Abstract
Frequency-Invariant (FI) beamforming is a well known array signal processing technique used in many applications. In this paper, an algorithm that attempts to optimize the frequency invariant beampattern solely for the mainlobe, and relax the FI requirement on the sidelobe is proposed. This sacrifice on performance in the undesired region is traded off for better performance in the desired region as well as reduced number of microphones employed. The objective function is designed to minimize the overall spatial response of the beamformer with a constraint on the gain being smaller than a pre-defined threshold value across a specific frequency range and at a specific angle. This problem is formulated as a convex optimization problem and the solution is obtained by using the Second Order Cone Programming (SOCP) technique. An analysis of the computational complexity of the proposed algorithm is presented as well as its performance. The performance is evaluated via computer simulation for different number of sensors and different threshold values. Simulation results show that, the proposed algorithm is able to achieve a smaller mean square error of the spatial response gain for the specific FI region compared to existing algorithms.
Highlights
Broadband beamforming techniques using an array of microphones have been applied widely in hearing aids, teleconferencing, and voice-activated human-computer interface applications
We find that having processed the signal in phase mode, the frequency range for the beamformer to achieve Frequency Invariant (FI) characteristics is wider
A selective frequency invariant uniform circular broadband beamformer is presented in this paper
Summary
Broadband beamforming techniques using an array of microphones have been applied widely in hearing aids, teleconferencing, and voice-activated human-computer interface applications. One design approach is to decompose the broadband signal into several narrowband signals and apply narrowband beamforming techniques for each narrowband signal [4]. This approach requires several narrowband processing to be conducted simultaneously and is computationally expensive. Another design approach is to use adaptive broadband beamformers. Such techniques use a bank of linear transversal filters to generate the desired beampattern. In order to have a similar beampattern over the entire frequency range, a large number of sensors and filter taps will be needed. As the name implies, such beamformers are designed to have constant spatial gain response over the desired frequency bands
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