The WPC-Design document reports that: "Transmitter use a differential bi-phase encoding scheme to modulate data bits in the Power Signal."

which encoding method do they mean? - Differential Manchester encoding?



From a communications standpoint, bi-phase coding means that the signal has two states that are distinguished only by the phase of the signal. The amplitude is constant. See binary phase-shift keying (BPSK or 2-PSK):

Differential BPSK (DBPSK) means that the difference of the current bits phase and the phase of the previous bit is taken. This is helpful when the absolute phase is not known and the phase change to the previous bit is used instead. https://en.wikipedia.org/wiki/Differential_coding

The quote

"Transmitter use a differential bi-phase encoding scheme to modulate data bits in the Power Signal."

does not state that a differential manchester code is used, but this type of code has the above mentioned properties.

  • \$\begingroup\$ I know I have seen it written, explicitely, that they use amplitude shift-keying, but I don't remember where. Still, I also seem to remember something about PSK, most probably in the same place... \$\endgroup\$ – a concerned citizen Apr 23 '18 at 5:41
  • \$\begingroup\$ So am I right if I use diff Manchester in combination with ASK? \$\endgroup\$ – Luigi Apr 25 '18 at 18:12
  • \$\begingroup\$ You can use differential ASK which is the same as differential BPSK with the phases 0 and 180 degree. If you need to remove the DC component (zero mean signal) than this can be ensured by Manchester (line) coding. Otherwise I do not see the benefit from using Manchester coding. \$\endgroup\$ – andresnm Apr 27 '18 at 10:36
  • \$\begingroup\$ I get it. But Qi-Charging is about transmitting a message, but I have to use the Manchester method to transmit the signal through diff ASK. Or which variant would you recommend. \$\endgroup\$ – Luigi Apr 27 '18 at 11:14

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