ξr PET 3

Aluminum thickness 10 µm

Line width 0.75 µm

Table 2. Tuning parameters of the antenna

Parameter Value

Tuning length, or dipole strand length ∆

Internal strand shrinkage a

Position of the S stub referenced to the center of the antenna ∆1

Height of the S stub h1

Length of S stub ∆2

Substratewidth

a ∆2

∆

h1

Substrate length

∆1ai14682

Antenna design presentation AN2631

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1.2 Flip-chip and strap footprintsFor an enhanced flexibility, customers may want to assemble XRAG2 E-straps or to use the flip-chip technology. The dimensions of the E-strap and flip-chip footprints are shown in Figure 2 and Figure 3 below.

Figure 2. XRAG2 E-strap dimensions

Figure 3. Antenna E-strap footprint

Figure 4. XRAG2 die brief description

2.50 mm

3.00 mm

0.65 mm

8.00 mm

0.70 mm

ai14683

2.50 mm

0.75 mm 0.75 mm

2.00 mm

ai14684

0.65 mmai14685

0.08 mm

0.10 mm0.12 mm

0.70 mm

AN2631 Antenna design presentation

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Figure 5. Antenna flip-chip footprint dimension

1. Refer to technical note TN0043 “XRAG2 die description” for more information.

0.24 mm

0.74 mm 0.48 mm

0.75 mm0.52 mm

0.21 mm

0.30 mm

ai14686

Antenna simulation AN2631

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2 Antenna simulation

2.1 Antenna impedance criteriaPrior to making antenna simulations, the target impedance criteria must be determined.

When the additional parasitic impedance on account of the XRAG2 assembly is known, the antenna impedance criterion is given by:

Zantenna = (ZXRAG2 TOT)* = (RXRAG2 + j XXRAG2 + j Xparasitic)*,

where ZXRAG2 TOT is the sum of the XRAG2 impedance and the parasitic impedance.This parasitic impedance depends on the properties of the adhesive material used for XRAG2 assembly and corresponds to a capacitance that adds up to the XRAG2’s intrinsic capacitance.

When the parasitic capacitance is unknown or has to be evaluated, the antenna can be simulated to match the XRAG2 intrinsic impedance. In this case, the antenna impedance criterion becomes:

Zantenna = (ZXRAG2)* (given in XRAG2 datasheet)

Since the antenna impedance will not match the total impedance of the mounted XRAG2, it is possible to design antennas for various frequencies or simply, to evaluate the frequency shift due to parasitic impedance on a single design. It is however recommended to do so on several antenna design variants in order to obtain a better evaluation of the resulting antenna mismatch. With this method, it is also possible to take into account errors due to simulation settings, material properties or other parameters that could affect the difference between real antenna and simulation.

The second method was chosen to develop the antenna presented in this document.

Note: To anticipate the antenna impedance mismatch, and to guarantee a series antenna resistance between 20 Ω and 30 Ω (values that give good results in antenna performance), a target simulation value around 30 Ω has been chosen (typical Rantenna variation is less than 10 Ω for 100 MHz frequency down-shift on simulation curve).

2.2 Antenna design tuning variables

2.2.1 Dipole strand length ∆

As described in Table 2, ∆ corresponds to the dipole strand length. For a given value of a, h1 and ∆1, a ±1 mm variation in ∆ (on each strand of the antenna) leads to a resonant frequency variation around ±20 MHz.

2.2.2 Dipole internal strand shrinkage a

The a parameter corresponds to the misalignment of the internal strand extremity to the antenna strand overall length ∆.

For a given value of ∆, h1 and ∆1, a 1 mm variation in a leads to a variation of around 5 MHz in the antenna resonant frequency.

AN2631 Antenna simulation

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2.2.3 Internal S stub height h1

The h1 parameter represents the height of the S stub above the internal strand of the antenna. A 1 mm variation in h1 leads to a variation of around 18 MHz in resonant frequency.

2.2.4 Internal S stub position ∆1

∆1 corresponds to the position of the S stub on the internal strand of the antenna. For a given value of ∆, a, and h1, a variation of a few millimeters has no effect on the antenna resonant frequency.

