J . P a c k . S c i . T e c h Vo l . 1 4 N o . 5 ( 2 0 0 5 )Packaging Material Implications in RFID Operations

Robert H. Clarke* and Krittika Tanprasert**
Radio frequency identification (RFID), although not a new technology, is relatively new tomany supply chains and retail store applications. Packaging plays a significant role in the successof RPID retail operations because RFID tags are placed directly on the packages Presently metalis the only packaging material widely known to interfere with RFID operation, though questions
exist about the impact of other materials. The objective of this study was to evaluate the effect ofcommonly used packaging materials and forms on 915 MHz RFID operations in terms of read
range and or readability. The evaluated materials were aluminum cans, plastic films, glass andcorrugated board. Aluminum cans containing an alcoholic beverage interfered with readability of
RHD tags both when tags are visible and invisible to the reader antennae. The impact was muchgreater when the tags were hidden. A sheet of glass, regardless of its color, reduced the read
range of RFID. Corrugated board shows promise for RFID operations for two reasons: it did notinterfere with the RFID system and it can also be used as a spacer to increase the readability of
packages containing products that interference with RFID readability. However, corrugated board
can absorb moisture when subjected to high humidity environments and this moisture adverselyaffected RFID readability. The curvature on packages also had impact on RFID operation range
Polyethylene stretch film does not have effect on RFID operation.

Introduction

Radio frequency identification (RFID) is one of the newest automatic identification anddata capture (AIDC) technologies for supply chain management. It has received a great deal ofinterest and has begun to be adapted by several suppliers, due especially to the mandates from
Wal-Mart and the US Department of Defense (DoD). Wal-Mart required RFID tagging on
cases and pallets in January 2005 for its top 100 suppliers [1] and for its next 200 suppliers by
January 2006[2]. The Department of Defense now requires RFID tagging on all individual
cases and pallets for some products shipped into the Defense Logistics Agency distribution
centers in San Joaquin, CA and Susquehanna, PA. It will require RFID tagging on all products
shipped to DoD locations by January 2007. [3] Both of these mandates require the use ofpassive transponders in the ultra high frequency (UHF) range (915 MHz). [2], [3]______________________________________________________________________________________________________*School of Packaging, Michigan State University East Lansing, Ml 48824 USA, (517) 355-7613, clarker@msu.edu**School of Packaging, Michigan State University East Lansing, MI 48824 USA, (517) 353-3367, tanprase@msu.edu- 2 9 9 -

Packaging

Material

Implications

in

RFID

Operations

An RFID system consists of RFID transponders (or tags), and a reader with system antennae
connected to a computer. RFID transponder consists of a chip, where product information are
stored, and antenna, which enable the chip to transmit the information. The system antennaacts as a conduit between transponders and readers. For passive transponders, which containno battery, the reader will send radio frequency signal and power to the transponder. The
transponder will send the signal that contains information in its chip back to the reader. The
reader will convert this signal to a useful form and send it to the computer.
RFID systems claim to have several advantages over existing barcode systems including:1) RFID allows the possibility of locating the object in addition to object identification, 2) the
speed of reading is faster, therefore, almost simultaneous reading of several transponders canbe achieved, 3) the transponders are more robust than barcodes, 4) the read range is often
longer than barcodes, and 5) no line of sight may be required. [4] The latter advantage allows
the possibility of placement of transponders inside packages so they do not interfere withpackages' appearance or cover vital information on the packages. In case of item or case leveltagging, non-line of sight, if allowed, can enhance the flexibility in packing or pallet pattern.
Although the non-line of sight requirement is a very attractive feature of RFID, there
has been a lot of controversy on this issue. The non-line of sight requirement can beinterpreted as meaning that all materials are radiolucent, meaning they are transparent to radio
frequency energy. This is not at all true for at least two common materials, metal and liquid,
and may be compromised with other materials. However, this does not mean that RFID
cannot be used in these situations, only that care must be taken in the particular application.
One other important issue about RFID is the readability of different transponder
orientation. Joe Jiner, Logistics and RFID Development Director at The Kennedy Group,
demonstrated that transponder location is critical by using a case of liquid product. He foundthat only 1 or 2 out of 6 possible transponders locations were successfully read. [5]. Greg
Matula, Hewlett Packard's Technical Lead for its RFID program and Worldwide RFID
Procurement Manager, mentioned that the tag orientation relative to the face of antenna
influenced readability. [6]From a Japan Electronic Industry Development Association (JEIDA) study, it was
found that for 125 kHz RFID systems, readability reduced significantly as the angle between
the face of antenna and the face of transponder increased from 0 (parallel) to 90(perpendicular). Despite the many references that identified interferences that create an
obstruction to RFID readability, there is no published research on how much these interferewith RFID operations other than the JEIDA study that was done using a 125 kHz RFIDs y s t e m .

