Finite-Q Elements and Predistortion
In addition to increased insertion loss, other undesirable features of predistorted networks are a wide range of element values, increased sensitivity to small element-value changes, increased mismatch between the filter's input impedance and the source resistance, and the appearance of passband ripples when the element q is small and differs from the design value. Consequently predistortion should only be used when q is relatively high and the exact response is desired. Otherwise, a more practical solution is the adjustment of the filter's bandwidth to accommodate losses as explained. In most cases the exact response is not a necessity; the lossy response is satisfactory, and the disadvantages associated with the predistortion method are then absent.
Finite-Q Elements and Predistortion, Page 1 of 2
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