Origin of This Chapter

The author of this book makes only a limited claim to the originality of this chapter. It has been re-written from Chapter 10 of US Department of the Air Force Manual 52 8, entitled Radar Circuit Analysis, published June 30, 1951. The entire chapter has been re-typed, edited, supplemented, and re-formatted. Some of this was done to more closely conform to latter-day technical writing standards, some to add more current information, some for clarification, and some to make it more closely resemble the style of the other chapters of this book. Most importantly, no information has been deleted or diluted, and useful information has been added. All the illustrations have been re-touched or re-drawn, and all the labeling in the illustrations has been re-typed. Some illustrations have been added; those taken from Manual 52 8 are so annotated.

One of the most significant areas of knowledge that differentiates the radar technician from others is waveguide and cavity technology. This book is intended for technicians with a foundation in electronics fundamentals, and knowledge of rf transmission-line theory is a necessary prerequisite for a good understanding of this chapter. Whatever the technician s background may be, it is unlikely that he knows much about waveguide and cavity theory if he has not previously been exposed to radar or some other type of microwave equipment.

Early radar systems operated at VHF, and even lower, frequencies. This imposed serious limitations because of the large size required of directional antennas.