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J.Pack.Scl Tech. Vol. 14 No.5 (2005)

Therefore, the objective of this research was to evaluate the effect of commonly used packaging
materials and package forms with 915 MHz RFID operations in terms of read range and/or
readability. The evaluated materials were aluminum, plastics film, glass and corrugated board.

Materials and Methods

RFID system
Two RFID systems, Matrics and Alien, were used in this study. The Matrics system now
owned by Symbol Technologies, Inc. of Oakland, CA, consisted of 4 antennae and a reader set
up on a frame to simulate the dock door portal. The width of the portal was 10 feet. On eachside of the portal there were two antennae. The reader was connected to Matrics Tag Tracking
3.0.1 software in a personal computer. The Alien system (Alien Technology, Morgan Hill,
CA) consisted of,a single antenna, linear or circular polarized, and a reader. The reader was
also connected to Alien software in a personal computer.

Evaluation of the RFID tag readability
The readability was evaluated by bringing tags on test objects toward the dock door
portal at a constant speed. The result of "read" or "no read" was recorded. The readability isevaluated by the probability of tag being read. The data is then analyzed via logistic regression
using MinitabR. A Hosmer-Lemeshow test is performed to verify the agreement between thepredicted probabilities and the regression to the experimental values (Ho: the predicted ando b s e r v e d v a l u e a g r e e ).

Evaluation of the RFID tag operation range
The operation range was evaluated by moving a tag on a test object away from anantenna. The height of the tag is approximately the same as the center height of the antenna.
The distance when the tag can no longer be read was recorded as an operation range of the
RFID antenna.

The effect of moisture content in corrugated board on the tag readability
The interference of various moisture contents with C-flute corrugated board was studied
using the Matrics system. Sixty-four empty corrugated board boxes with Matrics dipole tags
were exposed to varying storage conditions to alter the moisture content of the corrugatedboard. The storage conditions included: 22.2°C and 55% RH, 29.4-C and 70% RH, and 37.8°C
with 85% RH for approximately 96 hours, the time previously determined for the corrugated- 3 0 1 -

Packaging Material Implications in RFID Operations

board to reach the equilibrium moisture content. The boxes were arranged into 4 × 4 × 4column stack pallet pattern and the readability was evaluated immediately after removal fromthe conditioning chamber. The evaluation of readability was done in 25 replicates for eachlevel of moisture content. For each level and concurrent with the evaluation, the moisture
content of the corrugated board was determined according to ASTM D644-99 (Standard test
method for moisture content of paper and paperboard by oven drying). [7]The effect of aluminum on the tag readability
The effect of aluminum was studied through evaluation of tag readability in the presenceof 12 fluid ounce aluminum cans containing beer. Twelve cans were placed in each carton (11"×8"×4.5") and 64 cartons were placed in a 4×4×4 stack column pallet pattern. The tags wereplaced on a side panel or on the top panel of the carton with or with out a C-flute corrugatedboard spacer (cut to the same size as the surface area of the tag). The placement of spacers waseither on the back of the tag, or on both the front and back of the tag (single versus double
spacers). The tag readability evaluation was performed using the Matrics system with 25
replicates. The result was then compared with the readability of the tags on the empty cartons.

