A method to design a beamformer for broadband constant beamwidth is presented. Constant beamwidth is important in sonar systems for sea bottom observation and classification applications. For a given frequency band, a...A method to design a beamformer for broadband constant beamwidth is presented. Constant beamwidth is important in sonar systems for sea bottom observation and classification applications. For a given frequency band, a number of frequency points are chosen to represent the response of an arrary element. For each frequency point a beamforming weight vector can be deduced to satisfy the given beamwidth requirement by existing methods. Therefore, for a broadband array of N elements, each row of the N' M weighting matrix represents the frequency response of an element of the array which can be satisfied by a FIR filter designed by model - reference adaptive technique. The sum of outputs from a bank of N FIR filters provides a beamformed output and so it is very handy to be implemented by DSP hardware.展开更多
Adaptive broadband beamforraing is a key issue in array applications. The adaptive broadband beamformer with tapped delay line （TDL） structure for nonuniform linear array （NLA） is designed according to the rule of...Adaptive broadband beamforraing is a key issue in array applications. The adaptive broadband beamformer with tapped delay line （TDL） structure for nonuniform linear array （NLA） is designed according to the rule of minimizing the beamformer＇s output power while keeping the distortionless response （DR） in the direction of desired signal and keeping the constant beamwidth （CB） with the prescribed sidelobe level over the whole operating band. This kind of beamforming problem can be solved with the interior-point method after being converted to the form of standard second order cone programming （SOCP）. The computer simulations are presented which illustrate the effectiveness of our beamformer.展开更多
Circular-polarization discrimination appears in many antennas＇ applications. A compensation approach based on multilayer film structure is proposed to improve the axial ratio of the magnitude of the two perpendicular...Circular-polarization discrimination appears in many antennas＇ applications. A compensation approach based on multilayer film structure is proposed to improve the axial ratio of the magnitude of the two perpendicular modes of the lump ports. The goal is to widen the beamwidth of radiation that has an axial ratio less than 3 dB and thus reducing the complexity at the receiver. A transfer matrix method was developed to represent the multilayer film and characterize its performance. Simulation using high frequency structure simulator shows that a crossed dipole, as an example, can achieve a beamwidth of more than 30° at the frequency of 12.45 GHz after compensation. Finally, conclusions and future work about this compensation method are presented.展开更多
A new method of broadband constant beamwidth beamforming for arbitrary ge- ometry arrays is proposed. In this method, the response vector of an arbitrary geometry array is expanded into the form of sum of an infinite ...A new method of broadband constant beamwidth beamforming for arbitrary ge- ometry arrays is proposed. In this method, the response vector of an arbitrary geometry array is expanded into the form of sum of an infinite series, whose core function is the first kind Bessel function. The high terms of this series are truncated so that the array response vec- tors at different frequencies can be transformed to a reference frequency and then the constant beamwidth beamforming vectors are ready to obtain. With these beamforming vectors, beams at different frequencies are same as the reference beam. A reference beam optimizing method based on adaptive processing is also proposed to optimize the reference beam of arbitrary ge- ometry arrays. Computer simulation for a uniform circular array verified the effectiveness of the new method proposed.展开更多
文摘A method to design a beamformer for broadband constant beamwidth is presented. Constant beamwidth is important in sonar systems for sea bottom observation and classification applications. For a given frequency band, a number of frequency points are chosen to represent the response of an arrary element. For each frequency point a beamforming weight vector can be deduced to satisfy the given beamwidth requirement by existing methods. Therefore, for a broadband array of N elements, each row of the N' M weighting matrix represents the frequency response of an element of the array which can be satisfied by a FIR filter designed by model - reference adaptive technique. The sum of outputs from a bank of N FIR filters provides a beamformed output and so it is very handy to be implemented by DSP hardware.
基金supported by the National Nature Science Foundation of China (60472101)President Award of ChineseAcademy of Sciences(O729031511).
文摘Adaptive broadband beamforraing is a key issue in array applications. The adaptive broadband beamformer with tapped delay line （TDL） structure for nonuniform linear array （NLA） is designed according to the rule of minimizing the beamformer＇s output power while keeping the distortionless response （DR） in the direction of desired signal and keeping the constant beamwidth （CB） with the prescribed sidelobe level over the whole operating band. This kind of beamforming problem can be solved with the interior-point method after being converted to the form of standard second order cone programming （SOCP）. The computer simulations are presented which illustrate the effectiveness of our beamformer.
基金supported by the Hi-Tech Research and Development Program of China(2006AA01Z246)the National Natural Science Foundation of China(60702005)
文摘Circular-polarization discrimination appears in many antennas＇ applications. A compensation approach based on multilayer film structure is proposed to improve the axial ratio of the magnitude of the two perpendicular modes of the lump ports. The goal is to widen the beamwidth of radiation that has an axial ratio less than 3 dB and thus reducing the complexity at the receiver. A transfer matrix method was developed to represent the multilayer film and characterize its performance. Simulation using high frequency structure simulator shows that a crossed dipole, as an example, can achieve a beamwidth of more than 30° at the frequency of 12.45 GHz after compensation. Finally, conclusions and future work about this compensation method are presented.
基金the National Natural Science Foundation of China (No. 69802010).
文摘A new method of broadband constant beamwidth beamforming for arbitrary ge- ometry arrays is proposed. In this method, the response vector of an arbitrary geometry array is expanded into the form of sum of an infinite series, whose core function is the first kind Bessel function. The high terms of this series are truncated so that the array response vec- tors at different frequencies can be transformed to a reference frequency and then the constant beamwidth beamforming vectors are ready to obtain. With these beamforming vectors, beams at different frequencies are same as the reference beam. A reference beam optimizing method based on adaptive processing is also proposed to optimize the reference beam of arbitrary ge- ometry arrays. Computer simulation for a uniform circular array verified the effectiveness of the new method proposed.
