Microwave heating device with reflection protection

A microwave heating device with reflection protection, comprising:

• a microwave generator (22),
• a circulator (23),
• a water load (24),
• a microwave transmission device (25), and
• a reaction chamber (26);
• wherein a first port of the circulator (23) is connected to the microwave generator (22), and a second port of the circulator (23) is connected to the microwave transmission device (25);
• the microwave transmission device (25) is connected to the reaction chamber (26);
• the water load (24) comprises a waveguide section (21), a metamaterial structure layer (3) and an absorption tube (16);
• one end of the waveguide section (21) is connected to a third port of the circulator (23), and the other end is sealed by a metal plate;
• the metamaterial structure layer (3) is arranged in the waveguide section (21);
• a center of the metamaterial structure layer (3) has an accommodation space (4);
• the absorption tube (16) is arranged along an internal wall of the accommodation space (4) with a spiral extending form;
• both ends of the absorption tube (16) penetrate the waveguide section (21), and water flows in the absorption tube (16);
• relative dielectric constants of materials forming the metamaterial structure layer (3) gradually increase from outside to inside, so that microwaves passing through the metamaterial structure layer (3) are converged in the accommodation space (4);
• wherein the metamaterial structure layer (3) comprises multiple ring columns (5) nested in sequence from inside to outside;
• the accommodation space (4) is a cylindrical space with a radius of r;
• a radius of the metamaterial structure layer (3) is R;
• a relative dielectric constant of an external space of the metamaterial structure layer (3) is ε0;
• the relative dielectric constants at each position point of the metamaterial structure layer (3) constitutes a step function;
• a distance between the position point and a center of the accommodation space (4) is d, and R>d>r;
• each step of the step function intersects with another function ε(d)=ε0(R/d)2.