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

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Fit a plane on a 2d picture

My supervisor gave me the hint, to fit a plane on a 2 dimensional image and substract it from it before doing the fast fourier transformation to reduce low frequencies. I get the low frequencies ...
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2answers
16 views

Frequency modulation of audio signals. Does increasing the pulse width of frequency tone result in larger operating distance?

I have a simple frequency modulation scheme where in I am sending simple textual data by encoding it into specific frequencies(for example 'a' is converted to ASCII value of 97 and I use 10 ...
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2answers
46 views

How compute frequency of signal from zero crossing? [duplicate]

I need to compute frequency of a signal from zero crossing.It's possible to compute to frequency from zero crossing of a signal. Plz anybody help me about this with matlab .
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3answers
100 views

FFT bin interpolation for low frequency with DC offset

I have a noisy signal in I/Q format with a peak frequency that constantly changes between 0.5Hz and 4Hz. The sample rate is 64Hz. I want an output showing the current peak frequency with a maximum lag ...
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31 views

How to scale fundamental frequency to [0,1]?

[Sorry for the noobish question...] I have a signal which is known to be generated by a process operating at some known rate $f$ Hz and the sampling rate is also know to be $K$ Hz. Now I do a ...
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22 views

telehpone sample file sounds different after band filter, even though the filter filters frequencies, which should not be in the sample signal?

I am currently working with speech samples recorded over a usual telephone. I want to apply a band-filter and try to filter some noise before trying to apply speech detection algorithms. I read that ...
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1answer
58 views

What is the minimum sampling duration to capture a given frequency?

Due to the Nyquist rate, you need to sample twice as fast as the highest frequency you want to measure. Then when you do a FFT the number of samples determines the number of bins and thus the ...
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2answers
90 views

Instantaneous magnitude

I was reading this thread: How to get Instantaneous Magnitude for a Instantaneous Frequency From FFT? I have basically the same question, but I'm curious about more detail about the Hann window ...
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2answers
61 views

How do I identify CUTOFF frequency from my audio signal? [closed]

I was able to recorded an audio signal through the MIC and i applied FFT and Hanning window function to it. Now I want to know how do I identify CUTOFF frequency from it to apply the High Pass Filter. ...
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1answer
64 views

Signal Sampling

I am new in this field (junior year) and I have a question may a little lazy for the majority of the forum. I have a speech signal $ x(t)=0.4\cos(100πt)+0.3\cos(1800πt)+0.2\cos(980πt)$ and I know ...
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1answer
32 views

Determine Frequency Resolution samples

Can someone tell me if the way I solved this problem is right? Suppose I have a signal $X_a(t)= 0.5cos(700πt)+0.6cos(720πt)+0.1cos(780πt)$ where $F_s=8000Hz$ I want to determine the minimum samples ...
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1answer
35 views

Magnitude value of filter frequency response

Can someone help me with this problem: Suppose we filter signals with the below pre-emphasis filter: $$y[n]=x[n]-0.8x[n-1]$$ I have to calculate the impulse response of the filter (ok easy) and ...
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2answers
58 views

FM demodulation amplifier with saturation

I'm trying to understand how FM demodulation works. I read a lot on the internet and as far as I understand, the main process is to extract the phase difference (that is also the output) between a ...
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2answers
50 views

Fundamental frequency

Can someone help me: I have a signal which consist of three frequencies; for example, $f_1=800\,\text{Hz}$, $f_2=1050\,\text{Hz}$, $f_3=1600\,\text{Hz}$. How can i compute the fundamental frequency? ...
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1answer
63 views

PLL and zero crossing detection

Is there an Algorithm which can give un the frequency and phase of a three phase signal (three phase voltages) without using the zero crossing detection. I mean an algorithm which is done in open ...
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1answer
26 views

how to write a frequency modulation formula in FooPlot? [closed]

I have tried to write a Frequency Modulation of a sine by another sine, and i can't manage sin(x*sin(x*10)) please can you write the formula for me?
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26 views

How to transform one graph to a spectrum?

