Hsieh, S.F.Liu, K.J. RayYao, K.We propose a new class of hyperbolic Gram-Schmidt methods to simultaneously update and downdate the Cholesky factor of a sample covariance matrix efficiently with applications to sliding window recursive least squares (RLS) filtering problems. Several vectorized versions of this Gram-Schmidt approach are introduced, which include conventional column-updating, modified row/column- updating, and square-root-free methods. Comparisons to the existing known methods, such as Householder transformation and Givens rotation, are also given. Upon further reformulating these algorithms, a systolic triarray structure is proposed to facilitate VLSI implementations.en-USsignal processingalgorithmsparallel architecturesVLSI architecturesSystems IntegrationTechnical Report