TECHNICAL DATA

0647-EX-PL-2006 Text Documents

WAL-MART STORES, INC.

2006-11-14ELS_78733

TECHNICAL DATA: Explanation of UHF RFID emissions and bandwidth

Wal-Mart will be evaluating the performance of UHF RFID Readers in our Bentonville,
Arkansas laboratory. Readers destined for deployment at Wal*Mart sites in Europe,
Japan and in other markets of potential interest to Wal-Mart will be tested.

The transmission characteristics of UHF RFID Readers are specified in the standard
“Class-1 Generation-2 UHF RFID Protocol for Communications at 860 MHz – 960
MHz” (hereafter referred to as the Gen2 protocol). The Gen2 protocol has been ratified
and is published by EPCglobal Inc. The Gen2 protocol will be used in connection with
operations on all frequency ranges requested in this application.

The Gen2 protocol specifies three transmit modulation options for Readers, double
sideband (DSB) ASK, single sideband (SSB) ASK, or PSK. Readers send digital
commands to tags using one of these modulation formats then follows the command with
a continuous wave (CW) transmission. Therefore, possible Reader emissions are DSB
ASK, SSB ASK, PSK, and CW as indicated in 4(E) of the application.

Pulse Interval Encoding (PIE) is used to encode the digital bits (binary signaling scheme).
Encoding of “data-0” and “data-1” bits is shown in Figure 1. A data-1 bit is
distinguished from a data-0 by having a duration that is between 1.5 and 2.0 times the
length of a data-0.

1.5 Tari ≤ data-1 ≤ 2.0 Tari
Tari 0.5 Tari ≤ x ≤ Tari

PW PW

data-0

data-1
Figure 1: RFID Gen2 data encoding

The baseband data sequences are pulse shaped (filtered) to meet Japanese and European
radiated emission regulatory requirements prior to modulation of the carrier. Figures 2,
3, and 4 show examples of typical pulse shaping and the resulting Power Spectral Density
(PSD) of the transmitted DSB ASK, SSB ASK, and PSK signal, respectively. The
examples show waveforms and spectra for a 32 kbps data rate signal.

Time Domain Waveforms (pre-filter) Power Spectral Density
1.25 40
1
20

PSD (dBm/0.1 kHz)
0.75
0.5 0
0.25
-20
0
-0.25 -40
-0.5 PIE ASK -60
-0.75
0 25 50 75 100 125 -200 -100 0 100 200
Frequency (kHz)
Time Domain Waveforms (post-filter) Eye Diagram
1.25
1 1
0.75 0.8
0.5
0.6
0.25
0 0.4
-0.25 0.2
PIE ASK (DSB)
-0.5 ABS[signal] 0
-0.75
0 25 50 75 100 125 0 10 20 30 40 50
Time (µsec) Time (µsec)

Figure 2: DSB ASK baseband time and frequency domain waveforms (32kbps data
rate example)

Time Domain W aveforms (pre-filter) Power Spectral Density
1.25 40
1
20
PSD (dBm/0.1 kHz)

0.75
0.5 0
0.25
-20
0
-0.25 -40
-0.5
PIE ASK -60
-0.75
0 25 50 75 100 125 -200 -100 0 100 200
Frequency (kHz)
Time Domain W aveforms (post-filter) Eye Diagram
1.25
1 1
0.75
0.8
0.5
0.25 0.6

0 0.4
-0.25 PIE ASK (SSB)
0.2
ABS[signal]
-0.5 PIE ASK (DSB) 0
-0.75
0 25 50 75 100 125 0 10 20 30 40 50
Time (µsec) Time (µsec)

Figure 2: SSB ASK baseband time and frequency domain waveforms (32kbps data
rate example)

Time Domain Waveforms (pre-filter) Power Spectral Density
1.75 40
1.25
20

PSD (dBm/0.1 kHz)
0.75
0.25 0
-0.25
-20
-0.75
-1.25 -40
-1.75
PIE BPSK -60
-2.25
0 25 50 75 100 125 -200 -100 0 100 200
Frequency (kHz)
Time Domain Waveforms (post-filter) Eye Diagram
1.75 1.5
1.25
1
0.75
0.25 0.5
-0.25 0
-0.75
-0.5
-1.25
PIE BPSK (DSB) -1
-1.75 ABS[signal]
-2.25 -1.5
0 25 50 75 100 125 0 10 20 30 40 50
Time (µsec) Time (µsec)

Figure 3: PSK baseband time and frequency domain waveforms (32kbps data rate
example)

The bandwidth efficiency (bps/Hz) is used to relate the data rate to the 99% signal
bandwidth for each emission type. Bandwidths are listed in Table 1 for typical and
maximum data rates. Typical data rates correspond to modes prevalent in Readers
designed for operation in Japanese and European markets. Applicant believes these data
rates will apply in other countries, as well. Maximum bandwidths correspond to
maximum data rates allowed by the Gen2 protocol.

Table 1: Typical and maximum bandwidths for each emission type
Emission Type Bandwidth Typical Maximum Typical Maximum
Efficiency Data Rate Data Rate Bandwidth Bandwidth
(bps/Hz) (kbps) (kbps) (kHz) (kHz)
DSB ASK 0.20 48 128 240 640
SSB ASK 0.40 48 128 120 320
PSK 0.27 48 128 178 474

Baseband signals modulate an RF carrier at a frequency within the range listed in
Technical Data section of the application. The carrier is constrained to fall on channel
centers that are 200 kHz apart starting 100 kHz inside the frequency limits specified in
this application. The peak radiated transmit power (power assuming no modulation, that
is, a CW transmission) is listed in this application. The peak power is constrained by
Japanese and European regulations.

Document Created: 2006-11-14 15:30:51
Document Modified: 2006-11-14 15:30:51

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