多功能電子醫(yī)藥盒設(shè)計,多功能,電子,醫(yī)藥,設(shè)計 畢業(yè)設(shè)計（論文）中期報告 學(xué)院 班級 學(xué)生 姓名 指導(dǎo) 教師 課題名稱：多功能電子醫(yī)藥盒 簡述開題以來所做的具體工作、取得的進(jìn)展及下一步主要工作： 在畢業(yè)設(shè)計的最初階段, 認(rèn)真閱讀資料，了解蠶種新型消防車的基本原理及應(yīng)用前景、其工作原理以及控制方法。并進(jìn)行了以下幾步工作： （1）、查找整理資料，學(xué)習(xí)相關(guān)知識。 （2）、經(jīng)過查閱相關(guān)資料，選擇比較可取的電路,對所設(shè)計的電路進(jìn)行分析論證。 （3）、畫出系統(tǒng)的流程，畫出硬件設(shè)計圖。 之后,分析各部分模塊電路的具體作用，分析工作原理。查找元器件的主要功能特性、內(nèi)部結(jié)構(gòu)及各引腳的作用，盡量選擇最適合的元器件，列元件清單，購買器件。根據(jù)之前整理的資料進(jìn)行電路焊接。分模塊的對電路進(jìn)行調(diào)試，成功的調(diào)試完一些基本的單元電路，總結(jié)調(diào)試經(jīng)驗。 下一步的主要任務(wù): （1）、對未完成的電路繼續(xù)制作。 （2）、對單片機軟件進(jìn)行初始的編程。 （3）、軟件的后期調(diào)試及硬件電路的故障排除。 （4）、對整個電路進(jìn)行系統(tǒng)調(diào)試，達(dá)到穩(wěn)定，最后實現(xiàn)本課題所要實現(xiàn)的目標(biāo)。 一周的時間進(jìn)行畢業(yè)論文的準(zhǔn)備,最后準(zhǔn)備畢業(yè)答辯。 學(xué)生簽字： 年 月 日 指導(dǎo)教師的建議與要求： 指導(dǎo)教師簽字： 年 月 日 注：本表格同畢業(yè)設(shè)計（論文）一同裝訂成冊，由所在單位歸檔保存。 畢業(yè)設(shè)計（論文）任務(wù)書 題 目 (包括副標(biāo)題) 多功能電子醫(yī)藥盒 教師姓名 職 稱 系 別 學(xué)生姓名 學(xué) 號 班 級 成果形式 A論文 B設(shè)計說明書 C實物 D軟件 E作品 ■ □ □ □ ■ 任務(wù)下達(dá)時間 2009年 12月8日 1．畢業(yè)設(shè)計（論文）課題任務(wù)的內(nèi)容和要求： 采用凌陽單片機的語音技術(shù)，傳動技術(shù)，時間的記憶與存儲技術(shù)。 主要技術(shù)要求：①語音命令的正確識別。②解讀語音命令的發(fā)射。③語音命令的接收。④接收指令的執(zhí)行。若這四個技術(shù)指標(biāo)都能完成，設(shè)計任務(wù)便基本完成。 。 語音辨識原理簡圖如下： 聲學(xué)模式訓(xùn)練 語音模型 復(fù)雜聲學(xué)語音條件下的語音 輸入 語音匹配 語音模式訓(xùn)練 語音處理 語言模型 識別結(jié)果理解結(jié)束 2．畢業(yè)設(shè)計（論文）工作進(jìn)度計劃： 周 次 工作內(nèi)容 早進(jìn)入階段 第1-2周 第3-4周 第5-6周 第7-8周 第9-10周 查找相關(guān)資料，完成開題，了解畢業(yè)設(shè)計涉及的問題。 收集資料，進(jìn)行整理，學(xué)習(xí)單片機的相關(guān)知識，完成初步設(shè)計。 進(jìn)行方案論證，結(jié)合設(shè)計任務(wù)的具體要求，正式確定設(shè)計方案。 購買元器件、準(zhǔn)備必要的設(shè)備,焊接電路、調(diào)試。 調(diào)試硬件、軟件測試畢業(yè)設(shè)計作品。 完成畢業(yè)論文,準(zhǔn)備答辯。 教研室（學(xué)科組）主任簽字： 多功能電子醫(yī)藥盒 Multi-function electronic medical box 摘 要 20世紀(jì)中后葉，隨著大規(guī)模晶體管集成電路制造工藝的飛速發(fā)展，使計算機滲透進(jìn)城市的血液，成為人類社會生活中密不可分的一部分。越來越多種類的計算機投入社會生產(chǎn)，如果在人們的社會生活中所接觸到的計算機均使用不同的、自身特有的人機接口，就要求計算機使用者掌握多種計算機操作語言，這無疑成為人們使用計算機的一大障礙。因此人與計算機的溝通成為了擺在人類面前嶄新的課題。在音頻壓縮處理技術(shù)以及無線遠(yuǎn)程控制技術(shù)高速發(fā)展的局面下，人們開始考慮使用人類語言作為新的方式和計算機進(jìn)行無線遠(yuǎn)程對話。優(yōu)化人機接口，使計算機智能化，并且能聽懂遠(yuǎn)處傳來的人類語言，以人類的方式思考，徹底擺脫復(fù)雜的計算機語言和繁瑣的輸入方式是今后發(fā)展的一大方向。臺灣凌陽科技推出的16位MCU-DSP混合處理器SPCE061A可以實現(xiàn)上述的語音識別、數(shù)據(jù)編碼等功能。因此一款全新設(shè)計的人性化智能電子藥盒，會說話，能定時，更簡單。 本次設(shè)計為更多人帶來了便利，尤其是對于眾多不習(xí)慣于傳統(tǒng)復(fù)雜定時系統(tǒng)的人們使用多功能電子醫(yī)藥盒提高了人們的生活效率：針對年輕人，可以在忙碌的工作時提醒吃藥的時間；針對老年人，可以提醒按時吃藥、安全吃藥。今后，根據(jù)智能電子醫(yī)藥盒的設(shè)計理念，可將其移植到其他小家電等具有實際意義的產(chǎn)品中去。在人類與計算機的關(guān)系日益密切的今天，更為便捷、更為人性化、更為智能化的人機對話方式無疑是今后科技發(fā)展的新趨勢。 