# Questions tagged [amplitude]

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### Envelope detector for non-zero mean signal (Matlab)

I used hilbert transform to get an envelope signal. envelope = abs(hilbert(inputSignal)) This works for zero-mean signal: But, for nonzero-mean case, ...
2k views

### Quadrature modulation for FM and AM

This might be a naïve question, are these correct statements? Both amplitude and frequency modulated radio signals nowadays use quadrature modulation and demodulation as a mean to transfer and ...
95 views

### When to use raw signal strength, vs. when to filter first

I am collecting I/Q samples from an RTL SDR dongle. I notice the rtl_power utility provided for Linux filters and does other processing, before reporting signal ...
67 views

### ssbmod single sideband modulation artifacts

clc; clear all; close all; [c,fs]=audioread('60hz.wav') r=ssbmod(c,160, fs) r=r/max(max(abs(r))) audiowrite('artifacts.wav',r,fs,'BitsPerSample',24) I am trying ...
246 views

### Why does QAM use two cycles instead of one per byte?

If you look at this image, you can see that you have 256 possible binary values by modulating the amplitude (the radius of the trigonometric circle) and the phase (the degrees) of the carrier. ...
3k views

### Amplitude transfer function

Given a LTI-system $$y[n]=x[n]-2x[n-1]+y[n-1]- \frac{8}{9}y[n-2]$$ The transfer function $H(z)$ is: $$H(z) = \frac{1-2z^{-1}}{1-z^{-1}+ \frac{8}{9} z^{-2}}$$ How do I calculate the amplitude ...
3k views

### How do I calculate the frequency of the highest amplitude wave?

I have a number of values retrieved from a sampled signal that is generated randomly for no specific purpose. The task I am presented with (Quoted below): calculate the frequency of the highest ...
58 views

### amplitude at exact frequency in wide band signal

Could anyone suggest the most computationaly efficient method for finding amplitude of exact frequency having a noisy wide band signal. To be more specific about a task. I have some physical ...
217 views

### How do I find amplitude modulation effects in natural signals

It is relatively easy to discover overlaid (additive) signals in natural phenomena using wavelet decomposition, Fourier Transforms, CEEMD, etc, because addition in the time domain is the same as ...
5k views

### Extracting accurate phase and amplitude information from FFT with an arbitrary number of samples

This is a followup question to one I asked earlier based on the chat after the answer given by @hotpaw2, and cross-posted from stackoverflow since it was suggested it is more relevant to DSP. I have a ...
76 views

### DAPSK bit assignment for the amplitude difference

I am studying DAPSK(Differential amplitude phase shift keying) at the moment. I have a 64-DAPSK. We are using 4 concentric rings and 6 bits per symbol. The first two bits contain the information of ...
1k views

### DFT normalization for amplitude estimation

After an interesting recent answer, I'm doing some research on proper DFT normalization for sinusoidal peak estimation. It's clear that to get the correct amplitude from DFT peaks we need to normalize ...
88 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 ...
500 views

### How do I calculate the autocorrelation of a train pulse having only the pdf?

I have a pulse train of a fixed period, but a random amplitude following a Gaussian distribution $(\mu=0,\sigma=1)$. I know how to work with a random period or delay, but how do I proceed to calculate ...
492 views

### Scale of Amplitude in FFT (Matlab)

Using Matlab's FFT function, I am getting different Amplitude values in a particular frequeny, when I use different range of Bandpass filters centering around that particular frequency. What's wrong ...
89 views

### Why does the standard waveform from audio out get distorted when I reduce the amplitude?

In my attempt to generate a standard sine wave out of a sound card, I started using matlab which has a function soundsc for scaling the output ...
323 views

### Amplitude of an image

If I take a two dimensional image and conduct a fourier transform on it, I would get a two dimensional matrix of complex values. If I want to find the amplitude of each value, is that the same as ...
196 views

### In speech recognition applications, how are different voice amplitudes handled? (i.e loud vs. quiet tones)

I am doing some research related to real-time voice/hotword recognition engines. In most current implementations, input is divided into frames (overlapping or not), and audio features are extracted ...
885 views

### What's the fastest way to get the phase angle and amplitude of a COSINUS 50hz signal?

I'm not a DSP specialist.I'm working in transmission and distribution. I need to retrieve the amplitude and phase angle of a discrete 50Hz COSINUS signal as fast as possible. Right now I'm using a ...
592 views

### How to show the time history of a signal down-sampled ? under the rate of 25Hz & 40Hz and find its DFT analysis?

How to show the time history of a signal down-sampled under the rates of 25Hz & 40Hz and find its DFT analysis using Matlab ? The sample signal is in a data file (sensor_data.mat) its sampling ...
2k views

### What is the right way to extract particular frequency phase information from FFT?

Signals acquisition: Two proximity sensors are positioned Orthogonal to each other. These would be measuring the vibrations of a rotating shaft. Problem: Each of these 2 signals has two dominant ...
76 views

### What is the reason for “random” spikes in amplitude of a guitar waveform?

In the image below there is the waveform of a clean, strummed guitar note, where the absolute value of the amplitude values has been taken. At the point marked there is a momentary spike in amplitude ...
468 views

