Manchester code modulation

Discussion in 'Programmer's Corner' started by suki, Jul 18, 2010.

  1. suki

    Thread Starter New Member

    Jul 6, 2010
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    I have develop a circuit which taking a series of binary number and change it into Manchester code. then, I need to modulate the Manchester code, is it possible to modulate it into FSK because I found that Manchester code only can be modulated into PSK. help me to figure this out pls.
     
  2. hgmjr

    Moderator

    Jan 28, 2005
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  3. suki

    Thread Starter New Member

    Jul 6, 2010
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    thanks for the reply, however, i've built my manchester encoder. the problem now is with the modulation part. i need to modulate the manchester code, but when i try to simulate it with vco which i should get fsk as the result, i got uncertain pulses which i think is not correct. can u gv me any idea in modulating manchester code?
     
  4. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    Encoding the bit stream and modulating a carrier from the output are two different processes. The vco should just take the 1/0 voltages levels from the encoder and shift the frequency of the carrier

    [​IMG]

    http://www.maxim-ic.com/app-notes/index.mvp/id/3435
     
  5. suki

    Thread Starter New Member

    Jul 6, 2010
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    yes, it is two different process, but when i try with vco, it gave me uncertain pulses as shown in figure below. pls have a look on my circuit and results, is that looks ok? if not, is theres any suggestion for me to improve it?
     
  6. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    You need to remove the edge glitches and your vco carrier frequency looks to be too low for the bit-rate.

    For an example look at RDS where there are 48 (more than is needed) cycles of carrier per bit. http://en.wikipedia.org/wiki/Radio_Data_System
     
  7. suki

    Thread Starter New Member

    Jul 6, 2010
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    which edge glitches you are talking about? voltage divider or voltage summer?
     
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