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List and explain antenna parameters

Short answer

Antenna parameters include radiation pattern, directivity, gain, efficiency, beamwidth, bandwidth, input impedance, radiation resistance, polarization, effective aperture, side lobe level and EIRP. Directivity is D = 4πU_max/P_rad, gain is G = ηD, and HPBW is the half-power angle, for example 90° for a short dipole.

List the parameters of antenna and explain any three of them.

Antenna parameters are the quantities used to describe the performance of an antenna.

List of antenna parameters

  1. Radiation pattern
  2. Directivity
  3. Gain
  4. Radiation efficiency
  5. Beamwidth (HPBW, FNBW)
  6. Bandwidth
  7. Input impedance
  8. Radiation resistance
  9. Polarization
  10. Effective aperture (effective area)
  11. Front-to-back ratio, side lobe level
  12. EIRP

Explanation of three parameters

1. Directivity

D = U_max / U_avg = 4π U_max / P_rad

It is the ratio of the maximum radiation intensity to the average intensity. For a short dipole U = U0 sin²θ, P_rad = 8πU0/3, so D = 1.5 (1.76 dBi). For narrow beams D ≈ 41253/(θ1° θ2°). Isotropic D = 1; λ/2 dipole 1.64.

2. Gain

G = 4π U_max / P_in = η D

Gain includes losses, so G ≤ D. Expressed in dBi; dBi = dBd + 2.15. Also G = 4πAe/λ² for aperture antennas. Example: a 1.2 m dish at 12 GHz with 55 % efficiency has G ≈ 41.0 dBi.

3. Half power beamwidth (HPBW) The angle between the two directions of the main lobe where power is half (−3 dB) of maximum. For a short dipole, sin²θ = 0.5 gives θ = 45° and 135°, so HPBW = 90°; λ/2 dipole ≈ 78°.

        max
       .---.
 0.707/  |  \0.707
     /<HPBW>\
    /         \

A narrow beamwidth means high directivity and better rejection of interference from other directions.

✓ Answer checked by Claude Opus 5.5 (high effort)

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