Explain the common FIR filter design methods.

FIR design methods: Window method - design ideal filter (infinite), window with finite function, simple but limited control. Frequency sampling - specify frequency response at DFT points, inverse DFT gives coefficients. Parks-McClellan (Remez) - optimal equiripple design, minimizes maximum error in pass/stop bands, most common for precision filters. Least squares - minimizes total squared error, good for some applications. Design parameters: filter order (length), passband/stopband edges, ripple specifications. Higher order = sharper transition but more computation. Parks-McClellan is standard for communications; window method for less critical applications.