2012华科信号与系统试题(英语)
华中科技大学文华学院 信号与系统试卷
华中科技大学文华学院《信号与系统》期末考试A 卷课程性质：必修课 使用范围： 本科 使用时间：11年6月23 日 考试方式：闭卷学号________专业______班级 姓名____ 成绩（请考生注意：本试卷共6页）一、选择题（共10小题，40分） （ ）1. 函数3)(3t etδ- 等于：(A)0 （B ）3 （C ）)(t δ （D ）)(3t δ( ）2. 信号)(1t f 和)(2t f 的波形如图所示，设),(*)()(21t f t f t f =则)2(f 等于： （A ）1 （B ）2 （C ）3 （D ）4( )3.周期信号)(t f 的傅里叶级数展开式中仅含奇次谐波分量，f(t)是（A ）.偶函数 （B ）.奇函数 （C ）.奇谐函数（D ）. 偶谐函数 ( )4. 序列)(1k f 和)(2k f 如图所示，设)()()(21k f k f k f *=，则(1)f 等于：2)(A 3)(B 4)(C 5)(Dtt321（ ）5.信号)1()1(2---t et ε的傅立叶变换等于：(A)ej j ωω-+21 (B)e j 221ω+ (C)e j 221ω-(D)ej j 221+-+ωω（ ）6.周期矩形脉冲信号的频谱中，使其相邻谱线的间隔减小是（A ）. 周期T 减小 （B ）. 周期T 增大 （C ）.脉冲宽度τ减小 （D ）. 脉冲宽度τ增大（ ）7. 函数)()()(2t e t t f tεδ--=的单边拉普拉斯变换)(s F 等于：21)(+s A 2)(+s s B 21)(++s s C 2)(2+s s D ( )8. 单边拉普拉斯变换2)(-=s ss F 的原函数)(t f 等于： （A ）)(2)(2t e t tεδ-- （B ） )(2)(2t e t t εδ+ （C ）)]2()([2---t t e t εε（D ）)2(2)()2(22-----t e t et tεε( )9.序列)()3()(k k f kε--=的Z 变换)(z F 等于：[A]3-z z [B] 3+z z [C] 13-z z [D] 133+z z ( )10. 连续系统的系统函H （s ）的零极点分布如图，且已知2)(=∞H ，则系统的单位阶跃响应)(t g 等于：（A ）)()21(2t etε-+（B ）)()31(2t e t ε-+-（C ）)()41(2t e t ε-+- （D ）)()42(2t e t ε-+-二、填空题（共8小题，32分）1.=--)1()(k k εε_______________________2.如图所示信号)(t f 的单边拉普拉斯变换=)(s F3．卷积积分=*-)()(3t e t tεε4.tt t f πsin )(=的傅立叶变换=)(ωj F 。
英文版《信号与系统》第二章习题解答
Problems Solution
dx(t ) ∵ → 3 y (t ) + e 2t u (t ) dt
2e 3 h(t 1) = e 2t u (t )
the impulse 1 3 2(t +1) u (t + 1) response h(t ) = 2 e e
18
Chapter 2
∫
t
∞
h (τ )d τ =
0
t<0,t>2
sin (πτ )d τ =
1
∫
t
1
0
π
cos πτ | 0t
0< t<2
=
π
(1 cos π t )[u (t ) u (t 2 )]
12
Chapter 2
y (t ) = 2
Problems Solution
π
2
(1 cos π (t 1 ))[u (t 1 ) u (t 3 )] (1 cos π (t 3 ))[u (t 3 ) u (t 5 )]
∞
+∞
2
t
y (t ) = ∫ e (t τ 2 )u (t τ 2 )x(τ )dτ
∞
+∞
h(t ) = e
(t 2 )
u (t 2)
h(t τ )
(b ) y(t ) = x(t ) h(t ) = x′(t ) h (1) (t )
= h (1) (t + 1) h (1) (t 2)
0
e 3τ dτ
1 e 3(t 3 ) = 3 e 3(t 5 ) e 3(t 3 ) = 3
x(t τ )
t 3
华科2012博士入学英语试题_及参考答案
华科2012博士入学英语试题及参考答案Passage 1Recent years have brought minority-owned businesses in the United States unprecedented opportunities - as well as new and significant risks. Civil rights activists have long argued that one of the principal reasons why Blacks, Hispanics, and other minority groups have difficulty establishing themselves in business is that they lack access to the sizable orders and subcontracts that are generated by large companies. Now Congress, in apparent agreement, has required by law that businesses awarded federal contracts of more than $500,000 do their best to find minority subcontractors and record their efforts to do so on forms filed with the government. Indeed, some federal and local agencies have gone so far as to set specific percentage goals for apportioning parts of public works contracts to minority enterprises.Corporate response appears to have been substantial. According to figures collected in 1977, the total of corporate contracts with minority businesses rose from $77 million in 1972 to $1.1 billion in 1977. The projected total of corporate contracts with minority businesses for the early 1980's is estimated to be over 53 billion per year with no letup anticipated in the next decade. Promising as it is for minority businesses, this increased patronage poses dangers for them, too. First, minority firms risk expanding too fast and overextending themselves financially, since most are small concerns and, unlike large businesses, they often need to make substantial investments in new plants, staff, equipment, and the like in order to perform work subcontracted to them. If, thereafter, their subcontracts are for some reason reduced, such firms can face potentially crippling fixed expenses. The world of corporate purchasing can be frustrating for small entrepreneurs who get requests for elaborate formal estimates and bids. Both consume valuable time and resources, and a small company's efforts must soon result in orders, or both the morale and the financial health of the business will suffer.A second risk is that White-owned companies may seek to cash in on the increasing apportionments through formation of joint ventures with minority-owned concerns. Of course, in many instances there are legitimate reasons for joint ventures; clearly, White and minority enterprises can team up to acquire business that neither could acquire alone. But civil rights groups and minority business owners have complained to Congress about minorities being set up as “fronts (a person, group, or thing used to mask the identity or true character or activity of the actual controlling agent)” with White backing, rather than being accepted as full partners in legitimate joint ventures.Third, a minority enterprise that secures the business of one large corporate customer often runs the danger of becoming-and remaining-dependent. Even in the best of circumstances, fierce competition from larger, more established companies makes it difficult for small concerns to broaden their customer bases: when such firms have nearly guaranteed orders from a single corporate benefactor, they may truly have to struggle against complacency arising from their current success.1. The primary purpose of the text is to[A] present a commonplace idea and its inaccuracies.[B] describe a situation and its potential drawbacks.[C] propose a temporary solution to a problem.[D] analyze a frequent source of disagreement.2. The text suggests that the failure of a large business to have its bids for subcontracts result quickly in orders might causes it to[A] experience frustration but not serious financial harm.[B] face potentially crippling fixed expenses.[C] have to record its efforts on forms filed with the government.[D] increase its spending with minority subcontractors.3.The author would most likely agree with which of the following statements about corporate response to working with minority subcontractors?[A] Annoyed by the proliferation of “front” organizations, corporations are likely to reduce their efforts to work with minority-owned subcontractors in the near future.[B] Although corporations showed considerable interest in working with minorit y businesses in the 1970’s, their aversion to government paperwork made them reluctant to pursue many government contracts.