Uses
A microwave oven uses a magnetron microwave generator to produce microwaves at a frequency of approximately 2.4 GHz for the purpose of cooking food. Microwaves cook food by causing molecules of water and other compounds to vibrate. The vibration creates heat which warms the food. Since organic matter is made up primarily of water, food is easily cooked by this method.
A maser is a device similar to a laser, except that it works at microwave frequencies. Microwaves are also used in satellite transmissions because this frequency passes easily through the earth's atmosphere with less interference than higher wavelengths.
Radar also uses microwave radiation to detect the range, speed, and other characteristics of remote objects.
Wireless LAN communication protocols such as IEEE 802.11 and bluetooth also use microwaves in the 2.4 GHz ISM band, although some variants use a 5 GHz band for communication.
Cable TV and Internet access on coax cable as well as broadcast television use some of the lower microwave frequencies.
Microwaves can be used to transmit power over long distances, and post-World War II research was done to examine possibilities. NASA worked in the 1970s and early 1980s to research the possibilties of using Solar Power Satellite (SPS) systems with large solar arrays that would beam power down to the Earth's survace via microwaves.
The microwave spectrum is defined as electromagnetic energy ranging from approximately 300 MHz to 1000 GHz in frequency. Most common applications are within the 1 to 40 GHz range.
Microwave Frequency Bands are defined below:
Letter Designation Frequency Range
L Band 1 to 2 GHz
S Band 2 to 4 GHz
C Band 4 to 8 GHz
X Band 8 to 12 GHz
Ku 12 to 18 GHz
K Band 18 to 26 GHz
Ka 26 to 40 GHz
Q Band 30 to 50 GHz
U Band 40 to 60 GHz
V Band 46 to 56 GHz
W Band 56 to 100 GHz
For some of the history in the development of electromagnetic theory applicable to modern microwave applications see the following figures: