6
votes
Accepted
What kind of modulation is this?
Ok I did some signal forensics on the data capture and believe the modulation is a form of FSK.
The FSK modulation was +/- 20 KHz with a data rate of 38 KHz.
UPDATE: The OP discovery that this is ...
- 55k
5
votes
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FFT-based coarse carrier recovery for QPSK
A square operation creates an unmodulated tone for a BPSK signal at 2x the carrier frequency (a pure tone for the case that the signal was unfiltered or rectangular pulses with perfect phase and ...
- 55k
5
votes
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Sample rates, Samples per Symbol, and Digital Pulse Shaping
Yes the OP is correct in that you can implement pulse shaping in less than 2 samples per symbol for exactly the reasons that was outlined. However importantly we must also keep in mind having excess ...
- 55k
5
votes
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GNURadio signal degradation *above* Nyquist rate
That is above the Nyquist rate, so why is the signal degraded?
It's not degraded in any way form or shape. The perceived degradation is purely cosmetic but not functional. See for example: How is ...
- 48.2k
4
votes
Accepted
How do I extract data from a gnuradio flowgraph now that the message sinks have been deprecated?
So, the important takeaway from your introduction is that you have an application which needs to get chunks of items out of the flow graph repeatedly. Which means you're in the streaming case. (for ...
- 32.5k
4
votes
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Pulse shaping with RRC : Number of taps
See pages 5 and 6 and the plots on the following pages specific to number of samples per symbol in this very helpful reference by Ken Gentile on designing RRC pulse shape filters:
http://www.analog....
- 55k
4
votes
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Is Bluetooth Low Energy jamming possible with an SDR like the HackRF on GNURadio?
I am not revealing any big secrets here on jamming and anti-jamming techniques, nor would I condone creating any such interference. What I am about to say is quite simplistic and well known, but ...
- 55k
4
votes
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Clock recovery using Mueller and Muller adds noise affecting EVM or SNR (Two cases - GNU Radio & Python code)
Unlike the Gardner Loop, the M&M synchronizer should be performed after the RRC filter in the receiver for best performance. With cases of high RRC alpha, the M&M won't work as expected ...
- 55k
3
votes
Accepted
GNU Radio | Packet Encoder/Decoder | Unwanted bytes added to the transmitted stream
Packet Encoder and Decoder are broken; they drop data.
That's why they are in the deprecated category (for years now!). We've removed them, because as a project, GNU Radio has not been able to fix ...
- 32.5k
3
votes
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PLL phase and frequency characteristics
Before I address your questions, you should understand:
a. the integral branch of the loop filter maintains a average phase increment in units of radians/sample. It is not a frequency value, though ...
- 2,710
3
votes
Accepted
am I recording LTE uplink signals?
There's a lot of different domains of knowledge coming together here, so I'll split my answer into multiple sections, each answering an implicit question that you raise in your explicit question. Hope ...
- 32.5k
3
votes
How to adjust receiver gains to avoid saturation and quantization noise to optimise post digital processing?
This is a great question and comes down to the AGC design and optimizing the available dynamic range on the ADC, given a receiver minimum SNR, sensitivity and interference rejection requirements.
I ...
- 55k
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 ...
- 2,710
3
votes
Accepted
Cosine of amplitude 1 but GNU Radio shows FFT has amplitude > 30,000
Consider the formula for the DFT (which the FFT efficiently computes as an algorithm):
$$X(k) = \sum_{n=0}^{N-1}x(n)e^{-j2\pi nk/N}$$
Notice that it is a summation over $N$ samples total. Also note ...
- 55k
3
votes
Accepted
Source IO size "8" does not match sink IO size "4"
Double click your "Signal Source" to open its property dialog
Change the "output type" from "complex" to "float"
Click "OK"
Now you should be good.
- 46
3
votes
Accepted
How do I Correlation Estimate both for a pattern and its inverse in GNU Radio?
