简单叙述数字手机射频处理部分的基本组成及其功能。
手机的射频处理部分主要包括发送部分、 接收部分以及频率合成器三部分。 其中，发送部分包括带通滤波、 GMSK调制器、 中频或射频调制、 射频功率放大器、 双工器等电路；接收部分包括双工器、射频滤波、射频放大、混频、中频滤波、中频放大和鉴频电路；频率 合成器主要提供接收通路、发送通路工作需要的本振频率。
暂无解析
根据《中华人民共和国特种设备安全法》：本法所称特种设备，是指对人身和财产安全有较大危险性的锅炉、压力容器（含气瓶）、压力管道、电梯、起重机械、客运索道、大型游乐设施、场（厂）内专用机动车辆，以及法律、行政法规规定适用本法的其他特种设备。
《特种设备专业人员监督管理办法》中规定：有下列情形之一的，应当撤销《特种设备作业人员证》：（一）持证作业人员以考试作弊或者以其他欺骗方式取得《特种设备作业人员证》的；（二）持证作业人员违反特种设备的操作规程和有关的安全规章制度操作，情节严重的；（三）持证作业人员在作业过程中发现事故隐患或者其他不安全因素未立即报告，情节严重的。
练习：
1.The reason why background music is so popular isthat ______.
A.it can have a powerful effect on those who hear it
B.it can help to create a soothing atmosphere
C.it can boost sales or increase factory production erywhere
D.it can make customers eat their meals quickly
2.Background music means ________.
A.light music that customers enjoy mostB.fast music that makes people move fast
C.slow music that can make customers enjoy their meals
D.the music you are listening to while you are doingomething
3.Restaurant owners complain about background musicbecause ______.
A.it results in indigestion
B.it increases their sales
C.it keeps customers moving
D.it decreases their sales
4.The word"up-tempo music"probably means_____.
A.slow music
B.fast music
C.light music
D.classical music
试题">To begin with,"muzak"(音乐广播网 )was intended simplyto createasoothing(安慰)atmosphere.Recently,however,it's ecome big business —thanks in part to recentresearch.Dr.Ronald Milliman,an American marketing expert,hasshown that music can boost sales or increase factory roduction by as much as a third.But,it has to be light music.A fast one has no effect atall on sales.Slow music can increase receipts by 38%.This isprobably because shoppers slow down and have more opportunityto spot items they like to buy.Yet,slow music isn't alway sanswer.Dr.Milliman found,for example,that in restaurants slowmusic meant customers took longer to eat their meals,whichreduced overall sales.So restaurants owners might be welladvised to play up-tempo music to keep the customers moving—unless of course,the resulting indigestion leads tocomplaints!
练习：
1.The reason why background music is so popular isthat ______.
A.it can have a powerful effect on those who hear it
B.it can help to create a soothing atmosphere
C.it can boost sales or increase factory production erywhere
D.it can make customers eat their meals quickly
2.Background music means ________.
A.light music that customers enjoy mostB.fast music that makes people move fast
C.slow music that can make customers enjoy their meals
D.the music you are listening to while you are doingomething
3.Restaurant owners complain about background musicbecause ______.
A.it results in indigestion
B.it increases their sales
C.it keeps customers moving
D.it decreases their sales
4.The word"up-tempo music"probably means_____.
A.slow music
B.fast music
C.light music
D.classical music
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我国通过国际铁路联运可运达的国家有哪些?
We hoped that there will be no repetition of this kind of trouble in the future .
We regret that we are unable to meet your requirement for the time being as orders have been fully booked.
We have now decided to supply you with all the parts as itemized in your order and going to apply to the government agencies concern for export licenses.
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Importance of Education
In the earliest stages of man's development he had nomore need of money than animals have.He was content with very simple forms of shelter,made his own rough tools and weapons and could provide food and clothing for himself and his family from natural materials around him.As he became more civilized,however,he began to want better shelter,more efficient tools and weapons,and more comfortable and more lasting clothing than could be provided by his own neighborhood or by the work of his own unskilled hands.For these things he had to turn to the skilled people such as smiths,leather workers or carpenters.It was then that the question of payment arose.
At first he got what he wanted by a simple process ofexchange.The smith who had not the time to look after land or cattle was glad to take meat or grain from the farmer inexchange for an axe or a plough.But as more and more goods which had no fixed exchange value came on the market,exchange became too complicated to be satisfactory.Another problem arose when those who made things wanted to get stocks of wood or leather,or iron,but had nothing to offer in exchange until their finished goods were ready. Thus the difficulties of exchange led by degrees to the invention of money.In some countries easily handled things like seeds or shells were given a certain value and the farmer,instead of paying the smith for a new axe by giving him some meat or grain,gave him so many shells.If the smith had any shells left when he had bought his food,he could get stocks of the raw materials of his trade.In some countries quite large things such as cows or camels or even big flat stones were used for trade.Later,pieces of metal,bearing values according to the rarity of the metal and the size of the pieces,or coins were used.Money as we know it had arrived.
1.Exchange of goods became difficult because _________.
A man became more civilized
B smiths began to look after land or cattle in their spare time
C more and more goods which had no fixed exchange alues came to the marker
D farmers hadn't enough grain or meat to provide for
skilled workers
2.Money was not used until _______.
A paper was invented
B people practiced a simple process of exchange
C nothing could be offered in exchangeD the exchange of one thing for another became too complicated
3.The best title for this passage is _____.
A What is money
B What are money's functions.
C The importance of money
D The beginning of money