Questions tagged [gnuradio]

GNU Radio is a free software development toolkit that provides the signal processing runtime and processing blocks to implement software radios.

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1answer
510 views

What kind of modulation is this?

I'm trying to find out what kind of modulation and encoding is used by my window cover remote control, aiming to implement the same on a Raspberry Pi to add a bit of home automation. A colleague ...
6
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1answer
4k views

Large spike at the center frequency when using Ettus X310

I am using the Ettus X310 SDR and GNU radio. On the GNU radio schema I have a standard UHD USRP source block connected to a GUI FFT sink - basically I'm just displaying the spectrum of the raw signal ...
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2answers
3k views

How does transition width of a low-pass filter affect a message which is well within the pass-band?

I'm taking a communication systems course and we use GNURadio in the lab. In an exam, we had a simple question where we were asked to demodulate a Dual Side Band (with carrier) AM signal in GNURadio. ...
3
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1answer
3k views

GNU Radio - PSK Mod block - unexpected constellation diagram

I am simulating a QPSK modulation in GNU radio. Here is the flowgraph: . The source is a binary stream coming from the Random Source block. There are 4 PSK Mod blocks configured identically (4 ...
3
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1answer
203 views

GNU Radio loop bandwidth normalization

From GNU Radio documentation, the control_loop block proposes loop bandwidth values in the range $[\frac{2\pi}{200}, \frac{2\pi}{100}]$ in radians per sample. Some blocks, like the new timing symbol ...
3
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1answer
73 views

GNU Radio | Async FEC encoder/decoder loopback | Issue during decoding?

I have implemented a loopback flowgraph intending to perform the following: FEC encode (repetition code) an input stream in16_2.dat Store the encoded stream as <...
3
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1answer
827 views

Avoiding DC spike while decoding FSK signal

I am using the Quadrature Demod module in GNU Radio to decode an FSK signal, but the signal is appearing quite noisy. It has two distinct peaks centered around the advertised frequency, but they are ...
3
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1answer
101 views

Frequency components much less prominent at the receiver for multiple tones

I am trying to transmit a multi-tone signal from one USRP (N210) to another and have written an out of tree block to generate the multi tone signals using an ifft. The two USRPs are connected directly ...
3
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0answers
79 views

Synchronization and downsampling after matched filtering - GNURadio polyphase clock sync

I am trying to model a QPSK transmission. For this, I am using the software GnuRadio and more specifically the block polyphase clock sync. This block performs timing synchronization for PAM signals by ...
3
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0answers
106 views

GNU Radio | Transceiver loopback adapted | Transmission stops unexpectedly

(This is a follow up question to a previous question: link) I have implemented a flowgraph of a transceiver loopback inspired by the examples found at ...
3
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0answers
754 views

gnuradio: How can I change the value of the tag exiting the “Correlate Access Code - Tag” block?

Background: I have built a conventional demodulator in gnuradio and am trying to send payload data out of the flowgraph to an external Python script. I'm using gnuradio v3.7.12. It seems to me that ...
2
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1answer
97 views

FFT-based coarse carrier recovery for QPSK

An FFT-based coarse frequency acquisition block is being tested in GNU Radio. The algorithm used can be found on the GOES satellite user manual and is summarized in the figure below. The algorithm ...
2
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1answer
244 views

GNU Radio | Packet Encoder/Decoder | Unwanted bytes added to the transmitted stream

(A follow up question can be found here: link) In an attempt to understand how the packet encoding blocks work I tried to mimic the experiment performed by Aaron, published in this post, but reduced ...
2
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1answer
597 views

PLL phase and frequency characteristics

I'm currently working with BPSK carrier phase and frequency recovery in GNU Radio. I have been able to use Costas loop and Frequency locked loop (four carrier acquisition) which are based on the ...
2
votes
1answer
1k views

Pulse shaping with RRC : Number of taps

I am running a BPSK flowgraph in GNU Radio which is based on RRC pulse shape. I noticed that the BER is quite poor when the number of taps is low. However, using the number of taps around $20\times ...
2
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1answer
287 views

Denoising effect in GnuRadio OFDM Serializer block

Why does the OFDM serializer has such a strong denoising effect in the flow graph below ? Is that normal ? The upper constellation is AFTER the OFDM serializer block and the lower is BEFORE the OFDM ...
2
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1answer
396 views

Timing recovery in GNU Radio : Variable rate vs Fixed rate operation

I have been wondering about the implementation of timing recovery blocks in gnuradio. In literature, for asynchronous sampling, all that is needed are error detector (MM, ML, Gardner etc), a loop ...
2
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1answer
3k views

How do I extract data from a gnuradio flowgraph now that the message sinks have been deprecated?

