This book was featured on the Keysight RF Test blog with the following recommendation: "This book collects the essentials in one place, with the techniques, equations, explanations and examples that you’ll need to do the whole measurement job." The earliest version of this book appeared in the 1990's, the new edition has updates to cover recent developments such as "real-time" spectrum analyzers.
Logarithmic amplifiers provide an output voltage that is logarithmically scaled relative to the amplitude envelope of the input signal. Historically these have been used to provide logarithmic Y-axis scaling to spectrum analyzer displays, for example. This app note describes the basic block diagram and principles of operation of a log amplifier.
This application note from Agilent describes the challenges of measuring distortion products from your device under test. The challenges arise from the need to measure weak distortion product and harmonic signals in the presence of strong carrier signals, combined with the fact that the analog components in the test instrumentation produce their own unwanted distortion signals.