Questions tagged [software-defined-radio]

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3 votes
1 answer
79 views

Efficient frequency domain search for reduced number of hypotheses

In CDMA signals (such as GNSS) there are two unknown parameters when one receives the signal, residual carrier frequency and an unknown delay. Assuming the carrier frequency residual is known, what is ...
0 votes
1 answer
32 views

Min. sample duration for FFT of low frequent signals obtained from zeroIF receiver

I am new here and a beginner with SDR & FFT. For antenna pattern measurements, a flying probe antenna is to be used to sample the electromagnetic near-field in front of an antenna. A lightweight ...
1 vote
1 answer
102 views

Complex samples in OFDM signal, after fft-block at the receiver, have rotating amplitude towards zero even after phase correction

First of all, please consider my lack of experience/background in real time transmission using SDR especially if my explanation was expressed technically well.enter image description here I have ...
0 votes
0 answers
22 views

TRANSMIT 16QAM 5MHz Signal Via NI USRP 2900

I am trying to generate 5MHz signal. I am using NI USRP with matlab. I have extended the existing MATLAB QPSK Tx Rx to 16QAM, Now i am struggling with advacing the testbed to send and receive 5MHz ...
1 vote
1 answer
43 views

What is the standard data format for transferring IQ data between interfaces?

I've seen IQ data typically combined within a single 32 bit word when sending streams of data between different components. (i.e. I & Q are both signed fixed point integers with 16 bit word length ...
0 votes
1 answer
724 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 ...
1 vote
0 answers
40 views

I want to transmit a CW signal using SDR could be pluto or hackrf but I haven't used any one of them can anyone help me

I am using HackRF or Pluto SDR for transmission of a CW signal, after reading the documentation of the HackRF one SDR I found out that it transmits data in only 8-bit signed quadrature samples. Now I ...
14 votes
3 answers
6k views

Why do SDR receivers emit I/Q samples?

To my understanding hardware receivers for software-defined radio applications basically take the input signal, mix it with the tuning frequency to remove the carrier frequency and then sample the ...
1 vote
0 answers
107 views

QPSK Receiver: Blind coarse frequency offset esimation issue

In this single carrier QPSK receiver, is designed to receive QPSK data from a satellite in Low Earth Orbit. Since the satellite speed in this orbit is around 3000 m/s and our carrier frequency is 12 ...
1 vote
0 answers
32 views

How to effectively resolve bitstream from an array of signal amplitude

The other day, I asked about how to model a receiver from 1090MHz ADS-B and Mode S signal, link to the post. With the support from Mbaz. I thought that it was not accurate that if I used a Zero-IF ...
2 votes
1 answer
71 views

Modeling 1090MHz receiver for aviation transponder

I'm building a Mode S and ADS-B receiver for TDOA calculation. I am planning to use an SDR with Zero IF to receive the downlink 1090MHz replies from aviation transponders. Currently, I am modeling the ...
0 votes
2 answers
61 views

Transmitting data with QPSK using an SDR

My question assumes that I want to transmit some data using QPSK using and SDR. The SDR will be fed with IQ data and this will transmitted at a sample rate Fs and be up converted to a carrier ...
2 votes
0 answers
43 views

Triangulation by phase delay basic requirements

I'm trying to identify the relevant specifications/calculations for building a system (at least theoretically) to accurately triangulate the position of a 915MHz CW transmitter to within 1cm. I have ...
1 vote
0 answers
27 views

USRP N210 B & F Lights

During setup of a USRP N210 on MATLAB's Communications Toolbox Support Package for USRP Radio, the initial test failed on "Receive the signal and verify the frequency of the tone" field. ...
0 votes
0 answers
37 views

USRP N210 Connection Issues on Ubuntu 22.04 VirtualBox VM

I am running into consistent connection issues when trying to run a USRP N210 on a VirtualBox Ubuntu 22.04 VM. I built uhd from source on the ettus page, configured a static IP address in Ubuntu, ...
1 vote
0 answers
85 views

OFDM complex symbols have dynamic phase shift after the fft-block & before the BPSK demodulator at the receiver ,

I have transmitted and received an OFDM-signal using the same ADALM-Pluto-SDR's Tx/Rx Antenna. I have used BPSK baseband modulation with symbol freq=312.5 KHz, L (length of ifft)=64, fsampling=fsym*L=...
0 votes
1 answer
166 views

oQPSK symbol synchronization

I'm validating a C++ oQPSK receiver. The 5Mbps oQPSK signal is generated by a satellite emulator. The receiver structure goes as follows: SDR --> AGC --> Costa's Loop --> Delay --> ...
1 vote
0 answers
71 views

Why is bandwidth inversely proportional to mulitpath interference?

