Antenna Parameters
1. i) • Antenna radiation pattern or antenna pattern is defined as “a mathematical function or a graphical representation of the radiation properties of the antenna as a function of space coordinates.” • The radiation pattern is determined in the far-field region and is represented as a function of the directional coordinates. • Radiation properties include power flux density, radiation intensity, field strength, directivity phase or polarization [pic]
ii) ■ The angular separation between the two half-power points is referred to as HPBW. ■ Half-power beamwidth (HPBW) is the angle between two vectors, originating at the pattern’s origin and passing through these points of the major lobe where the radiation intensity is half its maximum ■ To find the points where the pattern achieves its half-power (-3 dB points), relative to the maximum value of the pattern: o Field pattern at 0.707 value of its maximum. o Power pattern (in linear scale) at its 0.5 value of its maximum. o Power pattern (in dB) at -3 dB value of its maximum.
[pic][pic]
iii) ▪ First-null beamwidth (FNBW) is the angle between two vectors, originating at the pattern’s origin and tangent to the main beam at its base.
[pic]
2. Radiation lobes is a “portion of the radiation pattern bounded by regions of relatively weak radiation intensity.” Various lobes can be sub-classified in major or main, minor, side and back lobes
[pic]
3. ▪ A major lobe (also called main beam) is defined as “the radiation lobe containing the direction of maximum radiation”. ▪ A minor lobe is any lobe except major lobe. ▪ A side lobe is “a radiation lobe in any direction other than intended lobe”. Usually a side lobe is adjacent to the main lobe and occupies the hemisphere in the direction of the main beam. ▪ A back lobe is “a
ii) ■ The angular separation between the two half-power points is referred to as HPBW. ■ Half-power beamwidth (HPBW) is the angle between two vectors, originating at the pattern’s origin and passing through these points of the major lobe where the radiation intensity is half its maximum ■ To find the points where the pattern achieves its half-power (-3 dB points), relative to the maximum value of the pattern: o Field pattern at 0.707 value of its maximum. o Power pattern (in linear scale) at its 0.5 value of its maximum. o Power pattern (in dB) at -3 dB value of its maximum.
[pic][pic]
iii) ▪ First-null beamwidth (FNBW) is the angle between two vectors, originating at the pattern’s origin and tangent to the main beam at its base.
[pic]
2. Radiation lobes is a “portion of the radiation pattern bounded by regions of relatively weak radiation intensity.” Various lobes can be sub-classified in major or main, minor, side and back lobes
[pic]
3. ▪ A major lobe (also called main beam) is defined as “the radiation lobe containing the direction of maximum radiation”. ▪ A minor lobe is any lobe except major lobe. ▪ A side lobe is “a radiation lobe in any direction other than intended lobe”. Usually a side lobe is adjacent to the main lobe and occupies the hemisphere in the direction of the main beam. ▪ A back lobe is “a