Comments, with reply, on ´Another algorithm for converting a low-pass function into bandpass form´ by K. Metzger

The commenter points out that the recursive algorithm described by K. Metzger in the above-titled letter (ibid., vol.76, no.5, p.634-5, May 1988) was published by him in the September 1980 issue of the IEEE Circuits and Systems Magaz (vol.2, no.3, p.3-5). He notes that the recursive technique is very useful not only for the low-pass to bandpass transformation, but also for performing the bilinear transformation used in digital filter design. The author replies that he was unaware of the earlier paper and thanks the commenter for calling it to his attention.