Interactive Circuit Synthesizer

V. Kukk, M. Koort

Tallinn Technical University
Estonia

Traditionally, circuit analysis is considered as simulation, ie numerical experiment. However, a designer usually needs some more sophisticated information, and so he has to interpret simulation results himself. Designers having experience with different simulators know that interpretation of the results might be much more complicated than formulation of simulation task. Conclusion is that analysis should be considered as a procedure that gives interpreted results that could be used as directly as possible for further design steps.

One example of frequent design problem is finding elements for compensation of distortions inserted by parasitics. Even if these distortions can be predicted, conventional synthesis methods do not include them because of complexity of the problem. A typical example is classical filter synthesis that is a set of very strict and reliable procedures but only for ideal components. Active filters designed by these classical procedures often need only some simple corrections to meet the specification. Usually, these elements can be calculated after complex simulations and following interpretation of the results in the 'circuit language'.

The conclusion is that an elementary tool needed for interpretation of simulation results (Analysis), is circuit synthesizer. The synthesizer must be interactive because the goal of the procedure is determined by user. Obviously, there exist some standard goals that can be predefined and implemented.

This paper considers a set of interactive procedures for synthesis of driving-point immitances. It is based on standard basic steps in Foster and Cauer procedures. A tool has the following facilities:

  1. menu based fully interactive synthesis (menu for every step),
  2. automatic generation of the set of different realizations,
  3. partial pole extractions and zero shifts (to control further steps and use of specific components),
  4. controlled corrections of transfer functions and equivalent transformations.
The procedures differ from classical synthseis because there is no guarantee for realization with real components. Vice versa, for synthesis of correction circuits, equivalent circuit must include negative elements. This accomplish the use of classical procedures and special expert knowledge has been introduced into programs.

The tool has been implemented inside the environment of system SPADE but is almost independent to be used in cooperation with other design systems.