Text this: Describing function matrix for multivariable systems and its use in multiloop PI design

            ______   _    _     _____     _____   
  ____     /_   _// | || | ||  |  ___||  / ____|| 
 |    \\    -| ||-  | || | ||  | ||__   / //---`' 
 | [] ||    _| ||_  | \\_/ ||  | ||__   \ \\___   
 |  __//   /_____//  \____//   |_____||  \_____|| 
 |_|`-`    `-----`    `---`    `-----`    `----`  
 `-`