| Antenna array is a kind of antenna system with high directivity,which has always been an important research topic in the fields of detection,positioning and antenna design.Limited by the wavelength of electromagnetic waves,the antenna array is costly and large in size,which limits its application in some low-cost civilian detection and positioning systems.The electrically small antenna array benefits from its small size and can be applied to some civil mobile systems that require high space constraints.Therefore,Offseting for the low radiation efficiency and low angular resolution of the electrically small antenna array has became an active and valuable research direction,and will also be widely used in many practical fields.In view of the defects of the electrically small antenna array,it is possible to find a solution from some animals in nature.Biologists have found that some small insects have a very high directional hearing ability,although the distance between their hearing organs is extremely small.In further research,it is reported that there is a coupling mechanism between the insect hearing organs,which enhances the extremely small phase difference between the received acoustic signals,thereby realizing super resolution directional hearing.The biomimetic antenna is a design method that refers to insect's coupled auditory organs to improve the resolution of the antenna array.First of all,the operating principle of the antenna array is introduced in this thesis,include the weak directional characteristics and mutual coupling of the electrically small antenna array,and also briefly analyzes the signal processing technology of the antenna array.The factors that restrict the phase difference enhanced effect of the biomimetic antenna array are analyzed and deduced.The relation between the phase difference enhanced factor and the mutual coupling in the antenna array is given.The design method of the biomimetic antenna array that realizes the arbitrary enhancement of the phase difference is proposed.The practicability of applying biomimetic antenna array theory to multi-element electrically small linear array is discussed.Based on the phase difference enhancement of the biomimetic antenna array,the characteristics of the dynamic expanded spacing between array elements of the electrically small biomimetic antenna array in the field of the Direction-Of-Arrival positioning are analyzed.Based on the operating principle of biomimetic antenna array,the passive coupling network of biomimetic antenna array is designed.The simulation results are consistent with the upper bound of the phase difference enhancement factor from theoretical deduction.The method of achieving larger phase difference amplification factor by attenuating output power is authenticated in the simulation.The correctness of passive coupling network design is verified by experiments.The biomimetic antenna array active coupling network which is designed for making up for the defects of the passive coupling network,achieves the combination of high phase difference enhancement factor and noise performance,and the gain of the amplifier suppresses the signal-to-noise ratio loss caused by the attenuation of the back-end coupling circuit.The corresponding active coupling network is designed,its performance is analyzed,and it is verified by experiments that the active coupling network can get better performance than the passive coupling network.Finally,the research work of this biomimetic antenna array is summarized,and the future research direction is expected. |
