Antenna Theory - FAQ's With Answers - 5.


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


21) What is meant by cross field?

Normally the electric field E is perpendicular to the direction of wave propagation. In some situation the electric field E is parallel to the wave propagation that condition is called Cross field.


22) Define axial ratio?

The ratio of the major to the minor axes of the polarization ellipse is called the Axial Ratio (AR).


23) What is meant by Beam Area?

The beam area or beam solid angle or WA of an antenna is given by the normalized power pattern over a sphere.

WA = ò ò4p Pn ( q,f ) dW
Where dW = Sin q dq.df


24) What is duality of antenna?

It is defined as an antenna is a circuit device with a resistance and temperature on the one hand and the space device on the other with radiation patterns, beam angle, directivity gain and aperture.


25) State Poynting theorem?

It states that the vector product of electric field intensity vector E and the magnetic filed intensity vector H at any point is a measure of the rate of energy flow per unit area at that point. The direction of power flow is perpendicular to both the electric field and magnetic field components.

ALSO READ:

- Effective Aperture & Directivity Of A Short Dipole Antenna.

- What is Polarization & What Are It's Different Types?

- Define beam width of major lobe?

- List out the expression of beam width for broad side array and end fire array?

- What is meant by antenna beam width?

- Differentiate broad side and End fire array?

- What is the need for the Binomial array?

- Define power pattern?

- ...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 Cyli...
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 »