Questions tagged [radio]
The radio tag has no usage guidance.
46
questions
1
vote
1answer
24 views
RF Downconversion using Heterodyne Principle
after a RF down-conversion using heterodyning principle, will there be an information loss?
If we translate to a fixed IF frequency, is there is an intuitive way of explain that the information can be ...
1
vote
3answers
47 views
Why does altering path length in radio transmission alter the phase of the received signal?
I do have a very naive yet bothering question:
Assume I send a sinusoid signal
\begin{equation}
A*cos(2\pi ft+ \phi_0)
\end{equation}
over a radio channel. Assume there is only a LOS-path for each ...
0
votes
4answers
55 views
Why is In-phase Quadrature sampling not used to record and store digital audio?
I/Q is a standard method to sample radio frequency and its use is even seen in some non radio signals like sonar. But it seems that it is not used to sample acoustic frequencies.
What property of ...
0
votes
1answer
20 views
5G NR Network Collision Avoidance
I'm looking for a technical explanation or a specification that explains exactly how 5G NR collision avoidance will work. I was watching a talk from the Mobile World Conference in Shanghai two years ...
0
votes
1answer
36 views
Wireless Channel Multiplicative Model
Let's assume a SISO channel in the equivalent baseband, the standard channel model (discrete) is:
\begin{align}
y(k) = h(k)x(k) + z(k) \tag1
\end{align}
Where $y(k)$ is the detected signal, $h(k)$ ...
2
votes
2answers
102 views
Why is the carrier suppressed by AM-DSB-SC modulation?
Lets say I have a message that is a sine wave at 1KHz. As I understand it, I can perform amplitude modulation by multiplying this signal with a carrier, lets say 10KHz, and this process is essentially ...
0
votes
0answers
23 views
modelling radar system for image generation
I am trying to find or derive some model for radar using python and blender which should hopefully create a simulation of what a radar image of the blender environment would look like.
I have been ...
2
votes
1answer
53 views
SDR spectrum anomalies
Is it normal to see periodic peaks going from 48.75 - 90 MHz? Also i was checking on my SDR dongle once and the whole band was raised above background offset for like a whole 50 MHz bandwidth and then ...
1
vote
0answers
36 views
What is DAB modulation in signal generators?
I am using R&S signal generator and for generating a DAB signal there is an option for mentioning the modulation level in %. For example, we can generate DAB modulation 50% . I can understand that ...
1
vote
0answers
98 views
How to setup filters to catch 4FSK deviations
I'm trying to demodulate a radio signal from Motorol DP4801 (MOTOTRBO) that follows DMR specification.
I'm receiving the signal by using HackRF with the rate sample 1 MHz. The radio uses frequency ...
0
votes
0answers
26 views
Techniques use for pulsar observation and data reduction
I am new to radio astronomy field i am looking for help and guides about some basic technique used to search the pulsar and how to reduce the data capacity.
0
votes
2answers
40 views
What do you mean by radio sensing a channel?
I am slowly getting into the field of wireless communications, in particular with WiFi based communications.
802.11 MAC mentions that
A station wishing to transmit first listens to the medium ...
0
votes
0answers
29 views
Will LoRa work from Earth to the Stratosphere
I'm unsure if this is the most suitable exchange however I thought it seemed most fitting personally, please correct me if I'm wrong. (I got redirected to here from the Network Engineering Exchange).
...
1
vote
0answers
40 views
Help in identifying low speed image transmission protocol over RF
In the seventies I worked for Muirhead on press fax machines that used to transmit pictures over radio and landline as I recall two FM systems were used a carrier 800 Hz modulated +- 150 Hz and 1900Hz ...
0
votes
0answers
151 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 ...
0
votes
1answer
112 views
Can a software defined radio with a frequency range of 300 MHz – 3.8 GHz detect AM (535 to 1705 KHz) and FM signals (88 to 108 MHz)?
I am interested in knowing whether BladeRF SDR with a frequency range of (300 MHz - 3.8 GHz) detect AM and FM frequencies? Also, how important is the sampling rate of the SDR. For example, BladeRF has ...
3
votes
0answers
194 views
Phase response of S11/S22 parameter for an RF attenuator? [closed]
I am new into the RF measurements. I was measuring the S11/S22 (reflection) parameters of an RF attenuator (with different attenuation levels, e.g., 10 dB) via a vector network analyzer from Rhode &...
0
votes
2answers
962 views
Trouble with time-syncing two radio signals using cross-correlation
I posted a similar question a while ago here (I'm posting this follow-up since I'd like to focus more on cross-correlation now). I have a setup where I have two software-defined radios connected to ...
0
votes
1answer
69 views
why transmitting a long pulse its spectrum gets spread?
I'm transmitting an RF signal with a CC1101 at 440 MHz.
This signal is a constant of 1, so the spectrum should be a delta.
Using a SDR dongle, I've checked the spectrum and it's wider than a delta ...
3
votes
2answers
808 views
Time Alignment of 2 Sensors Sampling the Same Signal with Different Hardware Delays
I have two radios sampling simultaneously, and I am trying to time-align their two signals (they will always start sampling at slightly different times with random delays due to hardware differences). ...
0
votes
1answer
2k views
Checking for VHF pulse with SDR and python
So I have a small NooElec Software Defined Radio and I've got it working well with my Raspberry Pi using GQRX as a controller and to visualize the SDR output.
My goal though is to use a python script ...
