Designing a perfect filter (i.e., flat passband, sharp transition band, and highly suppressed stopband) is always the goal of digital signal processing practitioners. This goal is reachable if we make no consideration of implementation complexity. In other words, the challenge of designing a high-performance filter is to leverage the distortion tradeoff in the passband, transition band, and stopband. In this article, we introduce a trick for designing a composite filter by cascading the base filter with a notch filter for sharpening its transition band. The stopband of the base filter is then further shaped by complementary comb filters (CCFs), which are simple in complexity. Performing a delicate calculation of all these component filters, the passband of the composite filter is flat, and a near-perfect filter is obtained with reasonable complexity.

中文翻译：

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设计具有尖锐过渡带和高度抑制阻带的复合滤波器的技巧 [提示与技巧]

设计一个完美的滤波器（即平坦的通带、尖锐的过渡带和高度抑制的阻带）始终是数字信号处理从业者的目标。如果我们不考虑实现的复杂性，这个目标是可以实现的。换句话说，设计高性能滤波器的挑战是利用通带、过渡带和阻带中的失真权衡。在本文中，我们介绍了一种设计复合滤波器的技巧，即通过级联基本滤波器和陷波滤波器来锐化其过渡带。然后，基础滤波器的阻带由复杂的互补梳状滤波器 (CCF) 进一步整形。对所有这些分量滤波器进行精细计算，复合滤波器的通带是平坦的，