folding frequency การใช้

• From theoretical analysis , we know the existing demodulation methods have limitations as following : one is that the subtraction of the two signals frequencies will display as the result of demodulation when we demodulate two time - domain adding signals without modulating information ( fault information ) ; the other one is that aliasing phenomenon will occur as a result of getting absolute value , detection or square in the process of generalized demodulation analysis , such phenomenon will result in some superfluous frequency composition on the frequency spectrum , which will puzzle the detec tion of mechanical vibration . if the sampling frequency is selected from a suitable range , the aliasing phenomenon will be avoided ; the last one is that aliasing frequencies will be produced in zoom demodulation analysis because this algorithm cannot employ digital low - pass filtering to avert the folding frequencies of higher harmonics in the process of zoom sub - sampling