Intuitive Approach to Active Digital Filter Design. Part III: Principle of Higher-order High-pass Filters

Intuitive engineering is a valuable skill that empowers engineers to effectively tackle problems using straightforward methodologies and simple calculations, rather than relying solely on complex techniques and higher mathematics. Recently, a comprehensive foundation for intuitive active digital filter (ADF) design has been published in a two-part series. Part I introduced the fundamental principles of first-order ADFs, demonstrating their application in designing low-pass, high-pass, band-pass, and band-rejection filters. Part II further explored the design of higher-order low-pass filters (LPFs), serving as a guide for the design strategy of high-pass filters (HPFs). This article continues the series on ADF design by focusing on second and higher-order active HPFs. Similar to Part II, popular filter approximations, such as Bessel, Butterworth, and Chebyshev are discussed and compared to their analog Sallen-Key counterparts. Additionally, second-order active high-pass filtering of electrocardiogram (ECG) signals is demonstrated, indicating its better ability to suppress baseline drift from ECG signals.