Antenna types

Antenna types 

Antenna types used in GSM:

• Omni-directional antennas (often used in rural areas)

• Directional antennas (preferable used in urban areas)

• Multi antenna systems

• Leaking cables (used e.g. in tunnels, buildings,…)

• Parabolic antennas (used for microwave and satellite links)

Antenna locations:

• Outdoor

• Indoor

Antenna pattern:

The (real) distribution of the radiated power as function of the direction is usually displayed in

horizontal and/or vertical antenna radiation patterns. For these diagrams, usually polar

coordinates graduated in decibels (dB) are used. Since an antenna is a passive component, due

to the conservation of energy an increase of the radiated power in one direction will reduce the

radiated power in an other direction. For sector antennas, the main lobe in the front direction

should be maximised whereas the back lobe should be minimised.

The sector width (e.g. 120° sector) should not be confused with the half power beam width. For

example, often 60°– 65° half power beam width antennas are used to realise 120° sectors.

Antenna parameters

• Frequency range

• Polarization

• Gain

• Half-power beam width

• Electrical tilt

• Front to back ratio

• Impedance

• VSWR and return loss

• Maximum power per input

• Input connectors

• Connector position

• Dimensions (height, width, depth)

• Weight

•Wind load (frontal, lateral, rearward)

• Maximum wind velocity

Half power beam width:

The opening angle between the points where the radiated power is 50 % (3 dB) lower than the

power transmitted in the main direction is called the half power beam width.

Antenna gain:

The gain of an antenna is given either in dBi (with respect to an ideal, isotropic antenna) or in dBd

(with respect to a dipole antenna):

Gain (dBi) = Gain (dBd) + 2.15 dB

Antenna tilt:

Two different tilt types can be distinguished: electrical tilt and mechanical tilt.

Mechanical tilt is achieved by corresponding mounting of the antennas using special mounting

devices.

Electrical tilt is a built-in function of an antenna. Either an antenna has or does not has this

function. Usually an electrical down-tilted antenna has just one (fixed) electrical (down)-tilt but

there also exist antennas where the electrical (down)-tilt is settable.

In addition to an electrical tilt also a mechanical tilt can be applied. The effective tilt is the sum of

both tilts