The effect of pallet stretch film on the tag readability
The readability of Matrics tags under polyethylene (PE) stretch wrap was also evaluatedusing the Matrics system. Each box contained twelve 32 fluid ounce PET bottles (9 _" tall, 3 _"diameter) filled with water. The water was used to stabilize the load while it was being stretch
wrapped. Forty-eight C-flute corrugated board boxes (13"×12"×10") were arranged in a 3×4
×4 column stack pallet pattern. The Matrics tags were placed so that those on the boxes
around the perimeter of the pallet were facing outward. The pallet load was stretch wrappedwith PE film using an automatic pallet stretch wrap machine (Highlight Inc., Wyoming MI)
with varying degree of stretch and total amount of stretch wrap. The first setting was for themachine to travel up and down twice. This setting was performed twice with percent stretchesof 45 and 150. The other setting was for the machine to travel up and down six times. The
percent stretch at this setting was 160. The readability of the pallet load with stretch film wascompared to the readability of the same pallet load without stretch film.

The effect of glass on the RFID tag operation range
The effect of a flat glass sheet on the operation range of Alien squiggle tag (Alien
Technology, Morgan Hill, CA) was studied on clear, amber and green glass. The tag wasplaced in front of, on the back of, or in between glass sheets, identified in the results as "front",- 3 0 2 -

J.Pack.Sci. Tech. Vol. 11 No.5 (2005)

Figure 1. Tag orientation and travel direction of Alien squiggle tag on the glass sheet"back", and "sandwich". The operation range was evaluated for the antenna for three tags
orientation (x, y and z-axis) as shown in Figure 1. The blank was performed in the samemanner with the tags placed in the same orientation and location but in the absence of a glass
sheet. The percent reduction of operation range is calculated by equation (1).
Operation range of blank - Operation range of sample
× 1 0 0Operation range of blank(1)

The effect of container curvature on RFID tag operation
The effect of container curvature on the read range of Alien squiggle tags was studied
using different sizes of graduated glass cylinders, ranging between 25 and 1000 mL. The tags
were placed in two orientations, the x and y-axis as shown in Figure 1. The studied was
conducted using the Alien system with either a circular antenna, linear antenna, or linear
antenna turned 90° from its usual orientation. These setting are designated as "circular","horizontal linear" and "vertical linear", respectively. The operation range was evaluated asprevious described.

Results and Discussions

The effect of moisture content in corrugated board on the tag readability
Corrugated fiberboard is widely used to construct shipping containers for the purpose ofcontainment and protection. Corrugated board has a chance to come into contact with an
RFID tag during case level and pallet level tracking. The corrugated board itself has little or noeffect on RFID operation since preliminary tests showed tags could be read through a 30-inch
thick stack of corrugated board under standard temperature and humidity conditions.
However, due to its hygroscopic nature, the absorption of moisture is a concern not only
because of the reduced strength caused by moisture but also because of the interference to- 3 0 3 -

Packaging Material Implications in RFID Operations

RFID operations.
The moisture content (dry basis) of corrugated board subjected to various environmental
conditions (temperature and relative humidity) is shown in Table 1. Figure 2 shows theprobability of a tag being read when affected by moisture content in the corrugated board. The
effect of moisture content on the probability of tag reads was also analyzed by logistic
regression. The model is shown in Equation (2)( 2 )where p (x) is the probability of tag being read.
However, the value predicted from this equation did not agree with the experimental data (Pvaluc of Hosmer-Lemeshow test < 0.05). Therefore, this model was discarded and theexponential decay type equation was used to draw a trend line in Figure 2.

