Comments, with reply, on "An adaptive digital pump controller for phase-locked servo systems" by G.-C. Hsieh et al

It is shown that the linearized model of the adaptive digital pump controller utilized for studying stability conditions and used in the simulations in a previously published paper (see ibid. vol.34, no.3, p.379-86, 1987) does not agree with the proposed circuit. A reply from the authors of the original paper is also included.<
>