An imaginary number is a part of a complex number. Complex numbers are an extension of the real numbers. A complex number has a real and an imaginary part. The imaginary unit (i) is equal to the square root of -1. The complex conjugate is a pair of complex numbers with identical real parts and imaginary parts which differ only in sign (e.g.: 3 + 7i and 3 - 7i).

Conversion of the analog signal to a series of digital values by measurement at a set of particular times; this utilizes the analog to digital converter. If the rate of sampling is less than twice the highest frequency in the signal, aliasing will occur. The duration of sampling determines how small a difference of frequencies can be separated.

See also Algorithm, Trigonometric Functions, Digitization, Exponential Functions, Imaginary Number, Logarithms, Point Spread Function.