Table 1. Moisture content of corrugated board subjected to various
environmental conditions for 96 hours
Storage condtion
Temperature, ℃ Relatve humidity, %
22.2
55.0
29.4
70.0
37.8
85.0

Moisture content (dry basis), %8.2±0.1
9.6+0.1
15.3±0.1

Figure 2 indicates the dependency of tag read probabilities on the moisture content ofcorrugated boxes. As moisture content of corrugated board increases from 8.2 to 9.6% (drybasis), the moisture content had large effect on reduction of tag readability. The tag readability
slightly decreased beyond 9.6% moisture content, but at a much lower rate. Most of theunread tags were located in the two bottom tiers of the pallet. Although the change in readprobability did not seem very large in magnitude due to the large number of test samples, thestandard error of the each value was relatively small (approximately 0.003).
After exposing the corrugated boxes to the high relative humidity environment, they
were returned to the standard condition (22.2°C, 55% RH) and kept there for more than 96
hours. The readability of the tags on those boxes was then retested. It was found that theprobability of reads dropped from 0.995 (8 tags not read) to 0.981 (29 tags not read). The
boxes were, again, returned to a high humidity condition (37.8°C, 85% RH) for 96 hours andthe readability was again evaluated. The result of this test shows no difference in the readprobability from the previous test for high humidity condition.
The difference in the readability when corrugated boxes were kept at the standard
condition was attributed to the hysteresis phenomena. At any given relative humidity, the- 3 0 4 -

J.Pack.Sci. Tech. Vol. 14 No.5 (2005)

Figure 2. The probability of Matrics tag reads when placedon corrugated boxes with various moisture contents,
arranged in 4×4× 4 column stack pallet pattern.

moisture content of the material is greater during desorption than during absorption. In
corrugated board, the difference between moisture content owing to the hysteresis phenomena
can be as much as 25% depending on the temperature and relative humidity. At 20°C andapproximately 55% RH, the difference was around 12.5% (based on absorption moisture
content). [8] The moisture content of corrugated board boxes when returned to standard
conditions after exposure to high humidity environment could be approximately 9.2% (drybasis), which is slightly lower than the moisture content of corrugated board exposed to thecondition of 29.4°C, 70% RH. In agreement with the estimated moisture content, the readprobability obtained from this testing was slightly higher than the probability obtained fromboxes exposed to 29.4°C, 70% RH.
The absorption of moisture content on corrugated fiberboard can have impact on RFID
operation. This is of concern for RFID operations in high humidity environments. In addition,
RFID operation in medium to low relative humidity maybe of concern if the corrugated board
has been exposed to high humidity. This situation may occur due to the prolonged exposure tohigh humidity environment, the leakage of liquid products, condensation due to temperaturefluctuations, and/or the respiration/transpiration of fresh produce.

The effect of aluminum on the tag readability
Metal, a common packaging material for the food and beverage industry has a very large
impact on the transmission of radio frequency. Metal does not allow radio frequency to passthrough it. It also changes the inductance of antennae (on both reader and tag) and retunes its
resonance frequency. In addition, there are published statements that metal also absorbs radio- 3 0 5 -

Packaging Material Implications in RFID Operations

frequency. In UHF, this may increase the read range of RFID system if enough air gap
between the metal and tag are provided. [9] To date, there is only one published data on theeffect of metal as an interference in operation range of low frequency RFID system (125 kHz).
It was reported that a metallic substance in front of the tag reduced the RFID system operating
range by 30-50%. The effect of metal behind the tag depends on the distance between the tag
and the metal. The distance between 3-6 cm (or more) will minimize the effect of metallic
substance behind the tag.
Table 2 shows the read probability of tags on 64 cases of beer cans in a pallet load.
When cases contained no aluminum beer can, the tag read almost all the time as indicated by
the high read probability. The presence of beer can support the statement that metal has aneffect on RFID operation, particularly in the case of hidden tags where the read probability
reduced from almost 1 to almost 0. The visible tags on the side panel were affected by thepresence of metal can at a much lesser extent. The effect of metal on the visible tag placed on
the top panel was much greater than those on the side panel. This may be a result of tag
orientation or proximity to the metal cans, but more research is required to tell which has thegreater

impact.

