Spectrum analyzer is a device used to examine the spectral composition of some electrical, acoustic, or optical waveform. Often, it measures the power spectrum. Spectrum analysis is concerned primarily with characterizing signal components, (such as, its spurious and harmonic components, modulation, noise). Spectrum analyzer is used to locate frequencies where microwave energy exists. There are analogue and digital spectrum analyzers. An analogue spectrum analyzer uses either a variable bandpass filter whose mid-frequency is automatically tuned (shifted, swept) through the range of frequencies of which the spectrum is to be measured or a superheterodyne receiver where the local oscillator is swept through a range of frequencies. A digital spectrum analyzer uses the Fast Fourier Transform (FFT), a mathematical process that transforms a waveform into its frequency components in the spectrum. As a result, computer programs can compute such transforms, and makes audio processing easier. FFTs have applications in much wider fields. Spectrum analyzer is used in the measurement analysis of Distortion measurements, Modulation measurements and Pulsed RF measurements.