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Published byTiffany Hood Modified over 9 years ago
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Test 1: Co-channel interference at the mobile unit
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Test 2: Co-channel interference at the cell site
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Lowering the Antenna Height
(a) on a high hill (b) in a valley
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In a Forested Area
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Reduction of Co-channel interference in a cellular mobile system
Increasing the separation between two co-channel cells Using directional antennas at the base station Lowering the antenna heights at the base station.
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Reduction of Co-channel Interference by Means of a Notch in the Tilted Antenna Pattern
A seven-cell cellular configuration
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Antenna Pattern 33°,45°,65°,85° Horizontal Beamwidth
Vertical Beamwidth Horizontal Beamwidth 33°,45°,65°,85°
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A typical pattern for a directional antenna of 120° beamwidth
(a) Azimuthal pattern of 8-dB directional antenna
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A typical pattern for a directional antenna of 120° beamwidth
(b) Vertical pattern of 8-dB directional antenna
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Antenna Tilting In general, the vertical pattern of an antenna radiates the main energy towards the horizon Only that part of the energy which is radiated below the horizon can be used for the coverage of the sector Downtilting the antenna limits the range by reducing the field strength in the horizon
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Mechanical Downtilting
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Mechanical Downtilt
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Mechanical Downtilt
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The Effect of Mechanically Downtilting Antenna on the Coverage Pattern
Vertical antenna pattern of a 120° directional antenna
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Notch appearing in tilted antenna pattern
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Mechanical Downtilting
is the down tilt angle d1 is the length of the upper antenna-mounting arm d2 is the length of the lower antenna-mounting arm h is the distance between d1 and d2
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Antenna Parameters Mechanical Downtilt Electrical Downtilt
HBW gets bigger Causes gain reduction HBW remains the same But can’t adjust downtilt (fixed)
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Suggested Method for Reducing Interference
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Umbrella-pattern Effect
Antenna in which the waves are guided downward in all directions from a central pole or tower to the ground, somewhat like the ribs of an open umbrella.
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