Microwaves – Basics, Applications and Effects

What are Microwaves?

Microwaves refer to the electromagnetic rays with frequencies between 300MHz and 300GHz in the electromagnetic spectrum. Microwaves are small when compared with the waves used in radio broadcasting. Their range is in between the radio waves and infrared waves. Microwaves travel in straight lines and they will be affected lightly by the troposphere. They don’t require any medium to travel. Metals will reflect these waves totally. Non metals such as glass and particles are partially transparent to these waves.

Microwaves are suitable for wireless transmission of signals of having larger bandwidth. Microwaves are most commonly used in satellite communications, radar signals, phones, and navigational applications. Other applications where the microwaves used are medical treatments, drying materials, and in households for the preparation of food.

Practically a microwave technique tends to move away from the resistors, capacitors, and inductors used with lower-frequency radio waves. Instead, distributed and transmission-line theory are more useful methods for design and analysis. Instead of open-wire and coaxial lines used at lower frequencies, waveguides are using. And lumped elements and tuned circuits are replaced by cavity resonators or resonant lines. Even at higher frequencies, where the wavelength of the electromagnetic waves becomes small when compare to the size of the structures used to process them, microwave has become a latest technology, and the methods of optics are used. High-power microwave sources use specialized vacuum tubes to generate microwaves.

Applications and Uses of Microwave:

Most common applications are within the range of 1 to 40 GHz. Microwaves are suitable for wireless transmission (wireless LAN protocol Ex- Bluetooth) signals having higher bandwidth. Microwaves are commonly used in radar systems where radar uses microwave radiation to detect the range, distance, and other characteristics of sensing devices and mobile broadband applications. Microwave technology is used in radio for broadcasting and telecommunication of transmission because due to their small wavelength, highly directional waves smaller and therefore more practical than they would be at longer wavelengths (lower frequencies) before the introduction of Fiber optic transmission. Microwaves are generally used in telephone for long distance communication.

Electro Magnetic Spectrum
Electro Magnetic Spectrum

Several other applications where the microwaves used are medical treatments; microwave heating is used for drying and curing products, and in households for the preparation of food (microwave ovens).

An application of microwave- microwave oven:

Microwave Oven is commonly used for cooking purpose without using water. High energy of the microwave rotates the polar molecules of water, fat and sugars of the food stuff. This rotation causes friction that result in heat generation. This process is called Dielectric heating. The excitation by the microwave is almost uniform so that the food will heat up uniformly. The cooking in microwave oven is fast, efficient and safe.

MICROWAVE-OVEN-PARTS
MICROWAVE-OVEN-PARTS

The microwave oven consists of a high voltage transformer that passes energy into the Magnetron, a Magnetron chamber, Magnetron control unit, a wave guide and the cooking chamber. The energy in the microwave oven has a frequency of 2.45 GHz with a wave length of 12.24 cm. The Microwave propagates as alternating cycles so that the polar molecules (one end positive and the other end negative) align themselves according to the alternating cycles. This self alignment causes rotation of the polar molecules. The rotating polar molecules hit other molecules and put them into motion. Microwave induced heating is more efficient if the tissue has high water content since there are free water molecules to rotate. Fats, sugars, Frozen water etc shows less dielectric heating due to the presence of less free water molecules. Microwave cooks the outer part of the food first and then the inner part similar to ordinary cooking using flame.

The cooking chamber of the microwave oven is a Faraday cage that prevents the microwave to leak out to the environment. The glass door of the oven helps to view the interior of the oven. The Faraday cage as well as the door is well protected using conductive mesh to keep the shielding. The perforations in the mesh are lesser in size so the microwave cannot escape through the mesh. Electrical efficiency of Microwave oven is high since the oven converts only a portion of the electrical energy. A typical oven consumes 1100 electrical energy to produce 700 watts microwave energy. The remaining 400 watts is dissipated as heat in the Magnetron. Additional energy is required for operating other components of the oven like lamp, cooling fan turntable motor etc.

Microwave Bands:

Microwaves are found at the higher end of the radio spectrum, but they are commonly different with radio waves based on the technology using them. Microwaves are divided into sub-bands based on their wavelengths which are providing different information. The frequency bands of microwaves are as follows:

Microwave Bands
Microwave Bands
Microwave frequency bands and their frequency range
Microwave frequency bands and their frequency range

L-Band:

L bands are having the frequency rage 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:

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:

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.

X-Band:

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.

Radar applications using microwaves
Radar applications using microwaves

Ku-Band:

Ku band
Wave meter for measuring in the Ku band

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 costal areas.

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.

V-Band:

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.

Microwave Radiation and its Effect on Health:

Radiation is an energy that comes from a source and travels through some medium or space. Generally RF radiation will be produced by several devices like TV and Radio transmitters, induction heaters and dielectric heaters. Microwave radiation will be produced by radar devices, dish antennas, and microwave ovens.

Microwave Radiation and its Effect on Health

Microwave radiation effect after phone call
Microwave radiation effect after phone call

Due to the microwave radiation, the body temperature may increase. There is a higher risk of heat damage with organs which are having poor temperature control, such as lens of eyes. Since radiation energy absorbed by the body varying with the frequency, measuring the rate of absorption is very difficult.

5 Advantages of using Microwave technology:

  1. It does not require any cable connection.
  2. They can carry high quantities of information due to their high operating frequencies.
  3. We can able to access more numbers of channels.
  4. Low cost land purchase: each tower occupies small area.
  5. High frequency/short wavelength signals require small antenna.

 5 Disadvantages:

  1. Attenuation by solid objects: birds, rain, snow and fog.
  2. It’s much expensive to build long towers.
  3. Reflected from flat surfaces like water and metal.
  4. Diffracted (split) around solid objects.
  5. Refracted by atmosphere, thus causing beam to be projected away from receiver.

Now you have understand the concept of micro waves and applications and effects from the above article so if you have any queries from the above topic or from the electrical and electronic projects leave the comments section below.

Photo Credit:

  • Microwave Bands By gstatic
  • Wave meter for measuring in the Ku band By gstatic
  • Microwave radiation effect after phone call By wikimedia

2 Comments

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