Background: I am writing a Python script that contains a gnuradio flowgraph object used to demodulate incoming IQ data. The flowgraph is started and runs while I periodically poll it for demodulated ...
2
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1answer
72 views

QPSK Phase Recovery : Maximum-likelihood Vs Costa's Loop

I have implemented a QPSK Costa's loop in GNU Radio and run some BER benchmarking. All is going well. Out of curiosity, I'm trying to implement the Maximum Likelihood phase recovery shown below. For ...
2
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1answer
134 views

Recovering data from mystery signal

I was scanning the airwaves using my RTL-SDR and found a signal being broadcast locally that I was able to receive. When I configure the SDR Console V3 software to NFM, I get the following audio. (Wav ...
2
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0answers
138 views

Dynamic loop bandwidth for a Costas loop

I'm using a Costas loop for carrier recovery. The BER vs SNR (from GNU Radio Simulation) curve for different loop bandwidths (0.03,0.05 and 0.07) is shown in the graph below. It can be seen that the ...
2
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1answer
825 views

O-QPSK constellation interpretation - GNU Radio

I am currently trying to recover the I&Q of a O-QPSK signal generate from the standard XBEE arduino module using a B200. I can get somehow get a "look-like" of a constellation. Here an screenshoot:...
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0answers
268 views

Is GNU Radio a good choice still? [closed]

I'm a newbie at DSP. I am starting a hobbyist project where I plan to monitor 100's of wildlife radio collar frequencies (at my job) and record how many "beeps" per minute are received. My software ...
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2answers
754 views

Sampling frequency lower than half of sampled signal frequency?

In GNURADIO when RTL-SDR Source block is placed there is a parameter Sample Rate (sps) and ...
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1answer
31 views

GNU Radio GMSK modulator

I'm looking at the GNU Radio GMSK modulator block. The Gaussian taps are somehow convolved with a rectangular window with 4 * samples-per-symbol taps owing to the fact for GMSK, the filter spans four ...
1
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1answer
75 views

How can an SDR recover a high-frequency signal?

How can software-defined radios operate at high frequency? The Nyquist rate dictates that you need to sample at twice the frequency to fully recover the signal. If my signal of interest is modulated ...
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1answer
403 views

Why am I seeing a negative frequency on FFT graph in Gnu Radio Companion? [closed]

I have a pretty simple flow here in GRC, but for some reason I'm seeing a negative frequency mirroring the 10khz signal that I'm generating. What's causing this negative frequency to show up in the ...
1
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1answer
194 views

am I recording LTE uplink signals?

I have this app in my phone which tells me the LTE UL frequency and power: so I went with my SDR and measured the received signal at that frequency: Now, how can I be sure this is the transmitted ...
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1answer
3k views

Why isn't this AM Demod GNU Radio flow graph working with different sampling rates?

I am trying to demodulate an AM signal in GNU Radio, and I am having problems with the sampling rates. I will start off with an example where the flow graph was working. The sampling rate is 256kHz, ...
1
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1answer
96 views

Offset QPSK detection in GNU Radio - Sample delay

An OQPSK detector is being tested in GNU Radio. The architecture was obtained from Michael Rice's Digital Communications - A discrete-time approach. The flowgraph is shown below. The modulator ...
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0answers
27 views

GnuRadio FM Receiver: Heterodyne vs Xlating vs Direct

I'm trying to build an FM receiver (and eventually transmitter) in GnuRadio that will be able to interact with my local repeater. Starting with WBFM (because I can consistently pull in broadcast ...
1
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1answer
93 views

GnuRadio's SNR estimators usage

I'm trying to calculate the SNR of a satellite signal using GRC, but all of the 4 offered estimators either have a lot of -NaN values or are ~35dB throughout the entire recording. (I just connected ...
1
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1answer
245 views

Residual carrier tracking with PLL

Residual carrier systems such as PCM/PM/NRZ and PCM/PM/Bi-phase are common in space applications. Compared to suppressed-carrier systems such as BPSK, the literature sources on residual-carrier ...
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0answers
230 views

