Design Of Broadband And Multi-frequency Filter Antennas

Wireless communication has had a century of development and accumulation since its appearance.With the continuous development of technology,life has higher requirements.Antennas in wireless communication systems are also moving towards portability,feature richness,high precision and faster communication.The filter antenna integrates the filter and the antenna into a whole,no additional matching circuit connection is required,reducing the size of the antenna,avoiding the losses.At the same time,it is ensured that the filtering antenna has the same good passband radiation as the traditional antenna.Filtering antennas have potential applications in wireless communication systems.Therefore,this thesis designs a dual-band filtering patch antenna,a filtering antenna with wide out of band suppression and a broadband array antenna with harmonic suppression.The main research results of the thesis can be summarized as follows:1.A dual-band filtering antenna is designed.Radiating patch,metal floor and microstrip feeder are placed on both sides of the substrate,respectively.A new resonant point is introduced by adding u-shaped groove.The resonant frequency of the two passbands is determined by the size of the patch and the size of the U-shaped groove.An asymmetric parallel-coupled line feeding structure is introduce to improve the selection characteristics of the antenna,and the feeder resonator is used to prevent the transmission of energy at a specific frequency and generate a radiation null at 5.3 GHz.In addition,split-ring resonators（SRRs）are introduced into the antenna to generate a radiation null at 3.5 GHz.The simulated gains are 7.7 d Bi and 7.2 d Bi,respectively.The dual-band filtering antenna has good radiation characteristics in the passband,and has a low profile and compact structure.2.A filtering antenna with wide out-of-band suppression is designed.The patch is coupled by metal microstrip lines through the gap in the floor.The patch antenna uses the antenna fusion approach to produce filtering effect,and adds slots on the radiation patch and the floor to generate radiation nulls on both sides of the passband,respectively,which improves the passband selectivity of the antenna.In order to increase the harmonic suppression performance of the antenna,microstrip feeder withπ-shape stub is designed,which successfully suppresses the harmonics at the high-frequency stopband.The average gain of the antenna is about 7 d Bi.The overall height is only 0.03λ₀.The measured results show that the antenna has good stopband suppression,good unidirectional radiation and low cross-polarization in the pattern.3.A broadband array antenna with harmonic suppression is designed.The antenna uses a 2×2patch array as the radiating element,and the feeding part uses the structure of microstrip line-slot-microstrip line.The array antenna has good passband selectivity.In order to further improve the antenna bandwidth and high-frequency stopband suppression characteristics,the microstrip feeder is improved into a fork shape,and the feeder is stepped.A pair of slits are introduced in the floor to suppress the high-frequency stopband.Open stubs were also added to extend the antenna harmonic suppression to 3.3f₀.The antenna bandwidth is（3.24-4.40 GHz）.The in-band average gain is 10.8 d Bi.Simulation software is used to simulate and optimize the antenna to verify the design.Antenna has better filtering characteristics and wider stopband suppression range.