關(guān)鍵詞：人性化；語音辨識；定時自動開啟藥箱；SPCE061A ABSTRACT In the 20th century, with the large after IC manufacturing process of the transistor, the rapid development of computer penetrate into the blood and become human cities in social life is part of it. More and more kinds of computer into social production, if the people's social life in contact with the computer use different, own human-machine interface, computer user requirements of computer language, mastering this undoubtedly become an obstacle of people use computers. So people and computer communication has become set before the human beings. In audio compression processing technology and wireless remote control technology rapid development situation, people began to consider using human language as a new way for wireless remote dialogue with the computer. Optimize human-machine interface, computer intelligence, and understand the distant human language in human's thinking mode, and get rid thoroughly sophisticated computer language and trival input method is one of the future development direction. Taiwan sunplus technology of 16 MCU SPCE061A microprocessor - DSP mix can be realized the speech recognition, data coding etc. Function. Therefore, a new design of human intelligence, can speak, labels&tags electronic timing, can simpler. This design is more convenience, especially for many not accustomed to traditional complex timing system of people use muti _ function electronic medicine boxes to improve people's lives for young people, efficiency: in the busy work can remind the medicine time, For the elderly, can remind medicine on time, the medicine safety. In the future, according to the intelligent electronic medicine box design concept, can be transplanted into other household appliances with practical significance to the product. The relationship between human and computer in today's increasingly close, more convenient and more intelligent, humanized is undoubtedly the man-machine dialogue mode in the new trend of development of science and technology. Key Words：humanity;speech recognition;time automatically open medicine cabinet;SPCE061A 畢 業(yè) 論 文 開 題 報 告 多功能電子醫(yī)藥盒 系 別： 班 級： 學(xué)生姓名： 指導(dǎo)教師： 2009年 12 月 8日 畢業(yè)論文開題報告 課題題目 多功能電子醫(yī)藥盒 課題性質(zhì) A B C D E □ □ ■ □ □ 課題來源 A B C D □ ■ □ □ 成果形式 A B C D E ■ □ □ □ ■ 同組同學(xué) 無 開題報告內(nèi)容（見附頁） 指導(dǎo)教師意見（課題難度是否適中、工作量是否飽滿、進(jìn)度安排是否合理、工作條件是否具備等） 指導(dǎo)教師簽名： 月 日 專家組及系里意見（選題是否適宜、各項內(nèi)容是否達(dá)到畢業(yè)設(shè)計（論文）大綱要求、整改意見等） 專家組成員簽字： 教學(xué)主任（簽章）： 月 日 附頁： 開題報告 一、設(shè)計的目的與意義 隨著我國國民經(jīng)濟(jì)的發(fā)展，針對生活節(jié)奏的加快和社會老齡化的趨勢，結(jié)合產(chǎn)業(yè)發(fā)展需要，設(shè)計出了多功能電子醫(yī)藥盒。 我國現(xiàn)有的電子醫(yī)藥盒從最簡單的藥瓶方式，到非常復(fù)雜的多層藥箱都有，在時間設(shè)定和語音的功能上，各式各樣。但是現(xiàn)在還沒有將時間設(shè)定、語音播放以及時間的記憶集中在一起的電子醫(yī)藥盒。 國外的一些發(fā)達(dá)國家對用藥的認(rèn)知水平較高，在電子醫(yī)藥盒的研究和開發(fā)方面相對較好。雖然已經(jīng)開發(fā)出體積很小的智能醫(yī)藥盒，同樣，在功能上還沒有將時間設(shè)定、語音播放以及時間的記憶集中在一起的電子醫(yī)藥盒。 使用多功能電子醫(yī)藥盒提高了人們的生活效率：針對年輕人，可以在忙碌的工作時提醒吃藥的時間；針對老年人，可以提醒按時吃藥、安全吃藥 二、工作原理 1. 