Research On The Frequency Reconfigurable And The Pattern Reconfigurable Antennas

With the complexity of the electromagnetic information and the diversification of the working environment, the requirement of wireless communication systems is becoming more and more strict. A well designed antenna is equivalent to a good energy converter, which plays an important role in that efficient transmission of electromagnetic waves. However, there are different requirements in application, which requires the communication system to work in different environment. This requires a multiple antenna to replace a single performance of the traditional antenna to accommodate that changing work environment. Reconfigurable antenna is widely used in wireless communication systems because of their variability in-frequency, direction and polarization.This paper mainly is from the theoretical analysis to the simulation, and finally to the experimental verification for the whole process to complete. The design and experiment process of the antenna are described in detail .In the third chapter of this paper, a frequency reconfigurable antenna with a wide L slot on the surface is described in detail. A good impedance matching is achieved by opening the L slot on the surface and the F type radiation patch on the microstrip antenna, and a PIN diode is used to switch the on-off modes to make the antenna work in two different frequency states. The two wide frequency states include 3.18-4.98 GHz and 4.88-5.88 GHz,which can cover the most frequency band of the WLAN and the WiMAX band. In this design, only one diode is used to realize more frequency bands of the wireless network and the wireless LAN, and the size of this antenna is very small(22.1 × 23.85 mm), which is one of the advantages of the design. Finally, the antenna is well measured, and the experimental results are consistent with the simulation.The fourth chapter introduced an antenna, which not only can achieve the frequency reconfigurable, but also can realize pattern reconfigurable. The design of the antenna is described in terms of the structure of the antenna, the optimized parameters,the reflection coefficient curves and the pattern. In the domestic and foreign literature,we can know that the different models of one antenna can be simply changed to achieve the combination of two reconfigurable models. What is more, the structure is simple and few to see. Therefore, this is also a major advantage of this design. The frequency of the antenna at the center frequency of 0.87 GHz and 0.94 GHz can be reconstructed, and at the same time, the two kinds of patterns can be achieved at 0.94 GHz and 1.14 GHz,and the three kinds of patterns can be realized at the same time at 3.3 GHz, which can cover the frequency bands of the UHF band and the WIMAX band. The experimental results are consistent with the simulation.The development of antenna is focus on high precision, high efficiency, low loss,low frequency and miniaturization. The future development of reconfigurable antenna has a long way to go.