Acoustically Actuated Piezoelectric Antennas

This thesis consists of researches on three important scientific problems:The mechanism and mathmatical modeling of piezoelectric resonators(PER)considering multiphysical fields;The mutual coupling and control methods of piezoelectric resonators;And interaction of elastic wave and EM wave in inhomogeneous mediums.The utmost goal is to promote power level and radiation efficiency of PER.To achieve this goal,a series key technology are developed which includes field-based circuit model method,array technology,and metal-loading method.And several innovative outputs are obtained.The detailed outputs of this thesis are listed below:1.By introducing antenna fields into piezoelectric equations,a systematic and thorough mathmatical description of PER is formulated considering multiphysical fields,and modes of elatic waves and EM waves generated by PER are analyzed.Based on this mathmatical formulation,field-based circuit model method is proposed to evaluate the performance of acoustically actuated antenna and arrays.2.Based on the measurement and verification results of a large number of scientific experiments,a verification and experimental application platform for the resonance mechanism of PER with multiphysical fields is built,and a packaging method and a frequency tuning method for piezoelectric PER are proposed to effectively measure the impedance and antenna field of acoustically actuated antennas.The experimental results show that the gap between the resonant frequency of the platform test and the theoretical one is 0.15%,and the gap between the field amplitude of the tested antenna and the theoretical one is 3.9dB.3.The EM coupling among PERs is analyzed by using the field-based circuit model method,and the coupling fields in PER and the antenna array layout strategy under different boundary conditions are obtained.By adjusting the boundary conditions,the small and large scale antenna array technology is realized,which greatly improves the power level and radiation efficiency of acoustically actuated piezoelectric antennas.Among them,the near-field of the four-element PEA array antenna with open boundary is increased by 10dB compared with the PEA unit.The near-field of the ten element PEA array antenna with boundary of parallel plate is increased by 15.5dB compared with the PEA unit.4.The interaction between elastic wave and electromagnetic wave in different media is analyzed by using the field-based circuit model methods,and the metal loading method is proposed to increase the effective length of PER,which further enlarges the power level of acoustically actuated antenna.Measurement shows that the near-field gain of 6dB is achieved by using 1m long wire.5.Utilizing the field-based circuit model method,the loss type and loss mechanism in PER systems are analyzed,and an evaluation method for the radiation efficiency of acoustically actuated antennas is proposed.On this basis,the radiation efficiency limit of the acoustically actuated piezoelectric antenna is obtained by using the limit conditions of materials and structures.Among them,the radiation efficiency of the PEA unit is 5-67 times higher than that of the traditional metal electric small antenna,and the radiation efficiency of the four-element PEA array is 1.3 times higher than that of PEA unit.