闽江学院高频电子线路期末考A卷____参考答案
完整word版,高频电子线路习题集(含答案),推荐文档
《高频电子线路》复习题（含解答）一、是非题（在括号内打“√”表示对，“×”表示错。
）1．多级耦合的调谐放大器的通频带比组成它的单级单调谐放大器的通频带宽。
（×）2．多级耦合的调谐放大器的选择性比组成它的单级单调谐放大器的选择性差。
（×）3．功率放大器是大信号放大器，要求在不失真的条件下能够得到足够大的输出功率。
（√）4．放大器必须同时满足相位平衡条件和振幅条件才能产生自激振荡。
（√）5．电感三点式振荡器的输出波形比电容三点式振荡器的输出波形好。
（×）6．在调谐放大器的LC回路两端并上一个电阻R可以加宽通频带。
（√）7．双边带（DSB）信号的振幅与调制信号的规律成正比。
（×）8．调频有两种方法，分别称为直接调频和间接调频。
（√）9．锁相环路与自动频率控制电路实现稳频功能时，锁相环路的性能优越。
（√）10．LC回路的品质因数Q值愈小，其选频能力愈强。
（×）11．调谐放大器兼有放大和选频功能。
（√）12．DSB调幅波中所包含的频率成分有载频、上下边频。
（×）13．LC回路的品质因数Q值愈小，其选频能力愈弱。
（√）14.调谐功率放大器是采用折线近似分析法。
（√）二、选择题（将一个正确选项前的字母填在括号内）1．欲提高功率放大器的效率，应使放大器的工作状态为（ D ）A．甲类 B．乙类 C．甲乙类 D．丙类2．为提高振荡频率的稳定度，高频正弦波振荡器一般选用（ B ）A．LC正弦波振荡器 B．晶体振荡器 C．RC正弦波振荡器3．若载波u C(t)=UCcosωC t,调制信号uΩ(t)= UΩcosΩt，则调相波的表达式为（ B ）A．u PM(t)=U C cos（ωC t＋m f sinΩt） B．u PM(t)=U C cos（ωC t＋m p cosΩt）C．u PM(t)=U C（1＋m p cosΩt）cosωC t D．u PM(t)=kUΩU C cosωC tcosΩt4．某调频波，其调制信号频率F＝1kHz，载波频率为10.7MHz，最大频偏Δf m＝10kHz，若调制信号的振幅不变，频率加倍，则此时调频波的频带宽度为（ B ）A．12kHz B．24kHz C．20kHz D．40kHz5．MC1596集成模拟乘法器不可以用作（ D ）A．混频 B．振幅调制 C．调幅波的解调 D．频率调制6．某丙类谐振功率放大器工作在临界状态，若保持其它参数不变，将集电极直流电源电压增大，则放大器的工作状态将变为（ D ）A．过压 B．弱过压 C．临界 D．欠压7．鉴频的描述是（ B ）A．调幅信号的解调 B．调频信号的解调 C．调相信号的解调8．下图所示框图能实现何种功能？（ C ）其中u s(t)= U s cosωs tcosΩt， u L(t)= U L cosωL tA．振幅调制 B．调幅波的解调 C．混频 D．鉴频9．二极管峰值包络检波器，原电路正常工作。
高频试卷(答案)
~ 学年第学期专业年级高频电子线路课程期末考试题A卷班级姓名学号标准答案一、选择题（每小题2分、共30分）将一个正确选项前的字母填在括号内1．二极管峰值包络检波器适用于哪种调幅波的解调( C）A．单边带调幅波B．抑制载波双边带调幅波C．普通调幅波D．残留边带调幅波2．欲提高功率放大器的效率,应使放大器的工作状态为（D）A．甲类B．乙类C．甲乙类D．丙类3．为提高振荡频率的稳定度,高频正弦波振荡器一般选用( B) A．LC正弦波振荡器B．晶体振荡器C．RC正弦波振荡器4．变容二极管调频器实现线性调频的条件是变容二极管的结电容变化指数γ为（C）A．1/3 B．1/2 C．2 D．45．若载波u C(t)=U C cosωC t，调制信号uΩ(t)= UΩcosΩt,则调相波的表达式为( B ) A．u PM（t）=U C cos（ωC t＋m f sinΩt）B．u PM（t）=U C cos（ωC t＋m p cosΩt）C．u PM（t)=U C（1＋m p cosΩt)cosωC t D．u PM(t)=kUΩU C cosωC tcosΩt6．某超外差接收机的中频为465kHz，当接收550kHz的信号时，还收到1480kHz 的干扰信号,此干扰为（C）A．干扰哨声B．中频干扰C．镜像干扰D．交调干扰7．某调频波，其调制信号频率F＝1kHz，载波频率为10。
7MHz，最大频偏Δfm＝10kHz，若调制信号的振幅不变,频率加倍，则此时调频波的频带宽度为（B）A．12kHz B．24kHz C．20kHz D．40kHz 8．MC1596集成模拟乘法器不可以用作（D) A．混频B．振幅调制C．调幅波的解调D．频率调制9．某单频调制的普通调幅波的最大振幅为10v，最小振幅为6v，则调幅系数m a为（C）A．0。
6 B．0.4 C．0。
25 D．0。
1 10．以下几种混频器电路中，输出信号频谱最纯净的是（C）A．二极管混频器B．三极管混频器C．模拟乘法器混频器11．某丙类谐振功率放大器工作在临界状态,若保持其它参数不变，将集电极直流电源电压增大，则放大器的工作状态将变为( D）A．过压B．弱过压C．临界D．欠压12．鉴频的描述是( B）A．调幅信号的解调B．调频信号的解调C．调相信号的解调13．利用石英晶体的电抗频率特性构成的振荡器是( B) A．f＝fs时，石英晶体呈感性，可构成串联型晶体振荡器B．f＝fs时,石英晶体呈阻性，可构成串联型晶体振荡器C．f s<f<fp时，石英晶体呈阻性，可构成串联型晶体振荡器D．f s〈f〈fp时，石英晶体呈感性，可构成串联型晶体振荡器14．下图所示框图能实现何种功能？（C) 其中u s（t）= U s cosωs tcosΩt， u L（t)= U L cosωL tA．振幅调制B．调幅波的解调C．混频D．鉴频15．二极管峰值包络检波器,原电路正常工作。
(完整word版)高频电子线路试卷及答案(共7套试卷)(word文档良心出品)
练习试卷一、填空题1. 丙类功放按晶体管集电极电流脉冲形状可分为__欠压、__临界__、__过压__ 三种工作状态，它一般工作在___临界____ 状态。
2. 振荡器的主要性能指标_频率稳定度_、_振幅稳定度_。
3. 放大器内部噪声的主要来源是__电阻__和__晶体管__。
4. 某发射机输出级在负载RL=1000Ω上的输出信号Us(t)=4(1+0.5cosΩt)COSWctV。
试问Ma=__0.5__，Ucm=__4V__，输出总功率Pav=__0.009W_ 。
5. 实现频率调制就是使载波频率与调制信号呈线性规律变化，实现这个功能的方法很多，通常可分为__直接调频__和__间接调频___两大类。
6. 相位鉴频器是先将调频信号变换成__调相-调频__信号，然后用___相位检波器___进行解调得到原调制信号。
二、选择题1. 频率在1.5—30MHz范围的短波主要依靠（ C ）方式传播。
A 沿地面传播B 沿空间直线传播C 依靠电离层传播2. 在实际振荡器中，有时会出现不连续的振荡波形，这说明振荡器产生了周期性的起振和停振现象，这种现象称为（ B ）。
A 频率占据B 间歇振荡C 寄生振荡4. 集成模拟相乘器是（ B ）集成器件。
A 线性B 非线性C 功率5. 自动增益控制电路是（ A ）。
A AGCB AFC C APC三、分析题（共4题，共45分）1. 通信系统中为什么要采用调制技术。
（8分）答：调制就是用待传输的基带信号去改变高频载波信号某一参数的过程。
采用调制技术可使低频基带信号装载到高频载波信号上，从而缩短天线尺寸，易于天线辐射，实现远距离传输；其次，采用调制可以进行频分多路通信，实现信道的复用，提高信道利用率。
2.晶体振荡电路如图1所示，若f1为L1C1的谐振频率，f2为L2C2的谐振频率，试分析电路能否产生自激振荡。
若能振荡，指出振荡频率与f!、f2之间的关系。
（12分）+V CC答：由图可见电路可构成并联型晶体振荡器。
高频电子线路期末考试试卷十套(含答案)
C 、负峰切割失真三、判断题，对的打“/D 、截止失真，错的打“X” （每空1分，共10分）标准答案（一）一、填空题（每空1分，共30分）1、 无线电通信中，信号是以电磁波形式发射出去的。
它的调制方式有调幅、调频、调相。
2、 针对不同的调制方式有三种解调方式，分别是检波、鉴频和鉴相。
3、 在单调谐放大器中，矩形系数越接近于1、其选择性越好；在单调谐的多级放大器中， 级数越多，通频带越窄、（宽或窄），其矩形系数越（大或小）小。
4、 调幅波的表达式为： uAM （t ） = 20 （1 +0.2COS100 n t ） COS107 n t （V ）;调幅波的振幅 最大值为24V ，调幅度 Ma 为20 %,带宽fBW 为100Hz ，载波fc 为5*106Hz 。
5、 在无线电技术中，一个信号的表示方法有三种，分别是数学表达式、 波形、频谱。
6、 调频电路有直接调频、间接调频两种方式。
7、 检波有同步、和非同步检波两种形式。
8、 反馈式正弦波振荡器按照选频网络的不同，可分为 LC 、RC 、石英晶振 等三种。
9、 变频器可由混频器、和带通滤波器两部分组成。
10、 列出三个常见的频谱搬移电路调幅、检波、变频。
11、用模拟乘法器非线性器件实现调幅最为理想。
二、选择题（每小题 2分、共20分）将一个正确选项前的字母填在括号内 1、下列哪种信号携带有调制信号的信息（ C ） A 、载波信号B 、本振信号C 、已调波信号2、小信号谐振放大器的主要技术指标不包含（ 谐振电压增益B 、失真系数丙类谐振功放其谐振回路调谐于（ 基波 B 、二次谐波 3、A B ）C 、通频带 A ）分量 C 、其它高次谐波 D 、选择性D 、直流分量 并联型石英晶振中，石英谐振器相当于（ A 、电容 B 、电阻 5、 反馈式正弦波振荡器的起振条件为 A 、|AF|=1 , C 、|AF|>1 , 4、 A+ $ F= 2n n $ A+ $ F 工 2n n6、 要实现集电极调制特性应使功放工作在（A 、欠压状态B 、过压状态 7、自动增益控制可简称为（ B ） B 、AGC Cc 、电感 B )B 、|AF| >1 , |AF| =1 ,B）元件 D 、短路线 $ A+ $ F = 2n n $ A+ $ F)状态C 、临界状态D 、PLLD 、任意状态8、利用非线性器件相乘作用来实现频率变换其有用项为（ B ）A 、一次方项 C 、高次方项9、如右图所示的电路是（ A 、 普通调幅电路 B 、 双边带调幅电路 C 、 混频器 D 、 同步检波器B 、二次方项 D 、全部项10、在大信号包络检波器中，由于检波电容放电时间过长而引起的失真是（A 、频率失真B 、惰性失真 U rc224IF O51、解：F^ = —8.33W60%R3 I-ull ~l~~l —1+CO-沪8.335= 3.3W （3 分）P V8.33CC二 347 mA（3分）R.21谐振放大器是采用谐振回路作负载的放大器。
高频电子线路考卷(含答案)
1、 高频功率放大器一般工作在丙类工作状态，它的效率 （D ）。
（A ）约为50%（ B ）约为78%（ C 大于50% 小于78% （D ）大于78% 2、 在低电平调幅、小信号检波和混频中，非线性器件的较好特性是（ C ）。
（A ） i= b0+b1u+b2u 1 2+b3u 3 （ B ） i =b0+b1u+b3u 3 （ C ） i =b2u 2 （ D ） i =b3u 3（A ）同频（B ）同相（C ）同频同相 （D ）没有要求 7、某变频器输入载波频率为 720kHz 的AM 调幅波，采用下混频，要求输出信号的载波 频率为720kHz,贝U 变频器的本振频率应为（ （A ） 1440 kHz （B ） 1185 kHz &为了提高高频小信号谐振放大器的稳定性， （A ）中和法 （B ）失配法（D ）选择Cb' c 小的晶体三极管 （E ）选择特征频率fT 高的三极管 9、 鉴频器所需的鉴频特性线性范围取决于 （B ）。
（A ）调制信号频率 （B ）最大频偏△ f m （C ）调频波的有效带宽 （D ）调频波的振幅变化10、 我国调幅收音机的中频为 （A ）。
（A ） 465KHZ （B ） 455KHZ （C 75KHZ （D ） 10.7MHZ 11、 在常用的反馈型LC 振荡器中振荡波形好且最稳定的电路是（ D ） （A ）变压器耦合反馈型振荡电路 （B ）电容三点式振荡电路 （C ）电感三点式振荡电路 （D ）西勒振荡电路1 短波的频率范围是指 1.5M~30MHz ，主要以下列何种 电离层反射和折射 方式传 播。
2 高频功率放大器用LC 并联谐振回路作负载，其主要作用是 选频和滤波 。
3 丙类谐振功放在输入单频信号时，其基极、集电极和发射极电流均为尖顶脉冲波、单项选择题（每空 1分，共计11分）3、高频谐振功率放大器原工作于临界状态，如果其它条件不变， 工作状态为 （B（A ）临界状态 （B ）欠压状态 负峰切割失真主要是由于 （C （A ）信号调制度太小 （C ）检波器交、直流负载不同 EC 增大时，放大器的 4、 5、 （C ） 过压状态 （D ）甲类状态 造成的。
(完整word版)高频电子电路期末考试试题
.电子信息科学与技术专业（本）2007 级《高频电子电路》试卷（A）一、填空题（每空 1.5分，共 30分）1.无线电通讯中信号是以形式发射出去的。
它的调制方式有、、。
2.二极管峰值包络检波器的工作原理是利用和RC网络特征工作的。
3.已知 LC回路并联回路的电感 L在谐振频次f0=30MHz 时测得 L=1H ，Q0=100，则谐振时的电容 C=pF和并联谐振电阻 R P=k。
4.谐振回路的质量因数 Q愈大，通频带愈；选择性愈。
5.载波功率为 100W，当 m a=1 时，调幅波总功率和边频功率分别为和。
6.某调谐功率放大器，已知 V =24V ， P =5W ，则当c60% ， P C,I =，若 PCC0CO0保持不变，将c提升到 80%，P c减小。
