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RFID Modulation and Encoding
Modulation
Sound is converted into electricity by a telephone and then transmitted as an analog signal.
These waves have 3 fundamental characteristics:
- Amplitude, meaning the height (intensity) of the wave
- Frequency, which is the number of waves that pass in a single second and is measured in Hertz (cycles/second) (wavelength, the length of the wave from crest to crest, is related to frequency.).
- Phase is a third characteristic that describes the point in the wave’s cycle at which a wave begins and is measured in degrees. (For example, changing a wave’s cycle from crest to trough corresponds to a 180 degree phase shift).
Most RFID tags were using ASK (Amplitude Shift Keying), FSK (Frequency Shift Keying) and PSK (Phase Shift Keying) for its analog modulation.
Picture 3. RFID modulation.
For encoding, most of them are using NRZ, Manchester,
Unipolar RZ, DBP (Differential Bi-Phase),
Miller and Differential Coding on PP Coding.
RFID Modulation and Encoding
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原文地址：http://www.cnblogs.com/shangdawei/p/4827844.html
