James Yates
EMC chamber setup

EUT antenna illumination position calculator.

Estimate practical antenna centre positions needed to illuminate a rectangular EUT with a circular antenna footprint. The calculation is numerical, so it is useful for chamber setup planning rather than as a replacement for the relevant test standard or antenna gain model.

Inputs

cm, treated as a circular illumination footprint
percentage of EUT area
cm. Width and height can be swapped; the result may change slightly due to finite sampling.
Advanced settings
Number of sample points along the longest EUT side. Higher is slower but more accurate.
Candidate centre spacing as a fraction of antenna radius.
Thorough tries more centre nudges and is useful near a borderline result.
Groups positions with similar height, averages each row to one y value, then retests coverage. This makes antenna positioning much easier in the chamber.

Result

Enter dimensions and press calculate.
Positions needed
–
antenna centre points
Estimated coverage
–
sampled area inside EUT
Mathematical lower bound
–
area-only minimum
Samples used
–
area test points
covered by antenna footprint estimated uncovered EUT area antenna centre position

Centre positions

Method The page first calculates an impossible-to-beat area lower bound using ceil(required area / circle area). It then searches for practical centre positions and tests the actual EUT area covered by the union of the circles.

The exact least-number circle-covering problem is not a simple closed-form formula for every rectangle and percentage, so this is a practical numerical optimiser. When row alignment is enabled, the optimiser averages similar y positions into common rows and only accepts the aligned result if the requested coverage is still met. Increase the resolution and search fineness if the result is borderline.