Overview

Now it is time to get into some common applications of microwave and wireless systems. When most people hear the term microwave, they immediately think of microwave ovens. That is natural and perfectly all right, since microwave ovens operate at 2.45 GHz, which is in the microwave and wireless frequency band. Also, a microwave oven is a small variation of radar, an application covered in this chapter. So, you can see how natural the association really is to someone who does not have a background in high frequencies.

The microwave oven is a device with a high-power tube (magnetron) that sends energy into food to be prepared. It does so by heating the moisture inside the food. That is why the food cooks from the inside to the outside. If you ever happened to put your finger on the center conductor of a coaxial cable with microwave energy propagating along it, you would notice a white mark on your finger. The mark would be below the skin, and the skin would not be broken. The microwave energy would use the moisture in your body and heat it to begin a cooking process below the skin. That is what happens when you put food into a microwave oven and turn it on. (If you look for the microwave oven on a microwave frequency chart, you will not find it designated as such. What you will find is a section called "microwave heating.")

Let us take a look at the electromagnetic...