Radiation Pattern of a Dipole Antenna
As a Function of Dipole Length

2003/5 Takuichi Hirano

Current Distribution is approximated by sine
i(z)=I0 sin(k0(h-|z|))

z is axis along the dipole and z=0 is a feed point.
i(z) is the current distribution as expressed in R.H.S.
|z| in the equation means the absolute value of z.
k0 is a wavenumber in free space (2*pi/lambda0).
h is a half dipole length l (h=l/2), or h is a monopole length.
I0 is the magnitude of the current.
Confirm that the magnitude of the current is zero at the ends of dipole: i(h)=i(-h)=0.
Sine function represents the shape of standing wave on the dipole antenna.

dB Pattern, Normalized by Maximum

E-Field（H-Field）Linear Pattern, Normalized by the Value of Half-Wavelength Dipole (Theta=90degrees)

[Mathematica 4.2 Source File]

• pat_dB.nb
• pat_lin.nb
• current.nb

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