Presentation Terrestrial Microwave, design, critera, application of terrestrial microwave.

1. Presentation on Terrestrial Microwave
Communication
 Presented by:
Amarendra K Yadav

2. Topics Covered
 Introduction
 Working
 Design considerations
 Applications

3. What is Terrestrial Microwave ?
 transmission systems consisting of at least two radio transmitter/receivers
(transceivers) connected to high gain antennas (directional antennas
which concentrate electromagnetic or radio wave energy in narrow beams)
focused in pairs on each other
 The operation is point-to-point; communications are established between two
and only two antennas with line-of-sight visibility
 Operating frequencies range for microwave are 2Ghz to 60Ghz which limits all
communications to line-of-sight
 Repeaters need to be used for long distance communication
 uses a parabolic dish to communicate using electromagentic waves onto
receiver antenna

4. Microwave Transmitter & Receiver Block
Diag.

5. Why Microwave ? (Advantages)
 Fast Deployement possible
 Felxiblity
 Link across mountains and rivers are economically feasible
 Low MTTR(mean time to recover)
 Less affected by natural calamities
 Less prone to accidental damage

6. Characteristics of Microwave
 Generally used frequency band is 3Ghz to 30Ghz
 Typically used for point to point communication
 Microwaves travel in straight lines & thus can be narrowly focused thereby
allowing other microwave communications using same frequencies with
almost no interference
 Microwaves cannot pass through big obstacles viz. buildings, mountains

7. Types of Microwave Links and
polarization
 Long haul (2Ghz-10Ghz)40km-80km
 Medium Haul (11-20Ghz) 20km-40km
 Short Haul (23-58Ghz) Few Kms
Polarization Types:
 Vertical Polarization: less prone to rain and environmental factors
 Horizontal Polarization: very much used to avoid interference but are more
prone to rain.

8. Requirements for microwave
communication
 required a clear line of sight(LOS) between points
 Parameters design like power, frequency, Rx level etc
 Antenna height calculation for clear LOS
 Fresnel ellipsoids and their clearance criteria concept is used to calculate
radio LOS
 Fresenel zone must be clear of all obstacle

9. What is LOS ?
 Line of Sight
Line of sight (LoS) 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
sort of an obstacle between them

11. LOS purpose and requirement
Purpose
 Establish LOS links
 Feasibility Studies
 Up gradation of existing links
Requirement of LOS Links
 Site location
 Planned antenna height
 direction of the other end of link
 Output
 LOS/NLOS

12. Output
 minimum antenna height
 exact antenna location
 panaroma pictures with landmarks
 forest,buildings sites etc

13. Limitation of LOS
 Curvature of earth
 Actual obstruction en-route in each hop
 RF effect of fresnel zone
 path loss
 transmitter power
 antenna gain
 transmission line loss
 frequency of operation
 received power
 receiver threshold
 signal to noise ratio
 Fade margin required
 Desired reliability of link

14. Fresnel Zone
• Area of constructive and destructive interference created when EM waves
propagation in free space is reflected(multipath) or diffracted as waves
intersect obstacles
• Fresnel Zone are specific employing ordinal numbers that corresponds to the
number of half wavelength multiples that represent the difference on radio
wave propagation path from direct path.
• Fresnel zone must be clean of all obstacles
• Typically first Fresnel zone (n=1) is used to determine obstruction loss
• Direct path between transmitter and the receiver needs a clearance above
ground of atlest 60% of radius of first Fresnel zone to achieve free space
propagation condition
• Earth radius factor K compensate the refraction in the atmosphere

16.  Clearence is defined as criterion to ensure sufficient antenna height so that in
the worst case of refraction(K is minimum), the receiver antenna is not
placed in the diffraction region
 Effe. Earth radius=K^True earth’s radius
 True earth radius=6371km
 K=4/3=1.33, standard atmosphere with normal refracted path

17. Clearance critera
Clearance of 60% or greater at minimum K suggested for central path
Clearance of 100% at K=4/3
Incase of space diversity, the antenna can have 60% clearance at K=4/3 plus
allowance for tree growth, building (usually 3m)

18. Microwave Link design process
• Loss/attenuation calculation
• Fading and fade margin calculation
• Frequency planning and interference
• Quality and availability calculation

19.  MW link design process is iterative and may go through many redesign phase
before the required quality and availability are achieved
 1. Frequency planning(Interference analysis)
 2. Link Budget
Propagation loss
Branching loss
Other loss
3. Fading prediction
Rain attenuation
Diffraction-refraction loss
Multipath propagation
4.Quality and Availability

20. Loss/Attenuation Calculation
 1. Propagation Loss: due to earth’s atmosphere
 2.Branching Loss: carries from network used to deliver the trx/rx output
to/from antenna
 3. Other Loss: Unpredicatbel and sporadic in character like fog, moving
objects crossing path profile, poor equipment installation, less then perfect
antenna alignment

22. Propagation Loss
 Free Space Loss: when the transmitter and receiver have a clear unobstructed
loss

 FSL is the loss in the signal strength of an EM wave that would be result from
LOS path through free space (usually air), with no obstruction nearby to cause
reflection or diffraction. It doesn’t include Tx,Rx antenna, gain and others
loss associated with network imperfection.

23. Vegetation Attenuation
 Provision should be taken for 5 years of vegetable growth.
 Obstacle Loss: also called diffraction loss or diffraction attenuation
 .one method of calculation is based on knife edge approximation
 .having an obstacle free 60% of Fresnel gives 0db loss

24.  Gas Absorbtion
 .primary due to water vapour and oxygen on atmosphere in radius relay region
 .absorption peak are located around 23Ghz for water molecule 50-70Ghz for
oxygen molecule
 .Attenuation depends as fog, temperature and absolute or relative humidity of
atmosphere.
 Attenuation due to precipitation:
 Rain attenuation increses with frequency and become major contribution in
frequency band above 10Ghz
 Horizontal polarization gives more rain attenuation than vertical polarization

25.  Ground Reflection:
 .Reflection give rise to multiple propagation
 .Direct ray at receiver may interfered with the ground reflected ray and the
reflection loss can be significant

26. Link Budget
 Calculation involving the gain and loss factor associated with the antenna,
transmission line, propagation environment to determine maximum distance
at which a transmitter and receiver can successfully operate

27. Some Pictures using MW in
Telecommunication