The results prove that DF could simplify the solve process and its shortcoming of restriction in approximately denotation, frequency unitary 1 and inapplicability in more commonly quadratic system are also shown at the same time.

• 结果证明：使用描述函数法能够简化该问题的求解，但也暴露出其存在着近似表示，频率归1以及更一般二阶系统不适用等方面的局限和不足。