Antenna Theory - FAQ's With Answers - 2.


This page contains basic questions and short notes on some of the keywords on antenna theory:


6) What are the different types of aperture?

  • Effective aperture.
  • Scattering aperture.
  • Loss aperture.
  • Collecting aperture.
  • Physical aperture.

7) Define different types of aperture?

Effective aperture (Ae):

It is the area over which the power is extracted from the incident wave and delivered to the load is called effective aperture.

Scattering aperture (As):

It is the ratio of the reradiated power to the power density of the incident wave.

Loss aperture (Ae):

It is the area of the antenna which dissipates power as heat.

Collecting aperture (Ae):

It is the addition of above three apertures.

Physical aperture (Ap):

This aperture is a measure of the physical size of the antenna.


8) Define Aperture efficiency?

The ratio of the effective aperture to the physical aperture is the aperture efficiency. i.e Aperture efficiency = hap = Ae / Ap (dimensionless).


9) What is meant by effective height?

The effective height h of an antenna is the parameter related to the aperture. It may be defined as the ratio of the induced voltage to the incident field.i.e H= V / E.


10) What are the field zones?

The fields around an antenna may be divided into two principal regions.
  • Near field zone (Fresnel zone)
  • Far field zone (Fraunhofer zone)


ALSO READ:


- What is meant by radiation pattern?

- Define Radiation intensity?

- Define Beam efficiency?

- Define Directivity?

- What is meant by Polarization?

- What is meant by front to back ratio?

- Define antenna efficiency?

- What is radiation resistance ?

- What is meant by antenna beam width?

- ...Return To Antenna Theory FAQ's Main Page.


Comments

Post a Comment

Popular posts from this blog

Circular Cylindrical Coordinate System (ρ, φ, z) - Field Theory.

Image
A Vector in Cylindrical system is represented as (A ρ , A φ , A z ) or A = A ρ a ρ + A φ a φ + A z a z Where a ρ , a φ and a z are the unit vectors in ρ, φ and z direction respectively. The physical significance of each parameter of cylindrical coordinates:      - The value ρ indicates the distance of the point from the z-axis. It is the radius of the cylinder .      - The value φ, also called the azimuthal angle , indicates the rotation angle around the z-axis. It is basically measured from the x axis in the x-y plane. It is measured anti-clockwise.      - The value z indicates the distance of the point from z-axis. It is the same as in the Cartesian system. In short, it is the height of the cylinder. Range of the variables: It defines the minimum and the maximum value that ρ, φ and z can have in Cartesian system.  0 ≤ ρ ≤ ∞  0 ≤ φ ≤ 2π - ∞ ≤ z ≤ ∞   Figure shows Point P and Unit vectors in Cylindrical Co-ordinate System. Cylindrical System - Unit v
Read More »

Electric Field Intensity (E) Due To a Circular Ring Charge - Field Theory.

Image
- Consider a circular ring of radius 'a' which carries a uniform line charge density ρ L as shown in figure. - We need to find out electric field at a point P (0, 0, h) on the z axis (z > 0). - Electric field intensity (E) due to any line charge (ρ L ) in general is given as: In this case, dl = a dφ (Since the differential part dl is a differential arc ) R 2 = a 2 + h 2 Consider the triangle shown in the above figure a a ρ + R = h a z → R = - a a ρ + h a z a R = R / | R | a R = - a a ρ + h a z / ( a 2 + h 2 ) 1/2 Substituting all these values in the above equations, the electric field intensity E becomes: - For every element dl there is a corresponding element diametrically opposite that gives an equal but opposite dE ρ so that the two contributions cancel each other. Hence contribution along a ρ due to symmetry adds up to zero. - Therefore the final electric field intensity at point (0, 0, h) has
Read More »

Electric Potential (V) Due To A Uniformly Charged Circular Disc - Field Theory.

Image
- Consider a circular disc of radius ‘a’ which carries a uniform surface charge density ρ s , C /m 2 . - Say the disk lies on x - y plane (or z = 0 plane) with its axis along the z axis as shown in the figure. - We need to find out electric potential (V) due to a circular disk at a point P (0, 0, h) on the z axis (z > 0). - Electric potential (V) at a point due to any surface charge (ρ s ) is given as: - In this case, ds = ρ dρ dφ (Since it’s a disc, the varying terms are radius ρ and angle φ ) R = (ρ 2 + h 2 ) 1/2 - Hence electric potential (V) is given as: - On solving further the equation becomes - As a → 0 , electric potential (V) also tends to zero i.e. V → 0. - Hence the electric potential at point (0, 0, h) is given as: ALSO READ:  - Gauss's Law - Theory. - Gauss's Law - Application To a Point charge. - Gauss's Law - Application To An Infinite Line Charge. - Gauss's
Read More »