Predicting multimode chassis resonance of single or nested rectangular computer enclosures

Designing standardized six-sided computer enclosures that contain multiple types of active circuitry across several products, it is critical to predict and qualify excited cavity resonances against the expected harmonic spectrum generated by the active circuits. Moreover, if the enclosure or chassis is housed within another enclosure, it is also important to predict resonances of the larger housing enclosure. This paper presents a simplified method of quickly determining rectangular chassis enclosure resonances using simple multimode resonant cavity formula and no electromagnetic field solvers. Key resonance frequencies are assigned a risk category depending on number of modes excited, and effective `Q´ of each resonance frequency.