A new method is described for designing FIR digital filters. A desired frequence response can be regarded as the sum of elementary frequence units （EFU） triangle shaped with different central frequence. Adding together the time sequences corresponding to these EFU

the filter’s impulse response can be obtained. The advantage of the method is that the time duration of the impulse response is about one third less than that obtained by the window method at a slight sacrifice of the pass-band ripple （within 2 percent）. The method can be used for designing filters with an arbitrary frequence response （such as low-pass

highpass

band-pass or band-elimination filter）

Hirbert transformers or differentiators.