The Research Of The Design Method On The Constant Beamwidth Beamformers

In recent years, broad band beamforming technology has become a researchhotspot in array signal processing area. It has been used widely in many areas, such ascommunications, radar and sonar and so on. The constant beamwidth broad bandbeamforming technology is how to get the optimal weight coefficients of the sensorarray and the coefficients of post-filters in essence. Based on the analysis andsummary of the related research at home and abroad, this article explores thefollowing three design methods of the constant beamwidth broad band beamformers.Firstly, the performance of the beamformer is studied, and the difference of thedesign methods between the narrow band beamformer and the broad band beamformeris researched.Secondly, the design methods of three kinds of the constant beamwidthbeamformer are studied, including the broad band beamformer based on spatialre-sampling, the broad band beamformer based on Fourier series and the broad bandbeamformer based on DFT interpolation. At first, the three design methods all use thealgorithm used in narrow band signal processing to get the optimal weight coefficientsof the sensor array at the reference frequency. And then, the three methods usedifferent algorithms to calculate the weight coefficients at other frequencies inbandwidth. Separately, the spatial re-sampling method uses the spatial re-samplingformula, the Fourier series method uses the Fourier series coefficients calculationformula, and the DFT interpolation method uses the interpolation to the sensitivityfunction of the continuous linear array. Again, the three ways all use the achievedweight coefficients to obtain the expected filter response of the sensor array. At last,the filter coefficients are calculated by using the least square adaptive algorithm intime domain.Finally, the design methods of the above three constant beamwidth broad bandbeamformers are simulated using MATLAB software. The simulation results verify theeffectiveness of the three design methods.