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Signal Characteristics
Published in Kevin Robinson, Practical Audio Electronics, 2020
A static phase relationship specifically applies to sine waves of the same frequency and it is not on the whole meaningful to talk about the relative phase of two more complex signals. Two arbitrary signals will constantly move in and out of phase with one another. When both are up at the same time or both are down at the same time they might be considered in phase, and when one is up as the other is down they can be said to be, to a greater or lesser extent, out of phase. This is not however a very useful analysis on the whole. Two sine waves of the same frequency will have a constant phase relationship, being either completely in phase or some specific degree out of phase. Phase is measured in degrees with 360° in a full cycle. If two sine waves of the same frequency are moved relative to each other they will continually move in and out of phase. Phase relationships become very important when multiple signals (be they acoustical or electrical) are being combined or otherwise manipulated. Comb filtering and other unwanted artifacts can result. Some electronic circuits are also capable of altering the phase relationships of various components of a signal. Sometimes this is an unwanted side effect (as in filters and EQs) and sometimes it is used to advantage (as in effects like phasers and flangers).
All About Wave Equations
Published in Bahman Zohuri, Patrick J. McDaniel, Electrical Brain Stimulation for the Treatment of Neurological Disorders, 2019
Bahman Zohuri, Patrick J. McDaniel
Analysis of Figure 2.65 indicates that interferometer is nothing more than being just a phase. The extent to which one wave is in step with another is known as its phase. If two identical waves are “in phase,” it means their peaks align so, if we add them together, we get a new wave that’s twice as big but otherwise exactly the, same as the original waves. Similarly, if two waves are completely out of phase (in what we call antiphase), the peaks of one exactly coincide with the troughs of the other so adding the waves together gives you nothing at all. In between these two extremes are all sorts of other possibilities where one wave is partly in phase with the other. Adding two waves like this creates a third wave that has an unusual, rising and falling pattern of peaks and troughs. Shine a wave like this onto a screen and you get a characteristic pattern of light and dark areas called interference fringes. This pattern is what you study and measure with an interferometer.
Interference and Diffraction
Published in Abdul Al-Azzawi, Photonics, 2017
When light waves from two light sources are mixed, the waves are said to interfere. This interference can be explained by the principle of superposition. When two or more waves of the same phase and direction go past a point at the same time, the instantaneous amplitude at that point is the sum of the instantaneous amplitudes of the two waves. If the waves are in phase, then they add together, resulting in a larger amplitude. This is referred to constructive interference, as shown in Figure 18.1(a). If the waves are out of phase with one another, then they cancel each other. This is referred to destructive interference, as shown in Figure 18.1(b). If the waves differ in amplitude and are out of phase with one another, then they add to give a partial cancellation or elimination. This is referred to as partial cancellation or elimination interference, as shown in Figure 18.1(c).
Design and Implementation of Digital Phase Locked Loop for Single-Phase Grid-Tied PV Inverters
Published in Electric Power Components and Systems, 2018
The key to achieving the synchronous with the grid voltage is to detect the phase angle information of the grid voltage. PLL is one of the most common methods to detect the phase angle of grid voltage due to its robustness, effectiveness, simplicity [8–12]. A typical single-phase PLL usually comprises of three parts: a phase detector (PD), a loop filter (LP) and a voltage controlled oscillator (VCO). A proportional-integral (PI) controller usually implements the loop filter, which outputs the estimated angular frequency. The integration of the angular frequency determines the phase-angle, which is conducted by the VCO. A phase detector is a frequency mixer or analog multiplier that generates a voltage signal that represents the difference in phase between two inputs. The phase detector (PD) can be constructed in a stationary frame (SF) [10–13] or in a synchronous rotating frame (SRF) [14, 15]. Figure 2 shows the block diagram of a stationary-frame based PLL.