This paper proposes a optimal method for designing frequency-invariant beamformers for circulararrays. First, the desired beampattern is expressed as a general complex weighted form. Second, the weighting vectors at ...
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ISBN:
(纸本)9781538648148
This paper proposes a optimal method for designing frequency-invariant beamformers for circulararrays. First, the desired beampattern is expressed as a general complex weighted form. Second, the weighting vectors at each frequency are accurately derived by approximating to the desired beampattern from the minimum mean square error perspective, all of which are found to be close-form functions of the desired complex weighting vectors. Third, a multiple optimization problem is formulated, and its solution gives the optimal desired weighting vector subject to different constraints. Finally, the weighting vectors at other frequencies can be directly computed based on the previously derived analytical functions. The proposed method provides flexible schemes to design different optimal frequency-invariant beamformers for circular sensor arrays. The good performance of the proposed method is demonstrated using simulations and experimental results.
Underwater acoustic localization plays an important role in marine explorations. However, the complex shallow-sea environment induces the multipath reflection which severely interfere the localization accuracy. To sup...
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ISBN:
(纸本)9798350363524;9798350363517
Underwater acoustic localization plays an important role in marine explorations. However, the complex shallow-sea environment induces the multipath reflection which severely interfere the localization accuracy. To suppress the multipath reflection induced interference and improve the estimation accuracy, we propose a method which based on circular sensor array. By using a uniform circular receiving array, the method estimate the target's azimuth through sweep-spread carrier (S2C) algorithm. To mitigate azimuth estimation distortion caused by array arrangement errors, we employ an array calibration method. The lake experiment results have verified our proposed method, leading to an average 64.7% error reduction in the azimuth estimation when compared with traditional method.
Designing beampatterns with constant beamwidth over a wide range of frequencies is useful in many applications in speech, radar, sonar and communication. In this paper, we design constant-beamwidth beamformers for con...
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Designing beampatterns with constant beamwidth over a wide range of frequencies is useful in many applications in speech, radar, sonar and communication. In this paper, we design constant-beamwidth beamformers for concentric ring arrays. The proposed beamformers utilize the circular geometry to provide improved beamwidth consistency compared to beamformers which are designed for linear sensorarrays of the same order. In the proposed configuration, all sensors on each ring share the same weight value. This constraint significantly simplifies the beamformers and reduces the hardware and computational resources required in a physical setup. Furthermore, a theoretical justification of the beamforming method is provided. We demonstrate the advantages of the proposed beamformers compared to the one-dimensional configuration in terms of directivity index, white noise gain and sidelobe attenuation.
Contactless current sensors that use arrays of magnetic field sensors are a good alternative to core-based current sensors because the omission of the magnetic core offers many advantages. Particularly, circular senso...
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Contactless current sensors that use arrays of magnetic field sensors are a good alternative to core-based current sensors because the omission of the magnetic core offers many advantages. Particularly, circular sensor arrays have proven to feature good robustness against various error sources. As rectangular bus bars are frequently used for local high-current power distribution systems, elliptic arrays would require less space than circulararrays. Up until now, no publication on magnetic interference errors of elliptic sensorarrays has been presented. This article examines the crosstalk error for different sensor distribution methods, aspect ratios, numbers of sensors, and offset angles with calculations and measurements. Therefore, an interference conductor is positioned at different angles and distances relative to the elliptic arrays. We show that the crosstalk error can be reduced with our elliptic designs in comparison to a circular design with an equal number of sensors and an equal length of the semimajor axis. The projection distribution typically offers a five times smaller crosstalk error compared to the uniform curve segment length distribution. To support the design of elliptical arrays, instructions for the optimization against interference errors for elliptic sensorarrays are given in this article. Thus, an optimal offset angle for the reduction of the crosstalk error is presented.
In highly efficient power electronic systems, circulararrays of magnetic field sensors offer numerous advantages compared to older magnetic core-based sensors. They feature low power consumption, low weight, and high...
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In highly efficient power electronic systems, circulararrays of magnetic field sensors offer numerous advantages compared to older magnetic core-based sensors. They feature low power consumption, low weight, and high immunity to external magnetic fields. In power converters, conductors with a rectangular cross section, a small height, and a large width are widely used. Thus, an elliptical sensorarray could reduce the space needed for the current sensor, e.g., in a power converter by a factor of four or more compared to a circular sensor array. In this work, we theoretically and experimentally study the sensitivity error caused by the change of the conductor geometry. Therefore, we calibrated different elliptical sensorarrays on a circular conductor and determined the sensitivity error for the use of flat conductors with different widths. This calibration on a circular conductor avoids a costly conductor-specific calibration of the sensorarray in the application. Two different distribution methods for elliptical sensorarrays and different ratios of the semiaxes are considered. In addition, the influence of the number of sensors and the starting position for the sensors are examined. The presented elliptical sensorarrays can be used to measure the current carried by a flat conductor largely independent of its width. For some aspect ratios, they even offer a lower sensitivity error than circular sensor arrays. In this article, design considerations for those elliptic sensorarrays are given.
Novel rectangular yokeless current transducer with the range 400 A using 16 microfluxgate sensors around the busbar conductor is presented in this paper. Compared to yokeless transducers utilizing the differential pai...
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Novel rectangular yokeless current transducer with the range 400 A using 16 microfluxgate sensors around the busbar conductor is presented in this paper. Compared to yokeless transducers utilizing the differential pair of magnetic sensors, our solution has much better suppression of the external currents (lower crosstalk). Compared to industrial transducers with yoke, the new transducer has 15-times lower noise, 7-times better temperature stability, and same crosstalk. sensor design and design of current monitoring system is presented together with the results of long-term field tests. Crosstalk error is examined in dependence on the number of the operating sensors and external current position.
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