Questions tagged [power-spectral-density]

The Power Spectral Density (PSD) is the distribution of signal power over frequencies.

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206 views

Reason for decrease in the PSD gain with increase in the number of FFT points

what is the reason for that? The gain should increase ideally I guess. This is the code I tried. As I increase the length of F by zero padding,the gain of PSD reduces. ...
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1answer
601 views

Average Power Spectral Density of PAM signals

I am reading through the PAM transmission scheme and about the power spectral density of the signals. Given that the Average Power Spectral Density of PAM Signals is: $$ \Phi_{ss}(f)=\Phi_{aa}\left(e^...
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192 views

AWGN Build vs Randn noise do not match

I am generating noise in two different cases with the same SNR once using AWGN command which is a built in command and second time using randn function with the correct scaling however I am getting ...
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1answer
298 views

Compute Power Delay Profile (PDP) from Delay Spread

I have data pertaining to channel obtained from measurements. In order to make use of this data, I need to convert it into a form as follows: ...
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2answers
413 views

Why use cross-spectral density to calculate frequency response?

I am taking a class about system identification and currently learning about cross-spectral density. My textbook says that the frequency response, G, of a system can be determined as $$G=\frac{S_{uy}}...
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1answer
52 views

How to transform flat-field corrected spectra to those under Standard illuminant E (ideal equal energy illuminant)

My ultimate goal is to convert a flat-field corrected hyperspectral image of reflectance (360nm-780nm) to corresponding CIEXYZ image and thus device-independent color image. By flat-field correction, ...
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2answers
770 views

Cross Power Spectrum

Is it necessary that cross power spectrum (CPSD) should always be between power spectrum (PSD) of individual signals, irrespective of the method we compute it? The images are shown below.
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2answers
214 views

Is there an equivalent time-domain operation to the spectrum averaging in Welch's method?

In Welch's method a time-series is segmented and then the subsequent FFTs of the segments are averaged. Is there an equivalent time-domain operation? I guess doing the the Welch estimate and ...
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1answer
678 views

How do I modulate complex time domain signal to a carrier frequency?

I want to modulate a complex time domain signal to a carrier frequency 1880MHz but the sampling frequency is 30M which is smaller than Fs. I did upconversion using ...
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1answer
432 views

Determining power spectral density from a sample

To start, I have absolutely no background in electrical engineering, I am a computer scientist by trade. I'm currently working on a project where I am attempting to code a function that uses the ...
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1answer
735 views

How to evaluate Spectral Density of DC component vs. AC component during computing PSD?

When computing the PSD, how to manipulate the DC component?  PSD integral is the total signal power, does it include the power of DC component? In other words, if there is one signal with DC value ...
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2answers
289 views

Calculate the harmonics in the power supply of $50\textrm{ Hz}$ using FFT

I need to calculate the harmonics in the power supply of $50\textrm{ Hz}$. If suppose I need to calculate up to 20 harmonics. Then my sampling frequency by Nyquist criteria should be : $$f_s \ge 2 ...
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1answer
242 views

Do I need to bandpass filter the signal before applying the Zoom FFT algorithm?

Let's say I have an acoustic signal that I want to make a spectrogram of filled with broadband noise and tonals, sampled at oh, $44100\textrm{ kHz}$, and I want to zoom in on the band between $2600\...
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1answer
413 views

Creation of Brownian noise as random walk

I am trying to create brown noise by integration of white noise (random walk). I created Gaussian white noise. The histogram shows Gaussian distribution and Welch (and also FFT) shows flat spectrum. ...
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35 views

How are phases dealt with when using FFT with blocks

An FFT of a signal returns a complex number, with a phase angle related to the starting location of each frequency within the signal. If I have break my signal into blocks, and FFT them individually, ...
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1answer
340 views

A query on Power spectral density (PSD)

Say a narrow band signal $n(t)$ has Power Spectral Density (PSD) $S(f)$. If the signal $n(t)$ got multiplied by $\cos(2\pi Ft)$, then what will the PSD of resulting signal in terms of $S(f)$ be? Will ...
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1answer
420 views

FFT processing gain

I am working on radar received signal which is $15000\times 2008$ matrix. Here each row corresponds to one chirp or one signal, this way there are 15000 signals. The difference among them is just the ...
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2answers
163 views

Why is “$1/\mathrm{Hz}$” unchanged while converting$\mathrm{V}^2/\mathrm{Hz}$ to $\mathrm{dB}/\mathrm{Hz}$?