7.功率放大器的分类，当 2 =时为甲类，当 2 =时为乙类；当<为丙类。
8.某调频信号，调制信号频次为400Hz ，振幅为 2V，调制指数为 30，频偏f=。
当调制信号频次减小为 200Hz，同时振幅上涨为 3V时，调制指数变为。
二、选择题（每题 2分，共 20 分）1.以下哪一种信号携带有调制信号的信息（）A.载波信号B.本振信号C.已调波信号D.高频振荡信号2.设AM 广播电台同意据有的频带为15kHz ，则调制信号的最高频次不得超出（）A.30kHz C.15kHz D.不可以确立3.设计一个频次稳固度高且可调的振荡器，往常采纳（）A.晶体振荡器B.变压器耦合振荡器C.RC相移振荡器D.席勒振荡器4.在调谐放大器的 LC回路两头并上一个电阻 R，能够（）A.提升回路的 Q值B.提升谐振频次C.加宽通频带D.减小通频带5.二极管峰值包络检波器合用于哪一种调幅波的解调（）A.单边带调幅波B.克制载波双边带调幅波C.一般调幅波D.残留边带调幅波6.以下表述正确的选项是（）A.高频功率放大器只好位于接收系统中B.高频功率振荡器只好位于接收系统中C.调制器只好位于发送系统中D.解调器只好位于发送系统中7.某丙类谐振功率放大器工作在临界状态，若保持其余参数不变，将集电极直流电源电压增大，则放大器的工作状态将变为（）A.过压B.弱过压C.临界D.欠压8.如右图所示电路，以下说法正确的选项是（）A.该电路因为放大器不可以正常工作，不可以产生正弦波振荡B.该电路因为没有选频网络，不可以产生正弦波振荡C.该电路因为不知足相位均衡条件，不可以产生正弦波振荡D.该电路知足相位均衡条件，可能产生正弦波振荡9.对于间接调频方法的描绘，正确的选项是（）A.先对换制信号微分，再加到调相器对载波信号调相，进而达成调频B.先对换制信号积分，再加到调相器对载波信号调相，进而达成调频C.先对载波信号微分，再加到调相器对换制信号调相，进而达成调频D.先对载波信号积分，再加到调相器对换制信号调相，进而达成调频10.已调波u(t )U m cos(c A1t )t，则其(t ) 表达式为（）A. A1tB. A1t2C. 2A1tD. A c t三、简答题（每题 5分，共 10 分）1.在接收设施中，变频器的作用是？变频器是怎么构成的，绘出变频前后的波形。
高频电子线路期末试卷及答案
2008－2009学年第一学期《高频电子线路》期末考试卷（A 卷）授课班号202601/2/3年级专业2006级通信,电信,电科学号 姓名一、单项选择（共15分，每空格1分。
）1. 谐振回路的品质因数Q 越大，通频带越（ ），选择性越（ ）。
A 宽B 窄C 好D 差2. 晶体管在工作高频时，其放大能力与低频工作时相比，放大能力（ ）A 增大B 减小C 不变3. 常用集电极电流流通角θ的大小来划分功放的工作类别，丙类功放（ ）A θ = 1800B 90O < θ< 1800C θ= 90OD θ< 90O4、电容三点式与电感三点式振荡器相比，其主要优点是 （ ）A 电路简单且易起振B 输出波形好C 改变频率不影响反馈系数D 工作频率比较低5.并联型晶体振荡器中，晶体工作在（ ）频率附近，此时晶体等效为（ ）元件。
A 并联谐振B 串联谐振C 电感D 电容6、同步检波器和变频器都是由非线性器件和滤波器组成，但所用的滤波器有所不同，同步检波器所用的为（ ），变频器所用的为（ ）A 低通滤波器B 高通滤波器C 带通滤波器7、若调制信号的频率是从 300Hz ～3000Hz ，那么，窄带调频时，调频电路中带通滤波器的 通频带宽度至少应为（ ）A 3000HzB 5400HzC 600HzD 6000Hz 8、某已调波的数学表达式为 t t t u 63102sin )102sin 1(2)(⨯⨯+=ππ， 这是一个（ ）A AM 波B FM 波C DSB 波D SSB 波9、设非线性元件的伏安特性为331u a u a i +=，它（ ）产生调幅作用。
A 能B 不能C 不确定10、比例鉴频器中，当输入信号幅度突然增加时，输出信号幅度（ ）。
A 随之增加B 随之减小C 保持不变11、设混频器的本振频率f L ，输入信号频率f C ，输出中频频率f I ，三者满足f L =f C +f I ，若有干扰信号 fn= f L +f I ，则可能产生的干扰称为（ ）A 交调干扰B 互调干扰C 中频干扰D 镜像干扰12、要避免惰性失真，应（ ）A 加大输入信号的调制度B 加大调制频率C 减小检波器的 RC 放电时间常数D 提高检波效率和滤波效果二、填空（共13分，每空格1分）1、LC 谐振回路有（ ）和（ ） 两种谐振方式。
word完整版高频电子线路期末试卷及答案
2008－2009学年第一学期《高频电子线路》期末考试卷（A 卷）姓名授课班号202601/2/3年级专业2006级通信,电信,电科学号题号一二三四总分审核评阅人得分）1分。
选择（共15分，每空格一、单项姚澄）。
Q越大，通频带越（），选择性越（1. 谐振回路的品质因数 D 差 B 窄 C 好A 宽）2. 晶体管在工作高频时，其放大能力与低频工作时相比，放大能力（ C 不变增大 B 减小A）3. 常用集电极电流流通角θ的大小来划分功放的工作类别，丙类功放（O0O0 Oθ< 90θ= 90 D = 180B 90 < θ< 180 C A θ）（ 4、电容三点式与电感三点式振荡器相比，其主要优点是输出波形好A 电路简单且易起振 B工作频率比较低C 改变频率不影响反馈系数 D）元件。
）频率附近，此时晶体等效为（ 5.并联型晶体振荡器中，晶体工作在（电容C 电感D A 并联谐振 B 串联谐振同步检波但所用的滤波器有所不同，、同步检波器和变频器都是由非线性器件和滤波器组成，6 ）），变频器所用的为（器所用的为（带通滤波器高通滤波器 C A 低通滤波器 B，那么，窄带调频时，调频电路中带通滤波器的～3000Hz7、若调制信号的频率是从 300Hz ）通频带宽度至少应为（A 3000HzB 5400HzC 600HzD 6000Hz36??t?10210?t)sin22u(t)?(1?sin这是一个（）， 8、某已调波的数学表达式为波 D SSB 波A AM 波 B FM 波 C DSB3ua?i?au9、设非线性元件的伏安特性为）产生调幅作用。
，它（31不确定能 B 不能 C A、比例鉴频器中，当输入信号幅度突然增加时，输出信号幅度（10 ）。
B 随之减小 C 保持不变A 随之增加，若有干 =ff，输入信号频率，输出中频频率f，三者满足f +f、设混频器的本振频率11f ICLLIC，则可能产生的干扰称为（） +f扰信号 fn= f IL镜像干扰 C A 交调干扰 B 互调干扰中频干扰 D页）7 页（共1 第河海大学常州校区考试试卷．12、要避免惰性失真，应（） A 加大输入信号的调制度 B 加大调制频率RC 放电时间常数 D C 提高检波效率和滤波效果减小检波器的评阅人得分二、填空（共13分，每空格1分）高远1、LC 谐振回路有（）和（）两种谐振方式。
(完整word版)高频电子线路复习考试题及答案 (2)(word文档良心出品)
2013—2014学年第二学期《高频电路》期末考试题（A ）使用教材：主编《高频电子线路》、 适用班级：电信12（4、5、6）命题人：一、填空题（每空1分，共X 分）1.调幅的几种调制方式是AM 、DSB 、SSB 。
3．集电极调幅，应使被调放大器工作于过压______状态。
5. 电容三点式振荡器的发射极至集电极之间的阻抗Z ce 性质应为容性，发射极至基极之间的阻抗Z be 性质应为容性，基极至集电极之间的阻抗Z cb 性质应为感性。
6. 通常将携带有信息的电信号称为调制信号，未调制的高频振荡信号称为载波，通过调制后的高频振荡信号称为已调波。
8. 解调是调制的逆过程。
振幅调制信号的解调电路称为振幅检波电路，它的作用是从高频已调信号中恢复出调制信号。
9. LC 串联谐振回路品质因数（Q ）下降，频带变宽，选择性变差。
10. 某高频功率放大器原来工作在临界状态，测得cm U =22v ，co I =100mA ，P R =100Ω，c E =24v ，当放大器的负载阻抗P R 变小时，则放大器的工作状态过渡到欠压状态，回路两端电压cm U 将减小，若负载阻抗增加时，则工作状态由临界过渡到过压 状态，回路两端电压cm U 将增大。
11. 常用的混频电路有二极管混频、三极管混频和模拟乘法器混频等。
12. 调相时，最大相位偏移与调制信号幅度成正比。
13. 模拟乘法器的应用很广泛，主要可用来实现调幅、解调和混频等频谱搬移电路中。
14. 调频和调幅相比，调频的主要优点是抗干扰性强、频带宽和调频发射机的功率放大器的利用率高。
15. 谐振功率放大器的负载特性是当CC V 、BB V 、bm V 等维持不变时，电流、电压、功率和效率等随电阻p R 的增加而变化的特性。
16. 混频器按所用非线性器件的不同，可分为二极管混频器、三极管混频器和模拟乘法器混频器等。
17. 在双踪示波器中观察到如下图所示的调幅波，根据所给的数值，它的调幅度应为2/3。
高频电子线路期末考试试卷及答案
高频电子线路期末考试试卷及答案班级：学号：姓名：装订线一、填空题：（20分）（每空1分）1、某小信号放大器共有三级，每一级的电压增益为15dB, 则三级放大器的总电压增益为。
2、实现调频的方法可分为和两大类。
3、集电极调幅电路应工作于状态。
某一集电极调幅电路，它的载波输出功率为50W ，调幅指数为0.5,则它的集电极平均输出功率为。
4、单向化是提高谐振放大器稳定性的措施之一，单向化的方法有和。
5、谐振动率放大器的动态特性不是一条直线，而是折线，求动态特性通常可以采用法和法。
6、在串联型晶体振荡器中，晶体等效为，在并联型晶体振荡器中，晶体等效为。
7、高频振荡的振幅不变，其瞬时频率随调制信号线性关系变化，这样的已调波称为波，其逆过程为。
8、反馈型LC 振荡器的起振条件是；平衡条件是；振荡器起振后由甲类工作状态逐渐向甲乙类、乙类或丙类过渡，最后工作于什么状态完全由值来决定。
9、变频器的中频为S L I ωωω-=，若变频器的输入信号分别为()t m t U u f s sm s Ω+=sin cos ω和t U u s sm s )cos(Ω-=ω，则变频器的输出信号分别为和。
10、变容二极管的结电容γ)1(0Dr j j U u C C += 其中γ为变容二极管的；变容二极管作为振荡回路总电容时，要实现线性调频，变容二极管的γ值应等于。
二、单项选择题（10分）（每空1分）1、具有抑制寄生调幅能力的鉴频器是。
A. 比例鉴频器B.相位鉴频器C. 双失谐鉴频器D.相移乘法鉴频器2、图1是电路的原理方框图。
图中t t U u c m i Ω=cos cos ω；t u c ωcos 0=图 1A. 调幅B. 混频C. 同步检波D. 鉴相3、下面的几种频率变换电路中，不是频谱的线性搬移。
A . 调频B .调幅C .变频D . 包络检波4、图2所示是一个正弦波振荡器的原理图，它属于振荡器。
图 2本科生考试试卷(A)（ 2007-2008 年第一学期）课程编号： 08010040 课程名称：高频电子线路..................A . 互感耦合B .西勒C .哈特莱D .克拉泼5、若载波频率为c f ，调制信号频率为F ，那么双边带调幅波的频带宽度为。
高频电子线路期末试卷附答案
高频电子线路一、填空题（每空1分，共13分）1．反馈式振荡器的振荡平衡条件是∑Ф=2nп和U f=U i。
三点式振荡器判别法则是X be和X ce电抗性质相同,X cb和它们电抗性质相反。
2．在大信号检波中，产生对角线失真原因是R L C L选得太大，放电太慢，跟不上输入信号包络线的变化。
产生负峰切割失真的原因是检波器交、直流负载电阻不等造成的。
3．模拟乘法器的应用很广泛，主要可用来实现调幅、同步检波和混频等频谱搬移电路中。
4．混频器按所用非线性器件的不同，可分为二极管混频器、三极管混频器和场效应管混频器等。
5．直接调频的优点是频偏大，间接调频的优点是中心频率稳定度高。
二选择题1．石英晶体谐振于fp时，相当于LC回路的（b）A．串联谐振现象 B．并联谐振现象 C．自激现象 D．失谐现象2．为了有效地实现集电极调幅，调制器必须工作在哪种工作状态（c）A．临界B．欠压C．过压3．判断下图是哪一类振荡器（c）A．考毕兹电路B．哈特莱电路C．西勒电路D．克拉泼电路4．谐振功率放大器与调谐放大器的区别是（ C ）A．前者比后者电源电压高B．前者比后者失真小C．谐振功率放大器工作在丙类，调谐放大器工作在甲类D．谐振功率放大器输入信号小，调谐放大器输入信号大5．如图所示为示波器测量正弦波波形参数的画面，若“VOLTS/DIV”的指示值是1V，则所测正弦波的有效值（D）A．4.6V B．2.3V C．3.25V D．1.63V6．石英晶体振荡器的主要优点是（C）A．容易起振B．振幅稳定C．频率稳定度高D．减小谐波分量7．无线通信系统接收设备中的中放部分采用的是以下哪种电路（ A ）A．调谐放大器B．谐振功率放大器C．检波器D．鉴频器8．调幅收音机中频信号频率为（A）A．465kHz B．10.7MHz C．38MHz D．不能确定9．一同步检波器，输入信号为u S =U S cosωC tcosΩt，恢复载波u r =U r cos（ωC＋Δω）t,输出信号将产生（ B ）A．振幅失真B．频率失真C．相位失真10．自动频率控制简称（B）A．AGC B．AFC C．APC11．锁相环路电路的作用是（B）A．维持工作频率稳定B．实现无频率误差的频率跟踪C．使输出信号幅度保持恒定或仅在很小的范围内变化12．要观察调谐放大器的谐振曲线，需要用到以下哪个仪器（D）A．示波器B．频率计C．高频信号发生器D．扫频仪13．若载波u C(t)=U C cosωC t,调制信号uΩ(t)= UΩsinΩt，则调频波的表达式为（B）A．u FM(t)=U C cos（ωC t＋m f sinΩt）B．u FM(t)=U C cos（ωC t－m f cosΩt）C．u FM(t)=U C（1＋m f sinΩt）cosωC t D．u FM(t)=kUΩU C cosωC tsinΩt14．无论是调频信号还是调相信号，它们的ω（t）和φ（t）都同时受到调变，其区别仅在于按调制信号规律线性变化的物理量不同，这个物理量在调相信号中是（D）A．ω（t）B．φ（t） C．Δω（t） D．Δφ（t）15．下图所示框图能实现何种功能？（ A ）其中u s(t)= U s cosωs t， u L(t)= U L cosΩtA．调幅B．检波C．混频D．鉴频三、简答题（每小题5分，共10分）1．为什么发射台要将信息调制到高频载波上再发送？答：1）信号不调制进行发射天线太长，无法架设。
