Filter Design for RF Systems

When designing an RF filter it would be ideal if the filter would allow signals within the pass-band through without any change in amplitude or phase. Filters like this could have a rectangular response, falling straight to their stop-band and giving the required level of stop-band attenuation. Unfortunately it is not possible to design RF filters like this, and real RF filter designs can only approximate to the ideal response curves and parameters. These approximations can then be used as the different types of filter that exist. These include the Butterworth, Bessel, Chebyshev, Elliptical, Gaussian and many more.