2021 Digital Signal Processing(University of Electronic Science and Technology of China) 最新满分章节测试答案

本答案对应课程为:点我自动跳转查看
本课程起止时间为:2021-02-26到2021-07-10

Topic1 Introduction of DSP Topic 1 Test

1、 问题:In an actual communication system, the input and output signal forms in the digital signal processing (DSP) module are usually respectively
选项：
A:Analog signal, Digital signal
B:Digital signal, Analog signal
C:Analog signal, Analog signal
D:Digital signal, Digital signal,
答案: 【Digital signal, Digital signal,】

2、 问题:Compared with analog signal process, the advantage of digital signal process includes
选项：
A:The accuracy of the DSP is more guaranteed.
B:The DSP system is corresponding to multiple functions.
C:The DSP has better reliability and repeatability.
D:The DSP has faster processing speed.
答案: 【The accuracy of the DSP is more guaranteed.;
The DSP system is corresponding to multiple functions.;
The DSP has better reliability and repeatability.】

【作业】Topic1 Introduction of DSP Topic 1 Homework

1、 问题: In the communication process, an analog signal needs to be processed digitally, and then be converted back to an analog signal after the processing is completed. Please briefly describe the process and explain which of the analog and digital signals are in the signal processing process. 
评分规则: 【 It is explained that in the process of communication, if an analog signal is to be processed by digital method, it needs to go through three processing steps of ADC, DSP and DAC to get 9 points, and if one step is less, 3 points will be deducted. If these steps are not answered, no score will be given.
It is explained that in the whole process of signal processing, analog signal (2 points for each, 4 points in total) is before ADC and after DAC, and digital signal (2 points for each, 4 points in total) is after ADC and before DAC. If the answer result is wrong or the question is not answered, no score will be given.
】

2、 问题: Give at least two examples to illustrate the application of digital signal processing encountered in daily life.
评分规则: 【 In the daily signal processing, digital processing methods are used, such as mobile communication system, digital camera, digital home theater, radar imaging, digital library, online shopping and other typical applications of digital signal processing. If  more than two applications are listed, you will get 10 points. 5 points will be deducted for less than 2 questions, and no score will be given for no answer or wrong answer.
】

Topic 2 Digital Processing of Continuous Signals-2 Topic 2 Test

1、 问题:A continuous-time signal xa(t) = 4sin(20πt) is sampled at frequency f=40Hz，determine the value of sample x[1] = _____
选项：
A:0
B:4
C:-4
D:1
答案: 【4】

2、 问题:Which of the following equation is right ？
选项：
A:
B:
C:
D:
答案: 【】

3、 问题:Consider the continuous-time signal xa(t) = 4sin(20πt)，which of the following frequencies won’t cause frequency spectrum overlap _
选项：
A:10Hz
B:20Hz
C:40Hz
D:80Hz
答案: 【40Hz;
80Hz】

4、 问题:The  sampling frequency is only determined by the highest frequency component of the signal.
选项：
A:正确
B:错误
答案: 【错误】

5、 问题:In the time domain， the procedure of restoring the original continuous-time signal from discrete sample values is called_
答案: 【interpolation】

【作业】Topic 2 Digital Processing of Continuous Signals-2 Topic 2 Homework

小提示:本节包含奇怪的同名章节内容

1、 问题:Continuous-time signal xa(t) is a linear combination of sinusoidal signals with frequencies of 300 Hz, 500 Hz, 1.2 kHz, 2.15 kHz, and 3.5 kHz. The signal xa(t) is sampled at a sampling rate of 2.0 kHz. When the resulting sequence passes through an ideal low-pass filter with a cutoff frequency of 900 Hz, we obtain a continuous time signal ya(t). What is the frequency component in the output signal ya(t)? 
评分规则: 【  After sampling，the original analog frequency f should be expanded periodically as （f+2000n）Hz（n being integer）（the description for 2 points）
After lowpass filering，the reserved frequencies （f+2000n）<900Hz300H–>300+2000×0=300Hz500H–>500+2000×0=500Hz,      1200H–>1200+2000x(-1)=-800Hz        2150H–>2150+2000x(-1)=150Hz        3500H–>3500+2000x(-2)=-500Hz     (Each  frequency is got correctly by the original analog frequency and lowpass filtering for 2 points）   So the frequency components in the output signal ya(t) are 150Hz,300Hz,500Hz,800Hz
】

