A New Technique for The Design Of Selective FIR Filters With Non-Linear Phase, and Arbitrary Amplitude Characteristics

Q. Al-Zoubi and M. Abo-Zahhad
Department of Electronics Engineering,
Hijjawi Faculty of Engineering Technology,
Yarmouk University, Irbid, Jordan
Email: zahhad@yahoo.com


A highly efficient method for the synthesis and design of lowpass FIR filters with low loss and non-linear phase characteristics in the passband and selective amplitude in the stopband is proposed in this paper. It is based on a separate approximation of the real and imaginary parts of the filter frequency response. The design process starts by specifying the amplitude and phase at a set of frequencies in the passband and a set of transmission zeros in the stopband. The passband amplitude and phase specifications are interpolated by a general polynomial H1(l). Another polynomial H2(l), that has no phase contribution, is determined to interpolate the stopband requirements. Then, the amplitude specifications in the passband are predistorted to take into consideration the effect of H2(l). The filter transfer function is formulated as the multiplication of the two polynomials. Several design examples with various constraints are presented to explain the main properties of the design algorithm and to demonstrate that the proposed design method leads to a significant saving in the arithmetic computations. Comparing with the existing exact linear phase methods, this method is simple and effective in the design of filters with better stopband characteristics.

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