What is Signals: Definition and 433 Discussions

In signal processing, a signal is a function that conveys information about a phenomenon. In electronics and telecommunications, it refers to any time varying voltage, current, or electromagnetic wave that carries information. A signal may also be defined as an observable change in a quality such as quantity.Any quality, such as physical quantity that exhibits variation in space or time can be used as a signal to share messages between observers. According to the IEEE Transactions on Signal Processing, a signal can be audio, video, speech, image, sonar, and radar-related and so on. In another effort to define signal, anything that is only a function of space, such as an image, is excluded from the category of signals. Also, it is stated that a signal may or may not contain any information.
In nature, signals can be actions done by an organism to alert other organisms, ranging from the release of plant chemicals to warn nearby plants of a predator, to sounds or motions made by animals to alert other animals of food. Signaling occurs in all organisms even at cellular levels, with cell signaling. Signaling theory, in evolutionary biology, proposes that a substantial driver for evolution is the ability for animals to communicate with each other by developing ways of signaling. In human engineering, signals are typically provided by a sensor, and often the original form of a signal is converted to another form of energy using a transducer. For example, a microphone converts an acoustic signal to a voltage waveform, and a speaker does the reverse.Information theory serves as the formal study of signals and their content, and the information of a signal is often accompanied by noise. The term "noise" refers to unwanted signal modifications but is often extended to include unwanted signals conflicting with desired signals (crosstalk). The reduction of noise is covered in part under the heading of signal integrity. The separation of desired signals from background noise is the field of signal recovery, one branch of which is estimation theory, a probabilistic approach to suppressing random disturbances.
Engineering disciplines such as electrical engineering have led the way in the design, study, and implementation of systems involving transmission, storage, and manipulation of information. In the latter half of the 20th century, electrical engineering itself separated into several disciplines, specializing in the design and analysis of systems that manipulate physical signals; electronic engineering and computer engineering as examples; while design engineering developed to deal with the functional design of user–machine interfaces.

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  1. Daniel Petka

    Why does a series of pulses generate a pitch?

    Here's the thing: the ear detects a pitch by splitting a sound wave into it's frequency components in the cochlea, which is in a way a spatial Fourier transform (ish...) But I never liked this analogy because it doesn't explain why I hear a pitch when a series of pulses entern my ear. A single...
  2. hilbert2

    Receiving High Freq Signals via Passive Downconverter

    I'm getting this type of device in mail, it is a passive microwave signal downconverter that converts a signal of up to 3.5 GHz to something that can be received with an RTL-SDR of upper frequency limit less than 1.5 GHz. Is it expected that I have to put the antenna-received high freq signal...
  3. SherLOCKed

    I Maximizing S/N in Angular Power Spectrum Signals

    The signal-to-noise ratio for angular power spectrum signal Cl under theoretical noise Nl, where Cl and Nl are functions of multipole l, is given as (S/N)^2= \sum (2l+1) (Cl/Nl)^2To increase the S/N we bin the power spectrum signal, if bin width \Delta l, this in principle decreases Nl by a...
  4. N

    Calculating delay b/w signals using correlation

    Hi all I am generating two signals of same frequency, i introduce a fixed delay in one of the signal and then try to find out the simulated delay using MATLAB 'gccphat' and 'finddelay' functions, but not able to measure correct delay. MATLAB Code script is given below: clc clear close...
  5. S

    Dictionary Learning: Reconstructing Incomplete Signals

    Hi guys! I am new here and I have a question related to the dictionary learning. For the dictionary learning, three critical elements are the dictionary, sparse coefficients and a signal for dictionary learning. Currently I have a dictionary D for learning all the signals in the set S, so for a...
  6. G

    I Are EM signals also analytical backwards in time?

    Hi. If I turn on an antenna, it starts sending out radiation. If I turn it off again, the radiation doesn't instantly disappear but dies out smoothly (exponentially?). But this also means the radiation is never completely gone. This looks time-asymmetric, which is weird for electrodynamics. It...
  7. T

    I Curious about an idea of a modified polariser to send signals with QE

    So I'm curious about an idea of using a specially modified polariser to send signals with quantum entanglement, curious to know what's more there is to learn about the idea, for better or worse, its possibilities or impossibilities. Ok so like in the Bell tests, measuring the spin of an...
  8. Ahmed1029

    I What Determines the Speed and Clarity of Signals in Wave Physics?