Recently, I studied a paper called "What Does Your Chair Know About Your Stress Level? It can be download at the link below. ...
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1answer
91 views

Beat Detection with Arduino

I'm trying to make a robot dance on several songs using Arduino. I need to understand how to get the rhythm from the songs, something like detecting the beats, calculating the bpm.. I'm not expert but ...
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1answer
47 views

Frequency of a noisy signal with fixed width pulses

My electricity meter has a front panel LED which pulses in proportional to the current energy rate. The frequency changes but the pulse width is set at 250ms. Due to environmental conditions there's ...
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22 views

What is the relationship between signal and its analytical version?

Hilbert transform is used to transfer signal into analytical signal. But why after the transform, the envelop and instant frequency (if the signal is monogenic) can be calculated. What is happened in ...
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71 views

Confusion in the spectrum of FSK modulated signal by using matlab fskmod module

I want to do a comparison of power spectral density of BFSK, 4FSK and 8FSK by using matlab baseband module "fskmod".Following is ...
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1answer
53 views

Correlation between Sin and Square wave

I would like to know how $\frac T2$ came for time period in the image below.Because I think the frequncy is 1 so time period should be 1.Is that correct? or can anyone help me.. The article from ...
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2answers
267 views

Simple and efficient algorithm to detect frequency and phase of a sine signal

I need an algorithm to detect frequency and phase of a pure sine signal. The frequency of the input signal changes between 0 and 100 Hz. The value of the signal gets captured with a frequency of 20 ...
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1answer
52 views

Codec Output has “Wavy” Amplitude on Chirp Input

I am sending a chirp that sweeps form 20Hz to 500Hz to an audio codec, CS42L52, connected to an MCU, STM32F405, and I am receiving a "wavy" amplitude output. There is no processing on the MCU, I pass ...
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41 views

calculating frequency spectrum using fft for video

How to process video with DFT/FFT - getting the frequency using PCO camera in c#,and how to interlink video frames with frequency transform.
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1answer
54 views

Given two waves, 441 Hz and 700 Hz, how many samples long is each wave's period if the sample-rate is 48 kHz?

The title says it all. I have two waves, Master and Slave. Master is at 441 Hz and Slave at 700 Hz. The sample-rate is 48 kHz. I want to know how to calculate the period of each wave in terms of ...
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52 views

What are the frequency components of a sampled signal after low-pass filtering?

A continuous signal $x_a(t)$ is a linear combination of sinusoids of frequency 250 Hz, 450 Hz, 1 kHz, 2.75 kHz and 4.05 kHz. The signal $x_a(t)$ is sampled at $f_s=$1.5 kHz, and the resulting digital ...
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1answer
42 views

Effect of Sampling frequency on RMS estimation

I have a simple, but interesting question for you. I have to compute the RMS (root mean square or standard deviation) value of a time signal which represents in my case a velocity mesasurement over ...
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33 views

Selecting the number of cycles for wavelet transform

I'm trying some wavelet analysis of EEG signals, using the phase lock measures from [1], specifically the S-PLV measure. In order to calculate that we perform a wavelet transform on the signals and ...
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2answers
59 views

Signal corrupted using peak (biquad) filter at low frequencies

I'm trying to process an audio stream through a series of peak filters at static frequencies that range from 0 to nyquist. If I start the range from anything below about 25Hz, the audio gets corrupted ...
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1answer
61 views

What is the shortest time period that can be used to find the frequency of a signal burried in noise and harmonics?

I have a continuous-time signal that is of the form $$x(t)=A \sin(2 \pi f t+\phi_1)+B \sin(2 \pi (5f) t+\phi_2)+C \sin(2 \pi (7f) t+\phi_3)+n(t)$$ sampled at 50us where $f$ is the frequency I want to ...
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1answer
64 views

frequency divider

How would one implement a frequency divider? I know I can resample up and then treat it as if I'm at the same frequency, however I want to divide the frequency of my signal by 2 and keep the same ...
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1answer
93 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 ...
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50 views

Simplest approach to classify signal based on its 'smoothness'?

