Controlled near-field boundaries to improve microwave heating performances

In this paper, we show that controlled near-field boundaries (CNFBs) fabricated from height-shiftable plate arrays (HSPAs) exhibit significant influences on the electromagnetic field distribution, which largely determines the performances of microwave heating; the significant influences provide a possibility to further improve the performances of microwave heating. First, the near-field boundary is proved theoretically having more influences on electromagnetic fields than the far-field boundary. Then, the CNFBs are fabricated by respectively placing three HSPAs, 2 × 2, 3 × 3, and 4 × 4, in a microwave reaction cavity (MRC). Based on the HSPA-MRC, three heating strategies are proposed to achieve extreme heating efficiency, excellent heating uniformity, and the best comprehensive heating performance, respectively. Compared with the conventional MRC, the proposed HSPA-MRC raises 56.27% heating efficiency and 394.64% heating uniformity. To validate the simulation results, a corresponding experiment system is built and experiments are carried out; the results of the experiments agree very well with simulations. Finally, the sensitivity of the proposed heating strategies is analyzed by heating samples with different shapes, sizes and materials.