Preliminary evaluation at STMicroelectronics RFID laboratory AN2631

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3 Preliminary evaluation at STMicroelectronics RFID laboratory

3.1 Anechoic chamber testingFigure 6 shows the architecture of the UHF bench test used at the STMicroelectronics RFID lab to characterize tags.

Figure 6. STMicroelectronics UHF test bench

In accordance with Section 2.1, antenna variants were simulated to match the conjugate value of the XRAG2’s intrinsic impedance over the 850-950 MHz range. The produced antennas mounted with both E-strap and flip-chip assembly, were characterized using the power/frequency characterization flow.

Figure 7 shows the characterization result for the antenna tuned to match the XRAG2’s conjugate impedance at 920 MHz and the design for E-strap.

Answer

decoding

Answer

receptionCommand

emissionCommand data

file creation

RF command creation

Demodulation

AN2631 Preliminary evaluation at STMicroelectronics RFID laboratory

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Figure 7. Evaluation result of XRAG2 tag mounted with strap

The anticipated frequency shift between the antenna simulated for the XRAG2’s intrinsic impedance and the measured resonant frequency is confirmed. Additional measurements made on different antennas either mounted with E-strap or flip-chip assembly evidenced an average frequency shift of 70 MHz with E-strap and 60 MHz with flip-chip mounting.

This frequency shift will be used for antenna matrix resonance frequency prediction in Table 4 and Table 5. It will be confirmed in the application example given in Section 6.

3.2 Read range evaluation in front of UHF readerPreliminary measurements using an UHF reader show a maximum read range of around 6 m under ETSI EN 302-208 conditions.

Tag tuningfrequency

Antenna simulationto match intrinsic XRAG2impedance

Antenna performance characterization according to ISO 18046-3 performance test methods

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4 Antenna performance characterization according to ISO 18046-3 performance test methods

Figure 8 here after shows the electric field threshold measurement of a sample of 5 tags simulated to match the XRAG2’s intrinsic impedance at 920 MHz. These tags are assembled with the XRAG2 using the flip-chip technology.

Figure 8. Tag’s minimum electric field threshold (ISO 18046-3)

Figure 9. Tag activation range

Figure 9 above shows the tag activation read range with the maximum available power defined in the EN 302-208 standard, 2W ERP. These results are in line with the preliminary evaluation made at the STMicroelectronics RFID lab with the UHF reader.

Tag electric field threshold versus frequency

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

820 830 840 850 860 870 880 890 900 910 920 930 940 950 960

Frequency (MHz)

E _t

hr (V

/m) Tag_1

Tag_2Tag_3Tag_4Tag_5

Tag activation range versus frequency

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

820 830 840 850 860 870 880 890 900 910 920 930 940 950 960

Frequency (MHz)

Act

ivat

ion

rang

e (m

)

Tag_1Tag_2Tag_3Tag_4Tag_5

AN2631 Antenna matrix generation

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5 Antenna matrix generation

5.1 Antenna tuning and material effectThe results presented in the previous section show that the expected frequency shift between the simulation and the measured tag resonant frequency is close to 60 MHz for flip-chip mounted antennas and close to 70 MHz for tags mounted with E-strap. These results can be used to estimate correct impedance criteria to simulate the antenna at a given frequency, taking the parasitic effect of assembly into account.

In order to complete this evaluation, the antenna resonant frequency was measured on various materials.

Table 3 shows a measurement example for two differentr antennas assembled with E-strap and flip-chip, respectively

According to Table 3, designing an antenna working at 960 MHz when put on a 5 mm-thick raw plastic material would request to simulate it to match an intrinsic XRAG2 impedance of around 1160 MHz.

To offer flexible design start solutions to customers, STMicroelectronics provides two matrixes of 42 antennas designed for flip-chip and E-strap XRAG2, respectively.

In both matrixes, each antenna has been optimized to match the XRAG2’s intrinsic impedance from 910 MHz to 1300 MHz by steps of 10 MHz, and then to cover customer needs for antennas working in air or thick materials, from 860 to 960 MHz.