Table 2. The probability of tag reads when placed on beer cases, with andwithout corrugated board spacer, when visible or hidden within the pallet.
Tag visibility

Product

VisibleNone
Alumnum beer can
Alumnum beer can
Alumnum beer can
None
Alumnum beer can
Alumnum beer can
Alumnum beer can

Invisible

SpacerRead probability
Side
Top
panel
panel
No spacer
1.000
1.000
No spacer
0.927
0.250
On the back
1.000
0.768
On the back and front 0.972
0.720
No spacer
0.997
0.998
No spacer
0.087
0.031
On the back
0.013
0.024
On the back and front 0.063
0.103

The addition of one or more corrugated board spacers between the tags was an attempt
to improve the readability by increasing the air gap between the metal and tag. In the UHF
frequency range, the air gap may increase the operation range. [9] The data of read probability
was analyzed by logistic regression to determine the effect of corrugated board spacer(s). The
regression equation is shown in equation (3) and (4) for the tags on the side and top panel,
respectively- 3 0 6 -

J. Pack. Sci. Tech. Vol. 14 No.5 (2005)

where H is height from the floor (H: 20.75, 32.75, 44.75 and 56.75 cm),
Vis is tag visibility (Vis: 0=hidden, 1=visible), andx1 and x2 are dummy variable representing the presence of corrugated board
spacer (presence on the back of the tag side (1, 0), presence on bothside (0,1), and not present (0,0)).
The regression result (data not shown) indicates that the 3rd and the 2nd order interaction
term in equations (3) and (4) were significant (p<0.05). Therefore, this model cannot be used
to evaluate the main effect of corrugated board spacer because the effect is dependent on
location of tag. To determine the spacer effect, the data from hidden and visible tags wereanalyzed separately for each tier in the pallet. The new logistic regression model is shown inequation (5) and the regression coefficients are presented in Table 3 and 4 for tags on the sideand top panel, respectively.

The p-value of H-L test in Tables 3 and 4 indicates that the regression model can be used
to predict the read probability for tags with interference of metal (p>0.05). The regression
coefficients from the model show the impact of the parameter on the probability of the tag
being read. Larger values indicate higher impact. The mathematical sign of the coefficientsshows the direction of impact. The positive sign means the probability increases with theincreasing value of the parameter. [10]For tags on the side panel (Table 3), the addition of spacers did not have a significant
effect on the readability of visible tags, with the exception of the improvement in readability inthe bottom tier of the pallet for tag placed in between two spacers. For the hidden tags, theaddition of one spacer on the back had a negative effect on the readability while the addition of
two spacers (front and back) had a negative effect on the two bottom tiers, but had no effect on
the top two tiers.

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Packaging Material Implications in RFID Operations

Table 3. Regression coefficients from logistics regression and the p-value and Hosmer-Lemeshow (H-L)
test results for cases with tags on the side panel
Visibility Height, cm
Visible20.75

Visible32.75

Visible44.75

Visible56.75

Hidden20.75

Hidden32.75

Hidden44.75

Hidden56.75

Parameter
Intercept
β0
x1
β3
x2
β4
p-value for H-L test
Intercept
β0
x1
β3
x2
β4
p-value for H-L test
Intercept
β0
x1
β3
x2
β4
p-value for H-L test
Intercept
β0
x1
β3
x2
β4
p-value for H-L test
Intercept
β0
xl
β3
x2
β4
p-value for H-L test
Intercept
β0
x1
β3
x2
β4
p-value for H-L test
Intercept
β0
x1
β3
x2
β4
p-value for H-L test
Intercept
β0
xl
β3
x2
β4
p-value for H-L test

