Antennas and Wave Propagation

Viva Questions:

Q1) What is an Antenna ?

Ans: we have several definitions for antenna, they are as follows :

• An Antenna is a transducer,i.e, it converts electrical signals to Electromagnetics Wave at the transmitter and vice versa at the receiver.
• An Antenna is a sensor and radiator of EM waves.
• An Antenna is a perfect impedance matching device.
• Any piece of conducting material or wire acts as an Antenna on excitation.

Q2) What is a Isotropic radiator ?

Ans: It is an Antenna which radiates equally in all directions. It is also called as reference antenna.

Q3) What is a Omni Directional Antenna ?

Ans: It radiates equally in all directions in azimuthal plane and radiates in single direction in elevation plane.

Q4) Name some of the Antenna Parameters ?

Ans: some of the Antenna parameters are as follows:

• Antenna Impedance
• Radiation pattern
• Radiation Intensity
• Directive Gain
• Power Gain
• Efficiency
• Effective area
• Front to Back ratio
• Antenna Bandwidth

Q5) What is a Radiation Pattern ?

Ans: Radiation pattern is the variation of electric field strength with respect to elevation angle.

Q6) What is Radiation Intensity ?

Ans: It is the radiated power per unit solid angle.

Q7) What are the units of Solid angle ?

Ans: Steradian

Q8) What is the effective length of an Antenna ?

Ans: It is the length of Antenna which is responsible for transmission or reception of EM waves.

It is always less than the actual length of an Antenna.

Q9) What is Antenna Bandwidth ?

Ans: It is the range of frequency over which antenna will perform satisfactory without any change.

Q10) What is Antenna Arrays ?

Ans: It is the system of Antennas similarly oriented or dis similarly oriented to achieve maximum gain or directivity.

Q11) What are advantages of Antenna Arrays ?

Ans: Advantages:

• Enhancement in gain
• Enhancement in directivity
• Reduction in Beam width

Q12) What are disadvantages of Antenna Arrays ?

Ans: Disadvantages:

• Side lobes increases
• Cost increases
• complexity increases
• more space is required for installation

Q13) What is a Broad side Array ?

Ans: If the principal maxima or Radiation pattern is perpendicular to axis of array then it is Broad side array.

Q14) What is End fire Array ?

Ans: If the principal maxima or Radiation pattern is along the axis of array then it is Broad side array.

Q15) What is Front to Back ratio in Antennas ?

Ans: It is the ratio of radiation in desired direction to that of radiation in opposite direction. For an ideal Antenna it is infinity.