[C] The significant response of corporations in the 1970’s is likely to be sustained and conceivably be increased throughout the 1980’s.[D] Although corporations are eager to cooperate with minority-owned businesses, a shortage of capital in the 1970’s made substantial response impossible4 According to the text, civil rights activists maintain that one disadvantage under which minority-owned businesses have traditionally had to labor is that they have[A] been especially vulnerable to government mismanagement of the economy.[B] been denied bank loans at rates comparable to those afforded larger competitors.[C] not had sufficient opportunity to secure business created by large corporations.[D] not been able to advertise in those media that reach large numbers of potential customers.5 The author implies that a minority-owned concern that does the greater part of its business with one large corporate customer should[A] avoid competition with larger, more established concerns by not expanding. 【B】concentrating on securing even more business from that corporation. [C] use its influence with the corporation to promote subcontracting with other minority concerns.[D] try to expand its customer bases to avoid becoming dependent on thecorporation.Passage 2Years of research had educated me about how sugar, fat, and salt change the brain. I understood some of the parallels between hyperpalatable foods and drugs of abuse, and about the links among sensory stimulation, cues, and memory. I'd met enough people like Claudia and Maria to understand how even the thought of food could cause them to lose control.But I wasn't fully prepared for the discoveries I made about irresistibility and whoosh, the Monster Thickburger and Baked! Cheetos Flamin' Hot, about indulgence and purple cows. Without necessarily understanding the underlying science, the food industry has discovered what sells.I was sitting at Chili's Grill & Bar in Chicago's O'Hare Airport waiting for a late-night flight. At a nearby table a couple in their early forties was deep into a meal. The woman was overweight, with about 180 pounds on her five-foot-four-inch frame. The Southwestern Eggrolls she had ordered were listed as a starter course, but the enormous platter in front of her had been heaped with food. The dish was described on the menu as "smoked chicken, black beans, corn, jalape?o Jack cheese, red peppers, and spinach wrapped inside a crispy flour tortilla," and it was served with a creamy avocado-ranch dipping sauce. Despite its name, the dish looked more like a burrito than an egg roll, an only-in-America fusion approach.I watched as the woman attacked her food with vigor and speed. She held the egg roll in one hand, dunked it into the sauce, and brought it to her mouth while using the fork in her other hand to scoop up more sauce. Occasionally she reached over and speared some of her companion's french fries. The woman ate steadily, working her way around the plate with scant pause for conversation or rest. When she finally paused, only a little lettuce was left.Had she known someone was watching her, I'm sure she would have eaten differently. Had she been asked to describe what she had just eaten, she probably would have substantially underestimated her consumption. And she would probably have been surprised to learn what the ingredients in her meal really were.The woman might have been interested in how my industry source, who had called sugar, fat, and salt the three points of the compass, described her entree. Deep-frying the tortilla drives down its water content from 40 percent to about 5 percent and replaces the rest with fat. "The tortilla is really going to absorb a lot of fat," he said. "It looks like an egg roll is supposed to look, which is crispy and brown on the outside."The food consultant read through other ingredients on the label, keeping up a running commentary as he did. "Cooked white meat chicken, binder added, smoke flavor. People like smoky flavor — it's the caveman in them.""There's green stuff in there," he said, noting the spinach. "That makes me feel like I'm eating something healthy.""Shredded Monterey Jack cheese.... The increase in per-capita consumption of cheese is off the chart."The hot peppers, he said, "add a little spice, but not too much to kill everything else off." He believed the chicken had been chopped and formed much like a meat loaf, with binders added, which makes those calories easy to swallow. Ingredients that hold moisture, including autolyzed yeast extract, sodium phosphate, and soy protein concentrate, further soften the food. I noticed that salt appeared eight times on the label and that sweeteners were there five times, in the form of corn-syrup solids, molasses, honey, brown sugar, and sugar."This is highly processed?" I asked."Absolutely, yes. All of this has been processed such that you can wolf it down fast...chopped up and made ultrapalatable.... Very appealing looking, very high pleasure in the food, very high caloric density. Rules out all that stuff you have to chew."By eliminating the need to chew, modern food processing techniques allow us to eat faster. "When you're eating these things, you've had 500, 600, 800, 900 calories before you know it," said the consultant. "Literally before you know it." Refined food simply melts in the mouth.1. It can be inferred from the author's description of the woman eating in paragraph four that(A) The woman prefers to eat at Chili's vs. other restaurants.(B) The woman truly enjoys the foods that she chooses to eat.(C) The woman's efficiency at cleaning her plate adds to her dining experience.(D) The author is disgusted by the woman's consumption.(E) The author believes the woman should take a course in healthy eating.2. According to the passage, the main reason people overeat is(A) because salt and sweeteners, like corn-syrup solids and brown sugar, are added to the food.(B) because we don't have to chew our food very much(C) because people like smoky flavor(D) because sugar, fat and salt change the brain(E) because we are used to eating quickly in this modern society3. The following are all ingredients in the egg rolls, EXCEPT(A) salt (B) binders (C) honey (D) spinach (E) dark meat chicken4. Which of the following statements best describes the main idea of the passage?