Comments on "A Matched Delay Approach to Subtractive Linear Phase High-Pass Filtering

We answer a question posed in the above footnote[1]{paper} by showing that derived high-pass slopes of up to 80 dB/decade with good phase linearity are achievable by using a truncated exponential low-pass filter alignment in a matched-delay subtractive filter. The performance of this filter is illustrated graphically. (1) T. K. Ng and M. Rothenberg, IEEE Trans. Circuits Syst., vol. CAS-29, pp. 584-587, Aug. 1982.