Corrective Networks

electrical networks used in multichannel communications apparatus and radio equipment (usually to reduce distortion of the signals passing through them) or in automatic control equipment and servomechanisms to impart to them the required static and dynamic characteristics. Various combinations of inductance coils, capacitors, and resistors are used as elements of corrective networks.

This distortion that takes place in complex signals upon pas-sage through the various circuits of radio equipment is of two types: frequency distortion, which is due to the unequal amplification and attenuation of different oscillation frequencies in a signal (that is, the amplitude-frequency characteristic of the circuit), and phase distortion, which is due to the unequal phase advance and retardation in different oscillation frequencies (that is, the nonuniformity of the signal’s group propagation time). In receivers for sound radio broadcasting and radio communications, only the frequency distortion is corrected, because the human ear is virtually unable to detect small phase distortions. In television and radar, the pulse-signal receivers have circuits that correct both frequency and, to a large extent, phase distortions. Phase distortions may also be corrected separately. In automatic control devices and servomechanisms, corrective net-works used mainly to perform differentiating and integrating operations on unmodulated signals are the most common. In automatic control systems they are used to perform more complicated operations on the signals. Such corrective networks are defined according to their amplitude-frequency characteristics.