(A) If you eat too much food too quickly, you'll gain weight and become unhealthy.(B) Because refined food is irresistible and easy to eat, it masks how unhealthy it is, leaving people unaware of the poor food choices they're making.(C) Chili's is one of the restaurants in the U.S. serving unhealthy food to consumers today.(D) Food consultants and authors are making Americans aware of their unhealthy eating habits, thus, creating healthier generations for years to come.(E) Refined foods, with salt, sugar, and fat hidden inside, are less nutritious and more damaging than whole foods.5. In the first sentence of paragraph four, the word "vigor" most nearly means(A) pleasure (B) flamboyance (C) lethargy (D) energy (E) craftinessPassage 3No very satisfactory account of the mechanism that caused the formation of the ocean basins has yet been given.The traditional view supposes that the upper mantle of the earth behaves as a liquid when it is subjected to small forces for long periods and that differences in temperature under oceans and continents are sufficient to produce convection in the mantle of the earth with rising convection currents under the mid-ocean ridges and sinking currents under the continent. Theoretically，this convection would carry the continental plates along as though they were on a （conveyer belt）and would provide the forces needed to produce the split that occurs along the ridge.This view may be correct：it has the advantage that the currents are driven by temperature differences that themselves depend on the position of the continents.On the other hand，the theory is implausible because convection does not normally occur along lines，and it certainly does not occur long lines broken by frequent offsets or changes in direction，as the ridge is.It has the advantage that the currents are driven by temperature differences that themselves depend on the position of the continents.Such a backoupling，in which the position of the moving plate has an impact on the forces that move it，could produce complicated and varying motionsAlso it is difficult to see how the theory applies to the plate between the Mid-Atlantic Ridge and the ridge in the Indian Ocean.This plate is growing on both sides，and since there is no intermediate trench，the two ridges must be moving apart. It would be odd if the rising convection currents kept exact pace with them.An alternative theory is that the sinking part of the plate，which is denser than the hotter surrounding mantle，pulls the rest of the plate after it. Again it is difficult to see how this applies to the ridge in the South Atlantic，where neither the African nor the American plate has a sinking part.Another possibility is that the sinking plate cools the neighboring mantle and produces convection currents that move the plates. This last theory is attractive because it gives some hope of explaining the enclosed seas，such as the Sea of apan. These seas have a typical oceanic floor，except that the floor is overlaid by several kilometers of sediment. Their floors have probably been sinking for long periods.These seas have a typical oceanic floor，except that the floor is overlaid by several kilometers of sediment. Their floors have probably been sinking for long periods. It seems possible that a sinking current of cooled mantle material on the upper side of the plate might be the cause of such deep basins.The enclosed seas are an important feature of the earth's surface and seriously require explanation because，in addition to the enclosed seas that are developing at present behind island arcs，there are a number of older ones of possibly similar origin，such as the Gulf of Mexico，the Black Sea，and perhaps the NorthSea.1. According to the traditional view of the origin of the ocean basins，which of the following is sufficient to move the continental plates？（A）Increases in sedimentation on ocean floors（B）Spreading of ocean trenches（C）Movement of mid-ocean ridges（D）Sinking of ocean basins（E）Differences in temperature under oceans and continents2. It can be inferred from the passage that，of the following，the deepest sediments would be found in the（A）Indian Ocean（B）Black Sea（C）Mid-Atlantic（D）South Atlantic （E）Pacific3. The author refers to a “conveyer belt ” in line 13 in order to（A）illustrate the effects of convection in the mantle（B）show how temperature differences depend on the positions of the continents （C）demonstrate the linear nature of the Mid-Atlantic Ridge（D）describe the complicated motions made possible by back-coupling（E）account for the rising currents under certain mid-ocean ridges4.According to the passage，which of the following are separated by a plate that is growing on both sides？（A）The Pacific Ocean and the Sea of Japan（B）The South Atlantic Ridge and the North Sea Ridge（C）The Gulf of Mexico and the South Atlantic Ridge（D）The Mid-Atlantic Ridge and the Indian Ocean Ridge（E）The Black Sea and the Sea of Japan5. Which of the following titles would best describe the content of the passage？（A） A Description of the Oceans of the World（B）Several Theories of Ocean Basin Formation（C）The Traditional View of the Oceans（D）Convection and Ocean Currents（E）Temperature Differences Among the Oceans of the WorldPassage 4In the eighteenth century, Japan‟s feudal overlords, from the shogun (shogun: n.<日>幕府时代的将军) to the humblest samurai (samurai: n.