Research On A Novel Precise Tunable Antenna With Multiband

With the rapid development of modern communication technology and the continuously demand of multifunction, bandwidth and high-capacity in wireless communication information systems, the needs of the antenna numbers in the same communications equipment will continuously increase, this will lead to many questions such as volume increases, weight increases, electromagnetic incompatibility and noise interference. Therefore,in order to expand system function while to meet the requirements as reducing the system volume, simplifying the hardware module, adjusting frequency flexibly, it’s a very good solution to take a single antenna with frequency tuning functionfor above questions.Also, it can greatly improve the equipment performance of the whole system and can solve the traditional design constrains to the development of wireless communication system, thus making the system having the flexible frequency and radiation performance.In this paper, researches on tunable antenna are designed based on microstrip antenna, it proposes two kinds of design proposal to realize tunable antenna, and also discusses their advantages and disadvantages. The paper’s main content is divided into the following section:Firstly, this paper briefly introduces the basic concept and the research background of the tunable antenna, also it analyzes and summarizes the Overseas and Domestic Research Status on frequency tunable antenna, and then introduces the basic parameters of antenna, compare with and select the solutions.Secondly, this paper uses traditional design method to design a kind of rectangular slot microstrip antenna fed by coaxial, through loading capacitor in the ground and on the sides of the radiation patch it can realize continuous frequency tuning of the antenna and impedance matching. What’s more, it can realize discrete frequency change by loading RF MEMS switches in the rectangle radiation patch slot. Then we can achievea large tuning frequency range. The simulation results prove that the antenna has 1.6GHz to 2.5GHz frequency range, and it’s return loss can be less than-10 dB in the whole frequency range.Then, this paper provides a new design method of the tunable antenna, the method is based on band-pass filter and UWB antenna. The methoduse band-pass filter to feed the UWB antenna, the resonance frequency of the antenna is decided by the filter. So, we can load the RF MEMS switches and varactors in the filter to control the resonance electronic length to change the resonance frequency of the antenna. This design thought subvert the traditional design thought, realizing tunable antenna on the premise of that do not change the input impedance and do not change the fed-line impedance. The simulation and experimental results prove the validity of the design, it’s return loss can reach less than-15 dB during 1.7GHz to 2.15 GHz, 2.27 GHz to 2.7GHz, 2.76 GHz to 3.15 GHz, whose impedance match is very good among the each case. Theoretically,the tuning frequency of the antenna can be as the same as the bandwidth of the UWB antenna.Finally, this paper compare the two design thought and analyzes their advantages and disadvantages.