(完整版)高频电子线路复习题(含答案),推荐文档
~ 学年第学期专业年级高频电子线路课程期末考试题A 卷班级姓名学号(一)一、选择题（每小题2 分、共30 分）将一个正确选项前的字母填在括号内1.在调谐放大器的LC 回路两端并上一个电阻R，可以（ C ）A．提高回路的Q 值B．提高谐振频率C．加宽通频带D．减小通频带2．在自激振荡电路中，下列哪种说法是正确的（ C ）A．LC 振荡器、RC 振荡器一定产生正弦波B．石英晶体振荡器不能产生正弦波C．电感三点式振荡器产生的正弦波失真较大D．电容三点式振荡器的振荡频率做不高3.如图为某收音机的变频级，以下正确叙述是（A ）A.电感三点式本机振荡电路B.双回路调谐放大器取出中频信号C．对接收信号构成共基放大电路D．以上说法都不对4.试用自激振荡的相位条件判别下图能产生自激振荡的电路（D ）A B C D5.功率放大电路根据以下哪种说法可分为甲类、甲乙类、乙类、丙类等（D ）A.电路特点B．功率放大倍数C．电流大小D．功放管静态工作点选择情况6．用万用表欧姆档测量小功率三极管的电极时，应该把欧姆档拨到（A ）A ．R ×100 或 R ×1k 档B ．R ×1 档C ．R ×10 档D ．R ×10k 档7.若载波 u C (t)=U C cos ωC t,调制信号 u Ω(t)= U Ωcos Ωt ，则调频波的表达式为（ A）A. u FM (t)=U C cos （ωC t ＋m f sin Ωt ）B ．u FM (t)=U C cos （ωC t ＋m p cos Ωt ） C ．u FM (t)=U C （1＋m p cos Ωt ）cos ωC tD ．u FM (t)=kU ΩU C cos ωC tcos Ωt8.MC1596 集成模拟乘法器不可以用作 （ C）A. 振幅调制B ．调幅波的解调C ．频率调制D ．混频 9. 某超外差接收机的中频为 465kHz ，当接收 931kHz 的信号时，还收到 1kHz 的干扰信号，此干扰为 （A ）A ．干扰哨声B ．中频干扰C ．镜像干扰D ．交调干扰10. 混频电路又称变频电路，在变频过程中以下正确叙述是（ C ）A. 信号的频谱结构发生变化B ．信号的调制类型发生变化C ．信号的载频发生变化11. 二极管峰值包络检波器，原电路正常工作。
高频电子线路期末总复习题
一、单项选择题
第二章选频网络
1、LC串联电路处于谐振时，阻抗（）。
A、最大B、最小C、不确定
2、LC并联谐振电路中，当工作频率大于、小于、等于谐振频率时，阻抗分别呈（）。
A、感性 容性 阻性B、容性 感性 阻性C、阻性 感性 容性 D、感性 阻性 容性
3、在LC并联电路两端并联上电阻，下列说法错误的是（）
3、非线性系统的主要特点是输出信号中除包含输入信号频率外，还会产生。
第五章高频功率放大器
1、减少高频功放晶体管Pc的方法是：减少集电极电流的和在集电极电流流通时最小；
2、丙类功放基极偏置电压VBB应保证晶体管工作在区。
3、谐振功率放大器工作于丙类，电流波形出现凹坑，为使其退出凹坑，可调整的参数有哪四个、、、，它们的变化趋势为（增大或减小）、、、。
2、给定并联谐振回路的 ， ，通频带 ，试求电感L，品质因素 ；又若把 加宽为 ，应在回路两端再并联一个阻值为多大的电阻？
3、下图是并联谐振回路。已知：f0=10MHz，Q=100，Rs=12kΩ，RL=1kΩ，C=40pF，匝比n1=N13/N23=1.3，n2=N13/N45=4。试求：
⑴试画出等效电路；
（1）集电极回路输出电压振幅值Vcm，集电极电流振幅值Icm1，输出功率PO。
（2）试说明该放大器工作在何种工作状态？当激励电压Vbm增加时，放大器过渡到何种工作状态？
2、某一晶体管谐振功率放大器，已知 , ， ，电压利用系数 ，求 、 、 、 ？
3、一谐振功放的输出功率Po=5W,Ec=24V。
(1)当集电极效率=60%时,求其集电极功耗Pc和集电极电流直流分量Ico；
⑵计算谐振回路的有载谐振电阻RP、有载品质因数QL和通频带BW0.7。
2020年福州闽江学院附属中学高三英语期末考试试题及参考答案
2020年福州闽江学院附属中学高三英语期末考试试题及参考答案第一部分阅读（共两节，满分40分）第一节（共15小题；每小题2分，满分30分）阅读下列短文，从每题所给的A、B、C、D四个选项中选出最佳选项ANational Disability Insurance Scheme (方案)The National Disability Insurance Scheme (NDIS) will transform the way Queenslanders with disability are supported and change the way disability services are funded and delivered.Under the scheme, Queenslanders with disability will have choice and control over how they access support and who delivers them. They will also have certainty that they will be supported throughout their lifetime to achieve their personal goals.The NDIS will have an effect on the following programs.School Transport Assistance Program for Students with DisabilityThe NDIS will not disrupt existing services for qualified students. The Queensland Government will also continue to provide school transport assistance for students with disability who are not qualified to receive funding via the NDIS.For more information about the School Transport Assistance Program, and to check your qualification, visit the Education and Training website.Taxi Subsidy (补助金) SchemeThe Queensland Governmenthas lengthened the Taxi Subsidy Scheme (TSS) membership for NDIS qualified members to 31 October, 2022. This will allow more time to solve transport support arrangements under the Commonwealth’s NDIS.You can find more information about the TSS and your qualification on the TransLink website.Disability Parking Permit SchemeNo changes will be made to the Disability parking permit scheme when the NDIS is introduced inQueensland. Current arrangements for this scheme will be maintained.You can find more information on this scheme, and check your qualification, on the Queensland Government website.Public Transport Concessions for People with DisabilityThere will be no change to concessions on public transport for people with disability when the NDIS isintroduced inQueensland. TransLink will continue to ensure concessions are provided for disabled persons travelling on public transport inQueenslandwhen the NDIS is introduced.You can find more information about public transport discounts for people with disability, and check your qualification, on the TransLink website,1.Which program helps drive the disabled to and from school?A.Taxi Subsidy Scheme.B.Disability Parking Permit Scheme.C.Public Transport Concessions for People with Disability.D.School Transport Assistance Program for Students with Disability.2.What can we learn about Taxi Subsidy Scheme?A.The scheme is for parking permit.B.The existing membership can be effective for longer time.C.There is no change to current arrangements for the scheme.D.The NDIS will not break off existing services for qualified students.3.What do the four programs have in common?A.They are all related to transport.B.They are all largely affected by NDIS.C.They all can be checked on the same website.D.They all provide discounts for disabled persons.BMark Bertram lost the tips of two fingers at work in 2018 when his hand became trapped in a fan belt. “It’s life-changing but it’s not life-ending,”he says.After two surgeries and occupational therapy, Bertram decided to ask Eric Catalano, a tattoo artist, to create fingernail tattoos. The idea made everyone in the studio laugh—until they saw the final result. “The mood changed,” Catalano recalls from his Eternal Ink Tattoo Studio in Hecker, Illinois. “Everything turned from funny to wow.”Catalano posted a photo of the tattoos, and it eventually was viewed by millions of people around the world. The viral photo pushed Catalano, 40, further into the world of paramedical tattooing. Now people who want to cover their life-altering scars come from as far away as Ireland to visit his shop.Leslie Pollan, a dog breeder, was bitten on the face by a puppy. She underwent countless surgeries but thosegave her no hope. She ultimately traveled six hours for a session with Catalano. HecamouflagedPollan’s lip scar, giving her back confidence.Though he is now known for his talent with intricate fingernail, Catalano uses the techniques he picked up years ago while helping breast cancer survivors. Those tattoos are among the most common paramedical requests. His grandmother had breast cancer, and her battle with the disease is one reason Catalano is so dedicated to helping those with the diagnosis.Catalano performs up to eight reconstructive tattoos each “Wellness Wednesday”. While he charges $100 per regular tattoo, he doesn’t charge for paramedical tattoos: A GoFundMe page established last year brought in more than $16,000, allowing Catalano to donate his work.