(封建时代的)日本武士,日本陆军军官), found themselves under financial stress. In part, this stress can be attributed to the overlords‟ failure to adjust to a rapidly expanding economy, but the stress was also due tofactors beyond the overlords‟ control. Concentration of the samurai in castle-towns had acted as a stimulus to trade. Commercial efficiency, in turn, had put temptations in the way of buyers. Since most samurai had been reduced to idleness by years of peace, encouraged to engage in scholarship and martial exercises or to perform administrative tasks that took little time, it is not surprising that their tastes and habits grew expensive. Overlords‟ income, despite the increase in rice production among their tenant farmers, failed to ke ep pace with their expenses. Although shortfalls in overlords‟ income resulted almost as much from laxity among their tax collectors (the nearly inevitable outcome of hereditary office-holding) as from their higher standards of living, a misfortune like a fire or flood, bringing an increase in expenses or a drop in revenue, could put a domain in debt to the city rice-brokers who handled its finances. Once in debt, neither the individual samurai nor the shogun himself found it easy to recover.It was difficult for individual samurai overlords to increase their income because the amount of rice that farmers could be made to pay in taxes was not unlimited, and since the income of Japan‟s central government consisted in part of taxes collected by the shogun from his huge domain, the government too was constrained. Therefore, the Tokugawa shoguns began to look to other sources for revenue. Cash profits from government-owned mines were already on the decline because the most easily worked deposits of silver and gold had been exhausted, although debasement of the coinage had compensated for the loss. Opening up new farmland was a possibility, but most of what was suitable had already been exploited and further reclamation was technically unfeasible. Direct taxation of the samurai themselves would be politically dangerous. This left the shoguns only commerce as a potential source of government income.Most of the country‟s wealth, or so it seemed, was finding its way into the hands of city merchants. It appeared reasonable that they should contribute part of that revenue to ease the shogun‟s burden of financing the state. A means of obtaining such revenue was soon found by levying forced loans, known as goyo-kin; although these were not taxes in the strict sense, since they were irregular in timing and arbitrary in amount, they were high in yield. Unfortunately, they pushed up prices. Thus, regrettably, the Tokugawa shoguns‟ search for solvency for the government made it increasingly difficult for individual Japanese who lived on fixed stipends to make ends meet.1. The passage is most probably an excerpt from(A) an economic history of Japan(B) the memoirs of a samurai warrior(C) a modern novel about eighteenth-century Japan(D) an essay contrasting Japanese feudalism with its Western counterpart(E) an introduction to a collection of Japanese folktales2. Which of the following financial situations is most analogous to the financial situation in which Japan‟s Tokugaw a shoguns found themselves in the eighteenth century?(A) A small business borrows heavily to invest in new equipment, but is able to pay off its debt early when it is awarded a lucrative government contract.(B) Fire destroys a small business, but insurance covers the cost of rebuilding.(C) A small business is turned down for a loan at a local bank because the owners have no credit history.(D) A small business has to struggle to meet operating expenses when its profits decrease.(E) A small business is able to cut back sharply on spending through greater commercial efficiency and thereby compensate for a loss of revenue.3. Which of the following best describes the attitude of the author toward the samurai discussed in lines 11-16?(A) Warmly approving(B) Mildly sympathetic(C) Bitterly disappointed(D) Harshly disdainful(E) Profoundly shocked4. The passage suggests that, in eighteenth-century Japan, the office of tax collector(A) was a source of personal profit to the officeholder(B) was regarded with derision by many Japanese(C) remained within families (D) existed only in castle-towns(E) took up most of the officeholder‟s time5. The passage implies that which of the following was the primary reason why the Tokugawa shoguns turned to city merchants for help in financing the state?(A) A series of costly wars had depleted the national treasury.(B) Most of the country‟s wealth appeared to be in city merchants‟ hands.(C) Japan had suffered a series of economic reversals due to natural disasters such as floods.(D) The merchants were already heavily indebted to the shoguns.(E) Further reclamation of land would not have been economically advantageous.汉译英北京，7月11日-中国警方命令一个报道中国社会和经济发展超过10年的知名西方时事通刊物志停刊，该刊物的英国编辑如是说。
信号与系统习题集英文版
信号与系统习题集第一部分：时域分析 一、填空题 1. =---)3()()2(t t u et δ()。
2. The unit step response )(t g is the zero-state response when the input signal is ( ).3. Given two continuous – time signals x(t) and h(t), if their convolution is denoted by y(t), then the convolution of )1(-t x and )1(+t h is ( ).4. The convolution =+-)(*)(21t t t t x δ( ).5. The unit impulse response )(t h is the zero-state response when the input signal is ( ).6. A continuous – time LTI system is stable if its unit impulse response satisfies the condition: ( ).7. A continuous – time LTI system can be completely determined by its ( ).8. =⎰∞∞-(t)dt 2sin 2 δt t ( ).9. Given two sequences }1,2,2,1{][=n x and }5,6,3{][=n h , their convolution=][*][n h n x ( ).10. Given three LTI systems S1, S2 and S3, their unit impulse responses are )(1t h ,)(2t h and )(3t h respectively. Now, construct an LTI system S using these threesystems: S1 parallelinterconnected by S2, then series interconnected by S3. the unit impulse response of the system S is ( ).11. It is known that the zero-stat response of a system to the input signal x(t) is⎰∞-=td x t y ττ)()(, then the unit impulse response h(t) is ( ).12. The complete response of an LTI system can be expressed as a sum of its zero-state response and its ( ) response.13. It is known that the unit step response of an LTI system is )(2t u et-, then the unit impulseresponse h(t) is ( ).14. =++-=⎰∞dt t t t t x ))1()1((2sin )(0δδπ( ).15. We can build a continuous-time LTI system using the following three basic operations: ( ) , ( ), and ( ). 16. The zero-state response of an LTI system to the input signal )1()()(--=t u t u t xis )1()(--t s t s , where s(t) is the unit step response of the system, then the unit impulse response h(t) is ( ).17. The block diagram of a continuous-time LTI system is illustrated in the following figure. The differential equation describing the input-output relationship of the system is ( )。
信号与系统2012-2013试题参考答案
transform P( ) and sketch the amplitude spectrum P( ) .
