Analytical modelling and calculation of pulsed magnetic field and input impedance for EMATs with planar spiral coils

The analytical expressions of magnetic flux density, pulsed eddy current and input impedance for EMATs with single-layer and double-layer planar spiral coils in frequency-domain were derived in terms of separation of variables and superposition theorem. The Truncated Domain Eigen-function Expansion method (TREE) was used to solving the infinite integral problem by series summation. The time-domain magnetic flux density, pulsed eddy current and Lorentz force were calculated through FFT-IFFT method. The calculated results of the proposed method were compared with those of time step FEM method and measurement. Their good agreement verifies the accuracy and validity of the proposed model and method.