Kindly help me for Coherent detection

[moonnightingale]

I am doing my project. My project is as mentioned below.
---- Selection of a source
---- selection and implementation of an M-ary bandpass modulation technique (Nyquist pulses must be used this time for the pulses that will be upconverted)

----- selection and implementation of a corresponding suitable demodulation technique (coherent or non-coherent)

---- performance comparison of simulated curve vs. theoretical curve along with time and freq. domain representation of the signals....

I have done first two steps. Kindly help me how to perform Coherent detection in Matlab. Can anybody send me its schematics or source code in Matlab.
Secondly kindly explain is coherent is detection technique or demodulation technique.
Thanks a lot

 

[DBurg]

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I have done first two steps. Kindly help me how to perform Coherent detection in Matlab. Can anybody send me its schematics or source code in Matlab.
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If I understood you clearly : here is a pusodo code
1) generate data bits --> data_gen
2) bits to symbols
3) upsample & signal shape
4) pass the sequence through the channel ( i.e add noise and/or convolve with channel impulse response
5) .... downconvert
6)demodulate
7)detect ---> data_detect
8)compare data_gen with data_gen
calculate umber of errors and divide by the total no of bits generated
do this again and again for different SNR
you have BER vs SNR
I think this is an coherent detection because you are assuming knowing the timing and everything is synchronized with the TX
but if non coherent then you have problems

Best
DBurgh

 

[moonnightingale]

Can u kindly explain me what u mean by
upsample and
downconvert

 

[DBurg]

I am sorry I meant by downconvert downsampling which is the opposite of upsampling and you can think of it as a way to represent the pulse shape in MATLAB and thats how you will use the Nyquist pulse shape , and use it again in the RX as Matched Filter,,, or if not neccessary ( in case that everything is perfect , eg no ISI ) you can neglect ( 3&5 ).

How to do upsampling :
you can use Matlab command : "upsample" which is simply add number of zeros after each value. you can read more about it from MATLAB help.
I hope that helped