Answer: X ( )
x (t )e jt dt
j t e dt
2
j j 1 (e 2 e 2 ) sin c j 2
1 t 3t (e e ), t 0 4
(c) Y ( s ) H ( s) X ( s)
1 1 1 1 1 1 1 ( ) . . ( s 3)( s 1) s 3 s 4 s 1 12 s 3
1 1 1 y (t ) et e3t , t 0 3 4 12
3.
A linear time-invariant continuous-time system has transfer function
H (s)
s 2 16 s 7 s 12
2
Compute the steady-state and transient response resulting from the input x(t ) 2 cos 4t , t 0 , with zero initial conditions. (where (cos t )u (t ) s s2 2 )
y (t ) 2 H (0) 2 H (50) cos(50t H (0)
2
H (50))
10 10 1 ； H (50) 0 j 10 j 50 10
y (t ) 2 0.3922 cos(50t 1.974)
6.
Given the input x(t ) 4 2 cos(10t / 4) 3cos(30t / 2) . Find the output y(t) to each of the following
华中师范大学信号与系统期末A卷2011改[英文]
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=
2π T
and
(
).
A ωs > 2000π B ωs > 4000π C ωs > 6000π D ωs > 8000π
专业：
院（系）：
6．We consider a signal that is the sum of two real exponentials: x(t) = 3e−2tu(t) − 2e−tu(t ) , the
region of convergence of x(t) is (
).
A ℜe{S} > −2 B ℜe{S} > −1 C ℜe{S} < −1 D ℜe{S} < −2
7．An LTI system is stable if and only if the ROC of its system function H(s) includes (
A f (t)
B f (t − t0 )
C δ (t)
D δ (t − t0 )
4．Consider Continuous-time signals f (t) and δ (t − t0 ) ，then we have f (t)δ (t − t0 ) =（
）.
A f (t0 )δ (t)
B f (t − t0 )
).
A the right-half plane B the left-half plane C the entire jω -axis 8．A causal LTI system is stable if and only if all of the poles of its system function H(s) lie in ( ).
信号与系统期末考试试题(有答案的)
信号与系统期末考试试题一、选择题（共10题，每题3分 ，共30分，每题给出四个答案，其中只有一个正确的）1、 卷积f 1(k+5)*f 2(k-3) 等于 。
（A ）f 1(k)*f 2(k) （B ）f 1(k)*f 2(k-8)（C ）f 1(k)*f 2(k+8)（D ）f 1(k+3)*f 2(k-3)2、 积分dt t t ⎰∞∞--+)21()2(δ等于 。
（A ）1.25（B ）2.5（C ）3（D ）5 3、 序列f(k)=-u(-k)的z 变换等于 。
（A ）1-z z （B ）-1-z z（C ）11-z （D ）11--z4、 若y(t)=f(t)*h(t),则f(2t)*h(2t)等于 。
（A ）)2(41t y （B ）)2(21t y （C ）)4(41t y （D ）)4(21t y 5、 已知一个线性时不变系统的阶跃相应g(t)=2e -2tu(t)+)(t δ,当输入f(t)=3e —tu(t)时，系统的零状态响应y f (t)等于（A ）(-9e -t +12e -2t )u(t) （B ）(3-9e -t +12e -2t )u(t)（C ）)(t δ+(-6e -t +8e -2t )u(t) （D ）3)(t δ +(-9e -t +12e -2t )u(t)6、 连续周期信号的频谱具有（A ） 连续性、周期性 （B ）连续性、收敛性 （C ）离散性、周期性 （D ）离散性、收敛性1、 周期序列2)455.1(0+k COS π的 周期N 等于（A ） 1（B ）2（C ）3（D ）4 8、序列和()∑∞-∞=-k k 1δ等于（A ）1 (B) ∞ (C) ()1-k u (D) ()1-k ku9、单边拉普拉斯变换()se s s s F 2212-+=的愿函数等于 ()()t tu A ()()2-t tu B ()()()t u t C 2- ()()()22--t u t D 10、信号()()23-=-t u tet f t的单边拉氏变换()s F 等于()A ()()()232372+++-s e s s ()()223+-s e B s()()()2323++-s se C s ()()332++-s s e D s二、填空题（共9小题，每空3分，共30分）1、卷积和[（0.5）k+1u(k+1)]*)1(k -δ=________________________2、单边z 变换F(z)=12-z z的原序列f(k)=______________________ 3、已知函数f(t)的单边拉普拉斯变换F(s)=1+s s，则函数y(t)=3e -2t ·f(3t)的单边拉普拉斯变换Y(s)=_________________________4、频谱函数F(j ω)=2u(1-ω)的傅里叶逆变换f(t)=__________________5、单边拉普拉斯变换ss s s s F +++=2213)(的原函数f(t)=__________________________ 6、已知某离散系统的差分方程为)1(2)()2()1()(2-+=----k f k f k y k y k y ，则系统的单位序列响应h(k)=_______________________7、已知信号f(t)的单边拉氏变换是F(s),则信号⎰-=2)()(t dx x f t y 的单边拉氏变换Y(s)=______________________________8、描述某连续系统方程为()()()()()t f t f t y t y t y +=++''''52该系统的冲激响应h(t)=9、写出拉氏变换的结果()=t u 66 ，=k t 22三、（8分）四、（10分）如图所示信号()t f ，其傅里叶变换()()[]t f jw F F=，求（1） ()0F （2）()⎰∞∞-dw jw F六、（10分）某LTI 系统的系统函数()1222++=s s s s H ，已知初始状态()(),20,00=='=--y y 激励()(),t u t f =求该系统的完全响应。
