9(2) 信号与系统 周建华 光电学院教学课件.pptVIP

9 The Laplace Transform Example ： 4 x(t) y(t) -7 6 5 9 The Laplace Transform 例题： -3 x(t) y(t) -2 4 2 也可由方框图，根据梅森公式，写出系统函数的表达式。 (2) Cascade form of the block diagram: Hi(s) is first-order or second-order system. If s is real pole, Hi(s) is first-order system. If s is conjugation imaginary pole, Hi(s) is second-order system. 9 The Laplace Transform 即，把H(s)因式分解为一阶或二阶子系统级联（相乘）的形式。 9 The Laplace Transform Example 9.30 Solution: first-order system first-order system 9 The Laplace Transform -1 x(t) y(t) -2 x(t) y(t) -1 x(t) -2 y(t) 9 The Laplace Transform Example Solution: first-order system second-order system 9 The Laplace Transform -1 x(t) y(t) -2 x(t) -2 y(t) 9 The Laplace Transform -1 x(t) -2 -2 y(t) (3) Parallel form of the block diagram: Hi(s) is first-order or second-order system. 9 The Laplace Transform 即，把H(s)部分分式展开为一阶或二阶子系统并联（相加）的形式。 9 The Laplace Transform Example 9.30 Solution: first-order system first-order system 9 The Laplace Transform -1 x(t) y(t) -2 - 9 The Laplace Transform Example Solution: 9 The Laplace Transform first-order system second-order system 9 The Laplace Transform -1 x(t) y(t) -2 x(t) -2 y(t) 9 The Laplace Transform -1 y(t) -2 x(t) -2 y(t) - 9.9 the unilateral Laplace transform 9 The Laplace Transform 如果拉普拉斯变换的积分下限变为： 我们把这种变换称为单边拉普拉斯变换。 Definition: the unilateral Laplace transform 9 The Laplace Transform 9 The Laplace Transform Note: If x(t)=0 for t0, its unilateral Laplace transform is identical to its bilateral Laplace transform 2. The ROC of unilateral Laplace transform must be a right-half plane. 3. If x(t)=0 for t0, its inverse unilateral Laplace transform is identical to its inverse bilateral Laplace transform. Example 9.32 9.33 9.34 Determine the unilateral Laplace transform for the following signals. (a) (b) (c) 9 The Laplace Transform Example 9.35 9.36 Determine the inverse unilateral Laplace transform for the following signal