| 1. |
|
|
| 2. |
|
|
| 3. |
- Dahl, Mattias, et al.
(författare)
-
Acoustic Echo and Noise Cancelling using Microphone Arrays
- 1996
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a new method to simultaneously perform 20 dB acoustic echo cancellation and 10 dB speech enhancement utilizing an adaptive microphone array. The system is based on a fast and efficient on-site calibration. Primarily intended for handsfree telephones in automobiles, the microphone array system simultaneously emphasizes the near-end talker and suppresses the handsfree loudspeaker and car noise. The method can also be used in other situations such as conventional speaker phones.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Nordberg, Jörgen, et al.
(författare)
-
Acoustic Echo Cancellation Employing Delayless Subband Adaptive Filters
- 1996
-
Konferensbidrag (refereegranskat)abstract
- The use of hands-free communication in cars, computer applications and video conferencing has created a demand for high-quality acoustic echo cancellation. In these applications these acoustic channel has typically a long impulse response in the order of 100ms. Typical lengths of adaptive FIR-filters can be 500-1500 taps. In order to reduce the complexity and also to improve the convergence rate, subband processing schemes have been suggested. This paper presents an implementation of a delayless subband adaptive filter. The study shows a possible suppression of about 30 dB and also a more rapid convergence compared to a fullband LMS-filter.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- Dahl, Mattias, et al.
(författare)
-
A New General Front-End Technique for Complex Quadratic Programming : Applications to Array Pattern Synthesis
- 2000
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a new practical approach to complex quadratic programming which solves the broad class of complex approximation problems employing finitization of semi-infinite formulations. The approximation problem may be general with arbitrarily complex basis functions. By using a new technique, the associated semi-infinite quadratic programming problem can be solved taking advantage of the numerical stability and efficiency of conventional quadratic programming software packages. Furthermore, the optimization procedure is simple to describe theoretically and straightforward to implement in computer coding. The new design technique is therefore highly accessible. The complex approximation algorithm is versatile and can be applied to a variety of applications such as narrow-band as well as broad-band beamformers with any geometry, conventional FIR filters, digital Laguerre networks, and digital FIR equalizers. The new algorithm is formally introduced as the quadratic Dual Nested Complex Approximation (DNCA) algorithm. The essence of the new technique, justified by the Caratheodory's dimensionality theorem, is to exploit the finiteness of the related Lagrange multipliers by adapting conventional finite-dimensional quadratic programming to the semi-infinite quadratic programming re-formulation of complex approximation problems. The design criterion in our application is to minimize the side-lobe energy of an antenna array when subjected to a specified bound on the peak side-lobe level. Additional linear constraints are used to form the main-lobe. The design problem is formulated as a semi-infinite quadratic program and solved by using the new front-end applied on top of a software package for conventional finite-dimensional quadratic programming. The proposed optimization technique is applied to several numerical examples dealing with the design of a narrow-band base-station antenna array for mobile communication. The flexibility and numerical efficiency of the proposed design technique are illustrated with these examples where even hundreds of antenna elements are optimized without numerical difficulties.
|
|
