The key difference between near field and far field is that near field is a region that is close to an antenna or a scattering object whereas far field is a region that is at a distance from an antenna or a scattering object.
We can define near field and far field as regions of the electromagnetic field around an object, e.g. transmission of an antenna or the result of radiation scattering off an object. We can observe near field behaviours close to an antenna or a scattering object, while the far field behaviours are common at far distances from the object.
CONTENTS
1. Overview and Key Difference
2. What is Near Field
3. What is Far Field
4. Near Field vs Far Field in Tabular Form
5. Summary – Near Field vs Far Field
What is Near Field?
Near field is the region that is closer to an antenna or a scattering object. This region is governed by multiple type fields and we can consider it as a collection of dipoles having a fixed phase relationship. The boundary between the near field and far field depends on the dominant wavelength that is emitted by the source and on the size of the radiating element.
In this type of region near an antenna, absorption of the radiation affects the transmitter load; as a simple example, we can show the magnetic induction that is created in a transformer. Moreover, in these types of regions, the electric and magnetic fields tend to exist independent from each other, and one field can dominate the other type of field.
What is Far Field?
Far-field is the region that occurs at a distance from the antenna or scattering object. It is the region where the field tends to act normal regarding electromagnetic radiation. This region is dominated by an electric or magnetic field having electric dipole characteristics.
In this type of region, the radiated power tends to decrease with the square of the distance, and the absorption of the ratio does not feed back to the transmitter. Moreover, each part of the electromagnetic field tends to be produced by a change in the other part, while the ratio of the electric and magnetic field intensity values can be given simply as the wave impedance.
What is the Difference Between Near Field and Far Field?
We can define the near field and far field as regions of the electromagnetic field around an object, e.g. transmission of an antenna or the result of radiation scattering off an object. The key difference between near field and far field is that near field is a region that is close to an antenna or a scattering object whereas far-field is the region that occurs at a distance from the antenna or the scattering object. Moreover, in the near field, the absorption of radiation does affect the load on the transmitter while in the far-field, the absorption or the radiation does not affect the transmitter.
The following infographic lists the differences between near field and far field in tabular form for side by side comparison.
Summary – Near Field vs Far Field
We can define the near field and far field as regions of the electromagnetic field around an object, e.g. transmission of an antenna or the result of radiation scattering off an object. The key difference between near field and far field is that near field is a region that is close to an antenna or a scattering object, whereas far-field is the region that occurs at a distance from the antenna or the scattering object.
Reference:
1. “Near Field versus Far Field.” NearFieldCommunication.org.
Image Courtesy:
1. “Felder um Dipol” By Original JPG (File:Felder um Dipol.jpg) due to Averse, SVG by Maschen. – Own work (CC0) via Commons Wikimedia
2. “Sidelobes en” By Timothy Truckle – Own work (CC BY-SA 4.0) via Commons Wikimedia