The High-Accuracy Logarithmic Receiver

There are numerous applications in electronics for a device which will derive "instantaneously" the logarithm of an applied function. If this operation can be accomplished accurately, the device has wide application in analog computing, for multiplying, dividing, and determining ratios. In addition, whenever compression of a wide dynamic range of signal levels into a restricted presentation range is desired, such a device is in general optimum. This paper shows how any arbitrary number of points distributed uniformly in amplitude may be made to fit a logarithmic response by means of the "successive detection" principle and how the deviation from true logarithmic response between these points can be essentially eliminated by use of the "multiple level detection" technique. The use of dc degeneration in an IF amplifier to stabilize tube characteristics is demonstrated, and three highly precise logarithmic receivers with bandwidths of 1.8 to 9 mc are described.