Frequently Asked Questions On Antenna Theory With Answers - 9.


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


41) What is meant by similar Point sources?

Whenever the variation of the amplitude and the phase of the field with respect to the absolute angle for any two sources are same then they are called similar point sources.

The maximum amplitudes of the individual sources may be unequal.


42) What is meant by identical Point sources?

Similar point sources with equal maximum amplitudes are called identical point sources.


43) What is the principle of the pattern multiplication?

The total field pattern of an array of non isotropic but similar sources is the product of the

  • Individual source pattern and
  • The array pattern of isotropic point sources each located at the phase center of the individual
  • source having the same amplitude and phase.


While the total phase pattern is the sum of the phase patterns of the individual source pattern and array pattern.


44) What is the advantage of pattern multiplication?

  • Useful tool in designing antenna.
  • It approximates the pattern of a complicated array without making lengthy computations.


45) What is tapering of arrays?

Tapering of array is a technique used for reduction of unwanted side lobes. The amplitude of currents in the linear array source is non-uniform; hence the central source radiates more energy than the ends. Tapering is done from center to end.


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 »