Platform interference has quickly become one of the most challenging issues for manufacturers building in wireless technology into new or existing products. Success depends on carefully designing the entire product to ensure minimal EMI. Proper circuit board layout and stack-up is a key factor for success. Cutting corners by simply “bolting on” a cellular modem to an existing product is a recipe for disaster.
Ken Wyatt tackles this in an informative article here. He describes measurement setups for general PC board noise characterization using a Rigol DSA815 Spectrum Analyzer. Near
field probes are used to narrow down the areas of noise generation and
to characterize the type of noise produced at the board. In this case, a
high frequency current probe is being used to measure the USB cable
harmonic currents coupled to the outside of the shielded cable.