In Compliance

A case study describing the influence of TFT LCD graphics on automotive radiated emissions testing and its impact to the FM band receiver. The underlying root-cause of the EMI issue is determined using a novel technique that decodes the display’s graphics into the transmitted RGB data and predicts the data’s impact to radiated emissions. The countermeasure implemented to resolve the issue is equally novel and does not involve any hardware optimizations. The use of test images to be used in component level EMC testing is also discussed.

In the rush to complete RF immunity testing on schedule, it is not all that unusual to overlook inherent test equipment limitations. While some test equipment characteristics such as power amplifier harmonics are obviously a limiting factor, the broadband characteristics of antennas, directional couplers, power meters and isotropic field probes can hardly be considered a limitation for most applications. However, when used with power amplifiers exhibiting significant harmonic distortion in Immunity test systems, the broadband characteristics of these devices can result in measurement uncertainty and unacceptable errors.

One hundred million volts, more or less. That is the potential that is developed as roiling masses of air and water and ice molecules furiously swap electrons during a thunderstorm. Charge separation, caused by the friction in the air, related to the mechanism of static built up by rubbing balloon on cat, fills the atmosphere with pockets of ions–positive and negative. As the voltages build, the normally-insulating air molecules stress and disassociate and filaments of current crackle across the sky, releasing mega-joules of energy in each stroke. The supersonic expansion of the ionized air along the stroke path, boiled to a plasma, cracks in a sonic boom, rolling across the sky as thunder.

The Method of Moments has become one of the most powerful tools in the RF engineer’s arsenal. In this chapter, we make the transition from theory to practice, first by attempting to compute the characteristics of a “short dipole” by hand, and then by demonstrating that a computer can do that in just a few seconds.

It is time to put these equations to work by computing the radiation from a simple structure, a short wire element.