Research And Design Of A Compact Microstrip Antenna With Broadband And Filtering Functions

Microstrip antennas have many advantages,such as low profile,light weight,easyily realize multi-polarization and multi-frequency,easy to be integrated with other devices and so on.But it has two inherent defects,the narrow bandwidth and the high order harmonics.Many scholars have done many researches to enhance the bandwidth of microstrip antennas,but the proposed broadband antennas still have many shortcomings,such as enlarging the antenna,increasing the thickness,the complex multilayer structure,radiating patch destroyed by slots.The methods of widening the bandwidth of microstrip patch antenna are studied in this paper.(1)A single-layer microstrip 2×2 filtering antenna array with three times bandwidth is proposed.The resonant circuits increase to three for the introduction of the T-shaped resonator,which effectively increases the bandwidth of antenna.The proposed antenna is fabricated and tested,and the experimental results verify the correctness of the proposed design theory.The proposed single-layer broadband microstrip array antenna has 12.6%relative bandwidth with high order harmonics suppressed.The fluctuation of the gain is very small in frequency band,while it decreases rapidly when it deviates from the band range,which makes the antenna have the characteristic of the filtering antenna.(2)A broadband patch antenna coupled by single resonator is proposed.The rectangular patch antenna coupled by single resonator can get a double-resonant structure,thus increasing the bandwidth of the antenna by two times.The single resonator structure not only makes the antenna more compact,but also increases the flexibility of the structure,and is beneficial to the design of the array.An example of the array coupled by single resonators is proposed in this paper.The proposed antenna has 6%relative bandwidth and also has the characteristics of high order harmonic suppression.(3)A single-layer broadband microstrip antenna coupled by asymmetric dual-resonator is proposed.Dual-resonator structure is introduced to make the antenna get three resonant circuits,resulting in wide band.The measured results are in agreement with the simulation results.The proposed single-layer broadband microstrip antenna has 11%relative bandwidth,and has the characteristics of high harmonic suppression.The proposed patch antenna is also compact,and the principle is clear and easy to be fabricated.