2、 问题:The following figure shows the discrete processing of continuous-time signals, where T1 and T2 are the sampling intervals of the ideal sampler and ideal interpolator, and f1 = 1 / T1 and f2 = 1 / T2. The digital processing system in the figure is an ideal low-pass filter with a cutoff frequency of π / 2. Assuming that the input signal is xa (t) = cos (4πt) + 0.5cos (8πt), in the following cases, determine the values of x [n], y [n] and ya (t) respectively.(a) f1=10Hz and f2=10Hz;(b) f1=10Hz and f2=20Hz;(c) f1=20Hz and f2=10Hz.
评分规则: 【 (a) f1 = 10Hz和f2 = 10Hz；x[n] = cos (0.4πn) + 0.5cos (0.8πn)y[n]= cos (0.4πn)ya(t)=cos(4πt)Each correct expression for 2 points.
(b) f1 = 10Hz和f2 = 20Hz；x[n] = cos (0.4πn) + 0.5cos (0.8πn)y[n]= cos (0.4πn)ya(t)=cos(8πt)Each correct expression for 2 points.
(c) f1 = 20Hz和f2 = 10Hz；x[n] = cos (0.2πn) + 0.5cos (0.4πn)y[n]= cos (0.2πn) + 0.5cos (0.4πn)ya(t)=cos(2πt)+0.5cos(4πt)Each correct expression for 2 points.
】

3、 问题:Consider the system shownAssume that the input continuous-time signal xa(t) with a band-limited spectrum Xa(jΩ), as shown in the following figure (a), is sampled at the Nyquist frequency. The digital processor is an ideal low-pass filter with frequency response H(ejω) as shown in (b) below, and its cut-off frequency is ωc=ΩmT/3, where T is the sampling interval. Draw the spectrum Ya(jΩ) of the output continuous time signal ya(t) as accurately as possible.
评分规则: 【 Based on the requirement，we know Ωs = 2Ωm
The cutoff frequency of digital frequency ωc = ΩmT/3 =π/3
Based on ω=ΩT，afer sampling, Ωs corresponding to 2π, so Ωmcorresponding to π, then Ωm/3 corresponding to π/3
So, the cutoff frequency of the digital filter is π/3，after lowpass filtering, the frequency range [-Ωm/3,Ωm/3] of figure(a) is reserved.
】

4、 问题:Try to judge whether the following signals are periodic sequence, if it is a periodic sequence, try to write the period.
评分规则: 【
】

5、 问题:The following figure shows the discrete processing of continuous-time signals, where T1 and T2 are the sampling intervals of the ideal sampler and ideal interpolator, and f1 = 1 / T1 and f2 = 1 / T2. The digital processing system in the figure is an ideal low-pass filter with a cutoff frequency of π / 2. Assuming that the input signal is xa (t) = cos (4πt) + 0.5cos (8πt), in the following cases, determine the values of x [n], y [n] and ya (t) respectively.(a) f1=10Hz and f2=10Hz;(b) f1=10Hz and f2=20Hz;(c) f1=20Hz and f2=10Hz.
评分规则: 【 (a) f1 = 10Hz和f2 = 10Hz；x[n] = cos (0.4πn) + 0.5cos (0.8πn)y[n]= cos (0.4πn)ya(t)=cos(4πt)Each correct expression for 2 points.
(b) f1 = 10Hz和f2 = 20Hz；x[n] = cos (0.4πn) + 0.5cos (0.8πn)y[n]= cos (0.4πn)ya(t)=cos(8πt)Each correct expression for 2 points.
(c) f1 = 20Hz和f2 = 10Hz；x[n] = cos (0.2πn) + 0.5cos (0.4πn)y[n]= cos (0.2πn) + 0.5cos (0.4πn)ya(t)=cos(2πt)+0.5cos(4πt)Each correct expression for 2 points.
】

