measurement期刊的投稿模板
IEEE是用latex编辑的，并不是用word
为了进一步提高《施工技术》杂志质量，现对题名、作者署名、中英文摘要、关键词、第一作者简介、插图、表格、参考文献的格式做统一说明。1. 题名 1）字数：20字以内。 2）中文题名：可以反映出论文中特定的内容，是简明词语的逻辑组合。 3）英文题名：以短语为主要形式，尤其以名词短语最为常见。且每个实词的首字母大写， 虚词小写（超过4 个字母的虚词首字母大写）。 4）不得使用非公知公用、同行不熟悉的外来语、缩写词、符号、代号和商品名称。2. 作者署名1）作者单位：准确列出所在单位的全称和英文名称。高校老师单位写到二级单位。例如： 同济大学土木工程学院。2）一个作者只能列出一个所在单位。 3）作者的英文署名满足汉语拼音格式。例如：Zhang Kewen3. 中文摘要 1）字数：150～200。 2）内容：包括研究背景、研究方法、研究内容、研究结果。力求结构严谨、表达简明。 语义确切。3）用第三人称。建议采用“对……进行了研究” ， “介绍了……技术” 、 “得出了……结论”等记述方法标明一次文献的性质和文献主题，不必使用“本文” 、 “作者”等作为主语。 4）使用规范化的名词术语，不得使用非公知的符号和术语。4. 英文摘要 1）字数：150～200。 2）内容：做到对中文摘要转译的准确性和简洁性。 3）常用一般现在时、一般过去时。5. 关键词 1）一般采用3～6 个关键词 2）经过规范化的词或词组，不得使用非公知的符号和术语。6. 第一作者简介 1）包括：姓名、单位、职务、职称、通邮地址、邮政编码、联系电话、E-mail。 例如： 2）请确保以上信息的正确性。由于以上信息将公开出版，作者有权选择保护隐私权的联系方式。但请在文章后面提供作者手机，以便及时和作者保持联系。本刊会严格为其保密。7. 插图 1）作为文字的辅助说明。 2）插图的图名须相应的做英语转译。例如： 图1 施工过程仿真控制面板 Fig.1 Control panel for construction simulation8. 表格 1）作为文字的辅助说明。 2）表格的名称须相应的做英语转译。例如： 表1 各桅杆底座中心坐标测量结果 Table 1 Measurement results of control coordinates in mast bases 9. 参考文献 1）最必要、最新的文献。 2）公开发表的文献。 3）采用标准化格式。例如：(依次列出常用的图书、杂志、规范、论文集和毕业论文的格式) [1] 江正荣. 建筑地基与基础施工手册[M].北京：中国建筑工业出版社，2005. [2] 周黎光,仝为民,杜彦凯,等. 中国石油大厦双向张弦梁工程预应力施工技术[J].施工技术， 2008，37(3). [3] 冶金工业部建筑研究总院. GB50205-2001 钢结构工程施工质量验收规范[S].北京： 中国计划出版社，2002. [4] 刘鹏伟，邓开国. 空间结构 5.12 汶川地震震害初步调查[A]//第十二届空间结构学术会议论文集[C]. 北京, 2008: 722-728. [5] 高恒.大跨预应力张弦结构的试验研究及其ANSYS二次开发 [D].北京： 北京航空航天大学，2006.
