Questions tagged [frequency]

Frequency in signal processing is the number of cycles (of the signal) per second.

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Tracking a sine wave with noise

This will probably be an extremely simple question for some one with any background in signal processing(not my background) Let say I have signal $$x(t)=A\sin(\omega t)$$ where A is known and $\omega$...
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White noise in range of frequencies [duplicate]

If I have this function: while (true) { frequency = 8000; wave = sin(sampleNumber*2*PI*frequency/sampleRate) sampleNumber++; } it will produce an ...
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Difference between OFDM and FDM

In Frequency Division Multiplexing we provide one channel to one user. Example like BandWidth of user1's voice is 200Khz. I provide one channel of 200KHz in FDM for uplink as shown in the figure. ...
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23 views

How to calculate bitrate of PAL?

I have to calculate the bitrate of PAL format $\ (576*720) $. I have the following data: $\ 25 $ frames per second Interlaced Interior representation is: $\ 4:2:0 $ $\ 8 $ bpp I have tried the ...
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37 views

DC Components and Frequency

I have started learning digital communication and was on line coding. I read there are certain characteristics that we need to keep in mind while choosing the right line coding method. One of these is ...
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17 views

relationship of frequency with range in Underwater acoustic channel

I am interested to know what range of frequencies can be used/ or are effective for wireless communication, within the underwater acoustic channel. I do know a table exists from \cite{...
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How do I find the peak frequency of a wav file in python?

I am fairly new to python and signal processing and I was given a task to record audio for 'x' seconds and then find the peak frequency in the audio file. So far I have successfully implemented the ...
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45 views

DFT and integer valued basis functions'sf requencies

In Matlab the function W=dftmtx(N) gives the DFT matrix of size N. Each row is computed for an integer frequency k. $W_{k,n} = e^{-i2\pi kn/N}$, k-th frequency, ...
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Correlation between frequency and initial phase estimates using FFT

Why is there a high negative correlation between frequency estimation errors and initial phase estimation errors when measured using FFT? I have a simple code showing this negative correlation. is ...
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35 views

Power and Energy of an Audio file

I have a question about calculating the power and Energy of an audio recording. I have imported a waveform of an audio recording in WAV format into Matlab and then calculated the energy and power in ...
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43 views

Aliased Signal's Frequency

So I have an incoming signal of 137.9 MHz and a sampling frequency of 1.4 MHz. Once sampled how do I calculate the aliased ...
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23 views

Digital carrier recovery

I was reading Chapter 2 from "Telecommunication Breakdown" by Johnson and Sethares and came across this paragraph: However, sometimes it is more cost effective to perform certain tasks in analog ...
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96 views

Butterworth cutoff frequency normalization

The issue: I am trying to reproduce the step detection technique as described in this paper. You can see the proposed step detection in the image below. The first part of this technique is to use a ...
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64 views

Is there a good method to extract a reference sin/cos from a group of signals?

For the removal of a pure interference from a group of sampled signals, if I know the exact frequency of the interference I can simply use an I/Q demodulation technique (i.e., a phasor projection) to ...
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48 views

STFT output frequency does not match sin wave frequency

I have the following function and pre definition for producing a sin and its' stft: ...
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50 views

How to find frequency and corresponding time for an audio signal?

I want to read in a sound file and get the frequency at each time interval of the signal. I thought that the best way to approach this is by applying FFT to small chunks of the signal. Because FFT ...
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1answer
40 views

Calculate aliasing of $x_a(t) = \cos{(2\pi300t)} + \cos(2\pi600t)$ when sampled with $F_s = 1000$

I'm asked to sample the signal $$x_a(t) = \cos{(2\pi300t)} + \cos(2\pi600t)$$ with sampling frequency $F_s = 1000$ and plot the magnitude spectrum for the resulting sampled signal. My thinking is ...
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What does a fractional frequency (for discrete-time signals) mean/how to interpret it? [closed]

This question has bugged me for a while as it's not addressed in any books I've read. I was wondering how folks from this community interpreted it. Below are my personal notes on the matter (please ...
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Is it possible to create a causal filter with a positively-sloped phase response?

I am currently prototyping a set of noise-cancelling headphones that utilize active EQ to modify the noise-cancelling signal, allowing the user to modify the frequencies that they hear or don't hear. ...
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Practical Signal Processing by Mark Owen Exercise 2.1. and 2.2

The following exercises don't have answers in Practical Signal Processing by Mark Owen. What is the author looking for here? A mathematical proof? 2.1 A cosine wave of frequency f is sampled at $t = ...
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Complex Spectral Phase Evolution (CSPE) Performance depending on signal windowing?

I am look into CSPE. "Signal Analysis Using the Complex Spectral Phase Evolution (CSPE) Method" The method is simple. It compares the original signal's FFT and shifted signal FFT in phase domain so ...
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2answers
218 views

Do Fourier frequencies actually exist in real life in form of “fundamental frequency”?

For me, this is a very awkward question to be asked, as at this point in my studies I'm supposed to be quite expert with elementary mathematical tools like Fourier transforms, but this has always ...
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Interpreting results of multiplying signal and wavelets in the frequency domain

I have followed a lot of stuff on mike cohens website and have managed to make a filterbank of Morlet wavelets and convolve with an incoming block of samples. This of course is a computationally heave ...
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75 views

Term for integral multiples of fundamental period?

As we know that a signal has fundamental frequency and integral multiples of fundamental frequency are known as harmonics I am curious about the term that will be used for integral multiples of ...
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Formant Analysis Frequency - What makes a peak value?

from spectrograms, how can you tell which peak is really a formant. Like why is the pink arrow the first formant. And in the spectrogram below, which has fewer samples, what makes a value the peak ...
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159 views

Chebyshev I or Chebyshev II?

