Questions tagged [sdr]

Software Defined Radio (SDR) is the implementation of radio receiver, detector and transmitter systems in software, as opposed to analog hardware or application-specific ICs. It usually uses a baseband sampled representation of the RF bandpass signals.

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Does anyone recognize this modulation?

I'm trying to extract the code of my garage remote, but i have some difficulty to find witch modulation has been used. At first I thought it was a simple digital modulation, but there is some strange ...
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2answers
121 views

Should I filter before calculating power, if I'm looking for relative changes in power?

I am building a "scanner" sort of program, which reads IQ samples from an rtl-sdr stick, and keeps track of the power on certain frequencies, in certain bands. I am interested in detecting activity ...
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591 views

IQ imbalance on quadrature signal

Hi I am attempting to develop a reasonable IQ balance mechanism for a quadrature signal coming from a software defined radio.I can balance out the amplitude and phase differences at one frequency ...
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35 views

RSP1A sample rate vs if bandwidth

I'm using the RSP1A SDR and I want to understand how to choose the best configuration for receiving a signal of 125 khz bandwidth. I would like to know if when choosing the option 200 KHz IF ...
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1answer
123 views

Digital FM Demodulation

I have created a Common Lisp Library to receive samples of an FM signal from BladeRF1 SDR. I want to write a subroutine to implement FM demodulation. The input should be in the format of IQ data. ...
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4answers
120 views

Detecting a three-tone signal in real-time

I'm new to digital signal processing, and I've been looking into FFT, filtering, Matlab etc. What I'd like is to build a program which will detect when a certain BEEP is transmitted through a trunked ...
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1answer
153 views

Best way to resample an OFDM signal without interpolating + filtering?

I am working on a custom transceiver with a sampling rate of 3.84 MHz (256 OFDM subcarriers at 15 kHz, although 56 subcarriers are null). I would like to resample the signal to 5 MHz, in order to use ...
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454 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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32 views

Signal view from two different receivers (of the same model)

I have two SDRs hooked up to two different computers, both radios tuned to the same frequency. They sample at 2Msps. What I would like to do is start up both (at 'about the same time'), and, after ...
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52 views

Considerations when determining squelch

I asked this question recently. From the comments I learned that squelch is not a hard and fast thing, and that many considerations might go into determining a reasonable value, depending on use, the ...
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385 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 ...
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394 views

Short VHF pulse detection from SDR

I need to detect a short (10ms) VHF pulse that occurs every 1.5s at a specific frequency (e.g., 150.20 MHz). I have an SDR that support IQ sample rates up to 10MSPS but due to computing constraints 2....
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326 views

Detect FSK high/low bits in presence of noise with only simple processing

I'm currently in the process of writing DSP code, based on the amazing RTLSDR project, and using this as a vehicle to teach myself the basics of DSP (I have an extensive background in software ...
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1answer
64 views

Modulating ofdm in audio spectrum

Trying to modulate audio with OFDM data. My fs = 44.1khz, i'm using 64 sub-carriers, but i'm only using 5 sub-carriers for data, so my bandwidth is about 3.445khz. I'm not sure how to properly write ...
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14 views

How to architect a “for loop” (frequency hopping) in gnuradio (companion)?

I have the setup where I send data via USRP Sink over an SDR and receive the response. However, this needs to be performed at different carrier frequencies, sequentially in time but continuously (the ...
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7 views

Simultaneous transmission of a D2D user

Can a D2D user (a device) transmit simultaneous different signals to a cellular user and a D2D receiver. If we suppose that the D2D device is equipped with SDR technology and can change their ...
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26 views

gnuradio extremely sluggish with QT (but seems OK with WX)

I am evaluating gnuradio with Ettus USRP X310 and 2xUBX-160 daugterboards, connected via GBit ethernet to a new Lenovo laptop running Win10 and gnuradio 3.7.13.5. I am testing it with the most basic ...
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54 views

Auto correlation , Time duration measurement for SDR calculation purposes

I'm a SDR and DSP beginner , I'm trying to find correlation between pulses I receive using a SDR, with a replica that I have (basically pulses with predetermined duration's). I've looked in this ...
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115 views

Not sure why I get errors of missing blocks when trying examples in Gnuradio Companion

I just started working with GNURadio without much of familiarity about this software. I found a couple examples online and I tried to run them but I get many Missing Block errors. Thats how it looks ...
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79 views

Which equipment to use for testing performance of AM, FM, and DAB

I want to test the performance of AM, FM and DAB radio in RTL-SDR. I want to measure sensitivity, adjacent channel selectivity, cross-modulation/blocking, and third-order intermodulation to be some of ...
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31 views

what waveform using to send qpsk signal with IQ tranceiver

I have an SDR tranceiver (AD9361 on fmcomms3) working with IQ channels, i wanted to make a c++ software that modulate and send a digital QPSK signal but i'm a beginner in digital signal processing and ...
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176 views

How to plot real time graph using python for the signals received from RTL SDR?

Using the below python code, I am able to plot a graph. Can anyone please tell me how to modify this code to plot the graph continuously in real time? ...
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41 views

Any ideas on creating a GNU radio block for scanning active frequencies (FM/AM/DAB/DVB-T)?

I am trying to create a GNU Radio block that scans the active frequencies, let's say for FM/DAB channel. I have seen scanner implementations in c++/python but are not compatible with GNU Radio. Can ...
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95 views

Why do IQ Impairements, Quadrature Skew and DC offset have these geometric effects on the constellation?

I'm studying telecommunications, and would like to be sure to understand the maths behind these effects. For IQ Imbalance and DC offset, it seems pretty clear why we observe a rectangle shape or a ...
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30 views

What is wrong with my PSD computation?

I'm trying to calibrate the RX of my SDR Board to become a measuring receiver. I.e, by connecting it to a known source of power (in my case, a frequency generator), at a fixed frequency, I'm trying to ...
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13 views

Correct way to calibrate RX into a measuring receiver

While playing with my SDR (Software Defined Radio) Board, I was interested in performing a TX output power table at different center frequencies and TX antenna gains. I have an RF frequency generator....
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153 views

RTL-SDR data types

I am using pyrtlsdr to read samples from an RTL-SDR. As in the example on the page, I am getting samples with sdr.read_samples(x). The RTL-SDR returns 16 bits per ...
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2answers
510 views

Curved noise floor and ugly unexplained peaks after FFT

It has been so long since I studied this at University, so I'll better ask here if I'm doing something really wrong here. I'm using a USRP frontend for L1 band surveillance. I want a 20MHz bandwidth, ...
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3answers
198 views

Zeros inserted in QAM Constellation

I need to ask about insertion of Zero Symbols after QAM modulation in a OFDM system. Such that the 4 QAM has a constellation with 4 corner and 1 center symbol indicating zero. What advantages or ...
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2answers
350 views

Adding a constant to a bandpass-signal in transmission

I do understand AM-DSB-SC and AM-DSB-TC, but can't see the point in adding a constant DC-offset of 2 in the upper part of this Simulink-model? Source
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39 views

Taking care of 'splash' onto adjacent frequencies

I have a system that should identify activity on a frequency (say in a 5kHz range), and report the frequency. I have a problem with this system - the signal strength is sometimes wider than 5kHz, or ...
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74 views

Coming up with a squelch value

I am building a scanning-type system. I have samples in $\textrm{dB}$ and I want to determine when to allow them through. I am trying to decide between allowing them through when they reach a ...
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95 views

When to use raw signal strength, vs. when to filter first

I am collecting I/Q samples from an RTL SDR dongle. I notice the rtl_power utility provided for Linux filters and does other processing, before reporting signal ...