    What exactly is a signal in wave physics? Is any wave considered a signal? Like, consider a superposition of harmonic plane waves, is the signals it carries considered the envelope(that travels at the group velocity) or the individual rippes that travel at a the phase velocity?
  9. C

    B How good are our ears? (Detectable Interstellar signals)

    How good are our ears / what can SETI and the like detect ? If we are listening for a radio signal broadcast by some advanced civilisation in our galaxy how sensitive would our "ears" have to be to detect a signal ? Obviously part of that equation would be how strong and how close the...
  10. L

    Engineering Adding two signals from different sensors in order to obtain a signal with very high dynamics

    hello I am working on a project concerning a measurement technique which consists of adding two signals from different sensors in order to obtain a signal with very high dynamics. and I would like you to help me because I saw your interventions concerning this system. I don't know yet if this is...
  11. A

    Engineering Signals & Systems with Linear Algebra

    Hello everyone, I would like to get some help with the above problem on signals and linear projections. Is my approach reasonable? If it is incorrect, please help. Thanks! My approach is that s3(t) ad s4(t) are both linear combinations of s1(t) and s2(t), so we need an orthonormal basis for the...
  12. A

    Engineering I/Q of Signals and Hilbert Transform

    Hello, would anyone be willing to provide help to the following problem? I can find the Fourier Transform of the complex envelope of s(t) and the I/Q can be found by taking the Real and imaginary parts of that complex envelope, but how can I approach the actual question of finding the carrier...
  13. BWV

    B Observers sending signals to measure expansion

    Googling you find a current expansion rate of ~70 km/s or 0.0002C but of course we don't observe this with objects in the solar system as local gravity prevents this expansion - otherwise a distances would increase by a light second roughly every 71 minutes (maybe I’m missing some here...
  14. PainterGuy

    Signals with the same frequency spectrums but different power levels

    Hi, I understand that if there are two signals whose spectrums consist of different set of frequencies, they can be separated using a filter such as bandpass filter on the receiver end. Is it possible to separate two signals who frequency spectrums are the same but power levels are different?
  15. Amitkumarr

    I Finding bias of the coin from noise corrupted signals

    Suppose there are two persons A and B such that both have a personal communication system which can transmit and receive bits. B has a biased coin whose bias is not known. A asks B to toss the coin 2000 times, send a 0 when a tail comes up and a 1 when a head comes up. It is known that whatever...
  16. A

    MHB How would I plot the following signals?

    I am extremely confused as how to go about this, any help would be greatly appreciated! The signals are: a) 𝑠(𝑛1, 𝑛2) = 𝑢(𝑛1, 𝑛2)𝑢(𝑛1, 𝑛2 + 2) b) 𝑠(𝑛1, 𝑛2) = 𝛿(𝑛1 − 𝑛2 + 1)
  17. dvscrobe

    Digitize AC Voltage & Current Signals - Solutions for Split CT

    I am looking to digitize AC voltage and current signals that are measurements from my breaker panel. Any thoughts on what could be used to digitize the AC current? This current would be coming from split CT.
  18. jisbon

    Engineering Signals in discrete form (scaling, shifting etc.)

    Attempting this question without any guidance from my professors unfortunately as they did not teach this bit. Searched online and also there aren't many questions like this. From what I know, (I) Having n-1 means you should shift right by 1, which means x[0] is now equals to 0? So x[n-1] = [0 5...
  19. Callum Plunkett

    Inverting Op-amp signals and Sawtooth waveform generation

    I’ve been asked to create a sawtooth wave form with four input voltages. After doing this I then added a second op-amp to both change the range of the wave form from -/+5v to -/+2.5 and DC offset of 2.5v to create a wave form that ranges from 0v – 5v as required by the question. For the most...
  20. Yalanhar

    Convolution of 2 Signals: Finding the Sum and Limits of y[n]

    ##x[n] = (\frac{1}{2})^{-2} u[n-4]## ##h[n] = 4^{n} u[2-n]## So I plotted x[k] and h[n-k] in picture but x[n] is 0 for n < 4, therefore ##y[n]## only has value for n >= 4. Therefore my sum is like that: ##y[n]=\sum_{k=4}^{\infty} 4^{n-k} (-\frac{1}{2})^k## ##y[n]=-4^{n}...
  21. N