EbNo, SNR, and BER simulation for BPSK with convolutional code

Im currently simulating BER performance of CCSDS convolutional code. Im having some troubles in specifying EbNo and SNR in gnuradio blocks. From matlab webpages on BER simulation for RRC pulse and ...
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0answers
96 views

Phase noise modeling using gnuradio IIR filter

I need some advice regarding phase noise modeling using gnuradio IIR filter. I'm trying to synthesize phase noise (multiplicative) with a given noise mask. In one paper, the authors were able to ...
1
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0answers
32 views

“Image Processing” [closed]

I'm an Italian student. I'm studying Gnu Radio and I would like to upload a photo, can I upload it with "file image source" or other blocks? I need to make FFT of an a image. -> image 2D Thank you ...
1
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0answers
78 views

Band-edge filtering for an RRC pulse-shaped manchester/biphase-encoded bitstream

Band-edge (derivative matched) filters can be used to generate an error signal for frequency locked loops (real part) or symbol timing loops (imaginary part). The derivation of the band-edge filters ...
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0answers
167 views

Blind equalization with constant modulus algorithm in GNU Radio

I'm currently simulating the effect of multitap channel on BPSK as well as its remedy i.e. equalization. The modem is expected to work with satellite TT&C transponder. The communication channel ...
1
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0answers
433 views

Carrier recovery with the Costas loop : PLL pull-in range

I have created a channel model in GNU Radio (a modified version of the default GNU Radio Channel Block). Its performance under AWGN (without timing, phase or frequency offsets) aligns properly with ...
1
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0answers
348 views

Software Defined Radio samples analysis using gnuradio and python

I'm trying to replicate what gnuradio is doing in "pure" python with a hackrf. Having mixed result, I decided to use the same data to compare the outputs I obtain. My gnuradio workflow is the ...
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0answers
1k views

USRP + GNU Radio as 1 GHz bandwidth spectrum analyzer

I have maybe not trivial but some interesting question. I need to create 802.11ac channels spectrum analyzer with USRP. Hardware: USRP B210 Software: GNU Radio 3.7.9 PC: Intel Core i3 i3210m 16 GB ...
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0answers
394 views

GNURadio Sending Short Packets

I'm trying to create a basic GNURadio flow graph that will transmit a short message in order to receive an appropriate reply back. I currently have the following flowgraph: I have a program that ...
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0answers
214 views

how can i use gr-specest in gnuradio? [closed]

hello Pr how can i use the fam and the gr-specest in the GRC for cyclostationary features ------------------------------------------------------------------------
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0answers
189 views

Unable to stabilize 8-PSK signal with self designed costas loop

I am trying to make a signal processing block which implements the costas loop to stabilize an 8-PSK signal. Here is the flowgraph with "costas_loop" being my block. My workflow is the following - <...
1
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0answers
392 views

How can I perform timing recovery from the envelope of PSK signals?

I'm trying to reimplement FDMDV in GNU Radio, largely for educational purposes. It consists of 15 PSK subcarriers, 75 Hz apart, 50 symbols/sec each. The center one is BPSK and alternates phase each ...
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0answers
269 views

Time recovery - GNU Radio

I read about Time recovery (as an example, the Mueller&Muller algorithm); it is linked to when you should sample your signal. I am currently working on a project with GNU Radio and there is ...
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0answers
343 views

Moving signal power normalization

I am using matched filters using GNU Radio to extract from noise a CW Morse signal. The filter actually performs pretty well in various SNR environments. My problem is that the threshold upon I decide ...
0
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1answer
1k views

Possible to Derive Receive Signal Power from RSSI?

My Set-Up I am sending packets at a specific frequency and with a specific gain from one N-210 USRP to another of the same model. NOTE: I have the transmitting USRP connected to a series of ...
0
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1answer
114 views

Better way to mute fundamental baseband frequency?

I'm working on a project to monitor the fluctuations and harmonics present on standard 120VAC mains power. I built an adapter that drops the voltage from 120VAC to 12V and then down to 0.5-0.6 VAC ...
0
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2answers
2k views

OFDM symbol acquisition block in GNU Radio gives rotating constellation even if there is no carrier offset. How is this possible?

Why does the constellation rotate when using OFDM Symbol Acquisition block in this flow graph below ? The only explanation I could think of would be carrier frequency offset but in this flowgraph ...