Restoration and Correction of Time Functions by the Synthesis of Inverse Filters on Analog Computers

Time functions of physical phenomena may be deliberately or inadvertently altered before recording by a system whose bandwidth is less than that of the signal. It is often desired to later restore such data by removing the effects of linear filters. This restoration may be accomplished by synthesizing inverse linear filters on either analog or digital computers. Approximations are sometimes necessary to insure stability of the inverse filter; compromises must be made between amplitude and phase distortion, dynamic range, bandwidth, and signal-to-noise ratio. Examples are shown in which test signals are first filtered and then restored. The analog computer treatment has proved useful in processing geophysical data.