Applications of Microwave - KUET

Applications of Microwave

Dr. Md. Mostafizur Rahman

Professor

Department of Electronics and Communication Engineering (ECE)

Khulna University of Engineering and Technology (KUET)

(Chapter 11)

Dr. Md. Mostafizur Rahman 1

Microwaves are used ;- Scientific

- Medical

- Military and Civilian War

- Industrial Applications

- Food - Chemical -Rubber -Textiles

-Plastics - Paper - Ceramic - Cosmetics

It is used in different industry for ;

Cooking Baking Puffing Drying Curing

Evaporating Sterilizing, Moulding … etc.


Advantages of microwave communications over medium

wave/short wave communications

-Microwaves are used in wireless communication to an accommodate increased number

of channels with a high S/N power ratio.

- Bandwidth can be a small fraction of the microwave carrier frequency (fc).

- Using higher fc the overall system bandwidth can be increased.

- More distinct channel can be transmitted at microwave frequency than at much lower

frequencies.

- High resolution radiation beam (narrow) can be generated with relatively smaller size

antennas.

- Noise are negligibly small (e.g. atmospheric noise, man made interferences caused by

electric transient, automobile ignition etc.)

- Since microwaves penetrate ionosphere and any possibility of ground reflected waves

and surface waves suffer heavy attenuation.

- It is a Line of sight (LOS) communication.

Microwave communication systems can be classified as - Terrestrial System -

Satellite System. Dr. Md. Mostafizur Rahman 3

RepeaterMultiplexed

Baseband

Signal

Multiplexed

Baseband

Signal

Fig. 11.9 Block Diagram of a Terrestrial Microwave Communication System

Terrestrial System


User

Terrestrial Link

Earth station

User

Terrestrial Link

Earth station

12 to 15 Transponder

22300

mil

es

Principles of a Satellite

Satellite Operates the following frequencies ;

- 6/4 GHz - 14/11 GHz - 17/12 GHz

Applications : Long distance telephone traffic, To relay TV signals across oceans and to Provide

national TV cables directly to the home, Internet etc….

Classified by Altitude :• Low Earth Orbit (LEO) Satellite [500 – 2000 km]

• Medium Earth Orbit (MEO) Satellite [5000 – 15000 Km]

• Geostationary (GEO) Satellite [35786 Km]

• Highly Elliptic Orbit (HEO) Satellite

Satellite


Fig. : Block Diagram of a typical Transponder

DuplexerLO

DuplexerLow noise

Down Converter BPFLNA TWTABPF

Uplink Signal at 6 GHz

Downlink Signal 4 GHz

Transponder : The stage between the reception of the uplink signal and converted into

downlink frequency and then transmission of that downlink signal to earth is called a

transponder. A satellite commonly contains 12 to 15 transponders having bandwidth with 36

MHZ each. Bangabandhu-1 Satellite have 40 transponder.


Fading : Fading is a phenomenon in which the received signal strength is reduced

or lost due to atmospheric effects and ground reflections.

Types of Fading :

- Absorption fading

- Reflection multipath fading

- Atmospheric multipath fading and

- Sub-refraction fading

Tx Rx

Reflection Multipath Fading

Tx Rx

Atmospheric Multipath Fading

Tx

Rx

Sub refraction Fading


Heating System and Microwave Oven(Chapter 11)








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Applications of Microwave - KUET