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Other methods of converting phase to amplitude, including mathematical algorithms such as power series can be used, particularly in a software NCO. Figure 1: Numerically controlled oscillator with optional quadrature output. When clocked, the phase accumulator (PA) creates a modulo-2 N sawtooth waveform which is
In signal processing, phase noise is the frequency-domain representation of random fluctuations in the phase of a waveform, corresponding to time-domain deviations from perfect periodicity . Generally speaking, radio-frequency engineers speak of the phase noise of an oscillator, whereas digital-system engineers work with the jitter of a clock.
Since the maximum output frequency is limited to /, the output phase noise at close-in offsets is always at least 6 dB below the reference clock phase noise. [ 6 ] At offsets far removed from the carrier, the phase-noise floor of a DDS is determined by the power sum of the DAC quantization noise floor and the reference clock phase noise floor.
Tuning gain and noise present in the control signal affect the phase noise; high noise or high tuning gain imply more phase noise. Other important elements that determine the phase noise are sources of flicker noise (1/f noise) in the circuit, [8] the output power level, and the loaded Q factor of the resonator. [9] (see Leeson's equation).
Thus, noise at f 1 is correlated with f 2 if f 2 = f 1 + kf o, where k is an integer, and not otherwise. However, the phase produced by oscillators that exhibit phase noise is not stable. And while the noise produced by oscillators is correlated across frequency, the correlation is not a set of equally spaced impulses as it is with driven systems.
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.
The two amplitude-modulated sinusoids are known as the in-phase (I) and quadrature (Q) components, which describes their relationships with the amplitude- and phase-modulated carrier. [ A ] [ 2 ] Or in other words, it is possible to create an arbitrarily phase-shifted sine wave, by mixing together two sine waves that are 90° out of phase in ...
A long list of noise measures have been defined to measure noise in signal processing: in absolute terms, relative to some standard noise level, or relative to the desired signal level. They include: Dynamic range, often defined by inherent noise level; Signal-to-noise ratio (SNR), ratio of noise power to signal power