I am new to DSP, and I am trying to recreate some analysis of a signal, They use a chebyshev I filter to go from a 100Hz signal to a 50Hz signal. Whereas I am currently using a chebyshev II filter, ...
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histogram bin size vs. data sampling rate

I have a set of numerical signals that give me a set of zeros calculated based on some numerical procedure. I make a histogram of those zeros. Here, a following problem arises: If the histogram ...
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282 views

In case of using a Doppler radar, do we have to use IQ demodulation to find the direction of a target?

I want to know the way to find the velocity of a target by using a doppler radar. I read some paper about it, In summary, send rf signal to a target receive the reflected signal from the target. ...
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How do I find the frequency of a particular bin in a cosine transform, and two other questions

I have a discrete series of values and I have applied a Discrete Cosine Transform to it, obtaining values like: ...
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May I know how to find Time frequency power spectrogram of a signal?

I am analyzing EEG signal and I am unable to understand the term Time-Frequency Power Spectrogram. Please Can anyone help me? Thank you in advance.
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89 views

How is frequency related to data rate?

How does (if it does) frequency affect/relates to Data Rate. Why for example using the same modulation, LoRa (in the physical layer), you get somewhere around 250kbps at 2.4Ghz and only 20kbps at ...
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638 views

What are real-valued and complex signals and why is the Fourier transform of a real-valued signal Hermitian?

I have confusions in these concepts: What are real-valued signals? What is the difference between it and complex signals? Why is it so that for real-valued signals, the spectrum of negative ...
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Temporally locating beats in an audio file

Imagine you have a long recording of a guitar player playing an arpeggio at a slow speed. To simplify, assume the tempo is 60 bpm or lower. I want to annotate this recording with the exact moments ...
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user multiplexing in NOMA system

when two users are multiplexed in downlink noma system using the same subcarrier i,the throughput can be expressed as How to form the throughput expression in downlink noma system when two users ...
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Downlink NOMA system

In what manner does subcarrier,frequency,channel are related in downlink NOMA. How does the subcarrier allocation takes place when users are getting grouped into clusters on the same frequency....
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249 views

What is the relationship between angular frequency and normalized angular frequency

This is a slide from my lecture notes: My professor used the following words " We denote digital frequencies with capital letters and analogue frequencies with lower case letters" The problem I have ...
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234 views

Noise power and bandwidth

$$N=kTB$$ In this formula for calculating noise power, why do we use the total bandwidth of the system? I mean our signal is at $f_0$ carrier frequency, why is it effected by a large bandwidth and ...
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26 views

Frequency spectra of a sampled process

I have a process $X$ with frequency spectra I sample this process with sampling frequency $f_s = 2$. What will the frequency spectra $R_z(f)$ of the sampled process $Z$ look like? I realize that ...
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240 views

How to increase resolution of FFT?

I have an input signal in the ( 0 - 20 kHz ) frequency range . When i sample this signal maximum sampling frequency is around 40 kHz . When i calculate the FFT using 1024 points i got resolution of ...
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162 views

Best Way to Extract Frequency from Signal [closed]

I want to send signal that compound from 16 different frequency over GSM. The problem is the GSM network is very noisy and I have only 400-3400 hz frequency available for use. I try using fft ...
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The Definition of Q Factor by an Equation and How to Graph

I am currently building an EQ in an music app, and it's relatively simple: 6 bands of fixed center frequency, and a Q knob to control the Q of all bands, because we do not currently have space for ...
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How to make sure that a sinusoid wave with different subsequent frequencies matches up?

A very basic formula to transform a sequence of notes into a signal would be: $$ x(t) = A\cos( 2 \pi (2^{current\_note}/12) t) $$ where $current\_note$ is $notes[\lfloor t / period\_per\_note\...
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87 views

Why do we use normalized angular frequency?

Let's say we want to generate a signal in MATLAB, using sin, representing the A-major chord (440 Hz, 550 Hz, 660 Hz, each with amplitude 0.1). I know we have to use the normalized angular frequency. ...
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81 views

Visualising OFDM subcarriers in the frequency domain

Im struggling to understand why in some images the frequency domain shows clear bars with amplitude and phase and with 0 frequency variation (it is clear that the frequency of the waves does not ...
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102 views

What is normalized angular frequency? [duplicate]

I am new to DSP, and I am self-studying. I came upon this question, and I am stuck at it. Could someone please help me? Here is the question: In order to digitally create a sinusoid with frequency $...
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3k views

Write a 440 Hz Sine Wave to .wav-File using Python and SciPy [closed]

This is my first post on DSP.SE! I'm a student in Computer Sciences and am just getting started with Signals and Systems, thus getting in touch with discrete signals and analyzing them. I wanted to ...
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142 views

How can I get the power of a specific frequency band after FFT?

I need help with my matlab code. I have recorded EEG data and now I want to analyse it in matlab. I want to find the mean power of specific frequency ranges (theta: 4-8 Hz,alpha: 8-12Hz etc.). For ...
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93 views

Why a DFT of two sinusoids is very noisy even with frequency sampling 5 times higher?

I've set up this case to try to understand DFT implementing a real case in Excel Frame Size $\;\color{blue}{(T = 5 \; s})$ Time Sampling $\;\color{blue}{(T_S = 0.1 \; s})$ Block Size $\;\color{blue}{(...
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Why is it called continuous-time frequency?

I'm just wondering about the CTFT. My lecturer refers to capital Omega $\Omega$ in the following as being the continuous-time frequency: Why is it called continuous-time frequency here but in the ...
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Break a signal into segments, add them together and then perform an FFT on the result

If you break a 4 second signal into 0.5 second segments, add them together and then perform an FFT on the resultant 0.5 second data. Will the FFT / frequency spectrum be the simlar to an FFT on the ...