Tag on side panel
Regression coef
p-value
1.324914.2116
1.8531<.0001
0.95210.00110.92033.1781<.0001
1 1.7458
0.94620.71380.41620.92034.5951<0.0001
1 0.7302
0.95981.11900.33620.92033.4761< 0001
11.62810.95130.41570.65280. 09203-2.0907<.000l-2.2132<0.0001-1.0038
0.00300.9999-3.1780<.000l-2.52200.0157-1.8259
0.01750. 9997-2.4423<.000l-1.4495
0.0018-0.50210.13951.000-1.9924<.000l-2.3116<.000l
0.28370.23561.000

For tags on the top panel of the cases (top panel), the addition of one and two spacers to
the visible tags improved the readability in a similar manner. For the hidden tags, the addition of
one spacer on the back did not improve the readability while the addition of two spacers
increased the probability of tag being read in the two bottom tiers. The effect was less in thebottommost tier.

Metal has a tremendous impact on RFID operation, particularly when the RFID tags are
hidden or in a less than ideal location. This may cause a lot of problems when trying to readseveral tags at once in the pallet load. When reading a tag one by one as in case level conveyor
tracking or pallet tag tracking, the problem may not be as serious as long as the tag is facing atleast one of the antennae. A corrugated board spacer can improve the readability of RFID in
the presence of metal interference in some situations, but it is not very effective. A larger sizeor a thicker spacer may be more efficient in improving the readability, or a better design of the- 3 0 8 -

J.Pack.Sci. Tech. Vol.ll No.5 (2005)

Table 4. Regression coefficients from logistics regression and the p-value and Hosmer-Lemeshow (H-L)
test results for cases with tags on the top panel
Height, cm Tag visibility
Hidden20.75

Hidden32.75

Hidden44.75

Visible56.75

Parameter
Intercept
β0
x1
β3
x2
β4
p-value for H-L test
Intercept
β0
x1
β3
x2
β4
p-value for H-L test
Intercept
β0
x1
β3
x2
β4
p-value for H-L test
Intercept
β0
x1
β3
x2
β4
p-value for H-L test

Tag on side panel
Reg.coef
p-value-2.7081<.0001-0.2903
0.3536
0.53830.04170.9997-3.6636<.000l-0.36420.46452.2457<.000l1.000-5.2933<.000l
0.40800.65590.69820.42171.000-1.0986<.000l
2.2929<.00012.0431<.0001
1.000

tag antenna might be devised.
The effect of pallet stretch wrap on the tag readability
Polyethylene (PE) is a commonly used pallet stretch wrap material. The impact of thestretch wrap radiolucency is very important to pallet level tracking. It is important to know
before hand if the stretch-wrap material will interfere with the pallet readability. This will
determine if the pallet tag needs to be placed on the outside of the stretch wrap or it isacceptable to place under the stretch wrap.
Figure 3 and equation (6) shows the read probability as a function of the weight ofpolyethylene stretch wrap around the load.

The parameter "W" in equation (6) is the weight of PE stretch wrap. The H-L test p-value of0.98 indicates the validity of the model to the experimental data. The slope of equation (6) is
not significant (p = 0.92), indicating that neither the presence nor the weight of this PE stretch
wrap interfered with tag readability. This agrees with the relatively straight line shown in
Figure3.
In term of pallet load tracking, the tags can be placed under the PE stretch wrap without
interfering with an RFID operation. Placement of the tag under pallet stretch wrap is moredesirable in order to prevent tags from being damaged, lost or stolen during shipping/handling.
This also allows the possibility of reading individual tags on cases in a pallet load without- 3 0 9 -

Packaging Material Implications in RFID Operations

Figure 3. The read probability of tags on a pallet load with of water filled casesand varying weights of polyethylene stretch wrap and % stretch

removing the stretch wrapping provided that the packaging and the product do not interfere.

