Comprehensible Explanations of Determination Methods of Three Basic System Properties and Examples

In the course of learning Signals and Systems, it is one of the emphases and difficulties to determine the basic system properties, such as linearity, time-invariance and causality. In teaching, it is found that students often only know the written expression of the determination methods, but do not understand the core of the determination methods. So they feel difficult to use. In order to help students to understand, this paper focuses on giving popular and common explanations to the traditional determination methods of the above three basic system properties, rather than sticking to the rigor of the theory. As for linearity determination, from the embodiment of additivity and homogeneity, the input signals are constructed; the discrimination of time invariance is considered from two aspects: time delay and the transformation of signals by systems; it is more convenience for judgment of causality to obtain the time relationship of output and input from some special moments. By means of the comprehensible explanations of the determination methods in this paper, students can easily understand and master the traditional determination methods of three basic system properties. More importantly, they can apply it to solve the determination problems of linearity, time invariance and causality of systems.