“Financially, it doesn’t make sense,” Catalano says. “But every time I see emotions from my customers, I am 100 percent sure this is something that I can’t stop doing.”4. How did people in the studio react to Bertram’s idea at first?A. They took it lightly.B. They found it creative.C. They were confused.D. They were impressed.5. What does the underlined word “camouflaged” in Paragraph 4 probably mean?A. Exposed.B. Hid.C. Ignored.D. Removed.6. What does Catalano say about his work with paramedical tattoos?A. It is flexible.B. It is demanding.C. It is profitable.D. It is rewarding.7. Which of the following can best describe Catalano?A. Humorous and experienced.B. Devoted and generous.C. Cooperative and grateful.D. Professional and tolerant.CIn June, 2021, a group of students from eight high schools in Winnipeg, the capital of Canada’s Manitoba province, will begin test-launching (试发射) a satellite the size of a Rubik’s cube.The one-kilogram Win-Cube satellite, named for its home city and its shape, will be put into low orbit. Once in space, it can perform for a few months or up to several years, communicating information that could help find the signs of earthquakes.There are 80 similar satellite projects worldwide, but this is the first high-school based program of its kind in Canada. 30 Manitoba high school students are having a hand in designing and building the satellite, in cooperationwith aerospace (航空航天的) experts and 10 students from the University of Manitoba, and with support from two other organizations.The Win-Cube project is not something that goes on a piece of paper; it is real-world engineering, allowing high school students to have an opportunity to learn more about the exciting world of engineering through their participation in this challenging program. It is also taken as a wonderful example of the unique partnerships within Manitoba. Designing, building and launching a satellite with high-school participation will bring this world-class educational project into reality and Manitoba closer to space“These Manitoba high school students deserve congratulations for their enthusiasm, innovation (创新), and a strong love for discovery,” said Education, Citizenship and Youth Minister Peter Bjomson. “We want to make science more relevant, interesting and attractive to high school students by showing them how classroom studies can relate to practical experience in the workplace or, in this case, in space,” Bjomson added.The Win-Cube program is mainly aimed at inspiring a strong desire for discovery on the part of the students. It also shows Manitoba’s devotion to research and innovation and the development of a skilled workforce—all important drivers of knowledge-based economic growth.8. What can we learn from Mr. Bjomson? .A. Those Manitoba high school students are worth praising.B. The study of space can be practically made in classrooms.C. Manitoba high schools are famous for the study of space.D. Scientific research is too far away from high school students.9. What is the primary purpose of the project ? .A. To find the early signs of earthquakes.B. To relate studies to practical.C. To help high school students study real-world engineering.D. To inspire a strong desire for discovery among the students.10. According to the passage, what can we know about the Win-Cube satellite? .A. It is named after Manitoba and its shape.B. It is intended for international communication.C. It is designed like a Rubik’s cube both in shape and size.D. It is challenged by university students around the world.11. What may be the best title for the passage?A. Manitoba SchoolB. Win-Cube ProgramC. Space Co-operationD. Satellite LaunchingDGlobally, people use roofs to dry out food, do their laundry and sleep. In Belfast, where we're based, there's a culture of enjoying looking down on the city from up high, because it's in a valley. But because we were a conflict area for a long time,many people didn't want to live, work or hang out in the city, and our roofs cape has been neglected.Rooftop projects can be as big or as small as you want. They can be used as social or cultural spaces, for green or blue public facilities. But it's not just about commercial opportunities; it can be as simple as an individual turning his/her city balcony into a mini garden or vegetable patch. It's not just about doing it on a rooftop because it's “cool”.It's about giving up the deep-rooted thought that roofs are off limits and embracing their challenges as opportunities. That can make a huge difference. For instance, we're helping turn the rooftop car park of a city central shopping centre into an outdoor space for employees, due to restrictions they now face indoors because of COVID-19.Using rooftops creatively allows us to cope with many of the challenges faced by cities today--be those environmental, social, technological, or cultural. At the moment,we're being forced to rethink how we use public spaces due to COVID-19. With lots of restrictions on enclosed areas, we should be acknowledging rooftops alternatives.For example,Rotterdam recently hosted a play that took place across its rooftops. Each roof lit up and hosted a different part of the