# Tagged Questions

Power spectral density. PSD shows the signal power distribution over the frequency.

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### How to convert fft plot into PSD(Normalized) vs Freqeuncy (Hz)

I am trying to convert my fft signal into PSD(Normalized) vs Freqeuncy (Hz) but can't get it right. I want to get some thing like shown in the figure. I found these figures in the literature. How to ...
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I haven't been doing much signal processing over the years and I'm wondering if my logic is sound. I'd appreciate any input. So, I have a data set with independent variable ($A$) in Frequency ($1\... 2answers 84 views ### Why Fourier Transform doesn't show obvious periodicity? I have a clearly 4Hz periodic signal (see image below). However when I apply a fourier transform, there is no peak at 4Hz. Also, when I do a power spectrum density (using Matlab's pwelch algorithm), ... 0answers 47 views ### Calculating the SNR from the power spectrum I have a signal that is sampled at 20 Hz. It has almost stationary behavior, with a main frequency around 1.0-1.5 Hz. This frequency range is to be expected and is of interest for further processing. ... 1answer 56 views ### How to calculate the discrete power of a discrete signal? If I have a time series defined by a series like $$x = [a_1, a_2, a_3, ..., a_n]$$ for time from$t = 1$to$t = n$How can I get to the power of the signal in this form: $$P_x = [p_1, p_2, p_3, ... 1answer 94 views ### Apply band pass filter (BPF) before calculating the power of a signal (PSD)? From my understanding PSD tries to give a good estimation on the power each frequency attributes to the overall signal power. If I am only interested in a frequency range (\omega_0 \leq \omega \leq ... 3answers 63 views ### Logaritmic amplitude squarewave This morning i was experimenting with GNU Octave. I created several signals(Sine, Saw tooth, square wave and noise). After this i used the periodogram. in the periodogram the square wave weren't ... 1answer 37 views ### Correlation in DSBSC modulation Suppose we have a DSBSC signal given by :$$s(t) = 10 \cos (2\pi f t + \phi ) \cdot m(t) $$where carrier is random signal with phase (\phi) uniformly distributed in [0,2\pi]. If ... 1answer 56 views ### Obtaining power spectral density without having knowledge about frequency bandwidth or sampling frequency of the signal in Matlab? Is there a way to plot PSD of a signal which show true frequency amounts ( not normalized one) without having knowledge about frequency bandwidth or sampling frequency of the signal in matlab ? 0answers 196 views ### How do we calculate Power Spectrum Density (PSD) which is given in dB/Hz and not just dB? I found many definitions for this quantity, PSD. In a document on signal analysis by National Instruments say that it is the amount of power in a unit bandwidth. Let's say P(f) is the power of the ... 1answer 60 views ### How to calculate the noise power for a non-stationary noise? With stationary noise we have constant mean and variance (let's assume it is Gaussian noise). My first question is, how is the noise power calculated and how it is related to the variance? Now, I ... 1answer 150 views ### PSD scaling due to the windowing I am struggling with the following problem for a while: If I have signal of duration N and I apply window (assume rectangular window) of size M < N how will this influence PSD of that signal after ... 1answer 169 views ### Conversion of FFT to PSD I would like to convert FFT data which is set of 396 values for 396 frequencies (from 4Hz to 399Hz by 1Hz) in unit of g's (gravitational akcceleration) to PSD in unit of (g^2)/Hz, is it possible? ... 2answers 748 views ### Power spectral density vs. FFT bin magnitude What's the difference between these? Both are measurements of some form of signal power, but surely there's some difference between the power they are measuring? 1answer 58 views ### Coherence vs. Magnitude Squared Coherence currently I am writing my masther thesis. The theory part is about the turbulent wind field generation, where the coherence (not magnitude squared) is used:$$\text{coh}(f) = \frac{|P_{xy}|}{\sqrt{P_{... 0answers 383 views ### Generate time-domain random signal from PSD Given an analytical description of the PSD, for example (MATLAB "pseudocode"): ... 2answers 131 views ### Can I see from the PSD if a system is a LTI system? I am studying the meaning of the power spectral density (PSD) and I am wondering whether I can see from the PSD of the input signal and output signal if a system is a LTI system? 1answer 159 views ### What is the best Algorithm to estimate the frequency for Almost-Periodic Data or complex periodic data? I’ve got what it looks like a periodic signal but the periods seem not equally repeated, I want to estimate the PSD, particularly I need to obtain the dominant frequency of this data. I’ve estimated ... 0answers 153 views ### Welch's Overlapped Method I am measuring wind speed using a number of different anemometers. These anemometers are placed on a structure which exhibits sinusoidal motion. Thus, the signal of the anemometers contains both the ... 0answers 366 views ### What is the best method to estimate the frequency(PSD) for noise signal I’ve been trying to estimate the frequency of a signal I obtained at 1000Hz sampling frequency. The dominant frequency is expected to be not more than 4 or 5 Hz. I’ve estimated the PSD using ... 0answers 47 views ### Can uneven sampled points generate valid PSD and spectrogram? My recording device samples signal at 100 Hz. At each sampling point, it generates 512 values (I assume due to non-ideal impulse in practice, so each impulse is actually a window with certain width ... 1answer 101 views ### Effect of number of data segments in Periodogram-based PSD In Welch or Bartlett method, original signal is divided into L segments, of D overlapping (D=0 in Bartlett method). Then FFT is done for each segment, and the result is the average of all segments' ... 1answer 229 views ### Is the periodogram squared-magnitude DFT or squared-average DFT? How is the periodogram defined? I have been searching the internet a lot, and I find two different definitions: periodogram is the squared magnitude of the DFT periodogram is the squared average of ... 1answer 203 views ### What's the number of data points in a Welch-based PSD? In Welch periodogram Power Spectral Density estimate, we devide the N-long signal into K segments, each of length L with overlapping D, such that N=L+(K-1)*D. In this paper, just above eqn (7), the ... 1answer 532 views ### Calculating the Power spectral density I've already asked this question on SO, but didn't get an answer, I tqake a shot here. I am trying to get the PSD of a real data set by making use of fftw3 ... 1answer 162 views ### Will using window in Welch's method introduce artificial peak in estimated PSD? I'd like to estimate the power spectral density of the signal attached here, the sampling rate is 100 Hz. If I don't do windowing (i.e., use boxcar window), the result seems to be a simple$1/f^2$... 2answers 3k views ### PSD estimate using FFT - scaling and units I know that similar questions have already been asked – I have read the answers, yet I am still not sure if I understand the topic properly at some points. I want to use FFT to calculate PSD ... 0answers 51 views ### Importance of phase of time-series for PSD I have$m$complex-valued time-series$z_m(t_n)$, which I am currently analyzing. I started by calculating their PSDs and CSDs. These exhibit an unexpected peak at a given frequency, which is present ... 1answer 119 views ### Only random signal has PSD? I heard from someone online who said: "Only random signal has PSD, determinate signal does not have. For example, period signal does not have PSD." I am very astonishing about this statement, but it ... 2answers 281 views ### What can we deduce about variance when we are given the noise spectral density? Given the noise spectral density${N_0\over 2} = a$, what can be deduced about the variance? In the case of a two-symbol canal(/cable), and when$T_0 = 1$. Is it that,$\sigma_X^2 = {N_0 \over 2} *...
Trying to understand whether or not I am calculating the PSD correctly. Below is the equation that I am using:  PSD_{rms}(f_{m} = m \cdot f_{res}) = \frac{PS_{rms} }{ENBW} = \frac{2 \cdot \left | ...