Questions and answers of "signal and system" in the first semester of the 22nd academic year of Xi'an University of Electronic Science and technology

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School of network and continuing education, Xi'an University of Electronic Science and Technology

2022 The first semester of the academic year

《 Signals and systems 》 Final exam questions

（ Comprehensive homework ）

Question no

One

Two

3、 ... and

Total score

The topic points

32

30

38

score

Test instructions ：

1、 Release time of big homework test questions ：2022 year 4 month 22 Japan ;

2、 The exam must be completed independently , If you find plagiarism 、 The same score is zero ;

3、 The answer must be 《 School of network and continuing education, Xi'an University of Electronic Science and Technology 2022 Spring final exam answer sheet 》（ individual

Personal answer sheet ） Handwritten completion , The handwriting is required to be neat 、 The roll surface is clean 、 neat ;

4、 Photos should be complete 、 Clear , A picture corresponds to a personal answer sheet （A4 paper ）, Upload correctly .

instructions ： Symbol (t)、(k) They are unit step function and unit step sequence .LTI Linear time invariant .

For the adder .

One 、 Multiple choice questions （ common 8 Little topic , Every little question 4 branch , common 32 branch ）

__ _ 1、

( ) be equal to

t

etd





  



(A) 1 (B) (C) (D)

0

(t) (t)

__ _ 2、

( ) be equal to

i

 i







(A) 1 (B) 0 (C)  (k) (D)  (k)

___ 3、(at),(a  0) be equal to

∑ The first 2 page （ common 4 page ）

A

B C

D

(t)

'(t) a(t)

1 (t)

a



__ _4、 f1(t) 、 f2 (t) The waveform is shown in the figure 4 Shown , f (t)  f1(t)* f2 (t) be f (2) 

(A)

(B) 1 (C)

(D) 2

1

2

3

2

___5、 f1(k) and f2 (k) The waveform is shown in the figure 5 Shown , f (k)  f1(k)* f2 (k) be f (1) 

(A) 0 (B) 1 (C) 2 (D) 3

__ _6、 It is known that f (t)  sin 2t (t) Then the image function of its unilateral Laplace transform F(s) 

(A)

(B) (C) (D)

1

s 1 2

1

( 1) 4

s

s



  2 4

s

s  2

2

s  4

7、 It is known that f (t) Spectral function of ( ) 1 , be

2

F j j

j

  



f (t) 

(A) e2t(t) (B) t  3e2t (C) (t)  3e2t (D) (t)

8、 It is known that

Then its bilateral Z Image function of transformation be equal to

1

( )

( ) 2 ( 1)

2

k

k

f k

k k







    









F(z)

A non-existent B

C

D

1 2

2

z z

z z



  1

2

2

z

z

z   z 

1

2

2

z

z

z

z







Two 、 Completion （ common 6 Little topic , Every little question 5 branch , common 30 branch ）.

t

f1(t)

-2

2

2

4

0

chart 4

t

f2 (t)

1

1

-1

2

0

1

2

-1

0

k

f2 (k)

3

1

-1

2

2

1

1

2

-1

0

k

f1(k)

chart 5 The first 3 page （ common 4 page ）

9、 The definition of convolution integral f1(t)* f2 (t) ; The definition of convolution sum

;

f1(k)* f2 (k) 

10、 It is known that f (t) The waveform is shown in the figure 10 Shown , be f (1 2t) 、 f '(t) The waveforms of are

;

;

chart 10

11、 Then its spectrum function

;

f (t)  g2 (t)  sgn(t) F( j) 

12、 has know single edge PULL universal PULL Si change in Of like Letter Count

, be Its the Yes Should be Of primary Letter Count

2

4

( )

3

2



 



s

F s

s

s

.

f (t) 

13、 Bilateral Z Transformation ＝

; Convergence domain

.

f (k)  (2)k (k) F(z)

14、 The signal flow diagram is shown in the figure below 14 Shown , be ＝

.

H(s)

1

-2

-3

-1

2

1

s1

s1

s1

chart 14

3、 ... and 、 Calculation questions （ common 4 Little topic , common 38 branch ）.

Please write down the simple steps to solve the problem ; Only the answer 0 branch . Please indicate the meaning of non general symbols .

15、 It is known that f (t) F( j) , y(t) df (t) * 1 .

dt

t





Seeking function y(t) The Fourier transform of Y( j).

16、 has know Sketch Statement some LTI system system Of tiny branch Fang cheng y''(t)  3y'(t)  2y(t)  3 f (t), And y(0 )  1,

y'(0 )  1, f (t)   (t) . seek （1） System function H(s) ;

（

2） Zero state response of the system ;（

3） Zero input response of the system .

yzs (t)

yzi(t)

f (t)

t

1

0

1

2

1 The first 4 page （ common 4 page ）