《信号与系统》试题及答案
2012年度教学质量综合评估测验卷《信号与系统》试题注：1、开课学院：信息工程学院学院。
命题组：电子信息教研组2、考试时间：120分钟，所有答案均写在答题纸上。
3、适用班级：信息工程学院通信工程专业及电子类专业。
4、在答题前，请在所发两张答题纸上认真填写所要求填写的个人信息。
1、下列说法不正确的是（ ）。
A 、一般周期信号为功率信号。
B 、 时限信号(仅在有限时间区间不为零的非周期信号)为能量信号。
C 、ε(t )是功率信号；D 、e t 为能量信号2、下列关于冲激函数性质的表达式不正确的是（ ）。
A 、)()0()()(t f t t f δδ=B 、()t a at δδ1)(=C 、)(d )(t tεττδ=⎰∞- D 、)()-(t t δδ=3、)2)(1()2(2)(-++=s s s s s H ，属于其极点的是（ ）。
A 、1B 、2C 、0D 、-2 4、If f 1(t ) ←→F 1(j ω)， f 2(t ) ←→F 2(j ω) Then[ ] A 、[a f 1(t ) + b f 2(t ) ] ←→ [a F 1(j ω) *b F 2(j ω) ] B 、[a f 1(t ) + b f 2(t ) ] ←→ [a F1(j ω) - b F 2(j ω) ] C 、[a f 1(t ) + b f 2(t ) ] ←→ [a F 1(j ω) + b F 2(j ω) ] D 、[a f 1(t ) + b f 2(t ) ] ←→ [a F 1(j ω) /b F 2(j ω) ] 5、下列说法不正确的是（ ）。
A 、H(z)在单位圆内的极点所对应的响应序列为衰减的。
即当k →∞时，响应均趋于0。
B 、H(z)在单位圆上的一阶极点所对应的响应函数为稳态响应。
C 、H(z)在单位圆上的高阶极点或单位圆外的极点，其所对应的响应序列都是递增的。
即当k →∞时，响应均趋于∞。
2012年 华中科技大学电信系考研 824《信号与线性系统》真题及答案(科学硕士)
二O 一二年华中科技大学招收硕士研究生 824《信号与线性系统》真题及答案（科学硕士）满分150，答题时间180分钟适用专业：通信与信息系统、信号与信息处理、电路与系统、电磁场与微波技术一、填空题（3分/空，共30分）1．连续时间信号24()j t x t eπ⎛⎫+ ⎪⎝⎭=的平均功率为 瓦；2．积分()sin 21t t dt δ∞-∞'-⎰的值= ；3．离散信号[]cos cos 54x n n n ππ⎛⎫⎛⎫= ⎪ ⎪⎝⎭⎝⎭的基波周期为 ；4．卷积积分()()()21*1t u t u t +--⎡⎤⎣⎦= ； 5．信号()sin sin 2*1t tt t ππππ-的傅里叶变换为 ；(注：*表示卷积) 6．周期序列[][][]310410h x n u n k u n k +∞=-∞=+----∑的傅里叶系数10a= ；7．已知()x t 的奈奎斯特抽样角频率为N ω，则()()cos N x t t ω的奈奎斯特抽样角频率为 ；8．一连续时间LTE 系统,，输入输出方程为()()()()2y t y t y t x t '''--=，如果该系统既不是因果系统也不是稳定系统，它的冲激响应为 ；9．序列[]()()01kk x n n k δ∞==--∑的z 变换为 ，收敛域为 。
二、选择题（2分/题，共20分）1．输入输出方程为[][]()()sin 1y n x n n δ=-的系统是（ ）的系统。
（a ）线性、因果、稳定 （b ）线性、非因果、稳定（c ）线性、非因果、不稳定 （d ）非线性、因果不稳定 2．以下冲激响应函数中，（ ）不对应稳定LTE 系统。
（a ）()()cos h t tu t = （b ）()()t h t te u t -= （c ）()()22t h t e u t =-+ （d ）()sin /h t t t =3．一个奇的且为纯虚数的信号，其傅里叶变换为一个（ ）。
通信工程专业英语习题答案
通信工程专业英语习题答案练习参考答案第1单元信号与系统1. 完形填空(1) band-limited, cutoff frequencies, to, between, the information rate is proportional to the bandwidth of the channel, on, to, by, by simply increasing the number of levels, noise will cause the receiver to mistake one level for another, no matter how elaborately the data is coded, between, theoretical maxima.(2) from, a loss of information , the twisted pair, addition of noise to the signal, depends on the signal frequency, the high-frequency components of the signal, over, between, through, of, with, including.(3) for, to, In some cases, over, (microwave relay, coaxial cable, or fiber), ADC, to, thereby achieving a reduction in required channel bandwidth, of, signal recovery, (Techniques such as filtering, auto-correlation and convolution).2. 英汉互译(1) “电信”（telecommunication）一词来源于希腊语tele（含义为“遥远的”）和拉丁语communicatio（涵义为“连接”）。
