The problem of existence of static controller in standard H-infinity c
ontrol problem or, equivalently, solvability of a couple of Riccati in
equalities with respect to the same Hermitian matrix is reduced to sol
vability of a single Riccati inequality. This inequality is presented
in a form which is bilinear with respect to unknown parameters. In a s
pecial case the inequality is transformed to LMI. (C) 1998 Published b
y Elsevier Science B.V. All rights reserved.