When computing power spectral density via Fourier transform and Parseval's theorem, one gets units of $V^2/Hz$ (e.g. Wiki). As a popular next step, the following unit conversion is widely used: $V^2/...
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1answer
80 views

find power of the signal

I have this signal: $$x(t)=\sum \mathrm{rect}\left(\frac {t-kT_0} {20}\right)+\mathrm{rect}\left(\frac {t-kT_0} {40}\right)+\mathrm{rect}\left(\frac {t-kT_0} {80}\right)$$ with $T_0=140$, pass it ...
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2answers
509 views

Frequency magnitude distribution of noise

By the Wiener-Khinchin theorem, we have a straightforward way to calculate the power spectral density for stationary noise. If we know the bandwidth of a system, we can further calculate the variance ...
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2answers
235 views

Need of $\tt abs()$ method when plotting a power spectral density for a given dataset

I am a newbie in signal processing and would like to know the significance of using the abs() function and squaring the values received as an output of ...
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1answer
2k views

Why DFT-SPREAD OFDM has lower PAPR than OFDM?

I just read 4G LTE/LTE-Advanced for Mobile Broadband, and found the content as below, If the DFT size M equals the IDFT size N, the cascaded DFT/IDFT processing would obviously completely cancel ...
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1k views

Interpretation of Clarke's Doppler power spectral density

What I understand of Doppler spread is that the relative motion between Transmitter (TX) and Receiver (RX) change the exposing time of signal. In rapport to a constant-distance TX-RX, a moving toward ...
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1answer
165 views

Cepstrum analysis - Cut off frequencies displayed

My inquiry is regarding the so called cepstrum analysis. By conducting some experiments, i have real time data at my disposal. The acquisition rate is 1600Hz. I wanted to try cepstrum analysis just ...
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1answer
15k views

Calculate the signal's average power

We have this signal: $$x(t)= 2 + 2\cos(2\pi f_0 t) + \frac{2}{T_0} \operatorname{sinc}\left(\frac{2 t}{T_0}\right)e^{j2 \pi 4/ T_0} + \operatorname{sinc}\left(\frac{2 t}{T_0}\right)e^{-j2 \pi 4/ T_0}....
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70 views

Epoching Data with no Events in mne?

I am new to Python and signal processsing, and I'm trying to create a spectrogram of EEG data taken during a course of general anesthesia. I would like to use MNE's ...
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365 views

How to choose notch frequencies for filtering line noise?

I'm using the function to filter out line noise at 60 Hz (and 120, 180 Hz) caused by electrical noise: ecogNotch In the case below I can effectively filter out the line noise with a notch filter at ...
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1answer
2k views

Average value of power spectral density

I have a spectra of power spectral density (PSD) (vector (1:1e6)) from experimental data (blue color). However I want to plot only average value of PSD (red curve)....
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734 views

Relationship between Wavelet transform and Fourier Power Spectral Density

Is there anyway to obtain the Fourier Power Spectral Density from a wavelet transform of a time series? I am particularly interested in this problem because I was wondering if there is any ...
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1answer
299 views

Oversampling while maintaining noise PSD

I'm designing a digital PID for control and stabilization of laser amplitude. The noise PSD of the laser intensity is around -140dB/Hz, and I want to servo that between DC and 100kHz. I think I've ...
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0answers
26 views

Appropriate model for IIR filter to compare with spectral ratios

A quick, basic question. I have measured spectral ratios - comparing a measured signal to an 'ideal' signal. I am fitting a specific, simple IIR filter to that data for transfer functions. So, if I'...
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1answer
376 views

Power Spectral Density of Sigma-Delta modulator

I am simulating a 3rd order SDM and I want to plot the PSD of the output. As you may know, the output is a sequence of pulses ranging from -3 to +4. The number of samples is $N$. The way I ...
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1answer
226 views

Confidence Interval For Frequency of Peak in Averaged Periodogram?

