The structure of all-pass matrices that satisfy directional interpolation requirements

All-pass matrices are considered which are permitted to have right-half plane (RHP) poles less than some specified number. This is an extension of the inner interpolation problem where no RHP poles are permitted. All-pass matrices which satisfy the directional interpolation requirements are obtained in closed form. The simple derivation provides an insight into the mechanism by which the interpolation requirements impose the infinity -norm restriction under the number condition of half plane poles.<
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