同济大学通信系统原理英文班练习题附答案.docx

1、同济大学通信系统原理英文班练习题附答案Chapter 1Homework:Fill-in Questions:1. In a M-ary communication system, each symbol contains ( ) bits information content.2. The purpose of communication is to ( transfer information ). Efficiency of the digital communication system can be measured by the specifications such as ()

2、 , () , ( ). And reliability can be measured by ( ) , ( ).3. The basic factors for measuring the merit of a communication system are (efficiency ), and ( reliability ).4. The main influence of constant parameter channel on signal transmission are usually described by their ( Amplitude-Frequency ) an

3、d ( Phase-Frequency ) characteristics.5. Common characteristics of random parameter channels are (transmission attenuation of the signal is varying with time ), (transmission delay of the signal varies with time ), and (signal arrives at the receiver over several paths ).Multiple-Choice Questions:1.

4、For analog and digital communications, which is (are) true? ( A B C D ).A. digital communication typically uses more bandwidth.B. analog communication cares more about fidelityC. digital communication cares more about probability for correct decisionD. digital communication typically uses analog car

5、rier to carry baseband signalsSingle-Choice Questions:1. The symbol rate of 16-ary digital signal is 1200Bd, then the corresponding information rate is ( D ); If with the same information rate, the symbol rate of 8-ary digital signal is ( D ).A. 1600b/s, 1200Bd B. 1600b/s, 3200Bd C. 4800b/s, 2400B D

6、. 4800b/s, 1600B2. Assume the delay difference of two paths in a random parameter channel is , the frequencies of maximum transmission loss are ( B ), the frequencies of minimum transmission loss are ( B ).A. kHz, kHz B. kHz, kHzC. kHz, kHz C. kHz, kHzTrue or FalseWhen there is no input signal, the

7、additive interference doesnt exist, but the multiplicative interference still exists. ( F )Chapter2Homework: 2.1, 2.4, 2.5, 2.6, 2.8, 2.11Fill-in Questions:1.AWGN noise is short term for ( Additive White Gaussian Noise ).2.The power spectral density and ( the autocorrelation function ) of a stationa

8、ry random process are a pair of Fourier transform.3.If bandwidth is 10 MHz, signal-to-noise ratio is 20dB, the Shannon capacity is C=( 66.6 Mbps ).Single-Choice Questions:1. Assume is a generalized stationary random process with zero mathematical expectation, then the average power of is ( D ).A. B.

9、 C. D. 2. For a narrow band random process , if is a Gaussian process, then ( A ).(A) and are also Gaussian processes; (B) Only is also Gaussian process;(C) and are not Gaussian processes; (D) Only is also Gaussian processes.Chapter31.Comparison of AM, DSB, SSB and FM these four communication system

10、, which has the best efficiency? Which has the best reliability? Which have the same efficiency?SSB has best efficiency. FM has the best reliability. AM and DSB have the same efficiency.2.What is the requirement on the characteristics of the filter for producing the VSB signal?3.What kind of baseban

11、d signal is suitable for VSB modulation?The analog baseband signal with D.C. component and low frequency component is suitable for VSB modulation.4.Let the expression of a FM modulated signal beFind: (1) the maximum frequency deviation of the modulated signal. (2) the frequency of the carrier. (3) t

12、he bandwidth and the average power of the modulated signal. (4) if the FM circuit constant is kHz/V, then the expression of the baseband signal can be written as:(1) (2) Hz(3) Hz W(4) Vthe baseband signal can be written as:5.Assume the amplitude of a FM modulated signal is 10V, the instantaneous fre

13、quency of the FM signal is:Find: (1) the expression of the FM modulated signal. (2) the maximum frequency deviation , the modulation index, and the bandwidth of the modulated signal.(1) (2) , , kHzFill-in Questions:1.Assume the expression of a FM signal is , the carrier frequency of this FM signal i

14、s ()Hz, the maximum frequency deviation is (5000) Hz, the bandwidth of this FM signal is ( ) Hz，the average power is (12.5 )W.Single-Choice Questions:1. Which analog modulation has the highest spectrum efficiency? ( C )(A) AM (B) DSB(C) SSB (D) VSBCalculation Questions:1.Let a baseband modulating si

15、gnal be a sinusoidal wave with the frequency 10kHz, and the amplitude 1V. It modulates the phase of a carrier with frequency 10MHz, and the maximum phase deviation of modulation is 10rad. (1) Calculate the approximate bandwidth of the phase modulated signal. (2)If the frequency of the modulating sig

