How to modulate Manchester Code

[suki]

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.

 

[(*steve*)]

It's a signal. You can modulate a carrier using FSK, PSK, AM, FM, or QAM if you feel like it.

However, manchester encoding is a scheme in which data and clock are encoded together using what is essentially a phase shift modulation. If you view the output as a signal, then it can be used to modulate another signal.

I'm not sure that you gain anything by doing this though. One has to ask "why not modulate using the original data stream?"

 

[suki]

thanks for the reply.

act i am investigating the circuit for NFC system, since i am not connecting with the computer for the source input, i try to feed with the manchester code instead. i am expecting to obtain the modulation for the input ive given. however, when i used the vco to modulate it, it is not giving me the correct answer. its giving me the uncertain pulses.

ive attached the circuit and simulation result. can u hv a look and give me opinion with the results?

 

[(*steve*)]

My worry is that if your clock and data are not changing state at *exactly* the correct time that you will get very short pulses at each data transition.

I would be looking for a method that removed that possibility..

 

[suki]

how about the circuit do u think? is it a make-sense circuit for u?

 

[(*steve*)]

I don't really understand why you use a voltage divider than an op-amp with gain. I also don't see exactly where those traces are coming from.

I suspect one of the traces shows runt pulses caused by propagation delay, but I can't be sure.

 

[suki]

can you give me any idea in how should i build the encoder and modulation part for this circuit pls? any simple idea. maybe i dont have to use the op-amp part and just directly feed into the vco. what do u think?

 

[(*steve*)]

What voltage swing does the VCO require? Do the logic and op-amp share a common 0V rail?

 

[suki]

the vco needs 5v. no, only the om-amp uses the 0v.

 

[(*steve*)]

If only the op-amp uses 0V, then what is the (presumably) 5V for the logic referenced to?