What is the purpose of modulating the output signal of a spread spectrum MEMS clock oscillator?
By modulating the output signal, the EMI on the output signal is ‘spread’ over a larger frequency ‘spectrum’. The total amount of energy is still present, but the spreading of the output power over the frequency band results in a reduction of EMI at any one frequency. As mentioned above, regulatory bodies like the FCC have maximum limits for peak EMI emissions (emissions at any one frequency within the spectrum). Thus, a MEMS clock oscillator can be used to pass FCC regulatory EMI test requirements by reducing EMI peak emissions.
