[PhasedArrayToolbox] IsotropicAntenna directivity issue

Hello. I don't understand behaviour of directivity function for IsotropicAntenna from Phased Array Toolbox (Matlab R2014b). I supposed, that for Isotropic Antenna its directivity D(phi, theta) = const = 1 = 0 dBi. But in Documentation Center's example D = const = 0.1102e-3. That's the code:

myAnt = phased.IsotropicAntennaElement();
ang = [-30,-20,-10,0,10,20,30; 0,0,0,0,0,0,0];
freq = 1e9;
d = directivity(myAnt,freq,ang)

Output

   d =

   1.0e-03 *

    0.1102
    0.1102
    0.1102
    0.1102
    0.1102
    0.1102
    0.1102

Could anybody explain this? Thank you.

Answer 1

[Honglei Chen]

Hi Vitaly,

You are right that the theoretical vale is 0 dBi. The directivity computation in this case is done using numerical integration with one degree spacing in both azimuth and elevation directions so the result is not exact.

[Vitaly Krepak]

Thank you!