Map 0 to 1 and 1 to -1 on both the reference sequence and the received bit sequence, and then correlate; an inversion will also just invert the sign.
If that mapping is hard to do on the received ...
- 32.5k
2
votes
Avoiding DC spike while decoding FSK signal
That looks very nice:
I don't 100% agree with your phrasing on this one:
however, my quadrature demod is capturing large amounts of noise during the idle periods.
Well, the quadrature demod ...
- 32.5k
2
votes
Accepted
Better way to mute fundamental baseband frequency?
To mute the fundamental frequency, consider using a notch filter such as the one shown in the figure below, where $\omega_n =2\pi 60/f_s$, where $f_s$ is your sampling rate, and $\alpha$ is chosen ...
- 55k
2
votes
Accepted
How does transition width of a low-pass filter affect a message which is well within the pass-band?
For an FIR filter there are 3 main components that determine the filter length for equiripple designs:
Passband ripple
Stopband attenuation level
Transition width (Width from the edge of the passband ...
- 2,891
2
votes
Accepted
Why am I seeing a negative frequency on FFT graph in Gnu Radio Companion?
The stock FFT (in GNU radio?) is a complex-to-complex transform. Thus any positive frequency peak you see represents a complex signal (phasor) that can include both real and imaginary components.
...
- 35.7k
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 ...
- 2,710
2
votes
Accepted
Communication between two USRP : mismatched spectra between transmission and reception
A few (hopefully useful) comments and ideas:
The HackRF One is not a USRP.
If you're receiving with an NI 2921 USRP, you should be using UHD to interface with it, not osmocom.
Use a standalone ...
- 15.4k
2
votes
Accepted
How can an SDR recover a high-frequency signal?
The high-frequency (RF) section of an SDR is all analog. Typically, the analog receiver downconverts the RF signal to an intermediate frequency that is within the Nyquist range of the ADC. As Stanley ...
- 15.4k
2
votes
Accepted
GNU Radio GMSK modulator
Let's say you want to filter a signal $x[n]$ through a Gaussian filter with impulse response $h_g[n]$ and a Moving Average (the "sqwave") filter with impulse response $h_s[n]$. Then the resulting ...
- 2,710
2
votes
Accepted
I wish to create a GNU Radio program in C++ that doesn't need GRC or Python, is there a reference or template for this?
you can create flowgraph in c++ like gqrx and i think GNU Radio Manual and C++ API Reference documents will help you. This is gnuradio c++ document for top_block if you could not use it let me know to ...
- 136
2
votes
Record Signal after Threshold Reach in GNU Radio
Sounds like you have a very workable approach:
Write a GNU Radio, Embedded Python, out-of-tree Python or C++, doesn't matter, which:
is a general block (not a ...
- 32.5k
2
votes
Accepted
Why samples per symbols $\geq 2$ in the GNURadio Constellation Modulator block?
The GNURadio Constellation modulator enforces a minimum of 2 Samples Per Symbol mostly due to simplicity and some practical reasons. Theoretically, if you're just transmitting PSK without any pulse ...
- 733
2
votes
Can I create my IF signal on SDR before bringing data to PC?
I think the formula you got the 1m resolution from is actually the one for pulse radars with non-interpolating single pulses. You can do better!
Note that in (linear-chirp) FMCW, the beat frequency, i....
- 32.5k
2
votes
GNU Radio Companion - generating a 4-QAM constellation - how to do it?
I then have a Chunks To Symbol block, where I arbitrarily have these following values for the Symbol Table [(-0.707 -0.707j), (0.707 -0.707j), (0.707 + 0.707j), (-0.707 + 0.707j)].
Sounds pretty ...
- 32.5k
2
votes
Accepted
Fractional Resampler - GNU Radio
"Phase shift" is poor terminology as time delay is not exactly the same, but the significance of the 0 to 1 factor is a fractional delay in units of samples.
The filter itself will always ...
- 55k
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