measurement期刊投稿模板
measurement期刊不是水刊SCI三区杂志，爱思唯尔出版期刊名字 MEASUREMENT期刊ISSN -2015最新影响因子 1.484通讯方式 ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND, OXON, OX5 1GB涉及的研究方向 工程技术-工程：综合出版国家 ENGLAND出版周期 Bimonthly年文章数 547
IEEE是用latex编辑的，并不是用word
measurement期刊投稿
不是水刊，《MEASUREMENT》发布于爱科学网,并永久归类相关SCI期刊导航类别中。
Receiver (radio)A radio receiver is an electronic circuit that receives its input from an antenna, uses electronic filters to separate a wanted radio signal from all other signals picked up by this antenna, amplifies it to a level suitable for further processing, and finally converts through demodulation and decoding the signal into a form usable for the consumer, such as sound, pictures, digital data, measurement values, navigational positions, etc.In consumer electronics, the terms radio and radio receiver are often used specifically for receivers designed for the sound signals transmitted by radio broadcasting services – historically the first mass-market radio application.Various types of radio receivers may include:Consumer audio and high fidelity audio receivers and AV receivers used by home stereo listeners and audio and home theatre system enthusiasts. Communications receivers, used as a component of a radio communication link, characterized by high stability and reliability of performance. Simple crystal radio receivers (also known as a crystal set) which operate using the power received from radio waves. Satellite television receivers, used to receive television programming from communication satellites in geosynchronous orbit. Specialized-use receivers such as telemetry receivers that allow the remote measurement and reporting of information. Measuring receivers (also: measurement receivers) are calibrated laboratory-grade devices that are used to measure the signal strength of broadcasting stations, the electromagnetic interference radiation emitted by electrical products, as well as to calibrate RF attenuators and signal generators. Scanners are specialized receivers that can automatically scan two or more discrete frequencies, stopping when they find a signal on one of them and then continuing to scan other frequencies when the initial transmission ceases. They are mainly used for monitoring VHF and UHF radio systems. In the context of home audio systems, the term "receiver" often refers to a combination of a tuner, a preamplifier, and a power amplifier all on the same chassis. Audiophiles will refer to such a device as an integrated receiver, while a single chassis that implements only one of the three component functions is called a discrete component. Some audio purists still prefer three discreet units - tuner, preamplifier and power amplifier - but the integrated receiver has, for some years, been the mainstream choice for music listening. The first integrated stereo receiver was made by the Harman Kardon company, and came onto the market in 1958. It had undistinguished performance, but it represented a breakthrough to the "all in one" concept of a receiver, and rapidly improving designs gradually made the receiver the mainstay of the marketplace. Many radio receivers also include a loudspeaker.Hi-Fi / Home theaterToday AV receivers are a common component in a high-fidelity or home-theatre system. The receiver is generally the nerve centre of a sophisticated home-theatre system providing selectable inputs for a number of different audio components like turntables, compact-disc players and recorders, and tape decks ( like video-cassette recorders) and video components (DVD players and recorders, video-game systems, and televisions).With the decline of vinyl discs, modern receivers tend to omit inputs for turntables, which have separate requirements of their own. All other common audio/visual components can use any of the identical line-level inputs on the receiver for playback, regardless of how they are marked (the "name" on each input is mostly for the convenience of the user.) For instance, a second CD player can be plugged into an "Aux" input, and will work the same as it will in the "CD" input jacks.Some receivers can also provide signal processors to give a more realistic illusion of listening in a concert hall. Digital audio S/PDIF and USB connections are also common today. The home theater receiver, in the vocabulary of consumer electronics, comprises both the 'radio receiver' and other functions, such as control, sound processing, and power amplification. The standalone radio receiver is usually known in consumer electronics as a tuner.Some modern integrated receivers can send audio out to seven loudspeakers and an additional channel for a subwoofer and often include connections for headphones. Receivers vary greatly in price, and support stereophonic or surround sound. A high-quality receiver for dedicated audio-only listening (two channel stereo) can be relatively inexpensive; excellent ones can be purchased for $300 US or less. Because modern receivers are purely electronic devices with no moving parts unlike electromechanical devices like turntables and cassette decks, they tend to offer many years of trouble-free service. In recent years, the home theater in a box has become common, which often integrates a surround-capable receiver with a DVD player. The user simply connects it to a television, perhaps