6 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 ...
MBaz's user avatar
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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 ...
Florian's user avatar
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5 votes
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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 ...
TimWescott's user avatar
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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 ...
Justme's user avatar
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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 ...
MBaz's user avatar
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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 ...
TimWescott's user avatar
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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 ...
Dan Boschen's user avatar
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5 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 ...
Dan Boschen's user avatar
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3 votes
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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 ...
Dan Boschen's user avatar
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3 votes
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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 ...
Dan Boschen's user avatar
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3 votes
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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_{...
Matt L.'s user avatar
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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 ...
Dan Boschen's user avatar
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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 ...
Marcus Müller's user avatar
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 ...
Perscitius's user avatar
3 votes
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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 $I_{n-1}$,$Q_{n-1}$, $I_{n}$, $...
Dan Boschen's user avatar
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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 ...
Andy Walls's user avatar
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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 ...
Marcus Müller's user avatar
3 votes

What is the name of this FFT technique for carrier recovery?

You can find very similar implementations as part of a "squaring loop" for carrier recovery, and this would be the closest name related to the fundamental operation provided - which is not ...
Dan Boschen's user avatar
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Symbol Sync blocks in GNU Radio seem to use PID (well, PI) for their clock sync feedback loops. Why not IIR/FIR?

Keep in mind that we are talking about a clock synchronization loop, so you need to think of the behavior from a control-systems perspective. FIR Just discard that notion right out. There are good ...
TimWescott's user avatar
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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: ...
blublublue's user avatar
2 votes
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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: ...
Andy Walls's user avatar
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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 ...
A_A's user avatar
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2 votes
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Trouble with time-syncing two radio signals using cross-correlation

It will work when you take the 2nd gradient of the signals: ...
Marco's user avatar
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2 votes
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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 ...
QMC's user avatar
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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 ...
Marcus Müller's user avatar
2 votes
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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 ...
Dan Boschen's user avatar
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2 votes
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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 ...
Marcus Müller's user avatar
2 votes
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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 ...
Andy Walls's user avatar
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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 ...
Ben's user avatar
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2 votes
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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. ...
Dan Boschen's user avatar
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