Linear phase requirement can be achieved by direct design with an FIR filter at
the expense of high order and high computational burden for the given specification.
Alternatively, IIR digital filters can be designed with much smaller order than their FIR
counterparts, but at the expense of the non-linear phase. In this paper, a new design of
linear phase IIR digital filter is presented by composing a zero phase efficiently
designed FIR digital filter with maximally flat group delay. The new IIR digital filter is
designed with a lower order satisfying the same roll-off magnitude response of the
corresponding FIR filter and preserving the approximate pass-band characteristics.