| Microstrip antenna has attracted great attention and be researched in antenna field due to the advantages of low profile,easy fabrication,light weight and easy integration.Metamaterials are artificial composite materials with sub-wavelength structure,and they can implement some singular physical features that are not available in nature.As a typical metamaterial structure unit,the split ring resonator has been widely studied and applied in many fields such as microwave devices and antennas.The split ring resonator structures also have brought breakthroughs in the aspects of high gain,small size and multi-bands of microstrip antenna.Aiming at the problems that the band(or the notch band)numbers of the microstrip antenna are limited,this paper proposes a method to improve them by introducing the split ring resonator structure to windmill quad-band antenna and dual-band notch ultra-wideband antenna.A new type of windmill multi-frequency antenna is designed in this paper.The characteristics of antenna are analyzed through electromagnetic simulation software CST.The relationships among the numbers of working frequency bands,the position of helical rings and the numbers of windmill blades are investigated firstly.Then,windmill microstrip antennas with dual-frequency,tri-frequency and quad-frequency characteristics are designed respectively.Through building relevant experimental platform and measuring the antenna's performance,the results show that the designed quad-band antenna can effectively work in UMTS(2.1GHz),WLAN(2.45GHz),Wimax(3.5GHz)and X-band satellite downlink communication(7.2-7.6GHz)with better gain.By introducing the structure of the split ring resonator,more working frequency bands can be obtained and the relationships among the geometrical size,position of the split ring resonator and the new derived frequency bands are further explored.Finally,this new antenna covers WLAN(5.2GHz)and WLAN(5.8GHz)bands,and this new frequency point can be tunable independently.Thus,increasing the number of antenna windmill blades and adding the split ring resonator structure can effectively increase the working frequency bands of the antenna.Above research can lay a technical foundation for the design of multi-frequency microstrip antenna and has a certain practical value.A multi-band notch ultra-wideband antenna also is designed in this paper.Based on the circular patch antenna,the ultra-wideband antenna is obtained with ‘‘I-shaped'' slot cut on the ground plane and it can realize obvious characteristics of dual notched bands by embedding two ‘‘C-shaped'' slots on the surface circular patch.Then the relationships among notch frequency band numbers,slot length and slot position are explored in here.In addition,by introducing the structure of split ring resonator and researching the relationships among the geometrical size,position of split ring resonator and the new derived frequency bands,tri-frequency and quad-frequency notch ultra-wideband antennas are designed accordingly.Finally,relevant experimental platforms are built and the experimental results are in agreement with the simulation results.The tri-frequency notch antenna can cover the frequency bands of Wimax(3.5GHz),WLAN(5.8GHz)and X-band downlink communication(7.2-7.6GHz),the quad-frequency notch antenna can cover the frequency bands of Wimax(3.5GHz),WLAN(5.2GHz),WLAN(5.8GHz)and X-band downlink communication(7.2-7.6GHz).Moreover,they all have good omnidirectional radiation characteristics.Therefore,Combination of slotting method and loading split ring resonator method can effectively increase the number of notch bands,which has certain guiding significance for the design of multi-frequency notch antenna. |
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