other components, and a set of loudspeakers.Portable radiosPortable radios include simple transistor radios that are typically monoaural and receive the AM, FM, and/or short wave broadcast bands. FM, and often AM, radios are sometimes included as a feature of portable DVD/CD, MP3 CD, and USB key players, as well as cassette player/recorders.AM/FM stereo car radios can be a separate dashboard mounted component or a feature of in car entertainment systems.A Boombox (or Boom-box)—also sometimes known as a Ghettoblaster or a Jambox, or (in parts of Europe) as a "radio-cassette"—is a name given to larger portable stereo systems capable of playing radio stations and recorded music, often at a high level of volume.Self-powered portable radios, such as clockwork radios are used in developing nations or as part of an emergency preparedness kit.History of radio receiversEarly developmentWhile James Clerk Maxwell was the first person to prove electromagnetic waves existed, in 1887 a German named Heinrich Hertz demonstrated these new waves by using spark gap equipment to transmit and receive radio or "Hertzian waves", as they were first called.The world’s first radio receiver (thunderstorm register) was designed by Alexander Stepanovich Popov, and it was first seen at the All-Russia exhibition in 1896. He was the first to demonstrate the practical application of electromagnetic (radio) waves,although he did not care to apply for a patent for his invention.A device called a coherer became the basis for receiving radio signals. The first person to use the device to detect radio waves was a Frenchman named Edouard Branly, and Oliver Lodge popularised it when he gave a lecture in 1898 in honour of Hertz. Lodge also made improvements to the coherer. Guglielmo Marconi believed that these new waves could be used to communicate over great distances and made significant improvements to both radio receiving and transmitting apparatus. In 1895 Marconi demonstrated the first viable radio system, leading to transatlantic radio communication in December 1901.John Ambrose Fleming's development of an early thermionic valve to help detect radio waves was based upon a discovery of Thomas Edison's (called "The Edison effect", which essentially modified an early light bulb). Fleming called it his "oscillation valve" because it acted in the same way as water valve in only allowing flow in one direction. While Fleming's valve was a great stride forward it would take some years before thermionic, or vacuum tube technology was fully adopted.Around this time work on other types of detectors started to be undertaken and it resulted in what was later known as the cat's whisker. It consisted of a crystal of a material such as galena with a small springy piece of wire brought up against it. The detector was constructed so that the wire contact could be moved to different points on the crystal, and thereby obtain the best point for rectifying the signal and the best detection. They were never very reliable as the "whisker" needed to be moved periodically to enable it to detect the signal properly.ValvesAn American named Lee de Forest, a competitor to Marconi, set about to develop receiver technology that did not infringe any patents to which Marconi had access. He took out a number of patents in the period between 1905 and 1907 covering a variety of developments that culminated in the form of the triode valve in which there was a third electrode called a grid. He called this an audion tube. One of the first areas in which valves were used was in the manufacture of telephone repeaters, and although the performance was poor, they gave significant improvement in long distance telephone receiving circuits.With the discovery that triode valves could amplify signals it was soon noticed that they would also oscillate, a fact that was exploited in generating signals. Once the triode was established as an amplifier it made a tremendous difference to radio receiver performance as it allowed the incoming signals to be amplified. One way that proved very successful was introduced in 1913 and involved the use of positive feedback in the form of a regenerative detector. This gave significant improvements in the levels of gain that could be achieved, greatly increasing selectivity, enabling this type of receiver to outperform all other types of the era. With the outbreak of the First World War, there was a great impetus to develop radio receiving technology further. An American named Irving Langmuir helped introduce a new generation of totally air-evacuated "hard" valves. H. J. Round undertook some work on this and in 1916 he produced a number of valves with the grid connection taken out of the top of the envelope away from the anode connection.Autodyne and superheterodyneBy the 1920s, the tuned radio frequency receiver (TRF) represented a major improvement in performance over what had been available before, it still fell short of the needs for some of the new applications. To enable receiver technology to meet the needs placed upon it a number of new ideas started to surface. One of these was a new form of direct conversion receiver. Here an internal or local oscillator was used to beat with the incoming signal to produce an audible signal that could be amplified by an