drama, while residents sat and watched, listening to the action through headphones. Are there any challenges? Rain is one. Also is health and safety. But there are creative and practical solutions to all the barriers we face. In fact,the challenges are what make rooftops so exciting----because they give you even more opportunities to be creative and solve problems. It is always a matter of trial and error.12. What can we learn about rooftops in the first two paragraphs?A. People enjoy getting together on rooftops.B. People can use rooftops to their own advantage.C. Rooftops are made good use of by locals in Belfast.D. Rooftops projects were launched for commercial reasons.13. How can rooftops benefit people in their life?A. Rooftops can be adapted to car parks.B. Rooftops help solve environmental problems.C. Rooftops can provide space for work and play.D. People can exchange their thoughts on rooftops.14. What will be possibly mentioned after the last paragraph?A. The new challenges of the future.B. Reasons for building rooftop projects.C. Exciting development of rooftop projects.D. Solutions to the challenges we are facing now.15. What is the author's purpose in writing the text?A. To introduce rooftop projects in Belfast.B. To encourage people to start rooftop projects.C. To analyze the current situation of rooftop projects.D. To offer suggestions on long-term city development.第二节（共5小题；每小题2分，满分10分）阅读下面短文，从短文后的选项中选出可以填入空白处的最佳选项。
2020-2021学年福州闽江学院附属中学高三英语期末考试试卷及答案
2020-2021学年福州闽江学院附属中学高三英语期末考试试卷及答案第一部分阅读（共两节，满分40分）第一节（共15小题；每小题2分，满分30分）阅读下列短文，从每题所给的A、B、C、D四个选项中选出最佳选项AThree Things to Do Before You Are 18Are you bored with your daily life? Here are some things you should try before you are 18.★Learn to swimSeriously, this is so important that it can save your life. If you can’t swim well, you won’t be able to dowater sports like waterskiing, surfing and diving. Even taking a boat trip will be dangerous for you. Make sure you do it.★Try at least one kind of team sportsBeing a good team player is an important skill in life. You can’t just think of yourself, but have to work well with other people. Other advantages of team sports like basketball, football and baseball are that they keep you fit and healthy, and they are also great fun. Teams usually have a good social life too—you’ll go to lots of parties and make many friends.★Collect somethingOne of the best hobbies for under-18s is collecting things. You could collect kinds of stamps, or you could collect things that make you remember what you have done, like cinema tickets for films you have seen or letters from friends. The best way to collect is to have a special album to put your collection in and to write what each thing means to you. That way you won’t forget.1. The most important reason for learning to swim is that ________.A. you might feel wellB. it can make you healthyC. you might easily do lots of thingsD. it can save your life2. The writer tells us that one of the best hobbies is to ________ .A. collect somethingB. do some water sportsC. send letters to your friendsD. play basketball with your friends23. The passage is mainly about ________before you are 18.A. good habits to keepB. skills to haveC. things to doD. sports to playBIf you’ve ever had a dog, you know just how deep a connection you can develop with “man’s best friend”. But a dog has a much shorter life span — about 12 to 15 years long — than humans, which means every dog owner has to go through the heartbreaking moment when their loving pet passes away.Why not make a clone of that dog then? This is the solution offered by a South Korean company, Sooam Biotech Research Foundation. The company has successfully cloned at least 400 dogs, mostly for US customers, ever since it pioneered the technique in 2005. Now, Sooam Biotech is planning to introduce their business toUKdog owners, offering them dogs that look just like their lost ones.Meanwhile, another dog is selected to supply an egg.Researchers then replace the DNA in the egg with that from the skin cell and implant the egg into the womb (子宫) of a female dog. The egg grows into a puppy over the following two months. To clone a dog, researchers first need to take a skin cell from a living dog or one that has just died.The whole process takes less than a day, but it comes at a shockingly high price — around £63,000 (614,000 yuan). But if you can’t afford it now, you can also save the cells in a laboratory and access them at a later date. Just like identical twins of humans, they share the exact same DNA but there will still be small differences between them. “The spots on a Dalmatian clone will be different, for example,” Insung Hwang, head of Sooam Biotech, toldThe Guardian. However, as magical as cloning might sound, there is no guarantee that the cloned dog will be a perfect replica of the original one.Dog owners will also have to accept the fact that personality is not “clone-able”. Apart from genes, personality is also determined by upbringing and environment, which are both “random elements [that] cloning technologies simply cannot overcome”, Professor Tom Kirkwood atNewcastle University,UK, toldThe Telegraph.Perhaps bringing our dogs back with cloning is not the best way to remember them after all.Kirkwood, a dog owner himself, pointed out: “An important aspect of our relationship with them is coming to terms with the pain of letting go.”4. According to the article, Sooam Biotech Research Foundation is ______.A. working on plans to help dog owners enjoy their pets longerB. offering a way to help dogs give birth to more puppiesC. providing a service that will make copies of pet dogsD. introducing a completely new technique to clone dogs5. Which of the following statements about dog cloning is TRUE according to the article?A. Dog cloning technology hadn’t been put into practice until recently.B. Dog cloning is very expensive and usually takes several months to complete.C. Dog