On ladder networks and continued fractions

Driving-point immittance of general ladder network can always be put in the form of a continued-fraction expansion, where all the quotient terms are positive-real functions. Recursion formulas for transmission (ABCD) parameters lead us to another form of continued fraction. These fractions, whose terms are not (in general) positive-real functions, are chained by means of negative signs. It is not the purpose of this letter to develop one special realization technique. The intention is only to show that driving-point immittance of ladder network can be represented as an expansion of negative-sign fractions, and thatt his expansion can be used, more or less successfully, for the realization of ladder networks.