Note: Each antenna design is marked with its simulated resonant frequency when matching the conjugate intrinsic impedance of the XRAG2. See Table 4 and Table 5 for antenna resonance frequency predictions in air.

5.2 E-strap antenna matrixFigure 10 shows the E-strap antenna matrix. This matrix is available as a single .dwg or .dxf AUTOCAD mask file, or separated .dwg or .dxf files for each antenna design. Conversion to other CAD file formats is possible on request.

Table 3. Antenna tuning shift between simulation and material

Resonant frequency

E-strap “936 MHz” antenna

∆sim(1)

1. ∆sim is the difference between the simulated resonant frequency and the measured resonant frequency.

∆air(2)

2. ∆air is the difference between the resonant frequency measured in air and the resonant frequency measured on different materials.

Flip-chip “932 MHz” antenna

∆sim(1) ∆air(2)

simulation 936 MHZ 932 MHZ

air 864 MHZ 72 872 MHZ 60

2 mm plastic 758 MHZ 178 106 770 MHZ 162 102

4 mm carton 818 MHZ 118 46 833 MHZ 99 39

5 mm plastic 736 MHZ 200 128 746 MHZ 186 126

Antenna matrix generation AN2631

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Figure 10. XRAG2 E-strap antenna matrix


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To facilitate resonant frequency optimization during simulation, two virtual lumped capacitances were inserted on the antenna to represent the XRAG2’s intrinsic capacitance (see Figure 11).

Figure 11. Simulated port impedance Z11

This is possible because the characterization of the XRAG2 impedance at 866 MHz, 915 MHz and 960 MHz show that the XRAG2 equivalent model is stable regarding frequency:

RXRAG2 = 10 Ω and CXRAG2 = 710 fF

During simulation, the Z11 impedance is calculated:

Z11 = Zantenna + j XXRAG2 = Rantenna + j Xantenna + j XXRAG2

In simulation results, the antenna resonant frequency is given by Im(Z11) = 0.

Figure 12. E-strap antenna matrix simulation results Im(Z11)

2 × CXRAG2 2 × CXRAG2

ai14687

Im(Z11)

Frequency (GHz)


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Figure 13. E-strap antenna matrix simulation results Re(Z11)

Table 4 summarizes the characteristics of the E-strap matrix antenna designs.

Re(Z11)

Frequency (GHz)

Table 4. E-strap matrix antena design characteristics

Simulated frequency in air on XRAG2’s

intrinsic impedance (MHz)

Re(Z11) (Ω) Im(Z11) (Ω) Im(Zantenna) (Ω) ∆ (mm) a (mm)Expected resonant

frequency in air after E-strap assembly

910.00 34.40 -2.14 -251.99 32.00 0.50 840.00

920.00 33.99 2.23 -244.91 31.00 -1.32 850.00

930.00 33.61 -2.06 -246.54 31.00 0.43 860.00

940.00 33.40 2.33 -239.55 30.00 -1.52 870.00

950.00 33.04 2.47 -236.86 30.00 0.00 880.00

960.00 32.70 -0.32 -237.16 30.00 1.67 890.00

970.00 32.09 -0.55 -234.95 29.00 -0.25 900.00

980.00 32.08 -0.51 -232.51 29.00 1.22 910.00

990.00 31.46 -1.41 -231.07 28.00 -0.73 920.00

1000.00 31.44 -2.05 -229.42 28.00 0.62 930.00

1010.00 31.15 -1.02 -226.13 27.00 -1.41 940.00

1020.00 30.83 -2.01 -224.92 27.00 0.00 950.00

1030.00 30.81 -0.84 -221.58 27.00 1.32 960.00

1040.00 30.26 -1.90 -220.52 26.00 -0.83 970.00

1050.00 30.38 -0.51 -217.04 26.00 0.39 980.00


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1060.00 30.27 0.28 -214.21 26.00 1.68 990.00

