Terrestrial Microwave presentation

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

10. 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

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

12. 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

13. 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

14. 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

15. 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)

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

17. 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

18. 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

19. 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.

20. 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

21. 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. Atte nuation 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

22. 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

23. 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

24. Some Pictures using MW in Telecommunication

25. Thank You !