What is Signal analysis: Definition and 43 Discussions

Signal processing is an electrical engineering subfield that focuses on analysing, modifying, and synthesizing signals such as sound, images, and scientific measurements. Signal processing techniques can be used to improve transmission, storage efficiency and subjective quality and to also emphasize or detect components of interest in a measured signal.

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  1. MisterH

    A Fitness function for window length of filter

    Fitness function for window length of filter On a sinusoidal signal with amplitude 1, and period P, an exponential moving average (EMA) (with alpha = 1/n), and a linear weighted moving average (LWMA) (with window length n) are calculated; when you subtract the EMA from the LWMA, it can be seen...
  2. koroshii

    I Acquiring a Small Dataset of a pulsar signal

    I am taking a class in signal processing. We have a final project in which we seek out "real-world" signal data and process and analyze it, and write a report on what we figured out. I thought it would be interesting to put my own interests into it and try to analyze a pulsar signal. My idea is...
  3. N

    A Sine Dipole formation using two hydrophones

    Hi all. I am trying to do MATLAB simulations for generation of SINE Dipole using two hydrophones spaced distance 'd' apart for signal coming from direction 'DOA'. The MATLAB code is given below. The confusion is that there is constant phase difference of 90 degree b/w SINE Dipole generated using...
  4. CricK0es

    Engineering How to find RMS, and Peak Voltages of this signal?

    Hi all! I have a complex waveform, something like what I have attached, and I need to extract the RMS and Peak Voltage from this. However, this signal can and will change after a number of cycles on a certain setting. So, this means the period and duration of pulse can change and so can the...
  5. M

    Engineering Reconstruct a signal by determining the N Fourier Coefficients

    %My code: %Type of signal: square T = 40; %Period of the signal [s] F=1/T; % fr D = 23; % length of signal(duration) dt=(D/T)*100; N = 50; %Number of coefficients w0 = 2*pi/T; %signal pulse t1= 0:0.002:T; % original signal sampling x1 = square((2*pi*F)*(t1),dt);%initial square signal...
  6. Michael Price

    A Resolving power of a radio telescope array: Quantum or classical?

    My question is: is the resolving power of an array of radio telescopes a quantum or a classical effect? The increase in resolving power of a single telescope, as aperture size increases, is easy to explain in terms of Heisenberg's uncertainty principle. But when we go an array of telescopes are...
  7. 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...
  8. Behrouz

    A Finding a specific amplitude-frequency in the time domain

    Hello, I have a signal and got the FFT result of that. I have shown them both below along with the MATLAB code. May I ask if there is any method to find the time zone(s) in the signal that a specific frequency has(have) happened? The reason I'm asking this is that I want to specify the time...
  9. A

    DC estimator algorithms

    I wanted to remove the dc component from a signal but i can't use the average method because i have only a half cycle sampled not a full cycle . Is there any algorithm or method that can remove the dc component using only a half cycle? (The signal is sin(x)+2*sin (2x) +3*cos (3x)+4*cos (4x) +5...
  10. S

    Struggling to choose my PhD topic

    <Moderator note: Moved from academic guidance to career guidance on Scott92's request. Reason: The question primarily addresses job opportunities in dependence of PhD subject.> Hey everyone, I'm a student who is currently undertaking a Master of Physics (coursework & research) at the...
  11. Peter Morgan

    A Stochastic signal analysis in QM

    [Moderator's note: This discussion has been spun off from another thread since it was getting into a more technical area only tangentially related to the original thread's topic. Some posts have been edited slightly for the new context.] They're too technical for the question here, and only...
  12. Jayalk97

    Quick question about linearization using the small angle method

    Hey guys, when you're linearizing a function that has a constant, what do you do to it? An example would be y = x^2 + 3, would you just linearize it using its derivative and get rid of the constant?
  13. Abdul Wali

    How to choose the sampling time for the delay unit

    hi, i am designing a fuzzy logic controller, i need to use a delay block for the change in error signal now i don't know that based on what factors should i choose the sampling time for this unit
  14. O

    Derive The Transfer Function from First Principles

    All, I need help deriving the Transfer Function of this circuit from first principles. http://i66.tinypic.com/24v3z9s.jpg
  15. Abdul Wali

    Time Delay Margin: Good Large or Small?

    I have a question regarding the time delay margin. I know the definition of time delay margin now I want to know that for the stability of the system is it good to have large time delay margin or small time delay margin?
  16. Abdul Wali

    MATLAB Matlab Derivative block analysis and filter design

    Hi, May someone helps me regarding this!? i have a controller which will control AC motor as attached. in this controller, a stage comes where I need to use a Derivative Block before point 'B' as shown in the attached picture " controller block diagram" [...
  17. N

    What is preventing me from achieving better accuracy for this delay?

