The current loop area on a PCB which will cause problems with regard to legislative emission requirements.
The E field strength limit at 3 m distance in Standards is 40 dBuVm^{1} or 100 uVm^{1}.
Considering OATS measurement with +6 dB inphase reflection from ground plane, the max loop area that will not exceed specified level can be determined from:
where:
E is radiation limit in microvolts per metre r is distance to measurement in metres f is frequency in MHz I is current in milliamps
See page 301 of "Noise Reduction Techniques in Electronic Systems" by Henry
Ott.