I have a project related to Signals of Opportunity and during my research on the communication signals that can be used for navigation purpose I saw that as references are given below signals that ...
2 votes
1 answer
680 views

Can you please help me in generating a chirp signal in GNU radio by creating a module of your own?

I am currently working on a FMCW radar using a SDR I have done the simulations in python and am moving towards simulations on GNU radio. In python it was easy to generate a chirp, just use the scipy....
2 votes
5 answers
4k views

What can be done with I/Q data which would otherwise be impossible?

As I understand it, I/Q data is the complex representation of any waveform. It enables us to understand two things at any arbitrary point in time: The projected amplitude of the waveform. The ...
1 vote
0 answers
48 views

DSP library for Software Defined Radio

Can anyone recommend a good C library for SDR? To be more specific I just need a function in C to compute coefficients for CIC compensation filter (I need to do it in real time, so Matlab is not an ...
1 vote
1 answer
98 views

Replicating SDR transmitter and receiver (shifting of a quadrature signal)

I am trying to implement an SDR transmitter and receiver based on the description here. ...
0 votes
1 answer
52 views

Does SDR configured with low sample rate automatically averages samples?

This is probably a basic question but I didn't find any answer online. Suppose we configure a SDR (least say, with a maximum sample rate of 100 Msamples/s) with a low sample rate (e.g. 1 Msample/s). ...
0 votes
0 answers
7 views

is it relevent to plot the parcimony of a signal in function of its SDR?

Whilst trying to compare the performance of three blind source separation methods, is it relevent to plot the parcimony of a signal in function of its SDR? Thank you...
0 votes
0 answers
31 views

How to determine the size of DFT bins to implement a bandpass filter with FFTW on SDR

I'm implementing a bandpass filter to isolate the amplitude of a UHF FM signal with a 12.5Khz bandwidth. I'm having difficulty isolating the correct bins and bin spacing, given my DFT to isolate the ...
0 votes
1 answer
334 views

TX RX text via gnuradio using hack rf

I have a problem here - either I'm stupid or my hack rf is broken I am trying to send text via 2 hackrf like in this tutorialusing GMSK The simulation returns the text is correct, but when I run the ...
0 votes
0 answers
137 views

Which type of modulation is used in this RF Signal?

I am working on reverse-engineering a few devices, I got some using ASK and FSK but I could not grasp this other one. I am attaching some photos from its captured signal took from URH (Universal Radio ...
0 votes
0 answers
107 views

FFT on SDR FM Radio Signal

I recorded a simple FM signal using my SDR (centered at 100.3e6 hz and sample rate of 2.048e6 per second). Without any transformation, I ran an FFT on the signal and it showed a signal with some width ...
0 votes
0 answers
163 views

SDR lose samples at high bandwidth (sample rate)

When receiving bandwidth (sample rate) is small (<~28 MHz), the signals are received without any distortion. When I choose high bandwidth (for example 40 MHz), sometimes the signals become ...
0 votes
1 answer
773 views

GNURadio GFSK demod missing data

we are trying to develop a flowgraph for cubesat operation. Our flowgraph for includes both downlink and uplink parts in one flowgraph. It uses SoapySDR as a driver of an SDR. Most of the used blocks ...
-1 votes
1 answer
58 views

gnuradio , SDR usrpx300

I use usrp x300 SDR. I'm confused about Bandwidth and sample_rate. How do I calculate them? is ...
0 votes
2 answers
248 views

Transmitting a 350 MHz signal

I'm currently on an SDR kick and reverse engineering and then emulating all of the remote controls in my house. There are numerous solutions to transmitting signals over 315 or 433 MHz and you can ...
0 votes
1 answer
911 views

Spectrum analyzer resolution bandwidth (RBW) for LTE signals

I am trying to measure the maximum output power of an SDR transmitting a 20 MHz LTE signal with a spectrum analyzer. Adjusting the resolution bandwidth (RBW) changes the power spectral density (PSD) ...
0 votes
1 answer
158 views

Why don't we need frequency and phase correction in AM and FM?

