Electronic operating at high frequencies can have problems with emission of high frequency noise. Once put inside an enclosure, the energy will add in phase at certain frequencies to cause resonances which will hinder the performance of the device. A good example of this phenomenon is seen in Figure 1. The amplifier was measured in the condition shown and subsequently remeasured inside of its enclosure. When put inside the enclosure the performance was severely degraded due to cavity resonances inside of the enclosure. The measured data is shown below in Figure 2.