# Questions tagged [frequency]

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

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18k views

### Why are sidebands generated in AM and FM?

When the signal is modulated onto the carrier in the electromagnetic spectrum, that signal occupies the small portion of the spectrum surrounding the carrier frequency. It also cause sidebands to be ...
12k views

### If Digital Signal has frequency components then why we don't use it

As we know there are two kinds of signals: analog signals and digital signals. And there are two common techniques for multiplexing the signals: Time Division Multiplexing (TDM) and Frequency ...
590 views

### Books that explain DSP well to those not directly in engineering?

I do work with computer graphics and am dipping my toes into ray tracing. That field involves a good number of the subjects covered in DSP (Fourier transform, time vs frequency space, etc) but I was ...
4k views

### I need advice about how to make an audio frequency analyzer

I just need some clarification of some very basic aspects of creating a frequency analyzer. I am writing a c++ program, so far it is just a media player, with a custom explorer. You can make ...
443 views

### Extraction of non-sinusiodal repetition rates

I have an auto-correlation function that was generated from a signal, and I am trying to extract its 'repetition rate' in order to calculate the dominant frequency of the pulse, but I am not exactly ...
3k views

### period of this signal

it could be a donkey question but I'm a little confused. I have this signal $w(t)=sin({\pi}0.1f)$. I have to calculate the period of this signal. $w(t)=sin(2{\pi}\frac{1}{20}f)$ the period of this ...
1k views

### Why does a wave continuously decreasing in frequency start increasing its frequency past the half of its length?

I'm trying to programmatically generate a wave (sine or square) with a continuously decreasing frequency. To do so, I simply multiply the starting frequency for a decreasing value, that linearly goes ...
20k views

### How to shift the frequency spectrum?

Lets say we have a spectrum ranging from -X MHz to +X MHz. I would need to correct the frequency error in the spectrum by shifting the zero component to the middle (0 Hz). If the output (the ...
2k views

### Efficient frequency offset estimation of known signals

Let's say that my receiver will be receiving known data signals that range from the very simple (tone) to the complex (known data sequence that is modulated (PSK/QAM/OFDM/etc.)). What are the most ...
3k views

### What's the best criterion for determining a frequency peak?

I'm writing an algorithm that analyzes results of discrete Fourier transform (DFT). The algorithm should detect amplitude peaks in predefined ranges of frequencies. This is an example of such a peak: ...
273 views

### Procedural wave generation, frequency shift issue

sorry for the long post but I want to try and get all the details in here in hopes it will help. I've been working on building a procedural audio system for use in XNA projects. First this is general ...
1k views

### Does down-mixing a signal before taking the fourier transform aid in signal detection?

Let us assume that we have a narrowband signal $s[n]$, at frequency $f_1$, and let us further assume that this $f_1$ is just below $\frac{f_s}{2}$, where $f_s$ is the sampling rate. Furthermore, let ...
1k views

### Noisy Frequency Estimation using Hilbert Transform

I'm looking for a way to estimate instantenous frequency with low time-variation. The following MATLAB function (save as test_fest.m) does this using the Hilbert ...
28k views

### What is the Gabor filter? And what are its main uses?

I'm doing research on the Gabor filter. When I Googled it, I found very long and complicated articles. Can anyone help me to find a simple explanation about it, or recommend a website or article to ...
244 views

### Modeling spring oscilliations with electric noise (50 hz)

I have Analog to Digital converter from which I get data of measurements of 1kg load. The aim is to model the simple spring-damper system, so that after entering correct initial data (x = a, x' =...
13k views

### Is there an algorithm for finding a frequency without DFT or FFT?

I was looking in the Android app store for a guitar tuner. I found a tuner app that claimed it was faster than other apps. It claimed it could find the frequency without using the DFT (I wish I still ...
2k views

### Find h[n] using DTFT properties

Using the DTFT property, find h[n] of a system where: Is it an FIR or IIR system?
1k views

### Detecting drum bpm in a noisy .wav file

I am looking for algorithm(s) to solve the following problem: Given a noisy .wav sound capture (some wind + friction noise on the microphone), how to detect the BPM of a soft drum beat? I have ...
2k views

### Apply wavelet transform to analyse EEG signal

I would like to apply The Morlet wavelet transform to analyse my EEG signals. I have many short signals each is only 1 min long. and they all recorded in 30Hz. I have Two questions: In the Morlet ...
301 views

### Angle modulation spectrum

Is angle modulation spectrum always discrete or this property only holds for periodic modulating signal?
4k views

### Choices of convention and notation for the Fourier transform?

The definitions of the Fourier transform and inverse Fourier transform I learned in college were $$F(j\omega) = \int_{-\infty}^{\infty} f(t) e^{-j\omega t}\ dt$$  f(t)=\frac{1}{2\pi}\int_{-\...
202k views

### What is meant by a system's “impulse response” and “frequency response?”

Can anyone state the difference between frequency response and impulse response in simple English?
579 views

### Weird results out of fourier transform of unknown signal, what am I doing wrong?

It has been a long time since I studied engineering, please forgive my mistakes. I got data sampled from a digital accelerometer. It is sampled at 20 hz, then collapsed into 1 second epochs. The data ...
77k views

### What is the physical significance of negative frequencies?

This has been one of the holes in my cheddar cheese block of understanding DSP, so what is the physical interpretation of having a negative frequency? If you have a physical tone at some frequency ...
1k views

### What mathematical model of audio can make possible pitch shifting of individual notes in (timbrally complex) polyphony?

My question is: What mathematical model of polyphonic sound can make possible the changing (i.e. pitch shifting) of individual musical notes in a multi-voice-in-single-channel audio recording of a ...
264 views

### Finding the input bit rate of an analogue input

Suppose I have 4 of 300bps synchronous digital input and 1 of analogue input with a bandwidth of 500Hz. The analogue input is sampled at 4bit using PCM. All the channels are multiplexed with TDM. As ...
384 views

### How can I calculate the frequency using different color bands?

Let's say that I have a 1 dimensional signal that has data which comes from one of 2 different spectral bands. The measurements come evenly mixed between the two bands. I'm interested in a method of ...
The Fast Fourier Transform takes $\mathcal O(N \log N)$ operations, while the Fast Wavelet Transform takes $\mathcal O(N)$. But what, specifically, does the FWT compute? Although they are often ...