Any physical quantity that carries some information can call as signal. FIR filters are designed with windowing techniques which will improve spectral response of filter. Signal can also be defined as any physical quantity that varies with time, space or any other independent variable. In this paper, new class window functions are proposed for FIR filter design. The new class of window functions is obtained using conventional windows and higher order polynomial windows which improve spectral response of filter than existing conventional windowing techniques in terms of RSA (Relative Side-lobe Attenuation).