I am averaging periodograms from sets of ~15-25 experimentally measured timeseries all of the same length. To do this I am just summing the power in each frequency bin over all periodograms and then ...
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1answer
2k views

Power spectrum of 2D image: result interpretation

Let's say I have an image, which is NxN pixels in size. If I calculate the fourier power spectrum of this image, I get NxN values, with the highest distinguishable frequency at +- N/2 in each ...
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1answer
2k views

When to use cross spectral density versus cross correlation?

All my life, I've used cross-correlation to analyze the strength of the relationship between an input signal and the output signal. I use this to determine which ...
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1answer
620 views

PIsarenko Harmonic Decomposition method for PSD estimation

i would like to present steps for estimation Power Spectrum density using Pisarneko Harmonic Decomposition i would like to present code for step 1 part ...
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2answers
1k views

VSD in rms voltage

I am looking at a datasheet where they show a graph: $V_{RMS}/\sqrt{Hz}$ as a function of frequency = VSD (voltage spectral density). The question is: how can a spectral density be in RMS? The root ...
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1answer
108 views

Is Spectral Coherence (MSC) dependent to the initial amplitude of the comparing signals?

Given the signals \begin{align} x(t) &= A_1\sin(\omega t)\\ y(t) &= A_2\sin(\omega t) \end{align} Do $A_1$ and $A_2$ play a role in the $C_{xy}$ coherence estimator? MATLAB's ...
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200 views

Applying periodogram-based PSD

For plotting a Power Spectral Density graph based on FFT results, I had used two different approaches, but they produced very different results, and it'd be great if anyone knows why. Note: From this ...
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2answers
489 views

Effects of averaged periodogram (Welch's Method) on resolution?

I'm trying to make an app(running on an android phone) that can detect the frequency of a guitar string being played. I know it'll be hard to detect that but that's a problem I'll deal with later. ...
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1answer
314 views

Interpreting dataset of a power spectrum

I am currently working with kaldi, and are trying to make spectrogram plots of different audio files. Kaldi is a speech recognition toolkit. Kaldi frames its input in frames of 25 ms with a ...
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3answers
494 views

How should this fft output be intepreted?

I am currently reading some code, so I can understand how this FFT output is actually been stored. I have a function which computes FFT of audio file, and stores is in the format. ...
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1answer
2k views

How to explain this BER vs SNR behaviour?

I wrote a script in MATLAB to simulate an LDPC created using an algorithm of a colleague of mine. The parity check-matrix is regular and has dimensions $1012 \times 1518$ and the code rate is $R=1/3$. ...
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3answers
307 views

Derivation of PSD of sampled bandlimited random process

When a bandlimited random process whose PSD \begin{equation} S(\omega) = \begin{cases} \frac{N_0}{2} & -10B<\omega<10B\\[2ex] 0 & \text{otherwise.} \end{cases} \end{equation} is ...
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2answers
2k views

RMS averaging in spectrum analyzers

While studying spectrum analyzers I ran into the concept of RMS averaging as a mean to reduce dispersion of data without affecting power spectral density (PSD). What is not really clear to me is how ...
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1answer
108 views

How to read off power at different frequencies

In MATLAB, consider a signal y and its Fourier transform Y: ...
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1answer
2k views

Estimate the wavelength of an oscillatory signal

I need to estimate the dominant wavelength of a signal that is looking like this: My first attempt was using scipy.signal.argrelmin in Python in order to detect the ...
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1answer
3k views

Scaling for a 2D Hanning Window

I am trying to find the PSD of a 2D set of data and representing it as a function of frequency in both these directions. I start with a 2D FFT and generate the 2D hanning window for a $M\times N$ ...
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1answer
252 views

How to fit Welch's window segments to a time series of variable length

I'm trying to write a small Welch's PSD method in R right now, but I've had trouble finding information on how exactly the window segments are fitted to a given time series. For instance, when the ...
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1answer
1k views

Comparing PSD two signals of different length

I have two time signals A and B which are of different length, length(A) < length(B). Now I calculated the cumulative PSD of both signals. What is the best way to compare this result? If I am ...