Multipole Approach In Metamaterials And Applicaton In Microwave Device

Metamaterials (MMs) make people have a qualitative change on their understanding to substance. They have opened a new research domain for electromagnetic field because of their unique electromagnetic properties and tremendous application value. MMs have a huge application prospect in the fields of satellite communications, radar, microelectronics, medical imaging and so on. This promotes the rapid development of MMs. In a sense, MMs have provided us with a new way to design materials of our own volition. We can design any values of epsilon, mu and refraction index. MMs also provide a new way for us to study some physical phenomena and obscure features. Therefore, to explore MMs’new properties and complete its theoretical system and analytical methods has a very significance in applications such as microwave devices.The research results in this thesis can be summarized as follows on the base of MMs’simulation and experiment.1. We have a research on the design method of ultrathin planar negative refraction index MMs and their applications in absorbers. Electromagnetic wave is incident on the side of traditional negative refraction index MMs. This makes the MMs have a cumbersome and thicker structure. Complex interference such as secondary scattering also exists in these MMs. Hence, we design a new type of planar and ultrathin MMs. The aporia of design this kind of MMs is how to achieve effective negative magnetic response in a limited plane. This thesis has designed two type of ultrathin planar negative refraction index MMs. Research on MMs’application in ultrathin planar absorbers is also studied. Experiments show that these MMs absorbers have a thickness of0.5mm (0.15λ0) with absorptivity of more than99%.2. We propose two design methods of combination and unique configuration methods to design dual-band MMs. Ring resonator is a basic element of MMs. Its eigenfrequency is strongly dependent to its own size. For this reason, we can regulate and control its resonant frequency by the way to change the unitcell’s size. The first way to design dual-band MMs in this thesis is the combination method. Different resonant frequencies can be achieved in one periodic unitcell by importing different unitcells with their own eigenfrequency. Nevertheless, the combination method will increase its unitcell size after introduce several different size. Thereby the MMs will produce a grating lobe effect similar to the frequency selecting surface. Then we improved the dual-band design method to unique configuration and verified by experiment. Experiments show that polarization angle and incident angle almost have no side effect on their characteristics.3. We propose an electric toroidal dipole model verified by simulation and experiment. Then multipole analytical method is built to analyze stereo MMs’ electromagnetic properties. Toroidal MMs have complex electromagnetic coupling among their effective’atoms’. Its interaction with electromagnetic wave has relationship with the resonant characteristics of the’atom’itself and cross coupling among these ’atoms’. Therefore, its resonance characteristic mechanism will become more intricate. But the method to calculate multipole scattered energy combined with current and electric/magnetic field distribution analysis has a clear physical picture of the internal mechanism. It also makes the design of stereo MMs more controllable. We have a research on toroidal MMs’coupling among multipole and scattered energy from circular dichroism. The circular dichroism at4GHz and9.5GHz links to the coupling among electric dipole, magnetic dipole and electric quadrupole moments. Then we verified a new multipole which can be achieved by a closed loop of magnetic dipole arranged head-to-tail. This new multipole is magnetic toroidal dipole. Based on the duality of electricity and magnetism, we first propose the electric toroidal dipole corresponding to the magnetic toroidal dipole. It can also be generated by a closed loop of electric dipoles arranged head-to-tail. We modeled U-shape stereo MMs to achieve electric toroidal MMs. This model has a peak of electric toroidal dipole energy at6.55GHz by inhibiting multipole energy. At the same time, we also use multipole analytical method when we design the negative refraction index MMs and absorbers. It’s used to calculate the scattered energy of electric dipole and magnetic dipole.4. We have designed and tested a dual-and broad-band band stop filter based on the complementary split ring resonator (CSRR). Combination method has been used to design this filter. Due to the narrow band of filters with traditional SRR, The complementary SRR can increase bandwidth effectively. Hence, we can achieve a dual-and broad-band band stop filter with relative bandwidth of11.1%and11.3at6.03GHz and7.10GHz, respectively. These results show that there are many advantages to design MMs-based devices, such as high selectivity, small size, strong resonance, multi-band and broadband.This thesis also explores MMs’other important characteristics. For example, we can design non-resonant MMs with small changes in electromagnetic parameters, low-loss MMs and absorbers based on high-impedance surface MMs. We can also have a summary on planar electric resonance unitcells. In a word, we designed a variety of MMs models. The method of multipole scattered energy combined with current and electric/magnetic field distribution analysis has been proposed. This method can be used to study the interaction between MMs and electromagnetic wave and MMs’internal mechanism. At last we explore MMs’application in microwave devices.