    Measurement of frequency deviation in FM signals

    Hi all Is there any way to measure frequency deviation in a recorded frequency modulated time domain data? The little research i have done on net mostly concerns with frequency deviation measurement using spectrum analyzer in real time i.e. data continuously received on spectrum analyzer while...
  22. M

    Signal Processing: DFT spectrum of sinusoid signals

    Hi, I was recently reading about the discrete Fourier transform and its application to a basic sinusoidal signal. If we know that it has an integer number of cycles in ## N ## samples (and thus no leakage), why would there be two peaks in the spectrum: one at ## m ## and another at ## N - m##...
  23. B

    Do neuron electrical signals generate an electromagnetic field or wave?

    I'm not sure where this belongs, I'm guessing biomedical, but I'm interested from a physics perspective. Do neurons generate an electromagnetic field? In other words, all the neural activity in the brain, does it generate electromagnetic fields? If so, what are the details of these fields? I...
  24. DaveC426913

    RF shielding to keep signals inside

    I may have blown a hole in my plot I can't sew back up. I need a way to shield RF emissions to keep them from escaping into the wilderness. It has to be impractical enough that it can only be implemented on a large scale such as a settlement, not on, say, a vessel.Core premises of the story: -...
  25. C

    MATLAB Deconvolving two signals with different sampling rates

    Hi, So i am in a fix now. I have a discrete time signal which is produced by a device with Nyquist frequency as 50MHz and 1088 samples (there is nothing i can do with the device to change the frequency or number of samples). I have an analytical signal which is produced in the frequency domain...
  26. MathematicalPhysicist

    Combination of discrete/continuous signals

    I am looking for literature in theoretical engineering that covers a topic of a signal which is both discrete and continuous. For example ##x[n,t) = t/n## where ##t## ranges over ##[0,\infty)\cap \mathbb{R}## and ##n## is discrete, i.e takes values in ##\mathbb{Z}##. I believe that this isn't...
  27. entropy1

    B Mixing two discrete audio signals

    Suppose I have two audiofiles in 16 bit PCM, both recorded on a level that, except for the noise and distortion, is maximally recorded, or that the maximum recording level results in the maximum PCM level. So, the signal is recorded on the maximum level such that there is no clipping. If we...
  28. A

    A Exploring Time Travel Teleportation: Computer Bytes & Radio Signals

    Time travel teleportation can be achieved in small scale experiment in millisecond. Using a computer byte in radio signals. I look forward for comments.
  29. D

    I have an op amp that does not tolerate signals below ground

    I have a lm224 operational amplifier that does not tolerate signals below ground. What operational amplifier tolerates signals below ground?
  30. R

    I Sum of many random signals

    For instance, here is an example from my own simulations where all underlying signals follow the same analytical law, but they have random phases and amplitudes (such that the sum of the set is 1). The thick line represents the sum: Clearly, the sum tends to progressively get flatter as ##N...
  31. TechTree

    Electronics Transmit RF signals directly to receiver in line of sight

    Hello, I am trying to transmit radio signals across a distance of just under 1km to the receiver. The receiver is in line of sight with the transmitter. I just need to send the data in the most direct way possible, almost like shining a laser through the air. I was wondering what type of antenna...
  32. T

    How to decompose a signal into its contributory signals

    Ok, so in the interest of full disclosure at the outset, I'm a 69 y.o. retired epidemiologist who has an interest in HRV signal analysis specifically, and physics as a whole--always have. Am not an EE, physicist or mathematician so be kind, if you will. This is my first post. In signal...
  33. Boltzman Oscillation

    How can I prove this discrete signal is periodic?

    Homework Statement Prove the discreet signal is periodic: Homework Equations for periodic funtions: x[n] = x[n + N] The Attempt at a Solution I made an equality (im going to leave the sigma out for simplicity): 2^(-abs(n-2m)) = 2^(-abs(n+N-2m)) I don't know what I need to do from...
  34. A

    These Are The Most Promising SETI Radio Signals

    Hi! Just in case someone is interested in SETI, I made a video about the most promising radio signals detected so far. Here it is: https://www.youtube...h?v=4MxNEfIfQjI Hope you enjoy it! What is the most promising SETI radio signal for you guys? Do you think we will discover an intelligent...
  35. M

    LF, MF, HF, VHF, and UHF signals and Walls

    How many walls does a HF signal has to go through before the signal starts to fade considerably? How about LF, MF, VHF, and UHF signals? From what I've read, lower frequencies go through more walls than higher frequencies before fading out, is that correct? Thanks a lot for reading this!
  36. P

    SR - Time dilation, space-time diagram, and radio signals

    Homework Statement P.S.: I'm not sure if it is allowed to ask multi-part questions. Two equally old sisters Alice and Barbara leave Earth simultaneously in opposite directions. The following velocities and distances have been measured in the Earth system. Alice travels with a speed of ##v_A =...
  37. AchillesWrathfulLove

    What does input and output signals mean?

