A Precision TVG for Echo Ranging Sonar

A sonar Time Varied Gain (TVG) circuit was designed in which the gain, as a function of time, is mathematically predetermined by theoretical equations that are programmed into the circuit by analog techniques. Essential to the design is a voltage controlled ac resistance device consisting of a transformer and two diodes. Use of this device as the output circuit of an amplifier results in a gain that, in decibels, is a linear function of the dc control voltage. This equivalence of decibels and dc voltages enables a simple analog computing circuit to satisfy the theoretical gain equations.