1070.00 29.94 -1.27 -213.76 25.00 -0.57 1000.00

1080.00 29.77 -1.74 -212.26 25.00 0.62 1010.00

1090.00 29.74 -0.22 -208.81 25.00 1.91 1020.00

1100.00 29.31 -1.32 -208.02 24.00 -0.47 1030.00

1110.00 29.26 -2.47 -207.30 24.00 0.71 1040.00

1120.00 29.29 -0.35 -203.35 24.00 1.91 1050.00

1130.00 29.06 3.54 -197.67 23.00 -0.85 1060.00

1140.00 28.93 -1.17 -200.61 23.00 0.48 1070.00

1150.00 28.85 -1.60 -199.31 23.00 1.74 1080.00

1160.00 28.72 0.22 -195.79 22.00 -0.99 1090.00

1170.00 28.52 -1.24 -195.57 22.00 0.13 1100.00

1180.00 28.54 -1.13 -193.82 22.00 1.30 1110.00

1190.00 28.53 -1.18 -192.25 22.00 2.45 1120.00

1200.00 28.27 0.60 -188.87 21.00 -0.47 1130.00

1210.00 28.34 0.35 -187.55 21.00 0.52 1140.00

1220.00 28.40 1.37 -184.99 21.00 1.61 1150.00

1230.00 28.41 0.97 -183.88 21.00 2.74 1160.00

1240.00 27.93 1.04 -182.32 20.00 -0.21 1170.00

1250.00 28.08 -0.60 -182.49 20.00 0.90 1180.00

1260.00 28.11 -0.51 -180.96 20.00 1.92 1190.00

1270.00 28.16 -0.86 -179.89 20.00 3.00 1200.00

1280.00 27.88 -0.60 -178.23 19.00 -0.13 1210.00

1290.00 27.83 -1.90 -178.15 19.00 0.94 1220.00

1300.00 27.94 -0.96 -175.86 19.00 1.85 1230.00

1310.00 27.47 -1.09 -174.65 18.00 -1.28 1240.00

1320.00 27.44 -1.69 -173.94 18.00 -0.32 1250.00

Table 4. E-strap matrix antena design characteristics (continued)

Simulated frequency in air on XRAG2’s

intrinsic impedance (MHz)

Re(Z11) (Ω) Im(Z11) (Ω) Im(Zantenna) (Ω) ∆ (mm) a (mm)Expected resonant

frequency in air after E-strap assembly


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5.2.1 XRAG2 flip-chip antenna matrix

Figure 14. XRAG2 flip-chip antenna matrix


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Figure 15. XRAG2 flip-chip antenna matrix simulation results Im(Z11)

Figure 16. XRAG2 flip-chip antenna matrix simulation results Re(Z11)

Frequency (GHz)

Im(Z11)

Frequency (GHz)

Re(Z11)


20/25

Table 5 summarizes the characteristics of the flip-chip antenna designs.

Table 5. Flip-chip antenna design characteristics

Simulated frequency in air on XRAG2’s intrinsic

impedance (MHz)Re(Z11) (Ω) Im(Z11) (Ω) Im(Zantenna) (Ω) ∆ (mm) a (mm)

