Signal and System

A signal as referred to in communication systems, signal processing, and electrical engineering "is a function that conveys information about the behavior or attributes of some phenomenon". In the physical world, any quantity exhibiting variation in time or variation in space (such as an image) is potentially a signal that might provide information on the status of a physical system, or convey a message between observers, among other possibilities. The IEEE Transactions on Signal Processing elaborates upon the term "signal" as follows:

The term "signal" includes, among others, audio, video, speech, image, communication, geophysical, sonar, radar, medical and musical signals.

Other examples of signals are the output of a thermocouple, which conveys temperature information, and the output of a pH meter which conveys acidity information. Typically, signals are often provided by a sensor, and often the original form of a signal is converted to another form of energy using a transducer. For example, a microphone converts an acoustic signal to a voltage waveform, and a speaker does the reverse.

Intro to Fourier Analysis

Fourier Series - part 1

Fourier Series - part 2

Fourier Series - part 3

Fourier Series - part 4

Intro to the Fourier Transform

Intro to the Discrete-Time Fourier Transform

Fourier Transform - Part 1

Fourier Transform - Part 2

Fourier Series - example square wave

Fourier transform - example rectangular pulse

Laplace Transform - example unit step

Intro to the Convolution

Convolution - example unit step with exponential

Convolution- example two rectangular pulses

Fast Fourier Transform (FFT)-tutorial