Study On The Miniaturized Huygens Dipole Fully Duplex Antenna With High Isolation

With the rapid development of the communication technology,the wireless communication equipment witness constant improvement of the development trend of the wireless communication equipment are larger capacity,lower delay and higher reliability.The development of the antennas,which are an important part of RF front-end,is the large scale,the array and the multi-function to meet up with increasingly complex communication systems.However,under the condition of limited space resources,when the electrical size of antenna is greatly reduced,the radiation performance of the antenna will degrade.Moreover,the reduction of the element spacing of the antenna array will lead to strong mutual coupling which would worsen the performance of the array.Therefore,it is necessary to develop the antenna elements and arrays suitable for limited space.The Huygens dipole antenna designed by near-field resonant parasitic（NFRP）technology has the advantages of high directivity,wide beam width,high performance and independent of the ground,which can save cost and space resources in many practical engineering applications.It is very suitable for compact antenna element.However,the integration of several antenna elements in a limited space will inevitably result in strong mutual coupling between adjacent elements,and then affect the overall efficiency of the array,which will seriously deteriorate the performance of the full-duplex system or MIMO system in which they are located.Therefore,for many specific wireless communication systems,not only the antenna elements in the array antenna need to have high performance,high directivity and small electrical size,but also the mutual coupling suppression between the antenna elements has higher requirement.In order to meet up with the requirement of the future communication system for the development of compact,low-profile Huygens dipole duplex antenna array with high radiation performance,this thesis contains two aspects,involving the low-profile,broadside radiating,and electrically small Huygens dipole antenna and the decoupling method for the high-density Huygens dipole antenna array:（1）A low-profile,broadside radiating Huygens dipole antenna with electrical size ka=0.76<1 is designed based on the NFRP technique.The antenna is composed of an Egyptian axe dipole（EAD）,a capacitive loading ring and a coaxial feed structure with impedance of 50Ω.The Huygens dipole antenna operates at its resonance frequency,f₀=1.512GHz,and achieves high directivity and performance while maintaining electrically small size and low profile.The Huygens dipole antenna has great advantages in many practical engineering applications,such as long-distance,point-to-point wireless communication,RFID and wireless energy transmission.（2）A decoupling structure for compact Huygens dipole in-band fully duplex antenna is proposed.The specially engineered scatter is printed on an additional layer and consists of a pair of face-to-face loaded meander-line resonators connected by a rectangular metallic strip.By placing the isolator in the middle of the two-element array composed of the electrically small Huygens dipole antennas,the mutual coupling between the two antenna elements can be significantly suppressed by the collaboration of the pair of meander-line resonators and the rectangular strip.Furthermore,a miniaturized Huygens dipole two-element antenna array loaded with the composite isolator is designed.The working center frequency is 1.511GHz.Without increasing the overall size of the array,stable radiation is maintained in the whole working frequency band.The isolation between the ports of the array is significantly improved,and the radiation performance of the array element can be optimized.The optimized array was fabricated,assembled and tested.The measured results,in good agreement with their simulated values,confirm that the developed decoupling structure not only increases the peak isolation level,but it also improves the peak realized gain in the broadside direction and the corresponding front-to-back-ratio（FTBR）value.