    I have 2 PERFECT data of the transmitter and receiver. From 2 data, I can calculate the delay estimation: Fs = 8e6; % sample rate ... for i = 1:2 [cc_correlation,lag] = xcorr(signal2(i), signal1); [cc_maximum, cc_time] = max(abs(cc_correlation)); cc_estimation...
  18. M

    Integral of absolute value of a Fourier transform

    Homework Statement Hi guys, I am going to calculate the following integral: $$\int_0^{f_c+f_m} |Y(f)|^2\, df$$ where: $$Y(f)=\frac{\pi}{2} \alpha_m \sum_{l=1}^{L} \sqrt{g_l}\left [ e^{-j(\omega \tau_l - \theta_m)} \delta(\omega - \omega_0) + e^{-j(\omega \tau_l + \theta_m)} \delta(\omega +...
  19. nacreous

    Calculate coefficients of expansion for vector y

    Homework Statement Let v(0) = [0.5 0.5 0.5 0.5]T, v(1) = [0.5 0.5 -0.5 -0.5]T, v(2) = [0.5 -0.5 0.5 -0.5]T, and z = [-0.5 0.5 0.5 1.5]T. a) How many v(3) can we find to make {v(0), v(1), v(2), v(3)} a fully orthogonal basis? b) What are z's coefficients of expansion αk in the basis found in...
  20. S

    A Correlation coefficient among trends

    Hi all, in several vehicles, I measured the engine torque and speed and the engaged gear while it was driven for around 100km/h. I computed the average engine speed and torque of all the times the vehicle was run with each gear and also I computed the relative frequency of the gear used. So for...
  21. D

    Lower Bound on Weighted Sum of Auto Correlation

    Homework Statement Given ##v = {\left\{ {v}_{i} \right\}}_{i = 1}^{\infty}## and defining ## {v}_{n}^{\left( k \right)} = {v}_{n - k} ## (Shifting Operator). Prove that there exist ## \alpha > 0 ## such that $$ \sum_{k = - \infty}^{\infty} {2}^{- \left| k \right|} \left \langle {v}^{\left (...
  22. D

    Identifying time and/or amplitude transformations

    So the question looks like this: Identify the time and/or amplitude transformations that must be applied to the signal x(t) in order to obtain each of the signal specified below. Choose the transformations such that time shifting precedes time scaling and amplitude scaling precedes amplitude...
  23. M

    Small signal analysis of a cascode amplifier

    Hello there. I am stuck trying to figure out the voltage gain of a cascode amplifier from a small signal analysis. The circuit seems to be under-determined for reasons I do not understand or maybe I am missing the perfectly obvious. Here's my small signal model: The only relation I can...
  24. Nemo's

    Fourier series neither odd nor even

    Homework Statement I'm trying to calculate the Fourier Series for a periodic signal defined as: y = x 0<x<2Π y = 0 2Π≤x<3Π Homework Equations Fn = 1/T ∫T f(t)cos(kwοt + θk)[/B] cn/2 + ∑k=1k=∞(cn)cos(kwοt+θk) cn= 2|Fn| θk=∠Fn The Attempt at a Solution I got Cn =...
  25. R

    Hilbert Transform Homework: Show Envelope is |m(t)|

    Homework Statement For a real, band-limited function ##m(t)## and ##\nu_v > \nu_m,## show that the Hilbert transform of $$h(t) = m(t) cos(2\pi \nu_c t)$$ is $$\hat{h}(t) = m(t) sin(2 \pi \nu_c t),$$ and therefore the envelope of ##h(t)## is ##|m(t)|.## Homework Equations Analytic signal...
  26. R

    MATLAB Fix Filtering Frequencies Code in Matlab w/o Built-In Filters

    I want to write a Matlab code which removes all frequency components from a .wav sound file except those within ##±25 Hz## of ##523 Hz## as well as its harmonics (up to the Nyquist frequency). I want to do this without using any built in filters. Here is my code so far: [s, Fs] =...
  27. R

    Identifying Fundamental Frequencies

    Homework Statement I have made a plot of a given .wav file in Matlab. The problem asks: find the fundamental frequencies of the 3 vibrating strings, and identify some of their harmonics. Homework Equations 3. The Attempt at a Solution [/B] So I made a Matlab plot of the power spectrum over...
  28. S

    Checking if a signal is stationary

    Hi all, I have a signal and I need to check if it is stationary. I segmented a signal into different segments and for each I calculated the average value. It is enough to assess a weak nonstationary? Is there any limit value of the deviation of the average value of each segment with respect to...
  29. P

