Signal Processing

Questions tagged [radio]

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3answers
90 views

How a diode-detector affects to Frequency Response?

I have a question related to crystal radio. I can't understand how a crystal detector (diode) shifts the spectrum from the carrier frequency to zero. The antenna receives bunch of signals and the LC ...
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3answers
48 views

Can the intelligence message of an FM signal be cross-modulated to another center frequency due to non-linearities?

Can the intelligence message of an FM signal be cross-modulated to a a different frequency by non-linearities, but with the FM modulating message remaining (relatively) intact on the new frequency? ...
2
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1answer
51 views

What is the functional difference between DSB and 2SB mixers, and why exactly would 2SB be better for radio astronomy?

The Astronomy SE question 2SB mixer in radio astronomy? asked in 2014 in its entirety: In literature about the instrumentation of radio astronomy, I frequently come across a type of mixer described ...
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0answers
26 views

Gnuradio scaling on Ubuntu issue

I have problem with scaling on gnuradio. When i use more than one WX widget - which shows parameters of signal - i can't see last widget. How can I deal with this problem - just to scale scopes, and ...
2
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1answer
73 views

Does Radio Communication Have to Account for the Doppler Effect?

I know that radio communications take place in specific frequency bands, and that the doppler effect can cause shifts in frequency when there is relative motion between the source and destination ...
1
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1answer
69 views

Difference between slow, medium, fast AGC

In digital receivers, at the RF level (not audio), I often read about "slow AGC" and "fast AGC", and sometimes even "medium AGC" (but I think the latter is for audio). From my understanding, the slow ...
1
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1answer
25 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 ...
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3answers
49 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
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4answers
79 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
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1answer
21 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
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1answer
40 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
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2answers
117 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 ...
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0answers
27 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
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1answer
61 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 ...
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0answers
51 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 ...
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0answers
108 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
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2answers
49 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 ...
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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). ...
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0answers
42 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 ...
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0answers
188 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
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1answer
117 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
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0answers
230 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
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2answers
1k 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
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1answer
81 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
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2answers
872 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
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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
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4answers
122 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
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1answer
75 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
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1answer
252 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 ...
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2answers
133 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
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1answer
49 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
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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
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1answer
2k 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
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0answers
177 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
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1answer
135 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
231 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
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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
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3answers
216 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
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1answer
166 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 ...
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0answers
59 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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0answers
87 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
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2answers
287 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?
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1answer
2k 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
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0answers
325 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
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2answers
153 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 ...
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0answers
37 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
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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
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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
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2answers
379 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
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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 ...

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