First of all, I have no experience with signal processing whatsoever and I may not even use proper terms so please bare with me. I am just humble software developer trying to find the simplest and the ...
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1answer
47 views

Can someone please help me out with audio, sampling frequency question

I really having a hard time to tackle the following question. It is asked to load a ".mat" file using load file.mat. And the result is two variables: Fs varaible ...
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123 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 ...
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76 views

Incorrect Frequency results when using Multiple Signal Classification (MUSIC)

I am using MUSIC (Multiple Signal Classification) to determine Direction Of Arrival (DOA) and frequency of signals impinging on an Antenna Array. I am using a function ...
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25 views

What filter should I pass to these signals to make them constant on every piece

I'm analysing the frequencies of something I'm recording (whistling), which is resulting like this (yes, it's super mario bros' beginning song: I'd like to filter it to make it remain like: in ...
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2answers
130 views

About frequency resolution [duplicate]

The frequency resolution of DFT is $\Delta f = \frac{1}{T_{0}} = \frac{1}{NT} = \frac{f_{s}}{N}$ where $f_{s}$ is sampling frequency, $T_{0}$ is sampling time, $N$ is number samples, and $T$ is the ...
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89 views

Can I ignore the Nyquist criterion?

If I have a signal with frequencies up to 2000 Hz but I'm only interested in the frequency range up to 500 Hz, is it correct to sample at 1000 Hz $(f_\mathrm s \geq 2 \cdot f_\mathrm{max})$? Or do I ...
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1k views

Determine whether a signal is periodic or not and get fundamental period

Here is my signal Cos(n/2)*cos(pi*n/4) cos(n/2) has period 4pi and cos(pi*n/4) has period 8 Now, the question is will the signal be periodic for fundamental ...
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1answer
150 views

How to normalize frequency in MATLAB

I know all about conversion of frequency from HZ to normalized frequency and from normalized frequency to angular frequency ,but I wonder how it is done in MATLAB. I have the following code: ...
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4answers
482 views

how to design a high pass filter to remove dc offset from signal

I want to design a high pass filter (f0*S/1+f0*S) in order to remove the dc offset from a signal ? (i.e. how to choose the frequency f0). Thanks, Hacene Ps : the filter is for matlab implementation, ...
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47 views

Calculating Energy Spectral Density from Magnitude and Phase data

I'm trying to do a program that can judge whether 2 audio files have the same pronunciation or not by comparing the frequency of them with each other. The first step, finding the magnitude and phase ...
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2answers
71 views

Tuning a radio to a certain frequency

I've a fundamental problem with understanding terminology used in DSP. What does it mean to tune a radio (for example, a software defined radio) to a certain carrier frequency $f$? The received signal ...
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2answers
120 views

What is the rate of change of amplitude? Frequency?

I know that frequency is not the same as the rate of change of amplitude, but why? Surely a high frequency is when your amplitude changes rapidly. Does an FFT perform something similar to ...
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78 views

Polarity inversion in frequency domain (polar coordinates)

I don't fully grasp how polarity inversion is performed in the polar coordinates of frequency domain. The frequency components of the signal do not change, so the amplitude part is going to stay ...
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1answer
73 views

what is the maximum instantaneous frequency of Dirac delta?

I wish to find the maximum frequency of $\sin(\varphi(t))$, where $\varphi(t)=u(t)$. We have $\omega(t)=d\varphi(t)/dt=\delta(t)$. What is the the maximum instantaneous frequency $\omega_{\max}$?
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Frequency-wavenumber filter

I have some data from a linear array and am trying to design a filter in frequency-wavenumber domain using 2D fourier transform. It is essentially a bandpass filter where I want to keep information in ...
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2answers
226 views

Android: fundamental frequency

I want to find the fundamental frequency for human voice in an Android Application. I want to use autocorrelation method. My code is this: ...