Electric field vs Radiation pattern

[Hanh Le]

Dear all,

I am confused about the difference between Electric field and radiation pattern. Do they have the same meanings?

 

[ankitmore]

the radiation pattern is the normalized power distribution which is defined as the vector cross product between the electric field and the magnetic field. This does not have to necessarily be the same as that of either the electric field or the magnetic field. In other words if in a particular direction the E field is maximum but the H field has a null then the radiation pattern there can have a null

 

[WimRFP]

The electric field can be "measured" at any place around the antenna, for the radiation pattern there are limitations with respect to the measuring distance.

The far field radiation pattern is "measured" at distances where the path length difference from any point on the antenna structure to the measuring point no longer depends on the measuring distance (Fraunhofer region). In this region, doubling the distance results in 6 dB reduction of power flux density (so E- and H-field halves).

The radiation pattern mostly shows the ratio between the power flux density of the DUT at certain distance in the far field zone, and the power flux density that would be generated by an isotropically radiating source (mostly expressed in dBi). Orientation (angle) towards the DUT is varied during this procedure

As in the far field E is perpendicular to H, E and H are in time phase, and E/H = 377, power flux density (average pointing vector S) = E^2/377 [W/m^2], in air or vacuum.

Note that that gain generally not equals directivity (because of not all electrically supplied energy is converted to radiation due to loss).