Analysis and design of microstrip antenna for rectenna of in-pipe micromachine using FDTD method

A circularly polarized microstrip antenna in a stainless steel pipe is analyzed by the finite-difference time-domain (FDTD) method with the PML (perfectly matched layer) absorbing boundary condition. The microstrip antenna is used as a microwave receiving element for in-pipe micromachine inspection. The numerical results agree well with the measured ones.