設(shè)計思路 本項目設(shè)計三倉與多倉的電子藥盒，支持設(shè)定每種藥物的服用時間，自動提醒和控制倉蓋開啟，提示出藥數(shù)量。同時，具有時間的記憶功能。采用凌陽單片機的語音技術(shù)，傳動技術(shù)，時間的記憶與存儲技術(shù)。 2. 實現(xiàn)功能 采用凌陽單片機的語音技術(shù)，傳動技術(shù)，記憶與存儲技術(shù)最終實現(xiàn)： 1) 語音提示后，倉蓋開啟和閉合的時間：1～2s； 2) 藥倉數(shù)量：4倉設(shè)計； 3) 能根據(jù)人的提示進(jìn)行藥物的選擇； 4) 人性化設(shè)計與友好的人機界面； 5) 24小時內(nèi)任意設(shè)定藥物服用提醒； 6) 語音互動，可以實現(xiàn)人機對話，具有小型機器人的識別能力； 7) 四倉設(shè)計，分為底倉、固定倉與常動倉，介紹如下： l 底倉：為藥物備用倉； l 固定倉：針對家庭中常常需要服用藥物的人所設(shè)計，服藥時間、數(shù)量等可進(jìn)行自行設(shè)定。 l 常動倉（分兩層）：針對生活中的易發(fā)性疾病所設(shè)計，服藥時間、數(shù)量等可進(jìn)行自行設(shè)定，具備語音識別功能，可根據(jù)語音提示，自動進(jìn)行藥物的選擇。 8）具有時間的記憶功能； 3. 硬件結(jié)構(gòu) 該系統(tǒng)可以被分為三個部分： 1）按鍵功能描述 時間調(diào)整鍵：可對現(xiàn)在時間及設(shè)定時間進(jìn)行調(diào)整，可實現(xiàn)5路定時提醒：對于時間調(diào)整，可進(jìn)行年月日小時分的設(shè)定 設(shè)定藥物鍵：通過此鍵可進(jìn)行服藥位置、時間及數(shù)量（最大為4）的設(shè)定，對于服藥位置，可進(jìn)行層數(shù)（最大為3）與格數(shù)（最大為6）的設(shè)定 采用默認(rèn)鍵：通過此鍵無需設(shè)定，即可享用標(biāo)準(zhǔn)方案：位置：一層2格；時間：早上8時，數(shù)粒：2粒 緊急救護(hù)鍵：按下此鍵，可以撥打緊急電話，及時將情況通知給用戶的子女，使老人盡快得到幫助。 2）定時的開啟 當(dāng)時鐘計時達(dá)到預(yù)定時間，液晶自動顯示藥品位置、種類及服用量，語音播報液晶屏上顯示的信息。同時，單片機控制步進(jìn)電機迅速轉(zhuǎn)動，自動開啟藥盒。一段時間后，進(jìn)入休眠模式，同時，單片機控制步進(jìn)電機迅速轉(zhuǎn)動，自動關(guān)閉藥盒。（藥盒支持手動開啟和定時自動開啟兩種方式） 產(chǎn)品功能圖（如圖） 三、課題的準(zhǔn)備情況及進(jìn)度計劃 序號 畢業(yè)設(shè)計階段性工作及成果 時間安排 1 收集資料確定設(shè)計方案 1～3周 2 機械部分的設(shè)計與制作 4～6周 3 電子控制電路系統(tǒng)設(shè)計 7～9周 4 設(shè)計說明書、使用說明書編寫 10周 5 總體校核完成畢業(yè)設(shè)計 11～13周 四、參考文獻(xiàn) [1] 劉海承等. MCU-DSP型單片機原理與應(yīng)用 北京：北京航空航天大學(xué)出版社，2003:45～46. [2] 羅亞非．凌陽 16位單片機應(yīng)用基礎(chǔ)．北京：北京航空航天大學(xué)出版社，2003: 49～56. [3] 鄭學(xué)堅，周斌．微型計算機原理及應(yīng)用．第三版．北京：清華大學(xué)出版社，2001: 101～104. [4] 歐陽斌林，等．單片機原理與應(yīng)用．中國水利水電出版社，2001: 225～233. [5] 李晶皎．嵌人式語音技術(shù)及凌陽16位單片機應(yīng)用．北京：北京航空航天大學(xué)出版社，2003: 97～102. [6] 潘松，黃繼業(yè)．EDA技術(shù)實用教程．第二版．北京：科學(xué)出版社，2005: 234～237. [7] 凌陽科技大學(xué)計劃.凌陽單片機在大學(xué)生電子競賽中的應(yīng)用，第一版，北京航空航天大學(xué)出版社，2005: 175～179. [8] 劉海成，秦進(jìn)平.MCU-DSP型單片機原理與應(yīng)用基于凌陽16位單片機，第一版，北京航空航天大學(xué)出版社，2006: 215～216. [9] 張齊，杜群貴.單片機應(yīng)用系統(tǒng)設(shè)計技術(shù)——基于C語言編程，第二版，電子工業(yè)出版社，2004 :191～193. [10] 侯媛彬.凌陽單片機原理及其畢業(yè)設(shè)計精選，第一版，科學(xué)出版社，2006:33～41. [11] 吳雙力，崔劍，王伯嶺.AVR-GCC與AVR單片機C語言開發(fā)，第一版，北京航空航天大學(xué)出版社，2004:163～169. [12] 徐煜明，韓雁.單片機原理及接口技術(shù)，第一版，電子工業(yè)出版社，2005:57～58. [13] 楊西明，朱騏.單片機編程與應(yīng)用入門，第一版，機械工業(yè)出版社，2004:341～344. [14] 嚴(yán)天峰.單片機應(yīng)用系統(tǒng)設(shè)計與仿真調(diào)試，第一版，北京航空航天大學(xué)出版社，2005:215～223. [15] Michael A. Miller.Data and Network Communications，第一版，科學(xué)出版社，2002:145～148. 