Sampled signal reconstruction and Nyquist frequency

The discussion focuses only on those remarks of J. Lynn Smith (see ibid., p.14, May 1996) that were directly related to earlier comments (see ibid., p.41, July 1995). It complements Marple´s (see ibid., p.24, January 1996) filter-bank analysis and tries to remove some clutter due to the improper test signals used. The frame of this discussion consist of the following three statements: the “successful” use of a sampling rate lower than the Nyquist rate is an illusion; the proposed method is nothing else than an analog form of the well-known filter banks, whose theory is consistent with the (correct) definition of the Nyquist frequency; and in general, the method can not be used with the zero-order hold operation, unless the filters are designed with frequency-dependent magnitude to compensate for the spectrum alteration produced by the sample-and-hold operation