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Spread-spectrum clocking, like other kinds of dynamic frequency change, can also create challenges for designers. Principal among these is clock/data misalignment, or clock skew. A phase-locked loop on the receiving side needs a high enough bandwidth to correctly track a spread-spectrum clock. [9]
Another common application is to get through EMC tests by using spread spectrum clock dithering of frequency to smear out single frequency peaks. [29] Another type of temporal dithering has recently been introduced in financial markets, in order to reduce the incentive to engage in high-frequency trading.
spread-spectrum clocking reduces EMI in systems that are clocked from the oscillators FSXO – Frequency Select Oscillator 20–100 ppm Those requiring frequency agility and multi-protocol serial interfaces. Clock output frequencies are changeable with hardware or serial-select inputs, reducing BOM and simplifying the supply chain
Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly changing the carrier frequency among many frequencies occupying a large spectral band. The changes are controlled by a code known to both transmitter and receiver .
Direct-sequence spread-spectrum transmissions multiply the symbol sequence being transmitted with a spreading sequence that has a higher rate than the original message rate. Usually, sequences are chosen such that the resulting spectrum is spectrally white. Knowledge of the same sequence is used to reconstruct the original data at the receiving ...
A phase-locked loop or phase lock loop (PLL) is a control system that generates an output signal whose phase is fixed relative to the phase of an input signal. Keeping the input and output phase in lockstep also implies keeping the input and output frequencies the same, thus a phase-locked loop can also track an input frequency.
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In some protocols, such as SATA, the symbol rate is intentionally varied by use of spread spectrum clocking, so assuming a fixed rate will lead to the eye grossly exaggerating the actual jitter present on the signal. (While spread spectrum modulation on a clock is technically jitter in the strict sense, receivers for these systems are designed ...