cloning is very popular among US andUKpet owners.D. Cloned dogs might develop different habits and characteristics even though they look very similar.6. Which of the following shows the correct order of the dog cloning process?a. an egg is taken from another dogb. a skin cell is taken from the pet dog and saved in a laboratoryc. the egg is placed in the womb of a female dogd. the DNA of the egg is replaced by the DNA from the skin celle. the egg grows into a puppy in two monthsA. acbde.B. adbce.C. bacde.D. badce.7. We can learn from the article thatKirkwood______ dog cloning.A. disapproves ofB. supportsC. is afraid ofD. is curious aboutCAfter finishing his dinner, Lin Xu opened a WeChat mini-program called "Clear Plate" on his phone and took picture of the empty plates. He was then awarded 157 credit points after the image was uploaded and recognized by artificial intelligence.“Users of the app can use their credit to buy gifts, such as books and cellphones to purchase charity meals donated to children in poor rural areas,” Lin said.A nationwide "Clear Your Plate" campaign is gaining steam online. Efforts to stop food waste and promote thrift are also being made by restaurants that have been urged to create an environment in which consumers are reminded not to waste food. They are also encouraged to offer different portion sizes so that customers can have more choices.The “Clear Plate” mini-program has become popular among young Chinese and currently has nearly 1 million users.Liu Jichen, founder of the startup that developed the app, said that the idea popped up at a dinner in 2017, when Liu found that a restaurant would give diners who polished off their food a card and offer small gifts after a certain number of cards had been collected.“Such an idea can be realized online,” Liu said. He formed a team to work on the project.Yet it was quite challenge for the AI system to identify whether the uploaded photos showed empty plates.To make the AI system smarter, Liu and his team, assisted by more than 1,000 others, spent half a yearcollecting over 100, 000 samples in canteens and restaurants across the country and used the data to train neural network. Dozens of enterprises, institutions and restaurants have contacted the startup to cooperate on the project.Through the visualized mini-program, people can clearly see the good results of saving food, which will effectively reduce waste, he noted. "We hope our efforts can start a new trend among the younger generation, encouraging them to carry out the virtue of cherishing food and developing the habit of thrift, " Liu said8. What is the main function of the APP "Clear Plate?A. Awarding credit points.B. Giving charity meals.C. Showing the empty plates.D. Encouraging saving food.9. How is the "Clear Your Plate" campaign carried out?A. Customers wasting food are punished.B. People join in it on mini-program.C. Restaurants limit customers' choices.D. People are encouraged to buy gifts.10. What was the most difficult when the app was created?A. Getting other people to cooperate with the team.B. Collecting samples in canteens and restaurants.C. Ensuring the app to recognize empty plates.D. Finding people to fund the app.11. What is the purpose of the writing?A. To introduce an app.B. To promote saving food.C. To praise a startup founder.D. To raise fund for poor children.DThe Gata used to look annoyed when they received power bills that routinely topped $200. Last September the couple moved into a 1,500-square-foot home in Premier Gardens, an area of 95 “zero-energy homes” (ZEH) just outside town. Now they're actually eager to see their electricity bills. The grand total over the 10 months they've lived in the three-bedroom house: $75. For the past two months, they haven’t paid a cent.ZEH communities are the leading edge of technologies that might someday create houses that produce as much energy as they consume. Premier Gardens is one of a half-dozen subdivisions (住宅开发项目) in California where every home cuts power consumption by 50%, mostly by using low power appliances and solar panels.Aside from the panels on the roof, Premier Gardens looks like a community of traditional homes. But inside, special windows cut power bills by blocking solar heat in summer and keeping indoor warmth winter.The rest of the energy savings comes from the solar units. They don't just feed the home they serve. If theygenerate more power than the home is using, the excess flows into the utility's power grid(电网). The residents are billed by “net metering”: they pay for the amount of power that they get from the grid, minus the kilowatts(千瓦) they feed into it. If a home generates more power than it uses, the bill is zero.That sounds like a bad deal for the power company, but it's not. Solar homes produce the most power on the hot sunny afternoons when everyone rushes home to turn up the air conditioner. "It helps us lower usage at peak power times," says solar expert Mike Keesee. “That lets us avoid building costly plants or buying expensive power at peak usage time.”What’s not to like? Mostly the costs. The special features can add $25,000 or more to the purchase price of a house. Tax breaks bring the cost down, especially in California, but in many states ZEHs can be extremely expensive. For the consumer, it's a matter of paying now for the hardware to save later on the power bill.12. Why is the Gata eager to see their electricity bills now?A. They want to cut down their utility' expenses.B. They want to know if they are able to pay.C. They want to see how much they have saved.D. They want to avoid being overcharged.13. What is special about the ZEH communities?A. They are built in harmony with the environment.B. They have created cutting edge technologies.C. They are subdivided into half a dozen sections.D. They aim to be independent in power supply.14. What does the "net metering" practice mean to the power company?A. More pressure at peak timeB. Reduced operational costs.C. Increased electricity output.D. Less profits in the short term.15. The author believes that buying a house in a ZEH community __________.A. is a worthy investment in the long runB. is but a dream for average consumersC. gives the owner great tax benefitsD. contributes toenvironmental protection第二节（共5小题；每小题2分，满分10分）阅读下面短文，从短文后的选项中选出可以填入空白处的最佳选项。