0
votes
4answers
120 views
how to eliminate interference in the same center frequency
I'm trying to receive an ASK signal in the 433 MHz center frequency with a bandwidth of 100KHz. I'm using a CC1101 transceiver connected to a Raspberry Pi GPIO ports. However, there is an intermittent ...
0
votes
1answer
70 views
how to guess what the interference source it could be
At work, we are in an industrial area, and there is always a signal that I receive inside my office which interferences with my tests.
This signal is in the 433 MHz and when I see the spectrum, ...
0
votes
1answer
237 views
Why is Error Vector Magnitude (EVM) measured as an RMS value?
I do understand Voltage/Current measurement of a Sine Wave is in RMS, as average yields a zero, and RMS gives a true 'DC equivalent' value. But I do not understand why an EVM measurement could be in ...
1
vote
2answers
120 views
What is the relation between the carrier frequency and the attenuation of electromagnetic waves?
For electromagnetic waves, what is the relation between the the carrier frequency, attenuation (absorption loss) and propagation distance?
I know that modulating high frequency carriers are required ...
-1
votes
1answer
48 views
Output eqaution of a repeater?
Assume we have a signal repeater, a simple repeater that amplifies the signal then transmits it as is.
Does the output power of the repeater is dependent on the received signal at the repeater ?
for ...
3
votes
4answers
1k views
How can the I and Q components of a quatrature signal be different from each other (apart from the 90º phase shift)
I've spent many hours reading and doing research about this. I don't attend any university classes or any type of classes that may approach such a topic. I am trying to learn this by my own without ...
5
votes
1answer
1k views
How do I convert a real baseband signal to a complex baseband signal?
I have radio telescope observations that have resulted in two real-valued signals (corresponding to the right- and left-handed circular polarizations).
The signals are sampled at rate $2B$, and ...
1
vote
0answers
168 views
What kind of signal modulation is more resistant to jamming?
I've understood that spread-spectrum type of modulations are more resistant to narrow band jamming, for obvious reasons. What is less obvious is why someone would try to jam for example a cellular ...
1
vote
1answer
133 views
How to accurately model wideband RF reflections?
I would like to model a transmitter and received pair, both sampling at the same bandwidth (not clock synchronized), where there are a number of reflectors. The time delay due to the reflectors can be ...
2
votes
1answer
223 views
Recommendation for good ressources on digital processing and D-QPSK
I've been a C++ developer for 10 years. Quite high level. And I am completely new to Digital Signal Processing.
I am trying to implement a Software Defined Radio. Specifically I am trying to receive ...
3
votes
1answer
1k views
Measuring signal phase difference between receivers
I am working on a project which aims to locate a transmitter.
I consider doing this using several receivers and measuring the phase differnces between them.
My problem is that arduino measures once ...
2
votes
3answers
198 views
Real world application of signal sparsity?
There are theories based on signal sparsity in frequency domain like Compressive Sensing, Sparse FFT, etc. Throughout searching and studying papers I found out Cognitive Radio is a good example of ...
0
votes
1answer
149 views
Receiving multiple signals at the same frequency at the same time
I'm doing a project for my school it's a communication platform for different mobile devices I'm gonna build and I need to send data from the devices to station am making, I figured how to use signal ...
1
vote
0answers
57 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 ...
0
votes
0answers
84 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 ...
1
vote
2answers
280 views
If you had supersonic hearing, would you be able to hear the carrier wave of an AM radio station?
Would you be able to hear the carrier wave of an amplitude modulated station, if you could hear in the MHz range, or would the high frequency be filtered out after rectification?
0
votes
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 ...
2
votes
0answers
304 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 ...
1
vote
2answers
147 views
Fully random PN sequence
Can a CDMA PN sequence be fully random, as in encryption-grade randomness, or must it be deterministic? I have tried the first bytes of SHA-256 hashes as PN sequences, but somehow they don't coexist ...
0
votes
0answers
36 views
Car engine audible through AM radio — what is this called?
A car's engine rotates in the range of 500 RPM to 6000 RPM. This is in the audible range. The car's engine is activated using spark plugs which are an electrical system at the same frequency (or some ...
5
votes
2answers
1k views
fmcw radar sampling requirements
I have been reading about "all-digital" or "software-defined radars". Lately, I was trying to simulate an FMCW short range radar in Matlab. One thing that struck me during the simulation is that to ...
1
vote
2answers
140 views
What are the fundamental reasons that suggest us to minimise transmission power for energy-efficient radio link design?
My question in short:
Under which scenarios minimising transmission power is beneficial in terms of transmitter energy-efficiency? is there any fundamental reason to keep a low-power oriented design ...
3
votes
2answers
361 views
Quadrature modulation
I have a question:
What is the difference between
$ I \cos(t) - Q \sin(t) $ and $ I \cos(t) + Q \sin(t) $
except that they are phase shifted 90 degrees ?
On the internet I can find both ...
0
votes
1answer
62 views
Modeling a signal through the environment
I have a signal that is composed of a sinusoid. I will send it over the air through radios. Part of the signal will go through processing on a computer, which means that it will be converted from ...
1
vote
3answers
691 views
Filtering out unwanted square wave (Radio: DCS/DPL signal)
I've need to remove a DPL/DCS signal from a recording. Roughly speaking, a DCS signal is a low frequency (67.15Hz) square wave sent at the same time, over the same carrier, as speech. Because it is a ...
