5
votes
Accepted
Maximum cross-correlation coefficient value for time delay estimation
As your plot shows, the second form allows for the correlation peak to be negative. Now, what does a strong negative cross correlation mean? It means the signals are very similar, except one has a ...
- 2,393
5
votes
Accepted
Digital PLL loses lock every time mesage crosses zero
You are having trouble because that's not a Costas loop. A Costas loop uses demodulated data in some form to change the phase that's expected from the signal.
You're just taking the I/Q ...
- 11.7k
5
votes
Accepted
Actual Sample Rate slightly off?
If you calculate the error, 44102/44100 is only about 45 parts per million. That is well within operating tolerance of many crystal oscillators used in consumer equipment to generate audio sampling ...
- 2,179
5
votes
Why is phase range between $-\pi$ and $+\pi$ (instead of $0$ and $2\pi$)?
It is just a convention, but it is useful in some cases. For example, the phase of the DFT of a real discrete-time signal is odd only if the angles are expressed in the range $[-\pi, \pi)$. Sometimes ...
- 14.6k
5
votes
Why is phase range between $-\pi$ and $+\pi$ (instead of $0$ and $2\pi$)?
First, when you're talking angles, in DSP pretty much all angles are $\mod 2\pi$. So $2\pi \equiv 0$. Usually it's more convenient to keep angles on the interval $\left [-\pi, \pi \right )$, because ...
- 11.7k
5
votes
Accepted
Synchronizing 2 time series signals at slightly different sampling frequencies
If you are confident that the relationship is a ratio of integers, then resampling would be a fine approach. One would be matched to the other by upsampling by 1008 and then downsampling by 996 which ...
- 48.2k
5
votes
What's the difference between frequency shift, frequency offset, phase offset, and phase noise?
To complement Dan's answer, this is the way I usually use these terms.
Frequency shift: a change in the frequency of a bandpass signal. It can be intentional, as when downconverting a signal in the ...
- 14.6k
4
votes
What's the difference between frequency shift, frequency offset, phase offset, and phase noise?
Frequency shift and frequency offset could reasonably refer to the same thing, but a shift suggests something that has moved (from one frequency to the next as would occur in a changing Doppler) while ...
- 48.2k
3
votes
Accepted
Loop bandwidth for symbol timing recovery
There is an optimum loop BW that maximizes the SNR, and this applies to both Symbol Timing Recovery as you inquire about as well as Carrier Recovery. The specific answer depends on the characteristics ...
- 48.2k
3
votes
Accepted
Acceptable Carrier Frequency Offset for Specific BPSK system
Bottom line: Either implement a (simple) carrier recovery algorithm or use DBPSK instead of BPSK if you are ok with the 3 dB SNR penalty in performance.
If you want to do synchronous detection of ...
- 48.2k
3
votes
Accepted
Is Spectral Coherence (MSC) dependent to the initial amplitude of the comparing signals?
From the definition of the (magnitude-squared) coherence
$$C_{xy}(f)=\frac{|G_{xy}(f)|^2}{G_{xx}(f)G_{yy}(f)}$$
with the cross-spectral density $G_{xy}(f)$, and the power spectra $G_{xx}(f)$ and $G_{...
- 87.2k
3
votes
What are the advantages of barker sequence over marker sequnce?
A big advantage of Barker Codes over a generic marker is strong correlation when the codes are aligned and very low correlation for all other shifts, even by one sample. This offers increased ...
- 48.2k
3
votes
Accepted
OFDM symbol acquisition block in GNU Radio gives rotating constellation even if there is no carrier offset. How is this possible?
Got me at that one! The "OFDM symbol acquisition" block is in fact not from gr-digital (where your other OFDM blocks come frome), but from gr-dtv, where it is used ...
- 29k
3
votes
Phase locking value / phase synchronization
There can be several ways to calculate the Phase locking value (PLV). For relatively mono-component and high SNR (well filtered)-Time domain signal can be converted into analytical signal using ...
