Active EMI / RFI Management.

Electro-Magnetic Interference (EMI) and Radio Frequency Interference (RFI) is one of the most challenging problems that the electronic design world faces. Solutions to these problems have a direct and significant impact on the performance, speeds, power, weight, costs and time to market of a product.
Billions of dollars and countless frustrating hours are spent in this effort to secure compliance to regulations laid down by governing bodies across the world. The current approach is by and large one of trial and error and very often degrades system performance and is not the most cost effective either.

LFC Semiconductor specializes in “Active Solutions” based on modulation techniques to spread the energy spectrum of periodic and aperiodic switching signals like clocks over a wider frequency band. This is an extremely effective way to combat these EMI compliance challenges and this article will be focused on this technology.

Statement of the problem:

What is EMI / RFI? EMI / RFI quite simply put, is the emission of unwanted electro magnetic energy. This energy is the equivalent of electrical smog and if not tightly regulated can interfere with the operation of other equipment. EMI is not caused by a single source but is typically the result

of some change in voltage or current. The higher the frequency of change and the larger the voltage or current change, the greater the EMI challenge.

For example, this switching waveform of a clock train can be viewed in the frequency domain as the sum of the frequency components of its Fourier decomposition. The amplitudes of these peaks are determined by the Voltage (amplitude), Duty cycle and Rise and Fall times of the signal.

Figure 1 – Frequency Domain Representation of a Periodic Signal