Group delay transfer functions with least squares error

This paper presents tables of group-delay functions, ranging in order from 3 to 11, which approximate a nominal one second delay over bandwidths up to 17.5 rad/s. The functions, which can be arranged in all-pole or non-minimum phase forms, are based on a least-squares minimization of the delay error and therefore exhibit `unequal ripple¿ characteristics. These and other features of the leastmean-square approximations are discussed and comparisons drawn with maximally-flat and equi-ripple forms. A versatile RC-active biquadratic section, which has been found particularly useful in implementing non-minimum phase functions, is also described.