Direction Of Arrival Estimation By Shaping Radiation Pattern And Feeding Arrangement Optimization Based On Modal Analysis

The antenna pattern synthesis technique is widely used in radar,sonar areas,etc.It is one of the crucial techniques in large antenna arrays.In radar applications,antenna arrays enhance signals from certain arears,while weaken or even suppress signals from other areas.In addition,antenna pattern synthesis technology is also applied to phased array antenna arrays,and is widely used in commercial scenarios such as ETC.However,there are relatively fewer research results for single antenna pattern synthesis.This work proposes a systematic and widely applicable antenna pattern synthesis method for single antennas based on characteristic mode analysis and compressed sensing theory.This work firstly applies this method to handset antenna design.Both the radiation pattern and radiation efficiency are less affected by the human head and hands.Due to the robustness to the user effect,the designed handset antenna has great application value.To obtain a desired pattern,we first calculate the weighting coefficient of each mode using the correlation between the characteristic field and the desired pattern.Afterwards,the feeding information,such as feeding numbers,locations,amplitude and phase,can be obtained.In this circumstance,the theory of compressed sensing is applied so that the feedings can be further optimized.The prototype of the handset antenna was fabricated and measured,with the desired pattern achieved.The measured results agree well with the simulated ones.This method is also applied to pattern synthesis for shipboard antenna,showing great applicable potential for three-dimensional structures.In another work,we also shape and control radiation pattern of antennas for improving the DOA estimation accuracy.Both the amplitude and phase information are employed in the steering vector,in order to eliminate phase ambiguity and provide accurate estimation without increasing the antenna array aperture.The optimal amplitude ratio between the antenna patterns are theoretically studied using the Fisher information and ambiguity function.Following the amplitude ratio criteria,a compact monopole-patch array and a dual-monopole array are designed specifically,which enhance the DOA estimation accuracy by over 60% and 20-40%,respectively,under medium SNR of 10 dB.The phase ambiguity has been eliminated in both arrays as well.The monopole-patch array requires phase calibration in the measurement,whereas the dual-monopole array does not.Experiments were carried out with the dualmonopole array in the anechoic chamber,achieving the estimation accuracy of 0.67 degree averaged over 360 degrees.