In this case we have In synthesis there are too many design approaches: Foster form Cauer form Brune‟s method realization Bott Duffin method etc. 3. The canonic network synthesis is complete only when the eleniel~t values are procedures for computing the element values of Foster and Cauer forms. Chapter 4. Synthesis of deriving point functions (one port networks) . Decompose F(s) into simpler forms. For driving point Cauer synthesis. Uses partial Synthesize as R-C impedance and R-L admittance in foster realization. Solution.

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A consequence of Foster’s theorem is that zeros and poles of the reactance must alternate with frequency.

Necessary and sufficient conditions for positive real functions. Cauer in Germany forj the importance of Foster’s work and used it as the foundation of network synthesis.

It is convenient in these circumstances to use the concept of immittancewhich can mean either impedance or admittance.

Properties of positive real functions. Plot of the reactance of an inductor against frequency. These are of interest because they can accomplish tasks a Foster network cannot.

These are called non-Foster networks. Goster of two port in terms of impedance, admittance, hybrid and transmission parameters. Result of supplementary examination. Consequently, the plot of a Foster immittance function on a Smith chart must always travel around the chart in a clockwise direction with increasing frequency.


Industrial Power and Automation. This is sometimes referred to as the driving point impedance because cauerr is the impedance at the place in the network at which the external circuit is connected and “drives” it with a signal.

Electrical Engineering Departments – Electrical Engineering. Foster’s work was an important starting point for the development of network synthesis. Restrictions on pole and zero locations for transfer functions. Network Analysis and Synthesis. From Wikipedia, the free encyclopedia. Cauer was interested in finding the necessary and sufficient condition for realisability of a rational one-port network from its polynomial function, a condition now known to be a positive-real functionand the reverse problem of which networks were equivalent, that is, had the same polynomial function.

Foster networks are only a subset of realisable networks, [14]. The theorem can be extended to admittances and the encompassing concept of immittances. Reactance is the imaginary part of the complex electrical impedance.

Elements of realizability – Brune. A non-Foster network could match an antenna over a continuous syntjesis of frequencies. The theorem states that the reactance of a passive, lossless two-terminal one-port network always strictly monotonically increases with frequency.

Foster’s reactance theorem

Network functions for one port and two port. Past the pole the reactance is large and negative and increasing towards zero where it is dominated by the capacitance. Foster used this property to develop two canonical forms for realising these networks.


This follows from the fact the impedance of L and C elements are themselves synthessi rational functions and any algebraic combination of rational functions results in another rational function. Leave application form for PG students and research students.

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Plot of the reactance of a capacitor against frequency. The poles and zeroes of an immittance function completely determine the frequency characteristics of a Foster network. The mathematics is carried out without specifying units until it is desired to calculate a specific example.

This monotonically increases towards zero the magnitude of the capacitor reactance is becoming smaller. In particular, synhtesis applies to distributed element networks, although Foster formulated it in terms of discrete inductors and capacitors. Plot of the reactance of a parallel LC circuit against frequency.

Practical non-Foster networks are an cuaer area of research. Introduction to Modern Network Synthesis. The network consequently must consist fostwr of inductors and capacitors and the impedance will be purely an imaginary number with zero real part.