audio amplifier.H. J. Round developed a receiver he called an autodyne in which the same valve was used as a mixer and an oscillator, Whilst the set used fewer valves it was difficult to optimise the circuit for both the mixer and oscillator functions.The next leap forward in receiver technology was a new type of receiver known as the superheterodyne, or supersonic heterodyne receiver. A Frenchman named Lucien Levy was investigating ways in which receiver selectivity could be improved and in doing this he devised a system whereby the signals were converted down to a lower frequency where the filter bandwidths could be made narrower. A further advantage was that the gain of valves was considerably greater at the lower frequencies used after the frequency conversion, and there were fewer problems with the circuits bursting into oscillation.The idea for developing a receiver with a fixed intermediate frequency amplifier and filter is credited to Edwin Armstrong. Working for the American Expeditionary Force in Europe in 1918, Armstrong thought that if the incoming signals were mixed with a variable frequency oscillator, a low frequency fix tuned amplifier could be used. Armstrong's original receiver consisted of a total of eight valves. Several tuned circuits could be cascaded to improve selectivity, and being on a fixed frequency they did not all need to be changed in line with one another. The filters could be preset and left correctly tuned. Armstrong was not the only person working on the idea of a superhet. Alexander Meissner in Germany took out a patent for the idea six months before Armstrong, but as Meissner did not prove the idea in practice and did not build a superhet radio, the idea is credited to Armstrong.The need for the increased performance of the superhet receiver was first felt in America, and by the late 1920s most sets were superhets. However in Europe the number of broadcast stations did not start to rise as rapidly until later. Even so by the mid 1930s virtually all receiving sets in Europe as well were using the superhet principle. In 1926 the tetrode valve was introduced, and enabled further improvements in performance.War and postwar developmentsIn 1939 the outbreak of war gave a new impetus to receiver development. During this time a number of classic communications receivers were designed. Some like the National HRO are still sought by enthusiasts today and although they are relatively large by today's standards, they can still give a good account of themselves under current crowded band conditions. In the late 1940s the transistor was discovered. Initially the devices were not widely used because of their expense, and the fact that valves were being made smaller, and performed better. However by the early 1960s portable transistor broadcast receivers (transistor radios) were hitting the market place. These radios were ideal for broadcast reception on the long and medium wave bands. They were much smaller than their valve equivalents, they were portable and could be powered from batteries. Although some valve portable receivers were available, batteries for these were expensive and did not last for long. The power requirements for transistor radios were very much less, resulting in batteries lasting for much longer and being considerably cheaper.SemiconductorsFurther developments in semiconductor technology led to the introduction of the integrated circuit in the late 1950s. This enabled radio receiver technology to move forward even further. Integrated circuits enabled high performance circuits to be built for less cost, and significant amounts of space could be saved.As a result of these developments new techniques could be introduced. One of these was the frequency synthesizer that was used to generate the local oscillator signal for the receiver. By using a synthesizer it was possible to generate a very accurate and stable local oscillator signal. Also the ability of synthesizers to be controlled by microprocessors meant that many new facilities could be introduced apart from the significant performance improvements offered by synthesizers.Digital technologiesReceiver technology is still moving forward. Digital signal processing where many of the functions performed by an analog intermediate frequency stage can be performed digitally by converting the signal to a digital stream that is manipulated mathematically is now widespread. The new digital audio broadcasting standard being introduced can only be used when the receiver can manipulate the signal digitally.While today's radios are miracles of modern technology, filled with low power high performance integrated circuits crammed into the smallest spaces, the basic principle of the radio is usually the superhet, the same idea which was developed by Edwin Armstrong back in 1918.
朋友，根据我多年从事文字工作的经验，我认为：如果投稿更有针对性，命中率会更高一些。这就关系到，你是哪里的？干什么的？写的稿件是什么体裁？什么内容？如果说投稿的话，最好投当地的报刊、网络或者是你从事的职业报刊发表，要投哪个媒体首先要研究哪个媒体，看它需要什么内容、什么体裁、什么格式的稿件，“对症下”，这样会更轻松一些、方便一些，命中率会更高一些。如果你能够告诉我你的具体情况（干什么工作，哪里的，写的小说的大致内容等），我可以给你一些建议。我1993年开始在部队时开始发表各类文章，包括：报告文学、新闻、诗歌、散文、小说、评论等体裁的，到目前，先后在《人民日报》《法制日报》《农民日报》《中国文化报》《法制文萃》《半月谈》《解放军报》《中国国防报》《中国绿色时报》《中国日报》《中国教育报》《人民公安报》《中国交通报》《中国安全生产报》《中国转业军官》《中国人事》《道路交通管理》等报刊发表的大约5000篇左右吧，有40多篇获奖。另外：投稿时，第一要有信心，第二要投对报刊媒体，这两点非常重要。祝你成功！
measurement期刊如何投稿