### Calculate amplitude of noise added Sine Gaussian signal from frequency domain

How to calculate the time domain amplitude of noise added Sine Gaussian signal from corresponding frequency domain. Here time domain amplitude is 2. How to get this from frequency domain. ...
1k views

### Amplitude of frequency in MATLAB FFT

I am trying to extract amplitude of specific frequency in Matlab FFT. Is it possible to use the abs(mag)... But I do not know in which sample to look for ...
48 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 ...
404 views

### Extracting amplitudes of components from FFT

I have a 4096-point FFT of a continuous pipe organ sound (no windowing). I wish to extract the relative amplitudes of the various harmonically-related sinusoidal components for voicing analysis. I ...
40 views

### Amplitudes and phases of transform of an image

I have recorded an image of a large macromolecule and after several types of image analysis, have obtained a rotationally averaged image, that is not quite perfect, but appears to show 6-fold symmetry....
1k views

### A clarinet has no even harmonics. What would produce no odd harmonics?

According to this link, the waveforms of clarinets do not have even-numbered components in their harmonic series: A closed cylindrical air column will produce resonant standing waves at a ...
3k views

### FFT Overlap in Matlab

I am getting incorrect amplitude of my signal post FFT (90% error) and it does not improve after applying any of the window functions prior to FFT. After reading a number of articles, I believe FFT ...
11k views

### Converting raw I/Q to dB

I am getting I/Q data from a software-defined radio. I want to do some stuff on signals in the data, but only if it exceeds a certain range. What is the general procedure to get dB (dBm, or anything)...
344 views

### How to find phase difference between 2 signals, one has an unknown function

I have a system that is forced by a sinusoidal function with specific amplitude, phase and frequency ( all these are known ahead of time). I get a deformation of sinusoidal form as well (think of a ...
78 views

### Phase difference betwen 2 signals, 1 signal with unknown function

I understand this question may have been addressed however I have a major difference. I started out with a sinusoid of form A*sin(2 pi freq t + phase) and I know ...
2k views

### Relationship between Fs (the Nyquist frequency), and the frequency used with a sine wave

Say you are given a vector t =[...] for the time to be used to generate a sine wave of a certain frequency say FHz. I have all the data for t so I can conclude what dt is (my dt = 1d-5). Now I am to ...
314 views

### Amplifying part of a signal

If I want to amplify a certain frequency in a digital signal, can I just take the FFT, increase the real part of the value for the frequency I want (leaving the imaginary part alone), and then take ...
417 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 ...
2k 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 ...
5k views

### Why FFT does not retrieve original amplitude when increasing signal length

I don't understand why FFT return different maximum amplitude as the signal length increase. I would except that with a large signal length according to the frequency, detected amplitude will be very ...
512 views

### Is phase and amplitude information necessarily lost when undersampling?

Is phase and amplitude information necessarily lost when undersampling if you have a constant periodic single frequency sinusoidal? My second question is: How can one determine the undersampling ...
3k views

### How is the symbol error rate for M-QAM, 4QAM,16QAM and 32QAM derived?

How do you derive the theoretical symbol error rate as a function of $E_\mathrm{b}/N_0$ for 4QAM? I know that the result should be $Q\left(\sqrt{2E_\mathrm{b}/N_0}\right)$ but I am ĺooking for the ...
154 views

### Amplitude Spectrum, Nyquist Frequency, mixed/min/max wavelets

The problem is here. Now I know the definition of mixed/max/min phase wavelets, whether the roots lie within the unit circle or not. Starting from n = 1, let $$x_t = ( 5, 6)$$ $$X(z) = 5 + 6z$$ ...
1k views

### Simulink for Amplitude Modulation

I am using Matlab Simulink to analyse Amplitude Modulation in Noise. I attached my system below. My problems: 1)In the mixer I am using a bandpass filter and another one after the envelope detector ...
2k views

### Java amplitude processing

I have some code that collects amplitudes from a complex sound like a song. I now want to plot a graph of amplitude vs time, for the graph plotting I use JavaFX. However I get about 9 million ...
4k views

### Adequate representation of frequency domain amplitude/magnitude of FFT of a signal

I'm quite new to the subject and am having fun playing around with the FFT. What I am currently doing is trying to sample an audio signal and display its frequency spectrum at the same time. This ...
122 views

### Obtaining the frequency and phase spectra from fourier transform?

For a question on my homework, I am given f(t) = e^(-a*abs(t)) and asked to find the Fourier transform of the function. I understand how to do that part, but then ...
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### Equal power crossfade

I am working on an audio system where I need to implement an equal power crossfade between two signals over a specified number of samples. Initially I implemented a linear fade but this creates a dip ...
176 views

### how to make fft ignore phase shift when only interested in magnitude

I have a signal that consists of a sine wave, on which I apply a rectangular window and then an FFT. I'm only interested in the magnitude of the sine wave, and I want it to stay the same even if the ...
229 views

### Estimating the amplitude of a particular frequency

I am relatively new to DSP and have been reading a lot on the internet. I have a couple of questions. I have a signal in the form of a function  f(x) = A_0 + A_1 \cos(\omega_1 x) + A_2 \cos(\...
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### Perform lowpass filter by hand

I've done research and could not find any resources on this topic. I have message signal composed of more sinusoids. Then I preform amplitude modulation, that is multiply that signal with higher ...