43 ms. A 1 is similar except with a rising edge.
Differential Manchester encoding shown in Figure 3.4a is a modi?¬?cation of Manchester
encoding used most prominently in token ring networks [28]. At ?¬?rst glance, Manchester
and differential Manchester encodings are indistinguishable as they both require a transition
in the middle of a bit window for synchronization, and may or may not have a
transition at the edge of a window. However, differential Manchester determines its
RFID standard
bit coding specification
Physical layer
waveform feature
library
Encoder
VHDL
Physical layer
waveform
features
Synthesis Decoder
VHDL
FIGURE 3.3
Generation ?¬‚ow for an RFID data encoder and decoder.
Design Automation for RFID Tags and Systems 39
value by examining the level between windows. As shown in Figure 3.4a, if there is a
transition between windows this encodes a 0 and if there is no transition this encodes a 1.
To support this case, we add an Lprev condition to our waveform representation as
shown in Figure 3.6. Depending on the previous level, our description describes a level
change for a 0 encoded bit and no level change for a 1 encoded bit. The if statement
determines which waveform to consider based on Lprev.
PIE and FM0 encodings are two different encodings used in the ISO 18000 Part 6C
standard. These encodings are shown in Figure 3.
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