Expected resonant frequency in air after

XRAG2 flip chip

910.00 31.10 1.52 -248.33 32.00 -0.37 850.00

920.00 30.94 0.92 -246.22 31.00 -2.00 860.00

930.00 30.43 0.57 -243.91 31.00 -0.37 870.00

940.00 30.19 -1.77 -243.64 30.00 -2.00 880.00

950.00 29.96 -1.05 -240.38 30.00 -0.47 890.00

960.00 30.08 1.67 -235.17 30.00 1.00 900.00

970.00 29.57 0.90 -233.50 29.00 -0.93 910.00

980.00 29.40 -1.72 -233.73 29.00 0.67 920.00

990.00 29.07 0.67 -228.99 28.00 -1.39 930.00

1000.00 29.55 1.59 -225.77 28.00 0.00 940.00

1010.00 28.60 0.65 -224.46 27.00 -2.00 950.00

1020.00 28.43 -0.19 -223.10 27.00 -0.55 960.00

1030.00 28.49 1.28 -219.46 27.00 0.71 970.00

1040.00 28.05 0.64 -217.98 26.00 -1.39 980.00

1050.00 28.39 -0.34 -216.87 26.00 0.00 990.00

1060.00 27.84 -1.74 -216.23 26.00 1.50 1000.00

1070.00 27.63 0.72 -211.77 25.00 -1.01 1010.00

1080.00 27.97 1.05 -209.47 25.00 0.19 1020.00

1090.00 27.18 -0.96 -209.55 24.00 -2.00 1030.00

1100.00 26.90 -1.09 -207.78 24.00 -0.73 1040.00

1110.00 27.18 -0.61 -205.44 24.00 0.45 1050.00

1120.00 26.82 -1.04 -204.04 23.00 -2.00 1060.00

1130.00 26.92 -1.71 -202.92 23.00 -0.78 1070.00

1140.00 26.77 -2.18 -201.63 23.00 0.45 1080.00

1150.00 26.91 1.28 -196.43 23.00 1.53 1090.00

1160.00 26.44 -0.81 -196.81 22.00 -1.06 1100.00

1170.00 26.79 0.60 -193.73 22.00 0.00 1110.00

1180.00 26.59 0.02 -192.66 22.00 1.23 1120.00

1190.00 26.19 -1.52 -192.58 21.00 -1.47 1130.00

1200.00 26.02 -1.42 -190.89 21.00 -0.36 1140.00

1210.00 26.24 -2.49 -190.40 21.00 0.84 1150.00


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1220.00 26.43 0.93 -185.43 21.00 1.75 1160.00

1230.00 26.04 0.77 -184.08 20.00 -1.19 1170.00

1240.00 26.16 -1.38 -184.74 20.00 0.00 1180.00

1250.00 26.19 -0.10 -181.99 20.00 1.07 1190.00

1260.00 25.90 -0.40 -180.85 19.00 -2.00 1200.00

1270.00 25.99 0.15 -178.88 19.00 -1.00 1210.00

1280.00 26.06 0.09 -177.54 19.00 0.00 1220.00

1290.00 26.17 1.52 -174.73 19.00 1.02 1230.00

1300.00 25.73 -1.71 -176.60 18.00 -2.00 1240.00

1310.00 25.88 0.18 -173.38 18.00 -1.14 1250.00

1320.00 25.92 -0.70 -172.95 18.00 -0.08 1260.00

Table 5. Flip-chip antenna design characteristics (continued)

Simulated frequency in air on XRAG2’s intrinsic

impedance (MHz)Re(Z11) (Ω) Im(Z11) (Ω) Im(Zantenna) (Ω) ∆ (mm) a (mm)

Expected resonant frequency in air after

XRAG2 flip chip

Antenna matrix application example AN2631

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6 Antenna matrix application example

To illustrate the use of the antenna matrix, three families of antenna samples have been produced. The targeted center frequencies are for example 860 MHz, 910 MHz and 960 MHz. The used assembly technology is flip-chip.

According to Table 5, the suitable antenna designs in flip-chip matrix are 920 MHz, 970 MHz, and 1020 MHz, respectively.

The performance evaluation results obtained by using ISO 18046-3 performance test methods are shown in Figure 17 and Figure 18.

Figure 17. Tag's minimum electric field threshold (ISO 18043-3) for 920 MHz



0123456789

1011121314

820 830 840 850 860 870 880 890 900 910 920 930 940 950 960

Frequency (MHz)

E_th

r (V/

m) 920-1

920-2920-3920-4920-5


0123456789

1011121314

820 830 840 850 860 870 880 890 900 910 920 930 940 950 960

Frequency (MHz)

E_th

r (V/

m) 7970-1

7970-27970-37970-47970-5

AN2631 Antenna matrix application example

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Measured resonant frequencies for the three tag families correspond to the predicted resonant frequency.

The minimum electric field of each tag family is in line with the electric field measured in Section 4: Antenna performance characterization according to ISO 18046-3 performance test methods, predicting a read range of around 6 m at the center frequency.


0123456789

1011121314

840 850 860 870 880 890 900 910 920 930 940 950 960 970 980

Frequency (MHz)

E-th

r (V/

m) 1020-1

1020-21020-31020-41020-5

Revision history AN2631

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7 Revision history

Table 6. Document revision history

Date Revision Changes

19-Oct-2007 1 Initial release.

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