Research On Fault Diagnosis Of Mixed-signal Circuits Based On DES Theory

With the fast development of the electronic technology, the complexity of the circuit system increases sharply, more and more electric circuits include digital and analog signal simultaneously, resulting in a greater difficulty in circuit testing. The present methods to test the electric circuits are mainly for digital or analog circuits, and there are few research on the mixed-signal circuits. So it is significant and valuable to study the test of the mixed-signal circuits.In this dissertation, the Discrete Event System(DES) theory is applied to establish a mathematical model applicable for most mixed-signal circuits. The keystone of the dissertation is to analyze the testability of circuit and diagnose the fault of circuit. The main work and contributions are summarized as follows:Firstly, the principle of the testability analysis based on the DES theory is thoroughly studied, the fault diagnosis model of the mixed-signal circuits is established. The simulation result indicates that it is feasible to test the mixed-signal circuits based on the DES theory.Secondly, in the research of the fault diagnosis of mixed-signal circuits based on the DES theory, how to find out the minimal test set of circuits is important and difficult. Considering the characteristic of the minimization of the test set of the mixed-signal circuits, a minimization approach for circuit test set based on discrete particle swarm optimization algorithm is put forward. With the "velocity-position" model, an optimum solution is searched in the result space by means of competition and cooperation among the particles of swarm. The experiment result testifies that the approach is efficient and robust.Thirdly, an approach to the fault diagnosis of mixed-signal circuits which combines the FTA (Fault Tree Analysis) method with the DES theory is used to reduce the redundant test vectors. The experiment analysis indicates that the approach is effective in improving the speed of testing.Finally, a virtual test system with a PCI DAQ device is proposed and designed so as to make the test of circuits operable. An experiment to test a factual mixed-signal circuit is done with the test system. The result validates that the DES theory is effective in testing and diagnosing the mixed-signal circuits.