Given a real strictly Hurwitz polynomialH_{n}(s) = a_{0}prod_{upsilon = 1}^{n} (s - s_{upsilon}), n = 3, 4, cdots ,the standard method of calculating the continued fraction expansion of{[odd H_{n}(s)]/ [even H_{n}(s)]}^{pm 1}about its pole at infinity uses Routh's scheme or Hurwitz's determinantsDelta_{r}, r = 1, 2, cdots , n, in the coefficients ofH_{n}(s)(on the equivalence of the two, see [2]). In filter theory, cases are often encountered where knowledge of the zeros ofH_{n}(s)precedes that of its coefficients, and one would then prefer to have formulas for the coefficients in the above continued fraction expansion directly in terms of the former rather than the latter. This is achieved by expressingDelta_{r}as bialternants in the zeros ofH_{n}(s)and readsDelta_{r} = (-)^{r(r+1)/2} a_{0}^{r}A(0, 1, cdots , n - r - 1, n - r + 1, cdots , n + r - 1)/A(0, 1, cdots , n - 1), where the alternant in the denominator is the Vandermonde ins_{1}, s_{2}, cdots , s_{n}, whereas the alternant in the numerator is obtained from it on replacing the exponents0, 1, cdots , n - 1by0, 1, cdots, n - r - 1, n - r + 1, cdots , n + r - 1. Examples includeH_{n}(s) = prod_{upsilon = 1}^{n} [s - j exp (2 upsilon - 1)j pi /2n]andH_{n}(s) = (s + 1)^{n}.

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Circuit Theory, IEEE Transactions on  (Volume:15 ,  Issue: 4 )

Dec 1968