Microwave Design
TERRESTRIAL MICROWAVE COMMUNICATION SYSTEM DESIGN
DESCRIPTION OF THE MICROWAVE BEAM: 1. The microwave beam behaves like a light beam and it tends to follow a straight line and azimuth. 2. The changes on temperature, pressure and relative humidity tends to refract the microwave beam. So it will follow on a slightly curved path. The radio horizon exists. 3. It is diffracted when grazing over an obstacle. A small shadow area created when some of the energy is redirected. 4. The beam can be reflected from relatively smooth terrain and water surfaces. The criterion of smoothness depends on the wavelength of the signal. 5. At 6 to 8GHz frequency band, rain attenuation is not a problem. But for frequencies 11GHz and above, rain attenuation is very serious. The amount of attenuation depends upon the rate of rainfall, the size of the drops and length of exposure. 6. Atmospheric absorption due to oxygen and water vapor also exists and its magnitude is a function of frequency and path length.
Things to consider in designing terrestrial microwave comm. System: * Site Considerations * Sources of Path Data * Path Profile * Interferences and Restrictions * Routes and Sites to be Avoided * Effects of Fading * Diversity Methods to apply * Reliability Objectives * Equipments
SITE CONSIDERATION:
1. A full description of each site by geographical coordinates, political subdivision, access roads and physical objects. 2. Any unusual weather conditions to be expected in the area including wind velocity, temperature and relative humidity. 3. A description of the physical characteristics of the site, indicating the amount of leveling required, removal of rocks, trees or other structure. 4. Relationship of the site to any airports. 5. The mean sea level elevation of the site and the path. 6. If possible the nearest location where commercial power is available. 7. The accessibility of the site
DESCRIPTION OF THE MICROWAVE BEAM: 1. The microwave beam behaves like a light beam and it tends to follow a straight line and azimuth. 2. The changes on temperature, pressure and relative humidity tends to refract the microwave beam. So it will follow on a slightly curved path. The radio horizon exists. 3. It is diffracted when grazing over an obstacle. A small shadow area created when some of the energy is redirected. 4. The beam can be reflected from relatively smooth terrain and water surfaces. The criterion of smoothness depends on the wavelength of the signal. 5. At 6 to 8GHz frequency band, rain attenuation is not a problem. But for frequencies 11GHz and above, rain attenuation is very serious. The amount of attenuation depends upon the rate of rainfall, the size of the drops and length of exposure. 6. Atmospheric absorption due to oxygen and water vapor also exists and its magnitude is a function of frequency and path length.
Things to consider in designing terrestrial microwave comm. System: * Site Considerations * Sources of Path Data * Path Profile * Interferences and Restrictions * Routes and Sites to be Avoided * Effects of Fading * Diversity Methods to apply * Reliability Objectives * Equipments
SITE CONSIDERATION:
1. A full description of each site by geographical coordinates, political subdivision, access roads and physical objects. 2. Any unusual weather conditions to be expected in the area including wind velocity, temperature and relative humidity. 3. A description of the physical characteristics of the site, indicating the amount of leveling required, removal of rocks, trees or other structure. 4. Relationship of the site to any airports. 5. The mean sea level elevation of the site and the path. 6. If possible the nearest location where commercial power is available. 7. The accessibility of the site