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.

 

Here is a link to the datasheet for a manchester endcoder/decoder IC. It has a detailed explanation of the method.

hgmjr

 

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?

 

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?

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

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

 

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?

 

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?

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

 

which edge glitches you are talking about? voltage divider or voltage summer?