Circularly Polarized Wave Through An Aperture Coupled Study

In this paper, we use the Finite-Difference Time-Domain (FDTD) method to study the coupling effects of linear polarized waves and circular polarized waves. Circular polarized waves have more advantages than linear polarized waves: circular polarized waves have less loss when penetrate through the rain and fog layer or the ionosphere, so they are easy to spread at bad weather. With the vector endpoint of electric field intensity paints circle in the space, the electric field of circular polarized waves transmit in a spiral way, so there is no polarization rotation as linear polarized waves. In the process of coupling of circular polarized waves into cavity with slots, there is always a certain energy coupling into the cavity no matter which direction the slots of cavity is. With the accumulation of energy in the cavity, it can be formed stronger coupling effects. So far, there is much study on coupling of linear polarized waves into cavity with slots, but the research on coupling effects of circular polarized waves has not been reported.At first of the paper, the applications of HPM pulse in the electronic warfare and the characteristics of HPM coupling effects on electronic device are introduced. The introduction of these situations shows that it is advanced and exploratory to do researches on HPM coupling effects. For the second, the characteristics, development process and difference equations of Finite-Difference Time-Domain method which based on Yee's difference algorithm are introduced. The time step and spatial step relations that is at the same time satisfy the stability condition and the numerical dispersion conditions is discussed and summarized. And the three-dimensional absorbing boundary conditions of FDTD form and local fine grid is discussed. Then primary research is done into the incident plane waves, so the polarized characteristics of electromagnetic waves characteristics of circular polarized waves and the incident linear polarized waves and polarized waves are analyzed, and physical model of coupling of HPM into cavity with slots is depicted. At last, coupling of linear polarized waves and circular polarized waves in the carrier frequency band 2GHz to 13GHz into cavity with slots is studied, and the relative coupling coefficient is analyzed. In the S-band, the coupling effects of circular polarized waves are stronger 10% to 30% than linear polarized waves on the same model. But in the X-band, the coupling effects of circular polarized waves are stronger 60% to 95% than linear polarized waves.The results show that the circular polarized waves have bigger transmission coefficient than linear polarized waves in the carrier frequency band 2GHz to 13GHz, and the transmission coefficient of circular polarized waves is nearly twice of linear polarized waves. Circular polarized waves are easier to couple into the cavity through slots, have less loss and more energy into the cavity in the coupling process than linear polarized waves, and will not have the complete mismatch polarization phenomenon. Because of asymmetric loss of energy, there are irregular elliptical polarized waves when circular polarized waves coupling into cavity with slots. With the special advantages, circular polarized waves have broad application prospects in the microwave weapons and electromagnetic compatibility.