Antenna Wave Propagation
SUBJECT: ANTENNAS AND WAVE PROPAGATION
1. Define an antenna. Antenna is a transition device or a transducer between a guided wave and a free space wave or vice versa. Antenna is also said to be an impedance transforming device. 2. What is meant by radiation pattern? Radiation pattern is the relative distribution of radiated power as a function of distance in space .It is a graph which shows the variation in actual field strength of the EM wave at all points which are at equal distance from the antenna. The energy radiated in a particular direction by an antenna is measured in terms of FIELD STRENGTH.(E Volts/m) 3. Define Radiation intensity?
The power radiated from an antenna per unit solid angle is called the radiation intensity U (watts per steradian or per square degree). The radiation intensity is independent of distance. 4. Define Beam efficiency? The total beam area ( ΩA) consists of the main beam area ( ΩM ) plus the minor lobe area ( Ωm) . Thus ΩA = ΩM+ Ωm . The ratio of the main beam area to the total beam area is called beam efficiency. Beam efficiency = ΣM = ΩM / ΩA.
5.Define Directivity? The directivity of an antenna is equal to the ratio of the maximum power density P(θ,φ)max to its average value over a sphere as observed in the far field of an antenna. D = P(θ,φ)max / P(θ,φ)av. Pattern. D = 4π / ΩA. . area(ΩA ). Directivity from Directivity from beam
6.What are the different types of aperture.? i) Effective aperture. ii). Scattering aperture. iii) Loss aperture. iv) collecting aperture. v). Physical aperture. 7.Define different types of aperture.? Effective aperture(Ae). It is the area over which the power is extrated 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
1. Define an antenna. Antenna is a transition device or a transducer between a guided wave and a free space wave or vice versa. Antenna is also said to be an impedance transforming device. 2. What is meant by radiation pattern? Radiation pattern is the relative distribution of radiated power as a function of distance in space .It is a graph which shows the variation in actual field strength of the EM wave at all points which are at equal distance from the antenna. The energy radiated in a particular direction by an antenna is measured in terms of FIELD STRENGTH.(E Volts/m) 3. Define Radiation intensity?
The power radiated from an antenna per unit solid angle is called the radiation intensity U (watts per steradian or per square degree). The radiation intensity is independent of distance. 4. Define Beam efficiency? The total beam area ( ΩA) consists of the main beam area ( ΩM ) plus the minor lobe area ( Ωm) . Thus ΩA = ΩM+ Ωm . The ratio of the main beam area to the total beam area is called beam efficiency. Beam efficiency = ΣM = ΩM / ΩA.
5.Define Directivity? The directivity of an antenna is equal to the ratio of the maximum power density P(θ,φ)max to its average value over a sphere as observed in the far field of an antenna. D = P(θ,φ)max / P(θ,φ)av. Pattern. D = 4π / ΩA. . area(ΩA ). Directivity from Directivity from beam
6.What are the different types of aperture.? i) Effective aperture. ii). Scattering aperture. iii) Loss aperture. iv) collecting aperture. v). Physical aperture. 7.Define different types of aperture.? Effective aperture(Ae). It is the area over which the power is extrated 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