TABLE OF CONTENTS The various methods and tools of the art of microwave direction finding have been presented with many details. Like all complex designs, there is often a single forcing function that governs. In some cases, it is performance; in others, size; in most, it is cost. To be complete, it is also necessary to be familiar with how the outputs of the DF system will be used in conjunction with other subsystems. Many of the techniques, methods, and devices discussed in this book are abstract. This chapter will examine the methodology of significant hardware aspects of passive direction finding from a practical viewpoint; that is, the analog processes of detection and amplification over wide dynamic DF range, associated signal processing, and the popular forms of radar warning and electronic intelligence DF display.
The logarithmic amplifier finds wide use in passive direction finding systems and can be a major factor in performance/cost trade-offs. These amplifiers are used to perform two essential functions. The first is the compression of a wide input dynamic range to a manageable output dynamic range; the second is to provide a convenient mathematical method to form the monopulse ratio for normalization. This is done by subtraction of the logarithmic outputs that form the logarithmic fractional ratio. In passive direction finding, the wide variation of pulse characteristics and the need to cover large instantaneous RF bandwidths have channeled the evolution of the logarithmic amplifier into specific configurations.
There are four basic types of logarithmic amplifiers: the...