不是水刊，《MEASUREMENT》发布于爱科学网,并永久归类相关SCI期刊导航类别中。
Measurement [0263-2241]期刊详细信息期刊名称Measurement缩略题名MEAS缩略题名MEAS J INT MEAS CONFED缩略题名MEASUREMENT JOURNAL OF THE INTERNATIONAL MEASUREMENT CONFEDERATIONISSN：0263-2241LCCN：sc 85004172同行评议：是 本刊收录在： Ei Compendex (2013年) 本刊收录在： Ei Compendex (2015年) 本刊收录在Web of Science： SCIE(2012版) 本刊收录在Web of Science： SCIE(2013版) 本刊收录在Web of Science： SCIE(2016版) 点击: 查看SCI影响因子(2009)Impact Factor:0.761; 5-Year Impact Factor:0.933 点击: 查看SCI影响因子(2010)Impact Factor: 0.846 ; Rank: 5154 点击: 查看SCI影响因子(2014)Impact Factor: 1.484, Rank: 4224 主题分类:Engineering: General and OthersPhysics: General and Others 期刊历史沿革:Related to: Industrial metrology [0921-5956]
IEEE是用latex编辑的，并不是用word
MEASUREMENT期刊怎么投稿
不是水刊，《MEASUREMENT》发布于爱科学网,并永久归类相关SCI期刊导航类别中。
Receiver (radio)A radio receiver is an electronic circuit that receives its input from an antenna, uses electronic filters to separate a wanted radio signal from all other signals picked up by this antenna, amplifies it to a level suitable for further processing, and finally converts through demodulation and decoding the signal into a form usable for the consumer, such as sound, pictures, digital data, measurement values, navigational positions, etc.In consumer electronics, the terms radio and radio receiver are often used specifically for receivers designed for the sound signals transmitted by radio broadcasting services – historically the first mass-market radio application.Various types of radio receivers may include:Consumer audio and high fidelity audio receivers and AV receivers used by home stereo listeners and audio and home theatre system enthusiasts. Communications receivers, used as a component of a radio communication link, characterized by high stability and reliability of performance. Simple crystal radio receivers (also known as a crystal set) which operate using the power received from radio waves. Satellite television receivers, used to receive television programming from communication satellites in geosynchronous orbit. Specialized-use receivers such as telemetry receivers that allow the remote measurement and reporting of information. Measuring receivers (also: measurement receivers) are calibrated laboratory-grade devices that are used to measure the signal strength of broadcasting stations, the electromagnetic interference radiation emitted by electrical products, as well as to calibrate RF attenuators and signal generators. Scanners are specialized receivers that can automatically scan two or more discrete frequencies, stopping when they find a signal on one of them and then continuing to scan other frequencies when the initial transmission ceases. They are mainly used for monitoring VHF and UHF radio systems. In the context of home audio systems, the term "receiver" often refers to a combination of a tuner, a preamplifier, and a power amplifier all on the same chassis. Audiophiles will refer to such a device as an integrated receiver, while a single chassis that implements only one of the three component functions is called a discrete component. Some audio purists still prefer three discreet units - tuner, preamplifier and power amplifier - but the integrated receiver has, for some years, been the mainstream choice for music listening. The first integrated stereo receiver was made by the Harman Kardon company, and came onto the market in 1958. It had undistinguished performance, but it represented a breakthrough to the "all in one" concept of a receiver, and rapidly improving designs gradually made the receiver the mainstay of the marketplace. Many radio receivers also include a loudspeaker.Hi-Fi / Home theaterToday AV receivers are a common component in a high-fidelity or home-theatre system. The receiver is generally the nerve centre of a sophisticated home-theatre system providing selectable inputs for a number of different audio components like turntables, compact-disc players and recorders, and tape decks ( like video-cassette recorders) and video components (DVD players and recorders, video-game systems, and televisions).With the decline of vinyl discs, modern receivers tend to omit inputs for turntables, which have separate requirements of their own. All other common audio/visual components can use any of the identical line-level inputs on the receiver for playback, regardless of how they are marked (the "name" on each input is mostly for the convenience of the user.) For instance, a second CD player can be plugged into an "Aux" input, and will work the same as it will in the "CD" input jacks.Some receivers can also provide signal processors to give a more realistic illusion of listening in a concert hall. Digital audio S/PDIF and USB connections are also common today. The home theater receiver, in the vocabulary of consumer electronics, comprises both the 'radio receiver' and other functions, such as control, sound processing, and power amplification. The standalone radio receiver is usually known in consumer electronics as a tuner.Some modern integrated receivers can send audio out to seven loudspeakers and an additional channel for a subwoofer and often include connections for headphones. Receivers vary greatly in price, and support stereophonic or surround sound. A high-quality receiver for dedicated audio-only listening (two channel stereo) can be