Radar is one of those special application areas for RF/microwave technology: it serves not only the military, but commercial, industrial, and sometimes even medical users. It has come a long way over its lifetime, a lifetime that largely coincides with the history of this magazine. Radar systems, whether for military or commercial purposes, have sustained more than a few of the companies in this industry, and should continue to do so for years to come.

The basic concepts of radar are more than 100 years old, although the first practical radar systems weren't produced until World War II. Radar, which is actually an acronym for radio detection and ranging, was originally developed for target and object detection. Early experiments in radar can be traced to the beginning of the 20th Century. In 1922, US naval researchers A. Hoyt Taylor and Leo Young were able to use electromagnetic (EM) energy to locate ships in the Potomac River in terms of bearing and distance, even in heavy fog. But the Navy would not seize upon the tactical benefits of radar until years later. The threat of air attacks during WWII provided the motivation.

Modern radar systems come in many shapes and sizes. The basic concepts are the same: transmitting pulsed EM energy and receiving the reflected return energy from an "illuminated" target to decipher the bearing and distance to that target. But modern radar systems benefit not only from advances in RF/microwave componentssuch as low-noise amplifiers (LNAs) with high gain and low noise figures for improved receiver sensitivity. They also continue to improve due to gains in digital signal processing (DSP), in the processing power of newer microprocessors and field-programmable gate arrays (FPGAs), and in the application of these minicomputers through advanced mathematical algorithms that enhance the principles of the radar range equation.

Although radar was born in warfare, it has come to serve many peacetime usesweather forecasting, for instance. Because radar can be used to measure precipitation, it can be employed to predict thunderstorms. It can also be used by police to detect the speed of vehicles. It is used in astronomy, for deep-space exploration without ever leaving the planet. It is used in air-traffic control systems to keep air vehicles within safe distances of each other. Millimeter-wave radars have even become accepted equipment in many high-end ground as well as air vehicles in anti-collision systems. And one of the more intriguing applications of radar systems is in ground-penetrating radars (GPRs), which can be used to detect objects buried under the ground.

A sampling of the history of radar systems can be found on the historical look back on p. 52. Those early radar systems were largely military in nature, eventually finding other places in civilian applications. Radar technology has matured with this industry, hopefully still with a great deal of growth and advancement left to it.