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Carrier frequency for QPSK

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stepbythink

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I need help to understand carrier frequency for QPSK.

For QPSK, are symbol rate and carrier frequency always the same?
I think so since basis functions are cosine and sine (at carrier frequency), and each cycle period brings phase information.

Please give any comments if i'm correct, thanks!
 

So, you are saying that a 10 GHz carrier, sending data with with a 1 Kbps qpsk modulation has a....10 Gbps symbol rate????
 
No...! I have been confused about how to translate the received signal to signal space for qpsk, and now clearer.
Phase signal has to be low-pass or slower in variation than carrier frequency. So, qpsk modulates 1 kbps (bit per second?) baseband signal with 10 GHz carrier frequency, and symbol rate is 1/2 k symbol per second...

Thank you for res!
 

Yes, it is important to lowpass filter the output. An I/Q mixer as a phase detector will have an inherent lowpass filter at the I and Q ports in the real world. You need to remember to add the digital equivalent of a LPF in a simulation.
 
biff44 said:
You need to remember to add the digital equivalent of a LPF in a simulation.
Click to expand...

I'm doing MATLAB simulation for QPSK, and I'd like to use LPF with less delay and phase rotation. Which filter is good? And how to calculate filter delay?
I'm happy to have any advice. Thank you!
 

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