Explain how umbrella pattern antennas are used as the cell site antennas

6. Explain how umbrella pattern antennas are used as the cell site antennas.

Umbrella-Pattern Antennas:

In certain situations, umbrella-pattern antennas should be used for the cell site antennas.

Normal Umbrella-Pattern Antenna:

For controlling the energy in a confined area, the umbrella-pattern antenna can be developed by using a monopole with a top disk (top-loading) as shown in Fig. 6.1. The size of the disk determines the tilting angle of the pattern. The smaller the disk, the larger the tilting angle of the umbrella pattern.

Broadband Umbrella-Pattern Antenna:

The parameters of a discone antenna (a bio conical antenna in which one of the cones is extended to 180◦ to form a disk) are shown in Fig.6.2a. The diameter of the disk, the length of the cone, and the opening of the cone can be adjusted to create an umbrella-pattern antenna.

High-Gain Broadband Umbrella-Pattern Antenna: A high-gain antenna can be constructed by vertically stacking a number of umbrella-pattern antennas as shown in Fig.6.2b.

Interference Reduction Antenna:

A design for an antenna configuration that reduces interference in two critical directions (areas) is shown in Fig.6.3. The parasitic (insulation) element is about 1.05 times longer than the active element.