Microwave ablation(MWA)is a cancer treatment method.The tumor tissue absorbs electromagnetic energy,which heats and kills it.A microwave ablation antenna plays a critical role in this process.Its radiation field must completely cover the tumor but not the healthy tissue.At present,the radiation pattern of most invasive ablation antennas is spherical.However,in the clinic,the shape of some tumors may be asymmetrical or the antenna cannot be inserted into the center of the tumor for some other reason.In order to solve these problems,a directional heating antenna for microwave ablation is proposed in this paper.The proposed antenna,operating at 2.45 GHz,consists of a monopole and a reflector.The feed is given by a substrate integrated coaxial line(SICL)and coplanar waveguide(CPW).The omnidirectional radiation field of the monopole is reflected by a reflector that is extended from the outer conductors of the SICL to form a directional radiation field.The impedance matching network is designed on SICL to match the antenna to 50 Ω.The antenna is fabricated using a mature printed circuit board(PCB).The reflection coefficient of the antenna in porcine liver tissue measured by a vector network analyzer shows good agreement with the simulations.Then,an ablation experiment in porcine liver is conducted with power of 10 W for 10 min,and the experimental results confirm the validity of the design.