The effect of glass on the RFID tag operation range
Glass, an inert and high barrier packaging material, is used extensively for primary
packages. This is particularly true for the pharmaceutical industry, where the FDA has
recommended widespread use of RFID for item level tracking by 2007. [9] To date, there areno published studies covering the effect of various glass types on RFID operation.
Figures 4 and 5 shows the operation range of tags on glass sheets when evaluated withcircular and linear-polarized antennae, respectively. When looking at the same tag orientationand placement on a glass sheet, it was found that the color of glass does not have an effect on
RFID operations. Therefore, for this study, the effect of glass color was ignored and a t-test
for comparing one population to a single value was used to analyze the data. Glass was foundto significantly reduce the read range for all tag locations and orientations for all antenna types(α=0.1).
In Figure 4, the operation range for a circular antenna system was about 60 inches for all
both x and z-axis tags when they were placed in front of, or behind, the glass sheet. The range
was much shorter for the same orientation when the tags were placed in between two glass
sheets of the same material. The read range for y-axis tag orientation, where the tags are facing- 3 1 0 -

J.Pack.Sci. Tech. Vol. 14 No.5 (2005)

Figure 4. Operation range of Alien RFID system with circular-polarized antenna for transponder in 3
orientations (x, y and z-axis) with the presence of a glass sheet. The transponder was in front(front), on the back (back) or placed in between (sandwich) glass sheets.

90° away from the antenna, was much shorter than the range of other orientations.
The effect of glass on a linear antenna system, shown in Figure 5, is similar to the effecton the circular antenna system, but the effect of orientation is different. The z-axis orientation
has the longest read range, which is longer than the read range of z-axis orientation for thecircular antenna system. Unlike the circular antenna system, the x-axis orientation tags could
not be read at all. The difference between the two types of reader antenna is how they emit
radio wave. The circular-polarized antennae emit radio waves in a circular pattern while linearpolarized antenna focuses the radio energy in one orientation. [11] Therefore, when tags are
not aligned with the orientation of the signal, an RFID system using linear antennae cannot
pick up the signal.
Figure 6 shows the percent reduction of operation range for circular and linear polarized
antennae. The greater number implies the greater impact of the presence of glass. From thisfigure, it is obvious that glass has the same magnitude of effect on the operation range whentags are placed on either side of a sheet of glass regardless of orientation and type of antenna.
The read range is reduced by approximately 50%. The placement of tags between two glass
sheets reduced the read range by about 80% for both type of antenna. One exception to this is
for the linear antenna system when the tag is oriented in the x-axis where 100% reduction
occurred when either one or two glass sheets were presented.

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Packaging Material Implications in RFID Operations

Figure 5. Operation range of Alien RFID system with linear-polarized antenna for transponder in 3
orientations (x, y and z-axis) with the presence of a glass sheet. The transponder was in front(front), on the back (back) or placed in between (sandwich) glass sheets.

Figure 6. The percent reduction of operation range for Alien RFID system with circular and linear-polarized antennae with transponders in 3 orientations (x, y and z-axis) in the presence of a glass
sheet. The transponder was in front (front), on the back (back) or placed in between (sandwich)glass sheet.

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J.Pack.Sci. Tech. Vol. 11 No.5 (2005)

Glass has a large impact on reduction of operation range of RFID particularly when thetags arc enclosed between two sheets of glass or when tag orientation is a problem. This may
affect the item level tracking but it does not mean that item level tracking of glass packages is
not possible. When reading a single tag, this will not create a problem since the tag can still beread. The problem may arise when attempting to read several tags at high speed. Because theread range is much shorter when glass is presence, the tags must remain in the operation range
longer for the reader to detect the existence and collect the data from all tags.

