Questions tagged [radio]

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Simulating RF interference (noise) to captured RF signals

I have carried out an approach to clean my RF signal captured in order to perform classification on a set of devices. However, a further extension to this study I aim to achieve is to evaluate the ...
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4 votes
3 answers
215 views

Undestanding antenna gain applicability

While searching for the info about antenna gain and why it is GAIN I found this interesting example: If the two antennas in the drawing are “welded” together, how much power will be measured at point ...
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Why do ATSC channels need 6MHz of bandwidth when they're digital?

If I'm understanding it correctly, an ATSC channel is a digital channel that uses 6 megahertz of bandwidth to send 19.38Mbps using 8VSB modulation. For analog broadcasts, that makes sense, but I'm ...
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1 vote
2 answers
76 views

Is digital (discrete) SSB plausible?

Do any examples of digital SSB modulation exist? If not, is it implausible for some reason? The closest thing I can find is something like 8VSB which comes very close to being single sideband. I read ...
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Conversion from phase noise to EVM

I have a phase noise specification for a digital QPSK transmitter at 8GHz (symbol rate 50 Mbaud). From that specification I am able to compute the RMS jitter in radians (47 mrad or 934 fs using the ...
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1 answer
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In wireless communications, is it true to say: The more the range, the more the delay spread?

The general idea which can be drawn by reviewing wireless channel models says that the longer the range/distance, the more the delay spread, even in LOS microwave links. But I really wonder why it is ...
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2 votes
2 answers
129 views

The transmission distance of a signal

I am no professional in this area so please forgive me if this question is too immature. And thanks in advance for any help and information. I want to know how to calculate the transmission distance ...
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1 vote
0 answers
22 views

Why do adjacent cells use different channels?

In chapter 15 of the book Wireless Communications by Andrea Goldsmith, Goldsmith gives a formula for an estimate of the signal-to-interference-ratio for the node on the edge of a cell in a cellular ...
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1 answer
474 views

How do I determine the carrier frequency of a given AM signal?

I am trying to figure out what the carrier frequency of a signal is given only its discrete-time domain information and the fact that it is a signal on the AM radio frequency band(550 - 1700kHz). Is ...
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1 vote
1 answer
190 views

Why is GPS 1575 MHz?

I’ve read that that frequency is a ‘window’ in weather, impacted less by raindrops for example. I otherwise would’ve thought that simply increasing the wavelength would decrease impact. I don’t ...
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1 answer
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Resources for the Basics on Signals and Electromagnetic Waves in the radio frequencies [closed]

What are some good books and videos, to learn about radio waves? For someone (me) who has never studied Math, Physics, or anything people generally consider ‘technical’.
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Unstable Phase in Channel Impulse Response

I'm using DW1000 UWB radio transceiver and extract its channel impulse response (CIR). The CIR output by the transceiver is the complex baseband CIR. In a static environment, the CIR is a LTI filter ...
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1 answer
127 views

Direct downconversion (IQ downconverter) with ASK modulation-- what kind of Balun do you need?

I have a simple but confused question. I am trying demodulate a 915MHz ASK modulated signal with direct downconversion. So what I am building up is: Antenna --> SAW bandpass filter @915MHz --> ...
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1 answer
24 views

Analysis Received Signal at receiver side

I'm trying to understand something which is really confusing me and I made my best to understand it but still confused. If I have transmitted and receiver. Assume I want to transmit S(t) data and ...
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39 views

OFDM symbols terminology explanation

I've already read and understand what does OFDM mean and what does it stand for and why we use it in our wireless technology today. My question that I didn't understand is what does it mean number of &...
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32 views

Forming the estimation manifold for a 2-D beamformer

Given an array of L sensors in a uniform planar array, with known positions in space, I would like to estimate both the angles of arrival and delays from a point source under multipath conditions ...
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0 answers
40 views

Transceiver for TDoA measurements

Could someone advise me on some module for making the TDoA position system for my research work? I need to have measurements with an accuracy of a few meters. It equals a bandwidth of about 20 MHz. I ...
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1 vote
0 answers
43 views

filter single radio station with sdr [closed]

I want to write a program to filter a single radio station using SDR. Not for any application just a stepping stone to learn. I am going to use C so it is easier for me to see the steps and things ...
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0 votes
0 answers
22 views

Determine the change of selectivity

I've stacked on solving this problem and can't find an answer in the web, so I decided to ask a question here. There are the problem: Preselector of boadcast receiver contains of one oscillation ...
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3 votes
0 answers
73 views

About discrete time model for wireless channel

I am trying to understand Section 2.2.3 of the book "Fundamentals of wireless communication" by Tse and Viswanath. In this section the authors explain how to go from the continuous time ...
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6 votes
3 answers
348 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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1 vote
3 answers
63 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? ...
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2 votes
1 answer
307 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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2 votes
1 answer
168 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 ...
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1 vote
1 answer
528 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 ...
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1 vote
1 answer
79 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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1 vote
3 answers
60 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 ...
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0 votes
4 answers
330 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 ...
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0 votes
1 answer
32 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 ...
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1 answer
63 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, $h(k)$ ...
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4 votes
3 answers
391 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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0 answers
43 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 ...
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2 votes
1 answer
121 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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1 vote
0 answers
93 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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1 vote
0 answers
216 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 ...
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0 votes
2 answers
65 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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0 votes
0 answers
37 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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1 vote
0 answers
44 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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0 votes
0 answers
425 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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0 votes
1 answer
161 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 ...
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3 votes
0 answers
346 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 &...
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0 votes
2 answers
2k 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 ...
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1 vote
1 answer
103 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 ...
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6 votes
2 answers
1k 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). ...
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  • 165
0 votes
1 answer
3k 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 ...
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0 votes
4 answers
148 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 ...
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-1 votes
1 answer
93 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, ...
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0 votes
1 answer
355 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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1 vote
2 answers
224 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 ...
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-1 votes
1 answer
57 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 ...
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