- 139
3
votes
Accepted
NDA timing estimation for mutli-level QAM(RC pulse)
Consider using a Gardner Timing Error Detector which in the following form is usable for higher order QAM:
$$TED = I_n(I_{n+1}-I_{n-1}) + Q_n(Q_{n+1}-Q_{n-1})$$
Where $I_{n-1}$,$Q_{n-1}$, $I_{n}$, $...
- 48.2k
3
votes
Symbol Synchronization for GFSK/FSK signals in GNU Radio
The Symbol Synchronizer block is a PLL-based synchronizer that is trying to estimate the symbol clock period and symbol clock phase (aka timing offset) based on the samples coming in that represent ...
- 2,680
3
votes
Accepted
Why are preambles repeated in communication systems
In case of IEEE802.11a, that's Schmidl&Cox synchronization. I go into a few effects of having that in this answer; and as I say there,
If in doubt, read the original Schmidl&Cox Paper Robust ...
- 29k
2
votes
Phase locking value / phase synchronization
If you have two numpy arrays of phase data theta1 and theta2 (in radians), you can calculate phase locking value in numpy without too much effort:
...
- 21
2
votes
Accepted
Band edge filter for raised cosine impulse
It looks like the filter you want is indeed $-ith(t)$. Here is some Octave code to get a visualization in the frequency domain:
...
- 2,680
2
votes
How to find the time instant where my sent signal and received signal can synchronize?
This is usually addressed via looking for a known pattern in the data frame.
The modulation scheme is not mentioned but when synchronisation is required, a Phase Locked Loop (PLL) is most commonly ...
- 10.5k
2
votes
Accepted
Trouble with time-syncing two radio signals using cross-correlation
It will work when you take the 2nd gradient of the signals:
...
- 36
2
votes
Accepted
FFT based symbol synchronization for digital demodulation
Symbol timing synchronization seems to be a complex topic although once you get some basic principles right, it all makes simple sense. The method you have referred to is known as Digital Filter and ...
- 784
2
votes
OFDM synchronization using training symbols
Claim
In OFDM receivers, special OFDM training symbols for which the data content is known, can be used to perform the synchronization process.
Be a bit careful about that statement.
There's ...
- 29k
2
votes
Accepted
Frequency Hopping Spread Spectrum Synchronization Methods
This can be accomplished by changing the carrier frequency using a Numerically Controlled Oscillator (NCO) which maintains an accurate and continuous phase versus time trajectory via the phase ...
- 48.2k
2
votes
Accepted
OFDM: How to do the carrier recovery of the quadrature(I/Q) demodulation
I can't find any way to make the carrier recovery,
I don't think you can or should really talk "carrier recovery" in OFDM systems; after all, OFDM is a multi-carrier system. So, you'd need to recover ...
- 29k
2
votes
Accepted
GNU Radio loop bandwidth normalization
I can only answer your second question:
"How can the loop bandwidth in GNU Radio synchronization be configured as a percentage of the symbol rate?"
The tracking loop in the symbol synchronizer block ...
- 2,680
2
votes
Digital PLL loses lock every time mesage crosses zero
It seems like your error jumps to -$\pi$ and then to $\pi$
I think you need to unwrap your phase. Let me explain with an example
Say that the output of atan2 block is $\pi - 0.001$ and then the ...
- 3,735
2
votes
Accepted
Blind Carrier Synchronization
One approach not yet mentioned is frequency multiplication by a factor of the number of phase positions used followed by a PLL for noise reduction and then a frequency divider by then same factor. ...
- 48.2k
2
votes
Accepted
PLL for Phase Demodulation and Carrier Tracking
Yes this is very common to have a dynamic loop bandwidth such that during acquisition the loop bandwidth is wider, and then once acquired to tighten it up for better noise performance.
A typical ...
- 48.2k
2
votes
Why does altering path length in radio transmission alter the phase of the received signal?
Yes indeed it will be (although we could argue that it may not be necessarily for all distances since the phase is cyclical!).
In free space the signal propagates at the speed of light, therefore ...
- 48.2k
Only top scored, non community-wiki answers of a minimum length are eligible