英文原文 Radio Receiver A block diagram for a modern radio receiver is shown in Fig..2-4.The input signals to this radio are amplitude-modulated radio waves. The basic electronic circuits include: antenna ,tuner, mixer, local oscillator ,IF amplifier, audio detector, AF amplifier, loudspeaker, and power supply. Fig.1 A Block Diagram For Modern Radio Receiver Any antenna system capable of radiating electrical energy is also able to abstract energy from a passing radio wave. Since every wave passing the receiving antenna. Induces its own voltage in the antenna conductor, it is necessary that the receiving equipment be capable of separating the desired signal from the unwanted signals that are also inducing voltages in the antenna. This separation is made on the basis of the difference in frequency between transmitting stations and is carried out by the use of resonant circuits, which can be made to discriminate very strongly in favor of a particular frequency. It has already been pointed that, by making antenna circuit resonant to a particular frequency, the energy abstracted from radio waves of that frequency will be much greater than the energy from waves of other frequencies; this alone gives a certain amount of separation between signals. Still greater selective action can be obtained by the use of additional suitably adjusted resonant circuits located somewhere in the receiver in such a way as to reject all but the desired signal. The ability to discriminate between radio waves of different frequencies is called selectivity and the process of adjusting circuits to resonance with the frequency of a desired signal is spoken of as tuning. Although intelligible radio signals have been received from the stations thousands of miles distant, using only the energy abstracted from the radio wave by the receiving antenna much more satisfactory reception can be obtained if the received energy is amplified. This amplification may be applied to the radio-frequency currents before detection, in which case it is called radio-frequency amplification or it may be applied to the rectified currents after detection, in which case it is called audio-frequency amplification. The use of amplification makes possible the satisfactory reception of signals from waves that would otherwise be too weak to give an audible response. The process by which the signal being transmitted is reproduced from the radio-frequency currents present at the receiver is called detection, or sometimes demodulation. Where the intelligence is transmitted by varying the amplitude of the radiated wave, detection is accomplished by rectifying the radio frequency current. The rectified current thus produced varies in accordance with the signal originally modulated on the wave irradiated at the transmitter and so reproduces the desired signal. Thus, when the modulated wave is rectified, the resulting current is seen to have an average value that varies in accordance with the amplitude of the original signal. Receiver circuit are made up a of a number of stages. A stage