2021届福州闽江学院附属中学高三英语下学期期末考试试卷及参考答案
2021届福州闽江学院附属中学高三英语下学期期末考试试卷及参考答案第一部分阅读（共两节，满分40分）第一节（共15小题；每小题2分，满分30分）阅读下列短文，从每题所给的A、B、C、D四个选项中选出最佳选项AAs a nation, we are getting bigger and eating more. But there are effective ways to control your appetite and eat only as much as you need.Keep away from low-nutrition snacksThat means ice cream, sweets, chips biscuits, cakes and any other salty orsugary snacks you eat between meals. Although we have a tendency to eat them, you can learn to live without these unhealthy-and-fattening-additions to your diet. Try to make it a habit to eat them only when offered at social events or as a special treat.Leave half an hour between main course and dessertHaving a break between courses gives your brain time to receive the fullness signal and make you more likely to refuse the sweet stuff. And, in fact, as soon as you feel the first signals of fullness, remove your plate from the table. That will tell your brain that food time is over.Make yours a small helpingPut an end to super-sized portions. You won’t be missing out—today’s small was the medium or large of a few decade ago. Select or serve yourself a modest portion and eat it slowly enjoying the flavors. Before you know it, small will feel just right. What’s more, ordering the smaller size leads to wearing the smaller size.Distract yourselfWhen you find yourself hunting down food, even though you’re even hungry, do something else for 20 minutes. Drink a large glass of water as thirst is often confused with a desire for food. Choose something that engages your brain as well as your hands, such as writing a letter or listening to a song. You could also go for a short walk or do something that you enjoy. If you think you really are hungry, set an alarm for 20 minutes’ time and if you still want to eat when it rings, fine. If not, the urge will have passed.1. Which way suits you better if you tend to order a large portion of food?A. Distract yourself.B. Make yours a small helping.C. Keep away from low-nutrition snacks.D. Leave half an hour between main course and dessert.2. Why should you have a break between main course and dessert?A. To give people time to chat.B. To have a good appetite for sweet stuff.C. To reduce appetite for dessert.D. To give the host time to remove your plate.3. When you find yourself pursuing for food, what should you do?A. Eat some biscuits.B. Eat some sugary snacks.C. Have some soft drinks.D. Listen to a lovely melody.BIt’s a little before8 a.m. when Mathias Schergen pushes open the side door at Chicago’s Jenner Elementary Academy for the Arts. He walks down the hall toward the office to sign in. It’s the same routine he’s had as Jenner’s art teacher for nearly a quarter century. “It’s going to be a good day,” a colleague calls out. “It’s a good day.” They hug. It seems like a typical Friday. Except it’s not. After 23 years at Jenner Elementary, Schergen is retiring. Even on his last day, there are still art projects to finish.Schergen leaves behind a richlegacyat this school. He’s won grants (拨款) for art projects. He turned an empty classroom into a museum. He’s pushed his students to make art about their lives. And he was awarded a Golden Apple — the most honorable teaching award in Chicago. But it wasn’t always easy. For years, Schergen taught in one of the city’s toughest neighborhoods. “When I first got my room, I noticed there were bullet holes in the window. That made me nervous,” he says. So he stuffed Beanie Babies in the holes to make it “look kind of funny”. “I didn’t even tell my wife for a whole year,” he says. “I didn’t want her to know.”With one hour to go, Schergen piles the chairs and sweeps the floor. He cleans out the sink for the last time. Fifth-grader Deontae Barnes, one of his best helpers, has watched him say goodbye all day. He wanders in the doorway. “Ah, come here, son,” Schergen says, signaling him over. He bends down for a hug. “Thank you for making these last days special and being a help to me.”When Deontae leaves, a reporter asks Schergen: When your kids ask why you’re retiring, what do you tell them? “I just tell them that grown people have dreams too,” he says. “I have other things in my life I have to do. It’s time. It’s just time.”4. Why is it a special Friday for Schergen?A. He was retiring on that day.B. He won an honor for his school.C. He was interviewed by a reporter.D. He received a Golden Apple award.5. What does the underlined word “legacy” in Paragraph 2 refer to?A. Art projects.B. Great achievements.C. Respect from students.D. Change in teaching.6. What made Schergen nervous when he first got to the school?A. Safety concerns in the school.B. The poorly-equipped classroom.C. Being misunderstood by his family.D. Students’ poor academic performance.7. What is the best title for the text?A.A Typical Day for an Art TeacherB. Time for Art ProjectsC. A Teacher’s Final Day at SchoolD. The Last Art ClassCFor years video games have been criticised for making people more antisocial, overweight or depressed. Bui now researchers are finding that video games can actually change us for the better and improve both our body and mind.Games can help to develop physical skills. Pre-school children who played interactive games have been shown to have improved motor skills, for example they can kick, catch and throw a ball better than children who don’t play video games. A study found that those who played video games were 27 percent faster and made 37 percent fewer errors than those who didn't.Games also benefit a variety