Custom Modulation Transmission

Moving to appropriate forum for questions on Pluto

RuchitV said:

Specifically, the IQ data I receive is not as expected and appears garbled.

What do you expect to receive?

RuchitV said:

In the provided QPSK example,

What example?

-Travis

I have made few changes and getting the correct IQ now. But still the demodulation is not happening as I want it to. I am using this example : https://in.mathworks.com/help/comm/plutoradio/ug/qpsk-transmitter-with-adalm-pluto-radio.html & https://in.mathworks.com/help/comm/plutoradio/ug/qpsk-receiver-with-adalm-pluto-radio.html . The basic idea is I would like to keep the same code and just change the part where mod and demod are working. The transmitter is working as expected but the receiver in not decoding the data.

Have you verified the unmodified example works? Why are you modifying it? Have you tried reaching out to MathWorks support as it is authored by MathWorks and not ADI?

-Travis

Yes I have verified the modified part. I am modifying it because I want a non QPSK custom Modulation. I am in touch with Mathworks and I am reaching out here because I would like to understand How exactly Pluto is working so that I can create my own modulations. Ideally I would like to give pluto some IQ, let pluto do it's job and then receive the same IQ back. But this is not the case some kind of sync are required. I would like to know what this is and how best to adapt these changes with different modulations.

What modulation are you using? Sync algorithms are generally modulation dependent.

-Travis

For now 4FSK. But later different modulations like ofdm.

The sync algorithms used for the QPSK example won’t work with FSK modulation.

-Travis

Yes I agree. Now to make this work we should start probing and see what is the error and how to fix it ? Right now the received IQ when plotted looks correct so all that is left is to extract symbols convert to bits and process them. Now which part requires correction or how to find. Because MATLAB in loop test works but when it comes to pluto it stops working.

You need to find sync algorithms that work for your modulation.

-Travis