The effect of curvature on RFID tag operation
Packaging can come in several shapes and some shapes do not provide enough flat
surface area for RFID tags, especially on primary packages. Many UHF tags arc relatively
large, and without redesigning the tag, they have to be deformed to adhere to some packages.
This may cause distortion of the re-emitted frequency waves and thus, interfere with the RFID
operation. [9]Figure 7 shows the read operation of tags on graduated cylinders of various diameters.
The figure indicates that the operation range of these tags in the system with circular-polarized
antenna was slightly larger than that of a horizontal linear antenna when the tags are in x-axis
orientation, yet very similar when the tags are in y-axis orientation. The reason for thisdiscrepancy with the data from previous section may be that the linear antenna system is moresensitive to the curvature of the tag. In both systems, the curvature starts to have effect when
the diameter of cylinder is below 1.5 inches. A tag on 0.7-inch diameter cylinder, where there

Figure 7. The operation range of Alien system with circular and linear antennae for tags on graduate
cylinders with different diameters, when the tags are placed in x and y-axis orientations- 3 1 3 -

Packaging Material Implications in RFID Operations

was an overlap of the tag antenna, could not be read. The interference may be a result of
detuning of the signal or the reduction of exposure to reader energy.
Since linear-polarized reader antenna is orientation sensitive, it is as expected that whenturning the reader antenna 90°, the read range was shortened. Unlike the horizontal linear
system, y-axis orientation tags in a vertical linear system have a larger operation range than xaxis tags. The range did not change much with the reduction of diameter of graduated cylinder.
This indicates that the curvature did not have as much influence as with the previous two
systems.
Like the effect of glass sheet, the curvature of packages may or may not interfere with
RFID operation in item level tracking. This depends largely on the degree of curvature as wellas the amount of tags being read at the same time.

C o n c l u s i o n

From our research, packaging materials were categorized, based on their interference in
RFID operation into 2 groups. The first group is those that have no effect on the operation.
This group includes polyethylene stretch wrap and corrugated boards that are not or have notbeen exposed to high humidity. The second group is those that have effect on the operation.
Aluminum can, glass and corrugated boards that are or have been exposed to high humidity arein this group. The curvature of packages, when the diameter reduces to a critical dimension(e.g. 1.5 inch in our case), also can interfere with the RFID operation. However, this result
does not indicate that the materials from the latter group and the packages with curvaturecannot be used in RFID operation. The result is intended to show that care must be exerted
when the RFID interference is presence in the RFID operation.

R e f e r e n c e s1) Anon, Talking RFID with Wal-Mart's CIO.. 2004, Business Week Online.
2) Anon, Wal-Mart Details EPC Rollout Plan. 2004, RFID Journal.
3) Roberti, M., DOD releases final RFID policy. 2004, RFID Journal.
4) Wright, G., Radio Tags, Technology Snags and Market Lags: Finding a Future for Radio
Frequency Identification.
5) Albright, B., RFID tag placement. 2004, Frontline Solution.
6) Ferrante, M.A., Are you ready?. 2004, Packaging Machinery Technology.
7) ASTM, D644-99(2 002) Stand ard Test Method for Moisture Content of Paper andPaperboard by Oven Drying, in Book of Standards Volume: 15.09.2002.

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J.Pack.Sci. Tech. Yol. lt So.5 (2005)

8) Eagleton, D.G. and J.A. Marcondes, Moisture-sorption isotherms for paper-based
components of transport packaging for fresh produce. Tappi Journal, 1994. 77(7): p. 75-81.
9) Philips Semiconductors, TagSys, Texas Instruments Inc., Item-level visibility in thepharmaceutical supply chain: a comparison of HF and UHF RFID Technologies. 2004,
Philips Semiconductors, TAGSYS, Texas Instruments Inc.
10) Ott. R.L. and M. Longnecker, An Introduction to Statistical Methods and Data Analysis.
5th ed. 2001, Pacific Grove, CA: Duxbury. 1152.
11) Anon, Glossary of RFID term. 2005, RFID Journal.

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