Topic 3-1 DTFT Topic3-1 Test

1、 问题:
选项：
A:
B:
C:
D:Undetermined
答案: 【】

2、 问题:
选项：
A:
B:
C:
D:
答案: 【】

3、 问题:Which of the following is true about the magnitude spectrum and phase spectrum of  DTFT？
选项：
A:DTFT of discrete-time signal can be divided into magnitude spectrum and phase spectrum, and both are complex function of ω.
B:The magnitude of a discrete-time signal is an even function of ω，while the phase spectrum of that is an odd function of ω.
C:If the phase spectrum of a discrete-time signal always has a discontinuous amplitude at πand -π with a jump of 2π, it is possible to be brought by phase wrap.
D:Magnitude spectrum and phase spectrum is the only form of DTFT of discrete-time signal.
答案: 【If the phase spectrum of a discrete-time signal always has a discontinuous amplitude at πand -π with a jump of 2π, it is possible to be brought by phase wrap.】

4、 问题:
选项：
A:It is absolute summable.
B:It is square summable.
C:Its DFT exists.
D:It has finite energy.
答案: 【It is absolute summable.;
It is square summable.;
Its DFT exists.;
It has finite energy.】

5、 问题:Which of the following is false about the relationship between DTFT and CTFT？
选项：
A:DTFT is only different from CTFT on the continuity and discreteness of time domain signal and the units in frequency domain. And DTFT can be transformed CTFT.
B:DTFT is always used to represent the spectrum of discrete-time signals，while CTFT is used to represent the spectrum of continuous-time signals. 
C:Spectrum of DTFT can be obtain by extending the continuous-time signal periodically by sampling frequency.
D:DTFT and CTFT are totally different concept for discrete-time signal and continuous-time signal and cannot be connected.
答案: 【Spectrum of DTFT can be obtain by extending the continuous-time signal periodically by sampling frequency.;
DTFT and CTFT are totally different concept for discrete-time signal and continuous-time signal and cannot be connected.】

6、 问题:During the solution of DTFT as follows, which propertie are used？
选项：
A:Linearity theorem
B:Time-shifting theorem
C:Differentiation-in-frequency theorem
D:Convolution theorem
答案: 【Linearity theorem;
Time-shifting theorem】

7、 问题:If a sequence x[n] is even, its DTFT must be conjugate symmetric.
选项：
A:正确
B:错误
答案: 【错误】

【作业】Topic 3-1 DTFT Topic 3-1 Homework

1、 问题: Calculate the DTFT of the following sequences
评分规则: 【 Correct DTFT fomula for 1 point, correct answer for 2 points.
Correct DTFT fomula for 1 point, correct answer for 2 points.
Correct DTFT fomula for 1 point, correct answer for 2 points.
Correct DTFT fomula for 1 point, correct answer for 2 points.
Correct DTFT fomula for 1 point, correct answer for 2 points.
Correct DTFT fomula for 1 point, correct answer for 2 points.
】

2、 问题:Calculate the IDTFT of the following DTFTs (Tip: No need to directly calculate IDTFT)
评分规则: 【 Euler formula for 1 point，correct h[n] result for 2 points.
Euler formula for 1 point，correct h[n] result for 2 points.
Euler formula for 1 point，correct h[n] result for 2 points.
Euler formula for 1 point，correct h[n] result for 2 points.
】

3、 问题:
评分规则: 【
】

4、 问题:Without calculating DTFT, determine which DTFTs have real values and which have imaginary values in the following sequences：
评分规则: 【 Based onThe DTFTs of even sequences are real, the DTFTs of odd sequences are imaginary. Because sequences in (a)(d)(e) are odd sequences, so their DTFT are imaginary, while sequences in (b)(c) are even sequences, so their DTFT are real.The symmetry that can be referenced correctly for 4 points. Each correct result for 1 point, and 5 questions in total are 5 points. Totally 9 points.
】

5、 问题: