Linear-phase FIR design using PSO method with Zero-phase Pre-design

Linear-phase FIR filters that was successfully designed by PSO method has good frequency-response shape (low output ripple). However, Linear-phase FIR has so many trigonometric terms and requires complex-number calculation. This leads to two major problems for PSO (and similar algorithms), slow and faulty convergence (especially at high filter´s order). This paper proposes `Zero-phase Pre-design´ technique. The technique firstly designs zero-phase FIR filter (using PSO) and then converts it to linear-phase FIR (the conversion is easy). For zero-phase FIR, we can mathematically reduce trigonometry terms and discard imaginary terms in design calculation, result in computation saving and less difficulty. Experimental results show that our technique prevents design failure and need less computation time.