Browsing by Subject "Spatial filters"

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    Extraction of sparse spatial filters using Oscillating Search
    (IEEE, 2012) Onaran, İbrahim; İnce, N. Fırat; Abosch, A.; Çetin, A. Enis
    Common Spatial Pattern algorithm (CSP) is widely used in Brain Machine Interface (BMI) technology to extract features from dense electrode recordings by using their weighted linear combination. However, the CSP algorithm, is sensitive to variations in channel placement and can easily overfit to the data when the number of training trials is insufficient. Construction of sparse spatial projections where a small subset of channels is used in feature extraction, can increase the stability and generalization capability of the CSP method. The existing 0 norm based sub-optimal greedy channel reduction methods are either too complex such as Backward Elimination (BE) which provided best classification accuracies or have lower accuracy rates such as Recursive Weight Elimination (RWE) and Forward Selection (FS) with reduced complexity. In this paper, we apply the Oscillating Search (OS) method which fuses all these greedy search techniques to sparsify the CSP filters. We applied this new technique on EEG dataset IVa of BCI competition III. Our results indicate that the OS method provides the lowest classification error rates with low cardinality levels where the complexity of the OS is around 20 times lower than the BE. © 2012 IEEE.
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    Resonant artificial structures to achieve extraordinary transmission at microwaves
    (IEEE, 2010) Scorrano L.; Ilotti F.; Özbay, Ekmel; Vegni L.
    In this contribution, the role of artificial resonant structures in increasing the transmission through sub-wavelength apertures is discussed. Those devices are capable to enhance the aperture equivalent electric and magnetic dipole moments and, consequently, the overall power transmission. The design details are given and the enhancement performances are then illustrated through the use of full-wave simulations. Such structures may find applications in different fields, such as high-resolution spatial filters, ultra-diffractive imaging systems, etc © 2010 EuMA.
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    Spatial filters based on EBG structures with anisotropic-like dispersion
    (IEEE, 2010) Serebryannikov, A.E.; Cakmak, A.O.; Çolak, Evrim; Özbay, Ekmel
    Bandpass and bandstop spatial filters based on the dielectric-rod EBG structures are proposed and validated for the frequency range from 18 to 25 GHz. The obtained experimental results are well consistent with the theoretical predictions. The exploited mechanism utilizes, in particular, anisotropic-like dispersion, which can occur in the conventional EBG structures made of isotropic materials.