low pass filter with minimal ringing I am trying to filter out some square wave signal to within a limited band (1/4 or 1/8 of the original), I realized that there's a lot of ringing in the wave when I use my filter (elliptical), I also tried Butterworth, and others (given in Matlab fir1, and classic iir filters) but the only filter that seems to give no ringing is Gaussian. So my question is, how should I go about designing a LPF with minimal ringing? (preferred characteristics: minimal pass band ripple, stop band of more than -50dB, relatively fast roll off). Also as I am trying to implement this in a DSP, low order filters such as IIR types are preferred.

Thank you for any help.
Generally the amount of ringing that you get is a function of the steepness of the filter in the frequency domain, regardless of filter type. 
At the same steepness an Elliptic will require a lower order but will have pretty much the same ringing as a Butterworth. 

Choosing between a linear phase or minimum phase will change the character but not the extent of the ringing. 

No matter how you slice it, a square wave contains a lot of high frequencies and once you filter those out, it's not a square wave any more.