Oblique projections and frames

Abstract

We characterize those frames on a Hilbert space H which can be represented as the image of an orthonormal basis by an oblique projection defined on an extension K. of H. We show that all frames with infinite excess and frame bounds 1 ≤ A ≤ B are of this type. This gives a generalization of a result of Han and Larson which only holds for normalized tight frames. ©2005 American Mathematical Society.