utilizing physical layer information to improve rfid tag
utilizing physical layer information to improve rfid tag
utilizing physical layer information to improve rfid tag
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Figure 5.2. RCS states in <strong>tag</strong> waveform.<br />
Figure 5.3. Conventional radio receiver.<br />
recovers the baseband signal. A Digital radio uses an RF front end, a high speed<br />
analog <strong>to</strong> digital converter and a digital down converter (DDC). The DDC is typically<br />
used <strong>to</strong> convert an RF signal down <strong>to</strong> baseband. It does this by digitizing at a high<br />
sample rate, and then uses purely digital techniques like multiplication, decimation<br />
and filtering <strong>to</strong> recover the baseband signal. Fig. 5.5 shows a block diagram of a<br />
digital down converter. We observe that the input <strong>to</strong> the DDC is a real signal while<br />
the output from the DDC is a complex signal. The DDC s<strong>tag</strong>e accomplishes this by<br />
using a local oscilla<strong>to</strong>r that generates a complex version of the carrier, with precise<br />
90-degree phase shift between its channels. The output signal thus is complex in na-<br />
ture and consists of an in-phase (I) and a quadrature phase(Q) component. Plotting<br />
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