Phase-conjugate arrays and phase-conjugated fields produced by the arrays

Phase Conjugate (PC) arrays can make sound waves travel backwards to converge, which can then be used to build the image of a noise source. This paper reviews and analytically studies three types of PC array (monopole PC array (PC/M), dipole PC array (PC/D) and perfect PC array (PC/P)) and the phase-conjugated fields produced by the arrays. The relationship between the sound field produced by the source and the phase-conjugated fields produced by the arrays are discussed. The various PC schemes are compared and analyzed from the evanescent wave component and the propagating wave component. The metrics of the focusing properties of PC arrays and the effects of the array element spacing on the focusing properties are discussed. The spatial resolutions of various PC schemes with different distances between array and source are studied numerically with linear arrays. The element deviation is also discussed. A numerical simulation shows that PC/D with half-wavelength element spacing is effective at near field focusing, and PC/M with half-wavelength element spacing is effective at a greater distance.