I am interested in antenna gain including both directivity and efficiency.

The pattern() function gives a few options for 'type' including 'directivity', 'efield', 'power', and 'powerdb'. It appears that 'directivity' ignores the antenna efficiency, while the others take it into account. I'm mainly interested in the antenna gain over a frequency range in a specified direction including both directivity and efficiency (preferably in dBi).

It seems like I can use the pattern() function with 'type' set to 'powerdb' and add 65.71 to get dBi gain, but I'm looking for confirmation that this is correct. I obtained that offset (65.71) by modeling a dipole at its tuned frequency and noting the difference between the 'powerdb' output and the 'directivity' output.

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function estgain = monopole_gain_vs_freq(h,w,f1,f2,fstep)

ant = monopole('Height',h,'Width',w);

fvec = f1:fstep:f2;

estgain = zeros(1,length(fvec));

for fidx = 1:length(fvec)

    estgain(fidx) = pattern(ant,fvec(fidx)*1e6,0,0,'type','PowerDb')+65.71;

end

Answer 1

[Vishwanath Iyer]

Hi Brian,

Antenna gain in any direction, when the antenna is without dissipative loss is equal to its directivity.

Dissipative loss can result from :

 a. Loss in the metal - finite conductivity
 b. Loss in dielectric - Loss tangent

These loss mechanisms contribute to the radiation efficiency of the antenna.

In Antenna Toolbox, all antennas are made out of Perfect Electric Conductors(PEC), i.e. infinite conductivity and hence no loss as in (a). Dielectric materials are not supported in Antenna Toolbox, so that rules out (b).

Notice that impedance mismatch has not been taken into account yet. If that is included, we would define a realized radiation efficiency and a realized gain.

So to summarize, for the present example antenna gain and directivity would be the same.