12年信号系统试卷
2012年华侨大学《信号与系统》期末试卷A （电科）班级______________ 姓名________________ 学号_________________一．填空题（第8题4分，其余每题3分）1．'()j t e t dt ωδ∞-∞=⎰ 。
2．信号0.02()()()T f t g t t nT δ=*-，其中周期抽样脉冲序列的周期1T =s ，则()f t 的频宽为 Hz 。
3．冲激序列1()()T n t t nT δδ∞=-∞=-∑的指数形式傅立叶级数为 。
4．()cos()()2x n n n πε=的Z 变换()X z ＝ 。
5．信号0.20.3()j n j n x n e e ππ-=+的周期是 。
6．某系统输入信号0()()()f t t t t εδ=-+，输出信号0()2(10)2(10)r t t t t εδ=--+-，该系统是 （失真/无失真）传输系统。
7．信号2(100)(60)Sa t Sa t +的奈奎斯特间隔是 。
8．已知01()2,3,1,0,0n f n =↑⎧⎫⎪⎪=-⎨⎬⎪⎪⎩⎭，02()3,1,0,0,2n f n =↑⎧⎫⎪⎪=⎨⎬⎪⎪⎩⎭，则12()()*()f n f n f n == 。
二．（6分）证明2()Sa t dt π∞-∞=⎰。
三．（7分）分析系统3()()ty t f d ττ-∞=⎰是否是线性、时不变、因果系统？请说明原因。
四．（12分）离散系统差分方程为311()(1)(2)()(1)483y n y n y n x n x n --+-=+-，求： （1） 系统的单位样值响应；（2） 画出系统级联形式的信号流图；（3） 判断此系统是否稳定并说明理由。
五．（15分）已知某线性系统如下图（a ）所示，其中()()()T n f t t t nT δδ∞=-∞==-∑，n 为整数，1T ms =，1()H f 如图（b ），2()H f 如图（c ）。
华中师范大学信号与系统期末考试(A卷)2016-2017
院（系）： 专业： 年级： 学生姓名： 学号：------------------------------------------------- 密 ---------------------------------- 封 ----------------------------- 线 ---------------------------------------------------------第 1 页(共 4 页)4.一个连续时间周期信号，其傅里叶级数表示为∑∞-∞==kt jke k t x 502)cos()(ππ，该信号是( )Consider the continuous-time periodic signal whose Fourier series representation is∑∞-∞==kt jke k t x 502)cos()(ππ, what is the signal ?A 不是实值函数 not realB 实奇函数real and oddC 实偶函数 real and evenD 不能确定cannot be ascertained 5.如果)(t f 的傅里叶变换是)(ωj F ，则)3()(-t t f δ的傅里叶变换是（ ）。
)(ωj F is the Fourier transform of )(t f , which of the following is the Fourier transformof )3()(-t t f δ?A ωj e f 3)3(-B ωωj e j F 3)(-C ωj e f 3)3(D ωωj e j F 3)( 6.有多少个信号在其收敛域内都有如下所示的拉普拉斯变换( ) How many signals have a Laplace transform that may be expressed as below?A 2个B 3个C 4个D 5个 得分 评阅人 II. 填空题Fill in the blanks （每空3分3 points for each correct answer ）1.一个连续时间线性系统S 的输入为,)(21t j e t x =对应的输出为,)(31t j e t y =输入为,)(2-2t j e t x =对应的输出为,)(3-2t j e t y =若输入),2cos()(3t t x =求系统S 的输出=)(3t y 。
【华南理工大学2012年考研专业课真题】信号与系统2012
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信号与系统-华南理工大学期末考试试卷
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通信专业英语部分答案（华中科技大学出版社）
通信专业英语部分答案（华中科技大学出版社）通信专业英语部分答案(LB整理)私人整理难免会有个别错误请见谅Part1Text 1 Fundament to commu1、信号signal 波特baud 单工simplex同步synchronous 信道channels 模拟analog数字digital 电磁的electromagnetic 串行口serial带宽bandwidth3、baud 波特率asynchronous 异步的full duplex 全双工Parallel 并行electromagnetic 电磁的discrete 离散的Simultaneously 同时的parity平等的4、第三个信道特征是传输模式，包括异步通信模式和同步通信模式。
在异步通信模式中，字符（由几个比特组成）是以不规则的间隔进行传送，用户输入数据时就是这种模式。
为了识别字符的起始时刻，异步通信模式使用了起始位和停止位，有时在字符的结束也使用一个额外的校验位。
校验位用于检错。
异步通信模式常用于低数据率传输应用，也在与PC机相连的大部分通信设备中使用。