As far as I understand, double sideband AM with carrier and FM can be demodulated via SDR (Software Defined Radio) without frequency or phase correction. For AM, received signal is $$r(t) = A(t)\cos(\...
1 vote
1 answer
146 views

Generating I Q samlpes for particular sample rate

I want to know what the sample rate of I and Q samples generated for transmission, in the function below from https://github.com/lyusupov/ADSB-Out/blob/master/ADSB_Encoder.py samples are generated ...
1 vote
0 answers
155 views

Amplitude modulation in SDR [closed]

I understand the theory of amplitude modulation. However, I couldn't understand it's implementation in SDR, which use IQ data, and I would like to learn end to end amplitude modulation system in ...
1 vote
1 answer
65 views

Is the phase of a IQ point related to the local oscillator frequency?

When considering a direct conversion SDR receiving or emitting architecture, we can "represent" the received or transmitted signal as the sum of two components, the I and Q component. Each ...
2 votes
1 answer
782 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 ...
2 votes
1 answer
135 views

Choosing the scaling parameters for a modem implementation

I have succesfully modeled a modem using floating-point data and with the following scheme, where the SRRC filter has gain G=6dB. ...
0 votes
2 answers
91 views

How to achieve a DC portable power source with low noise in 400 MHz frequencies

I am working on an SDR composed system that is plugged into a Raspberry Pi board powered by a 5V DC Power bank. The SDR is configured to measure a signal around 400 MHz. The noise floor measured by ...
0 votes
1 answer
436 views

USRP N210 Main clock rate and The transmission signal Sampling Rate

I am testing the transmission and receiving signal using two USRP N210. The communication setting as follows: ...
1 vote
0 answers
180 views

numerical time differentiation in GNURadio

I'm hoping to put together a cheap modulation monitor for wideband FM radio using an rtl sdr usb, on the FCC website, it's listed that the modulation percentage for an FM station is the actual ...
1 vote
1 answer
1k views

How to demodulate FM I/Q output from SDR#

Using SDR#, I saved the baseband I+jQ signal centered about a commercial FM station to a *.wav file. I want to write python code to demodulate this signal. I know that SDR# can read in that file and ...
2 votes
1 answer
247 views

USRP N310 RX gain lower than other SDR with same GNURadio script

In my company, we are using a GNURadio script with a PlutoSDR to receive packets coming from a transmitter located very far away. The receive power is really weak, our antenna is receiving something ...
1 vote
0 answers
64 views

CIR calculation from SDR data: RTL-SDR, bladeRF

We’re developing a prototype using bladeRF and various Python scripts for processing IQ samples. The system works mainly around 2.4 GHz frequencies: Wi-Fi and Bluetooth. One of the needed functions is ...
0 votes
0 answers
124 views

Biphase/Manchester floating-point decoder based on matched filter

I need to perform soft Viterbi decoding on a Manchester-encoded BPSK/QPSK signals. To that end, I need a floating point Manchester decoder. Most of the implementations I have seen operate on hard bits....
0 votes
0 answers
194 views

SDR - Manual FFT PSD vs pylab PSD

I am trying to calculate the power spectral density step by step using numpy FFT and comparing it to the PSD calculated by pylab PSD. Difference b/w plots of both methods can be visualized from in ...
2 votes
2 answers
1k views

How does the sample rate work on an SDR?

How can an SDR, which has a sample rate of about 32MHz record signals with a frequency of 1GHz? Shouldn't the sample rate be at least two times as high as the frequency or am i missing something?
-1 votes
2 answers
503 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
0 votes
0 answers
71 views

Interference between 121.5Mhz and 124.5Mhz

I'm new to Software Defined Radios and trying to find out if powerful signals are a cause of my own interference, a poor setup, or just a lot of traffic. I'm using a HackRF One with an ANT500 antenna. ...

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