Simple Formula for Eliminating Grating Lobes in EMAT Phased Arrays

EMAT phased arrays are advantageous compared with piezoelectric transducer (PZT) phased arrays because no direct contact with the specimen is needed. The performance of phased arrays can be improved as the spacing distance of the array elements increases. However, for avoiding the grating lobes, the array element spacing should be less than half the wavelength is usually accepted. In this paper, to eliminate the grating lobes, a simple formula is proposed to calculate the spacing distance of the array elements. The formula shows that the array element spacing is greater than half the wavelength can be used in some cases, e.g., the steering angle is relatively small. The validity of the formula is verified by simulated results and experimental results.