    The Complex Exponential

    In my electrical engineering textbook, they have an entire chapter devoted to the complex Exponential. I don't really understand it, nor do I understand its importance. I know it is extremely important, and need to understand why, and what exactly it is, and the wording of the online resources...
  30. K

    Different forms of the discrete Fourier Transform

    Hi I am trying to program excel to take the DFT of a signal, then bring it back to the time domain after a low pass filter. I have a code that can handle simple data for example t = [ 0, 1, 2, 3] y = [2, 3, -1, 4] So I think everything is great and so I plug in my real signal and things go off...
  31. S

    Identification of patterns

    Hi all, I have 40 signals recorded on a vehicle. Some signals are analog and some are digital with 4 different states. One signal (I call it A) is really important to me, it is positive and all the other signals lead to its variability. For example, when there is a state change in a couple of...
  32. C

    Response Signal Analysis

    Hi everyone! This is my first post here at PF after years of on & off lurking! So, I'll get straight to it. At work (yes work, not HW) I have a forcing function signal that acts on a spring-mass system. When the spring-mass system "tracks" the forcing function, the curves overlap...
  33. E

    BJT differential amplifier, small signal analysis

    Hello, I'm having some issues with small-signal analysis of BJT differential amplifiers. Let's say I have this BJT differential pair and suppose that Q1 and Q2 perfectly match: http://i50.tinypic.com/14ahdgn.jpg Suppose a small differential input is applied and consider the small–signal...
  34. E

    BJT small signal analysis: output resistance

    Hello, I'm studying BJTs and I have a doubt about deriving the output resistance in the small signal equivalent circuit. Let's consider the circuit below: To derive the output resistance, I'd write the following KCL: i_x = i_{rc} + i_c at this point, every example I've seen says R_o = R_c...
  35. H

    Signal Analysis: Time Segments & Characteristics

    Homework Statement Hi , The problem is how to analysis this signal in terms of time segments to understnd the characteristics/pattern of this signal Homework Equations There is no relevant equtions The Attempt at a Solution I have tried to use : RMS Wavlet FFT But which...
  36. S

    New to the forums need some help with signal analysis

    Im taking This class EEL3135 and I am very lost and confused as to how to study or where to find resources to understand the material. does anybody know of a good website for beginner signal analysis? or a good reference ebook etc to help me out with it? the ones i seen are far too advanced...
  37. C

    Signal Analysis - Using Convolution

    Homework Statement Consider the signal x(t)=cos(4t)+cos(5t)+cos(6t), and the SLIT with impulse response: h(t)=\begin{cases} 1, & \mbox{if } |t|<T \\ 0, & \mbox{if } |t|>T \end{cases} For what value of T is the output of the system y(t) equal to Acos(4t)+Bcos(5t), when x(t) is the...
  38. M

    BJT Small Signal Analysis

    Homework Statement The questions states to draw the output voltage (Vo) for two full cycles knowing that we have a sine source with 2v amplitude. Homework Equations The Attempt at a Solution I've found: Ic = 1.303 mA Av (gain) = 1 I can't figure out why the output signal gets clipped...
  39. T

    Limits of pitch and time resolution in signal analysis (FFT/SFTF)

    With DFT/FFT/SFTF or similar Fourier transforms, there's always a trade off between frequency and time resolution. It's like the 'uncertainty principle' for signal analysis. I have a few questions regarding this: 1: With a theoretical infinitely fast processor, is it possible to obtain...
  40. S

    MATLAB Matlab Audio Signal Analysis

    Hi, I am trying to get a plot of the sound's magnitude vs. frequency. I have managed to read in a wav file as a matrix. I then compute the fft of this matrix. When I plot the absolute value of this, I get a symmetric plot with peaks at the start and the end. What is this a plot of? Is it...
  41. F

    Signal Analysis - Invertibility

    I don't understand why my book is saying that this system is not invertible. y(t) = cos(x(t)) ? Wouldn't, arccos{ y(t) } = x(t) and therefore be an inverse system?
  42. F

    Basic signal analysis (system invertible)

    Ok I have this really simple question that is bugging me. Lets say you have the signal: y(t) = x(t-4) where y(t) corresponds to the output, and x(t) the input. I know this system is invertible, but I don't really know how to show that this is the case. I see that the output is x(t)...
  43. P

    Signal analysis problem

    Sorry, but I don't know where the topic about signal analysis should go..? ---------------------------------------------------------------------- I'm doing research about quantifying blood flow in the brain. Basically I need to know how to perform deconvolution (I think.) I have two...