Designs a linear phase FIR lowpass filter such that it:

- minimizes the filter order

- has a constraint on the maximum passband ripple

- has a constraint on the maximum stopband attenuation

-This is a quasiconvex problem and can be solved using a bisection.



　　minimize　 filter order n

　　　　s.t.　 1/delta <= H(w) <= delta　　 for w in the passband

　　　　　　　 |H(w)| <= atten_level　　　　for w in the stopband



　where H is the frequency response function and variable is

　the filter impulse response h (and its order/length).

　Data is delta (max passband ripple) and atten_level (max stopband

　attenuation level).