last highlighted date: 2023-02-03
Highlights
- Has it happened to you? When troubleshooting an electromagnetic interference (EMI) issue, you’ve tried various combinations of components and saw the signal of interest reduced. But another frequency signal unexpectedly raised above the limit line. Or, you introduced a chassis plane on your printed circuit board (PCB), only to find the radiated emissions became much worse instead of getting better. These are typical cases of “tuning the resonances of a circuit.”
- Multiple ferrites were used on the power leads of the camera, but the improvement was not significant enough to suppress the noise (this is another sign of structural resonances). The test also showed an “inconsistency,” as the same noise was measured a lot lower on some occasions (as shown in Figure 2b). We accidentally discovered that the difference in the emission results was caused by the door of the vehicle. When the door was open, the noise emission was significantly less than when the door was closed.