Browsing by Author "Pakiyarajah, D"

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item: Conference-Full-text
A low-complexity 2-d fir parallelogram filter for broadband beamforming with sparse linear arrays
(IEEE, 2023-12-09) Pakiyarajah, D; Edussooriya, CUS; Wijenayake, C; Madanayake, A; Abeysooriya, R; Adikariwattage, V; Hemachandra, K
Broadband beamformers designed as twodimensional (2-D) spatially-interpolated finite-extent impulse responses (FIR) filters, using a cascade structure, cannot employ sparse linear arrays despite significantly reducing the computational complexity. This happens due to the fact that the 2-D masking filter requires spatial samples equal to the spatial order at the input. Therefore, the output of the 2-D spatially-interpolated prototype filter should be computed for more than one spatial index. In order to address this limitation, we propose a 2-D spatially-interpolated FIR filter using a parallel structure. With the proposed structure, both 2-D spatially-interpolated prototype filter and the 2-D masking filter need to compute the output only for one spatial index, therefore allowing to employ sparse linear arrays. In order to support broadband beamforming, we design the 2-D FIR filter to have a parallelogram passband. Furthermore, we design the 2-D FIR filter to have linear phase response and to be optimal in the minimax sense. The simulation results confirm that the proposed 2-D FIR filter provides a considerable reduction in the number of antennas, compared to previously proposed 2-D FIR filters, with a slight degradation in the fidelity of enhanced broadband signals, which are distorted by strong radio frequency interference and noise signals.
item: Conference-Full-text
Minimax design of m-d complex-coefficient fir filters with nearly-constant low group delays
(IEEE, 2023-12-09) Pakiyarajah, D; Edussooriya, CUS; Wijenayake, C; Madanayake, A; Abeysooriya, R; Adikariwattage, V; Hemachandra, K
The optimal designs of multi-dimensional (M-D) complex-coefficient finite-extent impulse response (FIR) filters with low group delays predominantly consider only the minimization of the frequency response error. This leads to substantial deviation of the group delay from the desired constant group delay of such a filter, especially near the passband edges. In this paper, we propose a minimax design method for M-D complexcoefficient FIR filters with reduced group delay error. We incorporate constraints on phase response error while minimizing the frequency response error. We formulate the proposed minimax design method as a second-order cone programming problem. Design examples confirm that the proposed minimax design method significantly reduces the group delay error compared to previously proposed methods.