Cosine-modulated filter banks (CMFBs) have gained prominence over other filter bank types due to their simplicity and ease of design. In this paper, we detail the design of a digital filter and filter bank using the Schittkowski algorithm. This method provides a systematic and efficient approach for developing filter banks. The prototype filter was designed using the Interpolated Finite Impulse Response (IFIR) technique, which is an efficient method for designing linear filters. The effectiveness of the proposed method was assessed in terms of aliasing distortion and reconstruction error, demonstrating its capability in achieving high-quality signal processing. Our findings add to the existing body of knowledge and underscore the potential for further advancements in the design and optimization of digital filter banks.