of brain functions, including decision-making. People who play action-based games make decisions 25 percent faster than others, according to one study. It was also found that the best gamers can make choices and act on them up to six times a second, four times faster than most people. In another study by researchers from the University of Rochester in New York, experienced gamers were shown to be able to pay attention to more than six things at once without getting confused, compared with the four that most people can normally keep in mind.There is also evidence that gaming can help with psychological problems. At the University of Auckland in New Zealand, researchers asked 94 young people diagnosed with depression to play a 3D fantasy game called SPARX and in many cases, the game reduced symptoms of depression more than conventional treatment.8. In what way playing video games benefits very young children?A. Muscle control.B. Social interaction.C. Decision-making.D. The ability to focus.9. Which type of video game improves the decision-making speed?A. Interactive games.B. Action-based games.C. 3D fantasy games.D. Violent games.10. What is the authors attitude to video games?A. Indifferent.B. Objective.C. Worried.D. Critical.11. What is the text mainly about?A. The effects of different types of video games.B. The negative effects of playing video games.C. The beneficial effects of playing video games.D. The effects of games on people's behavior.DA Virginia teen is doing his part to make sure frontline health care workers are getting the meals they need to help them take care of themselves and others.Arul Nigam, 17, of Tyson's Corner, Va. , has had to make several adjustments since his school year ended abruptly in mid-March due to the coronavirus pandemic(新冠疫情).“We didn'thave any classes for like over a month and then after that there were a lot of technical difficulties. So I started to have a lot more free time,” he tells Yahoo Life. “It was really saddening, but it was also something that really surprised me, that our health care workers are facing something like that,” Nigam says. “So I wanted to see what I could do to help them because obviously, they're sacrificing so much and giving so much for all of us. ”In late March, the teen started fundraising efforts with the help of friends and family to help these health care workers receive much-needed meals. He also began doing research about what hospitals had the most amount of coronavirus cases, so he could prioritize those places first. He was also arranging for the orders to be fulfilled at local family-owned restaurants impacted by shutdown orders. So far, Nigam has delivered over 1,000 meals to 22 hospitals in 13 states, including New York, Massachusetts and Maryland.Nigam's efforts have not only helped health care workers, but restaurants as well. With quarantine restrictionstaking a toll onthe food industry, places like Best Coast Burrito in Oakland, Calif. , have lost business over the last few weeks. Best Coast's owner,Alvin Shen, tells Yahoo Life that being able to partner with Arul and others in efforts to feed those on the frontline has been a big help.12. What would Nigam probably do according to his words?A. Study at home by himself.B. Spend the more free time playing.C. Donate some money to health care workers.D. Do something helpful for health care workers.13. What is Nigam's priority when delivering food?A. The urgency of meals.B. The severity of the virus.C. The number of doctors.D. The position of hospitals.14. What does the phrase “taking a toll on” in the last paragraph mean?A. Turning a blind eye to.B. Keeping an eye on.C Causing lots of damage to.D. Answering completely for.15. Where can you probably read this text?A. Science fiction.B. Fashion magazine.C. Life magazine.D. Entertainment newspaper.第二节（共5小题；每小题2分，满分10分）阅读下面短文，从短文后的选项中选出可以填入空白处的最佳选项。
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2012 —2013学年第1学期闽江学院考试试卷（A ）
适用年级专业： 10级电子信息工程、10级电子信息科学与技术 考试形式：闭卷考试
考试课程： 高频电路
班级 姓名 学号 一、选择题：20 %
1，决定一台调幅收音机噪声系数的主要是 ( A )
(A)高频放大电路 (B)本地振荡电路 (C)中频放大电路 (D)音频放大电路
2，以下那些电路适合作为无线电广播的本地振荡电路 ( C )
(A)石英晶体振荡器 (B)RC 振荡电路 (C)LC 振荡回路
(D)压电陶瓷振荡电路
3，FM 广播中最大频偏与输入信号最大频率的比值称为 ( C )
(A)调频带宽 (B)信号增益 (C)调频指数 (D)调制度
4，对于SSB 信号属于 ( B )
(A)相位调制信号 (B)幅度调制信号 (C)频率调制信号 (D)角度调制信号
5，集电极调制的AM 波电路其LC 振荡回路工作于 ( A )
(A)过压状态 (B)欠压状态 (C)负反馈状态 (D)失谐状态
6，丙类高频谐振功率放大器的三极管工作时基极上的电流是 ( B )
(A)方波
(B)余弦脉冲波 (C)正弦波 (D)三角波
7，在信号幅度变化很大的时候，应该采用的电路是 ( A )
(A)AGC (B)AFC (C)APC (D)PLL 8， RC 振荡器与LC 振荡器相比较，正确的说法是： ( C )
A. 通常RC 振荡器的频率稳定度更好
B. 通常RC 振荡器的选频特性更好
C. 通常RC 振荡器在低频更有优势
D. 通常LC 振荡器在低频更有优势
9，下列信号中普通FM 波为 ( D )
10，石英晶体振荡电路中与其相连的电容作用是 ( C ) A 、能量交换 B 、稳定电压 C 、频率微调 D 、改变增益
二、简答题：30%
1，
答：一般采用LC 并联振荡回路 (3%)
原因：LC 并联回路谐振时阻抗大，可提高放大倍数。
(2%)
LC 回路具有选频作用，可对需要的频率进行选择，滤除带宽外的信号(3%) LC 的调谐电路简单。
(2%)
2， 什么是抑制载波双边带信号,英文简称是什么？它和普通AM 信号的区别在哪里(
解析
式、频谱图2个角度说明)？ (10%)
答：信号中没有携带载波的调幅信号叫做双边带信号，DSB (2 %)
DSB=A cos Ωt cos ωt AM==A(1+ m cos
Ωt) cos ωt (4%)
(4 %)
3， 完成以下PLL 电路框图，并简要说明其作用及原理（每空2分） 10 %
答：通过使得输出信号二分频后与输入信号同频同相，得到原输入信号二倍频的输出信号。
当输出信号有偏移时，其二分频信号与输入信号产生相位差，经过PD 得到与其正比的相位差信号，通过LF 得到控制信号，控制VCO 改变输出频率，从而获得稳定的二倍频信号。
（4%）
三、分析设计题：
30% 1,请分析以下LC （图 3% ）
答：因为若要LC 振荡电路起振，必须满足正反馈条件，也就是环路相移2n л(n=整数) （3%）
NPN 型三极管的集电极电压与基极电压存在的反相的关系，即 Vbe = -AVce （A 为常数，即电压增益）（3%） 作为X1、X2所在的电路支路，设X1、X2是同一性质的电抗元件，Vbe 、
Vec 同号若是相反性质的电抗元件,则异号 （3%）
当Vb 由于扰动升高时，导致 Vc 下降，相当于Vec 变大，如果Vbe 、
Vec 同号则Vbe 也要变大，导致Vb 继续升高，正反馈实现。
所以X1 必须是电容。
（
3%）
2，Us 为输入波形，分析下图各点波形,设图中二极管为理想二极管并作图表示。
比较C1、
R1电路与C2、R2电路的时间常数大小，并说明原因。
15 %
Us ：
（
1）Ud ：
（5 % 极性颠倒扣1分）
（2）Uo ：
（5 %）
（3）C1、R1电路的时间常数小于C2、R2电路的时间常数，因为C1、R1电路要对高频(载波)短路，C2、R2电路负责提取出低频(调制信号) （ 5 %）
四、综合题 20 %
1， 某LC 振荡回路，其中心频率f
0=800 kHz
．B
0.707=16kHz ，回路电容回路电感和 Q 值。
若电感线圈的Q L 值为97，问在回路上应并联多大的电阻才能满足带宽要求 10 %
2、请根据下面的信号矢量图，判断其为什么波（说明原因），并写出其时域表达式。
10 %
答：为普通AM 波 2 %
因为其波形矢量的旋转速度不变，因此载波频率恒定。
在波形矢量旋转过程中，波形矢量的顶端有两个各自相反方向旋转的矢量，它们大小相等、转速一致，二则的合成矢量叠加在载波矢量上，造成载波矢量的模变大变小，完成幅度调制 5 %
3%20(10.5cos(30))cos(500)AM U t t =⋅+⋅⋅⋅⋅。