Far Field Patterns of Aperture Antennas

Joachim Köppen DF3GJ ... Kiel, Aug 2016

- This tool computes the antenna pattern of square and circular dishes,
illuminated either uniformly or with a few laws. This is done for
a point source, which gives the theoretical pattern.
One enters the relevant data and clicks the
**point source**button. The result is shown as a blue curve. The magenta markings indicate the HPBW, and the green curve shows the width of the equivalent lobe with solid angle Ω_{A}if all the power emitted by the antenna (in the displayed range) were radiated at constant strength. - The computation of non-uniform illumination patterns takes some time!
- The pattern can also be computed for a few types of extended sources
which are specified by their angular diameter. If a point source pattern
is displayed, one clicks the
**extended source**button, and the result is shown as a red curve. The gray curve indicates the brightness across the face of the source. - Note that the 1 D source patterns give only approximate results, they require less time, so they can be good for a first rough view!
- From the observed pattern the FWHM (i.e. apparent HPBW), solid angle Ω
_{A}, and the beam filling factor of the source are given. **Display**: one may set the maximum offset angle and choose between linear, logarithmic and deciBel ordinates.**overplot**permits to superpose different plots, in order to compare different patterns.- The mouse position gives the coordinates of that point, allowing to read numerical values from the plot. In some browsers, these values may not correspond to the plot. If this happens, keep this page in its initial top-left corner position.
- Please note that due to the finite accuracy chosen to get reasonably fast computations, one may get weird results if one pushes the tool to extreme choices of parameters! For example, a source diameter larger than 10 times the antenna's HPBW - which nobody really needs to compute - leads to perturbations in the central part of the pattern ...