Gain-HPBW relation of uniformly illuminated circular dish antennas
Joachim Köppen DF3GJ Kiel, Jul 2018
Some brief explanations
The green curve is an approximative relation from Kraus:
gain = 41000/(HPBW_h * HPBW_v)
which uses the HPBWs (in degrees) in horizontal and vertical direction to estimate the
solid angle Ω
A of the antenna's main lobe. Kraus (Antennas for all Applications,
3rd ed., 1997) writes: "... formulas like [this] ... are useful in the context that if we know
that an antenna has a 1° pencil beam and small minor lobes, its gain is approximately 41 000
or 46 dB, give or take a decibel or two, but not that the result is accurate to 1/10 of a
decibel or better."
The red curve is a more accurate formula which is also consistent with the HPBW-diameter relation
HPBW = 58.95701° λ/Deff for evenly illuminated circular dishes.
The mouse position shows HPBW (half power beam width), BWFN (beam width between first nulls),
and the gain in dBi.