Antenna Array Analysis - Radiation Pattern And Theorems


The importance of Antenna propagation 

What is Antenna? It is defined as a transducer which converts an electrical signal into electromagnetic wave or vice-versa. There are various types of antenna. They are termed as a wire antenna, aperture antenna, array antenna, microstrip antenna, lens antenna, a reflector antenna, etc. The wire antenna is used in various fields. They are used in buildings, ships, air-crafts, automobiles, space-crafts, etc.

The microstrip antennas have a metallic patch on the grounded substrate. The reflector antenna is used in communication for great distances purpose.

In the lens antenna, incident divergent energy is collimated to prevent it from spreading in undesired directions.

Aperture antenna is widely used due to its higher frequency. It has an aperture i.e. opening with a certain geometrical shape.

In antenna propagation, the antenna array is defined as an arrangement of various radiating elements. Here, the various radiating elements are arranged in an electrical or geometrical configuration. It is very important and needed in antenna propagation.

The need of Antenna array

Why Antenna Array?
1. It is used in long-distance communication to achieve higher directivity.
2. It produces a higher gain compared to other antennas.
3. It does not need to speed up the dimension of single element antennas.

Types of Antenna array?
The various types of the antenna array are broadside array, end-fire array, etc. The broadside array is a type of antenna array where maximum radiation of the antenna is produced normal to the axis of the array. Similarly, the end-fire array is a type of antenna array where maximum radiation is along the axis of the array.

Radiation pattern in Antenna

The radiation pattern is very important in the antenna. The radiation pattern is defined as a graphical or mathematical representation of average power density as a function of space coordinates. It is of various types. They are termed as directional radiation pattern, isotropic radiation pattern, omnidirectional radiation pattern, etc.

In isotropic radiation pattern, the radiation is equally distributed in all directions. Similarly, in directional radiation pattern, the antenna having more radiation is in a certain direction than other directions. And, an omnidirectional radiation pattern, the radiation of an antenna is only in one direction.

Theorems related to Antenna propagation

There are various theorems related to antenna propagation.

1. Superposition theorem- In superposition theorem, the vector sum of the field strengths at that point due to each antenna equals to the field strength at a point due to a number of transmitting antennas.

2. Maximum power transfer theorem- Here, when the impedance is equal to the conjugate impedance seen looking back to the source than antenna transmits or absorbs the maximum power.

3. Compensation theorem- In compensation theorem, an antenna may be replaced by a generator of zero internal impedance. Here, the generated voltage at any instant is equal to an instantaneous potential difference that occurs across the antenna.

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