Analysis, design, and performance limitations of H∞ optimal filtering in the presence of an additional input with known frequency

A generalized γ‐level H ∞ sub‐optimal input decoupling (SOID) filtering problem is formulated. It is a generalization of γ‐level H ∞ SOID filtering problem when, besides an input with unknown statistical properties but with a finite RMS norm, there exists an additional input to the given plant or system. The additional input is a linear combination of sinusoidal signals each of which has an unknown amplitude and phase but known frequency. The analysis, design, and performance limitations of generalized H ∞ optimal filters are presented.