3
votes
Accepted
QPSK implementation with 2 BPSK
Your constellation points are the sum of {+1, -1} and {+1j, -1j}, so you get the points {+1+1j, +1-1j, -1+1j, -1-1j}, which have these odd multiples of 45° as angles.
That's one way to look at it.
The ...
- 29.6k
2
votes
spectral bandwidth of QPSK signal
Regardless of how $B$ is defined earlier in the Wikipedia article, the equation starting with where the Nyquist rate is introduced is a single-sided bandwidth:
$$f_p < 2B$$
Which state that (single-...
- 48.8k
1
vote
Accepted
How to choose sample offset values in timing synchronization for a QPSK demodulator?
The target offset is 0. This corresponds to zero timing error, and also has the highest slope (sensitivity) to a timing offset which is the ideal location to lock a loop.
The Gardner using three ...
- 48.8k
1
vote
Accepted
QPSK demodulation carrier frequency offset compensation on python
The OP is correct that the constellation is spinning due to a frequency offset, and removing the phase versus time is the right direction to take (which is frequency offset given frequency is the time ...
- 48.8k
1
vote
Why is the symbol duration in QPSK twice the bit duration?
In QPSK, we send 2 bits in one symbol in x secs.
So symbol duration is x secs.
Bit duration is x/2 secs.
In BPSK, one bit per symbol is sent.
So symbol duration is x secs and bit duration is also x ...
- 41
1
vote
QPSK: sampling frequency versus carrier frequency
A long and tedious harangue of little interest to the cognoscenti who should fast-forward to the last paragraph (after the dotted line separator) for the only relevant stuff.
A standard representation ...
- 20.2k
1
vote
Accepted
QPSK: sampling frequency versus carrier frequency
I reviewed your code and you are not yet running into timing offset issues as I suspected in my initial comments. You simply interpolated more samples per symbol by increasing the oversampling factor, ...
- 48.8k
1
vote
Accepted
QPSK InPhase and Quadrature
This requires understanding complex waveforms in time and frequency and what "negative" and "positive" frequencies are. If that isn't clear, start with these other posts and then ...
- 48.8k
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