# Tag Info

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

### 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 ...
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