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FILTER SYNTHESIS 1521
FILTER SYNTHESIS
ERNST LUEDER
University of Stuttgart
calculation of the values of the components by mathematical means from the functions approximating the specications. This step also provides the topology of the twoport. For approximations it is mathematically easier to handle the square of the magnitude |F*(jo)|2. For a lossless two-port in Fig. 1 F*(p) has the following properties [1,2]: 1. F*(p) is a rational function in p, real-valued for realvalued p; as a consequence, the coefcients in F*(p) are real-valued if the numerator and the denominator of F*(p) do not contain a common complex factor. 2. Stability requires the poles of F*(p) to lie in Re po0 and the degree of the numerator not to exceed the degree of the denominator. The denominator is