    What does input and output signals mean in terms of circuitry. Is it the current, the voltage, resistance? Also people usually show graphs for AC as Sinusoidal waves or sometimes they show square-waves etc. What are these signals referring to, and what does it mean for signals to have wave like...
  38. W

    B Implications of FTL signals in SR

    As I understand if it were possible to send a single faster than light then one can send a signal back into the past. What is the simplest way to explain how this would happen?
  39. R

    Coupling signals to a stripline transmission line

    Hello. I have a question about the place where signal enters or gets out from a line (strip or not) Sorry I don't know the exact word in english, may be tap or tapping ... For different lines 1/4 or 1/8 wavelength these points are sometimes @ a 1/4 from the cold point, sometimes elsewhere. I...
  40. ADDA

    Carrier Signals and demodulation of audio waveforms

    Is the failure to remove the carrier frequencies the problem with the audio output in the following videos?
  41. J

    Convolution theorem property about signals

    Homework Statement Homework Equations Laplace and then inverse laplace. The Attempt at a Solution Laplace of U(t-to) = 1/s e^(-tos) x(t)-->X(s) Laplace inverse 1/s means integration. e^(-tos) means delay on x(t) by to. I think answer should be C Book answer is D. How am I wrong?
  42. jsg94

    Determine impulse response given input and output signals

    Homework Statement Hello everyone, In the following problem I have to find the unknown impulse response g1(t) given the input and output signals, as shown below: (the answer is already there, at the moment I am trying to understand how to get there). Homework Equations [/B] I have...
  43. Giada

    Why do signals to tv aerials need to be polarised?

    is it because by polarising the em waves, it restricts the area needed to receive them, which makes it easier, otherwise you'd need to create moving tv aerials which wouldn't be convenient?
  44. F

    AC Signals in Arduino: Is It Possible?

    Hello Everyone, I have a question about the type of signals that are used in projects involving the microcontroller Arduino or similar ones. It seems that the currents and voltages in these microcontroller's projects all unidirectional, i.e. they can vary with time in different fashions but...
  45. R

    Counting clicks (signals) at a radio frequency receoved by a shortwave radio

    Hello. I'm an English language teacher researching the details of a class project; I use projects to develop language skills. I have a background in mechanical engineering but know little to nothing of electrical engineering, hence this post. Questions for members of this forum: Electrical...
  46. nothing909

    Voltage Calculation: What Are the Necessary Values?

    Question: The question and the solution are attached below. It asks to calculate the voltage and in the answers and the bottom, it says the voltage is 890mV. What are the values used to calculate this number? It tells me the equation V = sqrt (VR) but I don't know the values to to put into...
  47. M

    Question regarding phase shift between two signals

    Homework Statement Two sinusoidal voltages with amplitude 15Volts and frequency 2,771Hz are separated in time by 68% of a period. What is the phase shift in degrees between the two signals?Homework Equations y= Asin(omega)(x-h) The Attempt at a Solution I know my A is 15 and I'm pretty sure...
  48. N

    Transmit/Receive analog signals

    I'm completely new to transmitting/receiving signals, but I wanted to get a scope of what kind of components are out there that I could use to build this system. I wanted to read the voltage drop across a resistance thermometer (Vt) and send this signal wirelessly to another circuit, where I...
  49. J

    Generating Audio Signals from Lasers: Theoretical Possibilities?

    Say you have a red laser and pointed it at a ~175 nm antenna, then amplified the signal into a speaker. Would you then theoretically get a very high frequency audio signal (in the terahertz range, i realize this isn't practical)? My question is really on the nature of the light emitted from...
  50. M

    How does the use of a reflector affect the performance of a receive antenna?

    Do receivers only receive signals or they emit emf?