ABSTRACT
This chapter addresses signals that must be, somehow, captured by an instrument, and recorded and converted into electrical signals to be conveniently studied, analyzed, or applied. There has been a worldwide concern with the quality of the electrical energy supplied to consumers by utilities, which is normally related to transient variations and distortions in the alternating voltages. Harmonic analysis means determining the three most interesting characteristics of each harmonic content: amplitude, harmonic order, and phase. Signal distortion analyzers serve to decompose electrical signals into their most significant aspects, i.e., related to amplitude, frequency, and phase. The RF analyzers are of the heterodyne type usually with an intermediate frequency (IF) accurately generated by a local oscillator, i.e., tuning of the local oscillator shifts the various signal frequency components to the passband of a standard commercial IF amplifier. Spectral analysis is useful to determine the amplitude, frequency, and phase of each harmonic component for the observed signal.
