| 31. |
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| 32. |
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| 33. |
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| 34. |
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| 35. |
- Nordebo, Sven, et al.
(författare)
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Spatial Filter Designed Generalized Sidelobe Canceller for Broadband Implementations
- 1992
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Ingår i: International Symposium on Signal Processing and Its Applications. - Gold Coast, Australia : IREE Australia. - 909394288 ; , s. 577-580
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Konferensbidrag (refereegranskat)abstract
- A novel design procedure for the signal blocking matrix in the broadband generalized sidelobe canceller, is proposed. A 1-dimensional spatial filter is devised in order to prevent the target signal from reaching the cancelling adaptive filters. Simulations and calculations have been performed in order to verify the design
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| 36. |
- Nordebo, Sven, et al.
(författare)
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Weighted Chebyshev Approximation for the Design of Broadband Beamformers using Quadratic Programming
- 1994
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Ingår i: IEEE Signal Processing Letters. - New York : IEEE. - 1070-9908. ; 1:7, s. 103-105
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Tidskriftsartikel (refereegranskat)abstract
- A method to solve a general broadband beamformer design problem is formulated as a quadratic program. As a special case, the minimax near-field design problem of a broadband beamformer is solved as a quadratic programming formulation of the weighted Chebyshev approximation problem. The method can also be applied to the design of multidimensional digital FIR filters with an arbitrarily specified amplitude and phase. For linear phase multidimensional digital FIR filters, the quadratic program becomes a linear program. Examples are given that demonstrate the minimax near-field behavior of the beamformers designed.
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| 37. |
- Nordholm, Sven, et al.
(författare)
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Chebyshev Optimization for the Design of Broadband Beamformers in the Near Field
- 1998
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Ingår i: IEEE transactions on circuits and systems. 2 : Analog and digital signal processing. - New York : IEEE Circuits and Systems Society. - 1057-7130. ; 45:1, s. 141-143
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Tidskriftsartikel (refereegranskat)abstract
- The use of microphone arrays for video conferences, hands-free mobile telephony and computer applications has created the demand for near-field broadband beamformer design methods. Here, a general broadband beamformer design problem is formulated as a weighted Chebyshev optimization problem, and a method to solve the resulting functionally-constrained problem is presented. The formulation can also be applied to the design of multidimensional digital finite-impulse response (FIR) filters with an arbitrarily specified amplitude and phase. Numerical results that demonstrate the minimax near-field behavior of the designed beamformers are given.
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| 38. |
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| 39. |
- Nordholm, Sven, et al.
(författare)
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Sub-band Acoustic Echo Cancellation
- 1997
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Echo suppression is a vital part of every communications system. The use of handsfree communication in cars, computer applications and video conferencing have created further demands for high-quality acoustic echo cancellation. In these applications the acoustic channel has, typically, a long impulse response in the order of 100ms. Typical lengths of adaptive FIR-filters are 500-1500 taps, assuming a 12 kHz sampling frequency. In order to reduce the computational load and also to improve the convergence rate, subband processing schemes have been suggested. This paper presents a study of a delayless sub-band adaptive filter. The study shows a possible echo suppression of about 30 dB and also an improved convergence rate when compared to a fullband LMS-filter. The main issues discussed are filter bank design and a simple speech detector that gives a drastic performance improvement
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| 40. |
- Sjösten, Per, et al.
(författare)
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A Practical, Fast and Cost-efficient Algorithm Multiple Input, Multiple Output Active Noise Control Applications
- 2001
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Konferensbidrag (refereegranskat)abstract
- Active noise control has proven to be an efficient solution to low frequency noise problems in many different applications. A large part of these applications are concerned with harmonic noise control and typically require control systems with several inputs and outputs. As the systems grow, the demand for processor capacity increases rapidly, resulting in large and expensive hardware platforms. As multiple-input, multiple-output noise control is restricted to the control of periodic noise, a controller structure that is adapted to the signal type may significantly reduce the requirements on the hardware capacity. This paper discusses a complex, time-domain controller that is designed for the control of harmonic components. The structure of the controller is simple, easily implemented and can easily be extended to handle any number of noise references and any number of harmonics. The convergence properties of a multiple-input, multiple-output control system depends largely on the acoustic coupling between the active sources and the control sensors. To get accurate and stable control it is necessary to use normalization, i.e. a weighting function that optimizes the controller for each control source. With the presented controller structure, the use of normalization is straightforward and a number of different approaches for normalization is discussed as well as examples from practical inplementations.
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