16、nal is changed to 5kHz, calculate the bandwidth of the phase modulated signal.Answer: (1) We has known that: , and maximum phase deviation .The instantaneous phase of the carrier can be represented as:, where .Then, the instantaneous frequency deviation of the carrier can be represented as:d, and ma

17、ximum frequency deviation is .Hence, the frequency modulation index is: Thus, the approximate bandwidth of the phase modulated signal is (2) If the frequency of the modulating signal is changed to 5kHz, then the approximate bandwidth of the phase modulated signal is:.Chapter4Fill-in Questions:1.The

18、basic process, from( Sampling the analog signal ), ( the quantization ), and ( converting to binary symbols ) , is usually called as pulse code modulation (PCM).Single-Choice Questions:1. The purpose of nonuniform quantization is ( B ).A. Protect big signal B. Protect small signal C. remove quantiza

19、tion noise D. Increase quantization levels2. In Delta modulation, the best way to avoid overload quantization noise is ( A ). A. Increase sampling frequency B. Increase quantization stepC. Reduce sampling frequency D. Reduce quantization step3. The sampling theorem points out that if the highest fre

20、quency of a low-pass analog signal is , then the signal can be represented by its samples when the sampling frequency no less than ( B ). (A) (B) (C) (D) 4. If the samples obey uniform distribution over , then the quantization noise power is determined by ( C )(A) (B) and quantization interval (C) q

21、uantization interval (D) other parameters.Multiple-Choice Questions:1. Digitization of analog signals includes ( B、D、E )(A). Modulation (B). Quantization (C). Multiplexing (D). Source coding (E). SamplingShort-Answer Questions:1.In Delta modulation system, why we increase sampling frequency rather t

22、han quantization step to avoid overload quantization noise?Answer: Given the sampling frequency and the quantization step , then the slope of a step is:It is the maximum possible slope of a step-shaped wave, or it is called the maximum tracking slope of the decoder. When the slope of the input signa

23、l of the delta modulator exceeds this maximum, overload quantization noise will be generated. Therefore, in order to avoid overload quantization noise, it is necessary to make the product of and large enough, so that the slope of the signal can not exceed this product. One the other hand, the value

24、of is directly related to the magnitude of the basic quantization noise. If the value of is large, then the basic quantization noise must also be large. Therefore, only the method of increasing to increase the product can ensure that the basic quantization noise and the overload quantization noise d

25、o not exceed the limit.Fill-in Questions:1.( 2 )Baud/Hz is the highest possible unit bandwidth rate, and is also called as the Nyquist rate.2.The time-domain equalizer is used to overcome ( intersymbol interference (ISI) ).3.The basic process, from ( Sampling the analog signal ), ( the quantization

26、), and ( converting to binary symbols ) , is usually called as pulse code modulation (PCM).Single-Choice Questions:1. If the samples obey uniform distribution over , then the quantization noise power is determined by ( C )(A) (B) and quantization interval (C) quantization interval (D) other paramete

27、rs.Multiple-Choice Questions:1. Digitization of analog signals includes ( B, E )(A). Modulation (B). Quantization (C). Multiplexing (D). Source coding (E). Sampling2. Which are symbol code type for baseband digital signals? (A, B, C, D, E )(A). HDB3 (B). AMI (C). CMI (D). Biphasic code (E). 5B6B (F)

28、. BPSK (G).MSKShort-Answer Questions:1.Which are the design principles of code for digital baseband signal?As we know, the performance of a practical baseband transmission system can be found in its eye pattern (refer to the figure below). Please find out the characteristics in the figure 1, and poi

29、nt out their impacts on transmission performance.Answer:(1) The location of the central perpendicular line is the optimum sampling instant.(2) The middle horizontal line represents the optimum decision threshold level.(3) The perpendicular height of the shadow region represents the distortion range

30、of the received signal.(4) The slope of the bevel edge of the “eye” represents sensitivity of the sampling instant to the timing error.(5) Under no noise situation, the degree of the opening of the “eye is the noise tolerance; if noise at the sampling instant exceeds this tolerance, then error decis

31、ion may happen.Calculation Questions:1.Assume there are 4 overall transfer characteristics of baseband transmission systems shown in Figure 2. If symbol rate is 2000Bd, please illustrate whether they can transmit information without ISI? Which system has better transmission characteristic?Solution: symbol rate is 2000Bd, ISI exists in system (a) and (c), ISI does not exist in system (b) and (d).Since system (b) can be realized physically, and its system (d) cant be realized