Microwave Transmission Basics

What is Microwave ? 

• Microwave ( MW ) are a form of electromagnetic radiation with wavelengths ranging from 1m to 1mm
• Frequencies between 300MHZ to 300GHZ

 Microwave Transmission :

• Microwave transmission is the transmission of information ( Voice , data , television or radio signals ) by microwave radio waves.
• Microwaves are widely used for PPP ( Point - to -Point ) communications because their small wavelength allows conveniently sized antennas to direct them in narrow beams , which can be pointed directly at the receiving antenna.

Microwave Link / Hop

• The connection of two fixed microwave sites via a line of  light (LOS) path.
• It is called Hop

Microwave Key Parameters :

• Hertz ( HZ ) :

A measurement of a signal's electromagnetic frequency , expressed as a number of cycles per second.

KHZ : Kilohertz , MHZ : Megahertz , GHZ : Gigahertz , THZ : Terahertz 

• Frequency :

The rate of the wave's oscillation , measured in hertz ( HZ )

• Amplitude :

The strength of power level ofthe wave

• Phase :

The particular point in the cycle of a waveform , measured in degrees 

• Polarization 

The orientation of the electric field driving the wave 

Line Of Sight ( LOS )

It is a type of propagation that can transmit and receive data only where transmit and receive stations are in view of each other without any obstacles between them .

Examples are FM radio , Microwave and satellite transmission 

Antennas :

Antennas are devices that radiate or receive EM waves of certain frequencies 

Microwave Antenna :

An antenna designed to radiate and receive microwave frequencies , therefore is called a microwave antenna .

Waveguide :

A metallic physical transmission medium & waves propagate along it .

Microwave energy travels through guided media is called waveguide .

Waveguide Types :

Rectangular Waveguide

Circular waveguide 

Elliptical waveguide 

Corrugated Waveguide 

Properties of Microwave links :

Involve LOS communication technology.

Affected greatly by environmental constraints including rain fading .

Have very limited penetration capabilities through obstacles such as hills , building and tress .

Signals can be degraded during solar proton events.

Fading :

Loss in signal strength a cross a link caused by atmospheric disturbance link rain or snow that can scatter microwave signals .

The lower frequency microwave bands offer the greatest possible distance - theoretically allowing for links in excess of 50 KM

Microwave Frequencies :

Microwave Frequency & it's application 

Low Frequency VS High Frequency 

The lower frequency bands offer the greatest possible distance - theoretically allowing for links in excess of 50 KM.

Adaptive Transmit Power Control ( ATPC )

ATPC dynamically adjusts power levels to compensate for any link impediments .

Adaptive Modulation :

Is used dynamically switch modulation schemes according to the prevailing channel conditions .

Typical modulation schemes selected for adaptive modulation are 4QAM , 16QAM , 64QAM , 128QAM , 256QAM , 512QAM and 1024QAM