icrowaves are a type of electromagnetic radiation. They have various application areas including communications, radar and most important is cooking. In the last 50 years, microwave technology has begun to be used in the industrial field, mostly drying, tempering and processing of various products such as wood, foam, textile, coal and the processing of food with the most known. In microwave technology the product heated up from the core to the surface thus product`s surrounding`s temperature does not change much. In conventional traditional method this is not the case.
Figure 1 Electro Magnetic Spectrum
Microwaves have frequency range from 300 megahertz (MHz) up to about 300 gigahertz (GHz) and wavelengths from 1000 millimeters to 1 millimeter. Metals reflects these waves and nonmetals such as glass and particles are partially transparent to these waves. Microwaves are divided into sub-bands based on their wavelengths which can be offering different facts. The frequency bands of microwaves are as follows  :
L bands are having the frequency range between 1 GHz to 2 GHz and their wavelength in free space is 15cm to 30cm. These ranges of waves are used in navigations, GSM mobile phones, and in military applications. They can be used to measure the soil moisture of rain forests.
S band microwaves are having the frequency range between 2 GHz to 4 GHz and their wavelength range is 7.5cm to 15 cm. These waves can be used in navigation beacons, optical communications, and wireless networks.
C band waves are having the range between 4 GHz to 8 GHz and their wavelength is in between 3.75 cm to 7.5 cm. C band microwaves penetrate clods, dust, smoke, snow, and rain to reveal the earth’s surface. These microwaves can be used in long-distance radio telecommunications.
The frequency range for S-band microwaves is 8 GHz to 12 GHz having the wavelength in between 25 mm to 37.5 mm. These waves are used in satellite communications, broadband communications, radars, space communications and amateur radio signals.
These waves are occupying the frequency range between 12 GHZ to 18 GHz and having the wavelength in between 16.7 mm to 25 mm. “Ku” refers to Quartz-under. These waves are used in satellite communications for measuring the changes in the energy of the microwave pulses and they can determine speed and direction of wind near coastal areas.
Figure 2 Microwave frequency bands and their frequency range
K-Band and Ka-Band:
The frequency range for K band waves in between 18 GHz to 26.5 GHz. These waves are having the wavelength in between 11.3 mm to 16.7 mm. For Ka band the frequency range is 26.5 GHz to 40 GHz and they are occupying the wavelength in between 5 mm to 11.3 mm. These waves are used in satellite communications, astronomical observations, and radars. Radars in this frequency range provide short range, high resolution and high amount of data at the renewing rate.
This band stays for a high attenuation. Radar applications are limited for a short range of applications. The frequency range for these waves is 50 GHz to 75 GHz. The wavelength for these microwaves is in between 4.0 mm to 6.0 mm. There are some more bands like U, E, W, F, D, and P having very high frequencies which are used in several applications.