relatively inexpensive; excellent ones can be purchased for $300 US or less. Because modern receivers are purely electronic devices with no moving parts unlike electromechanical devices like turntables and cassette decks, they tend to offer many years of trouble-free service. In recent years, the home theater in a box has become common, which often integrates a surround-capable receiver with a DVD player. The user simply connects it to a television, perhaps other components, and a set of loudspeakers.Portable radiosPortable radios include simple transistor radios that are typically monoaural and receive the AM, FM, and/or short wave broadcast bands. FM, and often AM, radios are sometimes included as a feature of portable DVD/CD, MP3 CD, and USB key players, as well as cassette player/recorders.AM/FM stereo car radios can be a separate dashboard mounted component or a feature of in car entertainment systems.A Boombox (or Boom-box)—also sometimes known as a Ghettoblaster or a Jambox, or (in parts of Europe) as a "radio-cassette"—is a name given to larger portable stereo systems capable of playing radio stations and recorded music, often at a high level of volume.Self-powered portable radios, such as clockwork radios are used in developing nations or as part of an emergency preparedness kit.History of radio receiversEarly developmentWhile James Clerk Maxwell was the first person to prove electromagnetic waves existed, in 1887 a German named Heinrich Hertz demonstrated these new waves by using spark gap equipment to transmit and receive radio or "Hertzian waves", as they were first called.The world’s first radio receiver (thunderstorm register) was designed by Alexander Stepanovich Popov, and it was first seen at the All-Russia exhibition in 1896. He was the first to demonstrate the practical application of electromagnetic (radio) waves,although he did not care to apply for a patent for his invention.A device called a coherer became the basis for receiving radio signals. The first person to use the device to detect radio waves was a Frenchman named Edouard Branly, and Oliver Lodge popularised it when he gave a lecture in 1898 in honour of Hertz. Lodge also made improvements to the coherer. Guglielmo Marconi believed that these new waves could be used to communicate over great distances and made significant improvements to both radio receiving and transmitting apparatus. In 1895 Marconi demonstrated the first viable radio system, leading to transatlantic radio communication in December 1901.John Ambrose Fleming's development of an early thermionic valve to help detect radio waves was based upon a discovery of Thomas Edison's (called "The Edison effect", which essentially modified an early light bulb). Fleming called it his "oscillation valve" because it acted in the same way as water valve in only allowing flow in one direction. While Fleming's valve was a great stride forward it would take some years before thermionic, or vacuum tube technology was fully adopted.Around this time work on other types of detectors started to be undertaken and it resulted in what was later known as the cat's whisker. It consisted of a crystal of a material such as galena with a small springy piece of wire brought up against it. The detector was constructed so that the wire contact could be moved to different points on the crystal, and thereby obtain the best point for rectifying the signal and the best detection. They were never very reliable as the "whisker" needed to be moved periodically to enable it to detect the signal properly.ValvesAn American named Lee de Forest, a competitor to Marconi, set about to develop receiver technology that did not infringe any patents to which Marconi had access. He took out a number of patents in the period between 1905 and 1907 covering a variety of developments that culminated in the form of the triode valve in which there was a third electrode called a grid. He called this an audion tube. One of the first areas in which valves were used was in the manufacture of telephone repeaters, and although the performance was poor, they gave significant improvement in long distance telephone receiving circuits.With the discovery that triode valves could amplify signals it was soon noticed that they would also oscillate, a fact that was exploited in generating signals. Once the triode was established as an amplifier it made a tremendous difference to radio receiver performance as it allowed the incoming signals to be amplified. One way that proved very successful was introduced in 1913 and involved the use of positive feedback in the form of a regenerative detector. This gave significant improvements in the levels of gain that could be achieved, greatly increasing selectivity, enabling this type of receiver to outperform all other types of the era. With the outbreak of the First World War, there was a great impetus to develop radio receiving technology further. An American named Irving Langmuir helped introduce a new generation of totally air-evacuated "hard" valves. H. J. Round undertook some work on this and in 1916 he produced a number of valves with the grid connection taken out of the top of the envelope away from the anode connection.Autodyne and superheterodyneBy the 1920s, the tuned radio frequency receiver (TRF) represented a major improvement in performance over what had been available before, it still fell short of the needs for some of the new applications. To enable receiver technology to meet the needs placed upon it a number of new ideas started to surface. One of these was a new form of direct conversion receiver. Here an internal or local oscillator was used to beat with the incoming signal to produce an audible signal that could be amplified by an audio amplifier.H. J. Round developed a receiver he called an autodyne in which the same valve was used as a mixer and an oscillator, Whilst the set used fewer valves it was difficult to optimise the circuit for both the mixer and oscillator functions.The next leap forward in receiver technology was a new type of receiver known as the superheterodyne, or supersonic heterodyne receiver. A Frenchman named Lucien Levy was investigating ways in which receiver selectivity could be improved and in doing this he devised a system whereby the signals were converted down to a lower frequency where the filter bandwidths could be made narrower. A further advantage was that the gain of valves was considerably greater at the lower frequencies used after the frequency conversion, and there were fewer problems with the circuits bursting into oscillation.The idea for developing a receiver with a fixed intermediate frequency amplifier and filter is credited to Edwin Armstrong. Working for the American Expeditionary Force in Europe in 1918, Armstrong thought that if the incoming signals were mixed with a variable frequency oscillator, a low frequency fix tuned amplifier could be used. Armstrong's original receiver consisted of a total of eight valves. Several tuned circuits could be cascaded to improve selectivity, and being on a fixed frequency they did not all need to be changed in line with one another. The filters could be preset and left correctly tuned. Armstrong was not the only person working on the idea of a superhet. Alexander Meissner in Germany took out a patent for the idea six months before Armstrong, but as Meissner did not prove the idea in practice and did not build a superhet radio, the idea is credited to Armstrong.The need for the increased performance of the superhet receiver was first felt in America, and by the late 1920s most sets were superhets. However in Europe the number of broadcast stations did not start to rise as rapidly until later. Even so by the mid 1930s virtually all receiving sets in Europe as well were using the superhet principle. In 1926 the tetrode valve was introduced, and enabled further improvements in performance.War and postwar developmentsIn 1939 the outbreak of war gave a new impetus to receiver development. During this time a number of classic communications receivers were designed. Some like the National HRO are still sought by enthusiasts today and although they are relatively large by today's standards, they can still give a good account of themselves under current crowded band conditions. In the late 1940s the transistor was discovered. Initially the devices were not widely used because of their expense, and the fact that valves were being made smaller, and performed better. However by the early 1960s portable transistor broadcast receivers (transistor radios) were hitting the market place. These radios were ideal for broadcast reception on the long and medium wave bands. They were much smaller than their valve equivalents, they were portable and could be powered from batteries. Although some valve portable receivers were available, batteries for these were expensive and did not last for long. The power requirements for transistor radios were very much less, resulting in batteries lasting for much longer and being considerably cheaper.SemiconductorsFurther developments in semiconductor technology led to the introduction of the integrated circuit in the late 1950s. This enabled radio receiver technology to move forward even further. Integrated circuits enabled high performance circuits to be built for less cost, and significant amounts of space could be saved.As a result of these developments new techniques could be introduced. One of these was the frequency synthesizer that was used to generate the local oscillator signal for the receiver. By using a synthesizer it was possible to generate a very accurate and stable local oscillator signal. Also the ability of synthesizers to be controlled by microprocessors meant that many new facilities could be introduced apart from the significant performance improvements offered by synthesizers.Digital technologiesReceiver technology is still moving forward. Digital signal processing where many of the functions performed by an analog intermediate frequency stage can be performed digitally by converting the signal to a digital stream that is manipulated mathematically is now widespread. The new digital audio broadcasting standard being introduced can only be used when the receiver can manipulate the signal digitally.While today's radios are miracles of modern technology, filled with low power high performance integrated circuits crammed into the smallest spaces, the basic principle of the radio is usually the superhet, the same idea which was developed by Edwin Armstrong back in 1918.
IEEE是用latex编辑的，并不是用word