Research And Design Of Radiation Pattern Reconfigurable Antenna

In recent years,due to the advantages of reconfigurable antenna that can achieve good performance in a variety of different operating modes,many researchers have paid extensive attention to it.And because of the advantages of reducing the volume of the antenna,reducing the cost,having various functions and being easy to apply in diversity,it has a broad application prospect.As a new type of antenna,reconfigurable antenna can reconstruct the parameters of the antenna and have different working modes that can be switched,which is essentially realized by changing the structure of the antenna and then changing the current distribution of the antenna.In this paper,the phase of the antenna is controlled by using PIN switching diode,so as to change the phase relationship among various antenna elements and realize the reconfigurable performance of the antenna radiation pattern.The main research includes:Firstly,a reconfigurable antenna array with a central frequency of 2.45 GHz and a monopulse radiation mode for wireless local area network(WLAN)access points was designed.Three phase converters capable of ±90° phase switching were used to form a monopulse comparator network.The simulation and measurement results show that the reconfigurable performance can be achieved by controlling the PIN switch diodes and properly combining the phase difference.In the far field test,the reconfigurable monopulse antenna can achieve good performance of sum beam,azimuth difference beam,elevation difference beam and bidifference beam.Secondly,a 1×4 array antenna with circular polarization performance working in2.45 GHz is designed.The circular polarization antenna adopts microstrip truncated antenna.At the same time,the second and fourth element antennas are rotated to enhance the circular polarization performance.In the feeding part,3 phase converters capable of ±90° and 2 phase converters capable of ±45° phase switching are adopted,and the reconfigurable performance is achieved by properly controlling the switching state of the PIN diodes on them.The beam switching function is realized by proper combination of phase difference.In the simulation,the beam reconfigurable array antenna can achieve good beam switching performance at theta= +43°,-43°,+14° and-14°.Finally,based on the design principle of Butler matrix,an asymmetric 3×4 Butler matrix is designed.The purpose of this work is to develop an antenna array feedind network for multiple input multiple output(MIMO)applications based on an asymmetric Butler matrix.In addition to the same beams generated by the symmetric beamforming network,the asymmetric structure can also generate other beams in the normal direction of the array.The proposed asymmetric Butler matrix has higher isolation and broadband characteristics.The array antenna can be used in transmission and reception systems to ensure multi-user MIMO(MU-MIMO)service.