Digital Signal Processing - 中国大学mooc

1st Week: Unit 1 Introduction

1.1 Signals and Digital Signals随堂测验

1、For the time signal, please select the correct answers in the following statement.
    A、A continuous-time signal must be an analog signal
    B、A discrete-time signal must be a digital signal
    C、An analog signal must be a continuous-time signal
    D、A digital signal must be a signal with discrete-valued amplitudes

1.2 Digital Signal Processing and Application随堂测验

1、The reliability of digital system comes from the fact that digital signals are represented in two states: 0 and 1. 0 and 1 are represented by the level and the presence or absence of pulses, and can be well recognized and restored to 0 and 1, even if they are disturbed by noise within a certain range.

Unit Test for Unit 1

1、If you want to digitize the speech signal for subsequent processing, the speech signal must be passed through:
    A、anti-aliasing analog filter
    B、D / A conversion
    C、digital filter
    D、A / D conversion

2、The digital signal is a discrete-time signal with discrete-valued amplitudes.

2nd Week: Unit 2 Discrete-Time Signals in the Time Domain

2.1 Time Domain Representation of Discrete-Time Signals随堂测验

1、
    A、0
    B、5
    C、4
    D、uncertain

2、The left-sided sequence is the anti-causal sequence.

2.2 Operations on Sequences随堂测验

1、
    A、
    B、
    C、
    D、The rest of the options are wrong

2.3 Operations on Finite-Length Sequences随堂测验

1、
    A、-4
    B、3
    C、4
    D、10

2.4 Classification of Sequences随堂测验

1、Let x[n] and y[n] be conjugate-symmetric and conjugate-antisymmetric sequences respectively, then the sequence u[n]=x[n]y[n] is
    A、conjugate-symmetric sequence
    B、conjugate-antisymmetric sequence
    C、conjugate-symmetrical part
    D、conjugate-antisymmetric part

2.5 Typical Sequences随堂测验

1、
    A、
    B、
    C、
    D、

Unit Test for Unit 2

1、
    A、5
    B、10
    C、
    D、10/3

2、Express as a linear combination of delayed unit sample sequences.
    A、
    B、
    C、
    D、

3、
    A、
    B、
    C、
    D、

4、The length of the sequence obtained by linear convolution of length-M and length-N signals is
    A、M + N
    B、M + N -1
    C、M + N +1
    D、M * N

5、
    A、
    B、
    C、
    D、

6、Regarding the unit step sequence, the correct descriptions are
    A、finite length sequence
    B、causal sequence
    C、infinite length sequence
    D、right-sided sequence

3rd Week: Unit 3 Discrete-Time Signals in the Frequency Domain

3.1 Review of Continuous Time Fourier Transform (CTFT)随堂测验

1、The Fourier transform does not reduce the amount of data recording the signal.

3.2 Discrete-Time Fourier Transform (DTFT)随堂测验

1、
    A、1
    B、
    C、
    D、

3.3 Discrete-Time Fourier Transform (DTFT) Theorems随堂测验

1、
    A、
    B、
    C、
    D、

Unit Test for Unit 3

1、
    A、
    B、
    C、
    D、

2、For a discrete time sequence x[n], its DTFT must satisfy
    A、
    B、
    C、
    D、

3、
    A、
    B、
    C、
    D、

4、Let denote the DTFT of the sequence then
    A、0
    B、-3
    C、-5
    D、uncertain

5、Let denote the DTFT of the sequence then
    A、3
    B、11
    C、31
    D、uncertain

6、The DTFT of discrete time signal h[n] is then h[n] =
    A、
    B、
    C、
    D、

7、

8、The sequence x[n] has the same magnitude spectrum as its delayed sequence x[n-5].

4th Week: Unit 4 Sampling and Recovery of Analog Signal

4.1 Analysis of Sampling in Time Domain随堂测验

1、Continuous-time sinusoidal signals of different frequencies may get the same discrete-time sequence after sampling.

4.2 Analysis of Sampling in Frequency domain and sampling theorem随堂测验

1、The relationship between the sampled signal spectrum and the original signal spectrum is
    A、The sampled signal spectrum is a periodic copy of the original signal spectrum and multiplied by 1 / T (T is the sampling interval)
    B、The sampled signal spectrum is the same as the original signal spectrum
    C、The sampled signal spectrum has no relationship with the original signal spectrum
    D、The rest of the options are wrong

2、A 4 second long continuous-time signal is sampled uniformly without aliasing to produce a finite-length sequence containing 8500 sample points. The highest frequency component that may exist in the continuous-time signal is
    A、2125 Hz
    B、1062.5Hz
    C、4250Hz
    D、uncertain

4.3 Recovery of analog signal随堂测验

1、Which of the following filters is the reconstruction filter that recovers the analog signal from the discrete-time signal?
    A、Analog high-pass filter
    B、Digital low-pass filter
    C、Digital high-pass filter
    D、Analog low-pass filter

Unit Test for Unit 4

1、When sampling a continuous-time signal with a maximum frequency , to satisfy the Nyquist criterion of the sampling theorem, the range of the sampling interval T is
    A、
    B、
    C、
    D、

2、Sampling two continuous-time sinusoidal signals with frequencies of and at the sampling frequency , if the two sequences obtained after sampling are equal, they need to meet
    A、
    B、
    C、
    D、No requirements for and

3、Consider the continuous-time signal , is in units of seconds, and the discrete-time sequence is obtained after sampling, then the sampling frequency is
    A、4000 Hz
    B、1/8000 Hz
    C、8000 Hz
    D、2000 Hz

4、A continuous-time signal xa(t) is composed of a linear combination of sinusoidal signals of frequencies 300Hz, 500Hz, 1.2kHz, 2.15kHz and 3.5 kHz. The signal xa(t) is sampled at a 3 kHz rate, and the sampled sequence is then passed through an ideal lowpass filter with a cutoff frequency of 900 Hz, generating a continuous-time signal ya(t). What are the frequency components present in the reconstructed signal ya(t)?
    A、300 Hz
    B、850 Hz
    C、1200 Hz
    D、500 Hz

5、The cut-off frequency of the reconstruction filter used to recover the analog signal is the sampling angular frequency.

6、Anti-aliasing filtering is only required before sampling an analog signal of unlimited bandwidth.