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Mobile Phone Antennas Made Simple

Antennas come in all shapes and sizes, from vehicle whip style antennas, marine grade, vandal proof, desktop, wallmount, ceiling mount and even antennas shaped like lamp posts.

We will explain the difference between each antenna and the common terms, so you can select the appropriate antenna for your application.

Directivity





i) Omni-Directional Antennas
- These antennas will receive a signal from all directions and are often called a whip antenna. They are useful in situations where the mobile device is constantly moving such as on a vehicle, where the location of the nearest mobile tower is not known or when there is not a clear line of site to the tower and the signal is bouncing off nearby objects. Omni-Directional antennas are usually lower in gain.







ii) Directional Antennas
- As the name suggest these antennas are designed to receive a signal from a particular direction. Sometimes called a beam or yagi antenna, they are often much higher gain. They are ideal in low to medium signal areas where there is line of site or near line of site to the tower.

 


Gain

Antenna Gain is not an amplification of a signal, it's the antennas effectiveness in focusing radio frequency energy in a particular direction. The higher the gain the more focused the antenna is and the narrower the field of reception. Antenna gain is either measured in:

dBi - "dB isotropic" compares the focus applied by an antenna to a "Isotropic Radiator" (an imaginary sphere)

dBd - 'dB dipole" compares the antenna to the power received by a loss less half-wave dipole antenna.

If an antenna's gain is only listed with a dB reference then it could be either a dBd or a dBi measurement.

To convert between the two:

  • dBi = dBd + 2.15
  • dBd = dBi - 2.15

Radiation Pattern



The radiation pattern diagram is used to describe the strength of the radiation field in various directions from the antenna. Radiation patterns are three dimensional, measuring both the sending and receiving signal of an antenna.

 

 

 

Beamwidth

The beamwidth of antenna specifies the boundaries within the antenna's radiation pattern and therefore its limits of receiving or transmitting a signal.

The wider the bandwidth the larger the angle at which the antenna can receive a signal. Beamwidth will also affect the gain of an antenna, generally the smaller the beamwidth and therefore more concentrated the signal, the higher the gain will be.

Omni-Directional antennas have a 360° beamwidth and receive a signal from all directions.



Polarisation

Different polarisation can be achieved by positioning the antenna vertically or horizontally. By doing this you modify the radiation pattern of antenna changing its beamwidth. Horizontal polarisation will usually provide a wider beamwidth and vertical polarisation will provide a higher/lower beamwidth in orientation to the earth. Omni-directional antennas always have vertical polarisation.

Bandwidth

The antenna bandwidth refers to the range of frequencies the antenna can support efficiently. A wideband mobile phone antenna will generally cover the 800-900 MHz bands as well as the1800-2100 MHz bands.

Mobile Phone Antenna Designs

Omni Antenna

Omni Antennas radiate signal in a 360° donut pattern. They are one of the most versatile antennas due to their ability to receive and transmit in any direction.

Because their beamwidth pattern is not concentrated in a particular direction they are generally lower in gain than other types of antennas.

Typical uses are for marine, vehicle and building applications.

Typical Gain: 0 - 9dBi

Yagi Antenna

A Yagi is ideal for point to point and line of site applications. Made from stainless steel or aluminum, they consist of a long boom with elements strategically placed along at intervals.

The more elements, the higher the gain. Longer elements support lower frequencies, shorter elements support the higher frequencies.

Yagi Antenna are usually high in gain and good for long distance communications.

Typical uses include being pole mounted on a building.

Typical Gain: 10 - 16 dBi

Ceiling Mount

Ceiling Mount Antennas are used for in building signal dispersion, usually in a cellular repeater application.

They are mounted on a ceiling, pointing towards the ground and provide a 180° beamwidth in all directions below.

Panel Antenna

A panel antenna is often used as an alternative to a Yagi in higher frequency applications or when a low profile directional antenna is required.

They can also be used as an indoor wallmount antenna in cellular repeater applications to focus the signal in a particular direction.

Parabolic / Grid Antenna

Parabolic antennas are ideal for long range communications, providing a very focused directional signal.

The dish plate acts as a reflector to highly concentrate the signal in a particular direction.

Parabolic antennas are usually very high gain.

Typical Gain: 15 - 25 dBi

Sector Antenna

Sector Antennas are commonly used on mobile phone towers.

They are directional, but provide a relatively unfocused signal enabling them to service wider coverage areas.

On a mobile phone tower they are positioned in groups around the tower to provide a 360° coverage area similar to that of an omni directional antenna. The big difference is they provide a much higher gain and reach.

Sector Antennas are usually adjustable so they are tilted in a 60,90,or 120 degree angle to customise the coverage area.