Text 2 switching technology1、交换技术switching technique存储转发传输技术the store-and-forward transmission technique 数据块block of data 电路交换circuit switching 分组交换packet switching 带宽bandwidth多路通信Multiplexed communications面向连接Connection-oriented3、分组交换网络是连接计算机常用的方式，它采用（与电路交换方式）完全不同的交换方法。
在分组交换网络中，待传的数据可分为若干个数据包，然后将它们复接到高速线路上传送。
一个数据包通常含有数百个字节，它带有数据标识，使网络硬件可以识别并将它传送到指定的目的地。
信号与系统2011-2012参考答案
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x[0] x[1] x[2] x[3] 1 2 4 8 v[0] v[2] v[3] 2 0 6 2 3 0 6 4 6 0 12 8 0 24 16 0 48 v[1] 3 12 24
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X ( s) Y (s) 1 s 1 2 3 s2 s s 1 ( s 2) 2 4 Y ( s ) s 2 2 s 16 H ( s ) s 3 4 s 2 8s
《信号与系统》试题及答案
信号与系统》试题及答案2012 年度教学质量综合评估测验卷《信号与系统》试题 题组：：1、开课学院：信息工程学院学院 题组2、：题纸上。
电子3、类适专用业班级：信息工程学院通信工程专业及 电子4、类在专答业写所要求填 卷面题型及分值：)题 答 不 内 线 封 密名姓研12组0 分钟，所有答案均写在答 发两张答题纸上认真填 。
总总分二 三 四 五 六 七 八 九 十100 20 20 60一、选择题(每小题 2 分，共 10小题。
每一小题仅有一个选项是正确的。
共计 20 分)列说法不正确的是( 一般周期信号为功率信号。
时限信号 (仅在有限时间区间不为零的非周期信号 )为能量信号。
ε(t)是功率信号； 1、 A 、 B 、 C 、)。
D 、 e t 为能量信号 列关于冲激函数性质的表达式不正确的是( 2、 A 、 C 、 3、 A 、 4、 f (t) (t) f (0) (t)H(s)B、(at))d (t)D 、 1ta(-t)(t)(s2s 1()s (s 2)2)，属于其极点的是(B 、2C 、 )。
1 If f1(t) ←→ F1(j ω)， f2(t) ←→ F2(j ω) A 、[a f1(t) + b f2(t) ] ←→ [a F1(j ω) *b F2(j ω) ] B 、[a f1(t) + b f2(t) ] ←→ [aF1(j ω) - b F2(j ω) ] C 、[a f1(t) + b f2(t) ] ←→ [a F1(j ω) + b F2(j ω) ] D 、[a f1(t) + b f2(t) ] ←→ [a F1(j ω) /b F2(j ω) ] 5、下列说法不正确的是( )。
A 、H(z)在单位圆内的极点所对应的响应序列为衰减的。
即当趋于 0。
Then[ D 、-2k →∞时，响应均B 、H(z)在单位圆上的一阶极点所对应的响应函数为稳态响应。
C 、H(z) 在单位圆上的高阶极点或单位圆外的极点， 其所对应的响应序列都是递 增的。
华中科技大学文华2012级本科《大学英语（四）》期末考试口语考试题及考试须知
华中科技⼤学⽂华2012级本科《⼤学英语（四）》期末考试⼝语考试题及考试须知⼝语考试须知考⼝语：五道题⽬中参加⼝语考试的学⽣只选择其中⼀题，根据⾃⼰可选的话题进⾏充分准备。
写出你要讲的话题⽂稿，考试时应脱稿⽽出。
每⼈⼀次3---4分钟，⽂稿当时要交给⽼师。
下⾯是⼝语考试题，选择其中⼀题：1、Tell me about a holiday you have takenYou should say:When and where you went on the holidayIf it is a popular holiday destination what you did on the holiday and what was special about it.2、Tell me about a city you have visited.You should say:Where the city is and when you went thereWhat people can see and do in that cityWhy that city is special and explain why your visit to that city was memorable.3、Tell me about your experience of learning English.You should say:When you started learning English and whyHow you have learnt English and with which peopleHow it has changed your life so far and say why you think it will be useful to you in the future4、Tell me about one of your friends.You should say:Who the friend is and how you first met him I herWhat you enjoy doing togetherWhat he / she is like and looks like and explain why your friendship is so special.5、Tell me about a book you have read,You should say:Which book it was and when you read itWhat feelings you had whilst reading itIf you have read other books by the same author and how it influenced you, if at all.Nothing is impossible to a willing heart!!Never say give up,Never say give in,Never say never选题教师：朱⽼师2014年5⽉12⽇希望同学们做好充分准备，展⽰出⼀个学期在听⼒、⼝语、翻译中有实实在在的收获。