is a single transistor connected to components which provide operating voltages and currents and also signal voltages and currents. Each stage has its input circuit from which the signal comes in and its output circuit from which the signal, usually amplified, goes out. When one stage follows another, the output circuit of the first feeds the signal to the second. And so the signal is amplified, stage by stage, until it strong enough to operate the loudspeaker. Radio Waves Radio Waves are a member of the electromagnetic of waves. They are energy-carriers which travel at the speed of light (ν), their frequency(?) and wavelength(λ) being related , as for any wave motion, by the equation ν=?* λ where ν=c=3.0*108 m/s in a vacuum (or air). If λ=300m, then ?=ν/λ=3.0*108 /(3.0*10 2)=106Hz=1MHz. The smaller λ is, the larger ?. Radio Waves can be described either by their frequency or their wavelength. But the former is more fundamental since, unlike λ (and ν ), f does not change when the waves travel form one medium to another. Radio Waves can travel form a transmitting aerial in one or more of three different ways. Surface or ground wave.. This travels along a ground, the curvature of the earth’s surface. Its range is limited mainly by the extent to which energy is absorbed form it by the ground. Poor conductors such as sand absorb more strongly that water, and the higher the frequency the greater the absorption. The range may be about 1500km at low frequencies (long wave, but much less for v. h. f.). Sky wave. This travels skywards and, if it is below a certain critical frequency (typically 30MHz), is returned to earth by the ionosphere. This consists of layers of air molecules (the D,E and F layer), stretching form about 80km above the earth to 50km, which have become positively charged through the removal of electrons by the sun’s ultraviolet radiation. On striking the earth the sky wave bounces back to the ionosphere where it is again gradually refracted and returned earthwards as if by 'reflection '. This continues until it is completely attenuated. Space wave. For v. h . f., u. h. f. and microwave signals, only the space wave, giving line-of sight transmission, is effective. A range of up to 150km is possible on earth if the transmitting aerial is on high ground and there are no intervening obstacles such as hills, buildings or trees. Oscillators Electrical oscillators are widely used in radio and television transmitters and receivers, in signal generators, oscilloscopes and computers, to produce A.C. with waveforms which may be sinusoidal, square, sawtooth etc. and with frequencies from a few hertz up to millions of hertz. Oscillatory circuit When a capacitor discharges through an inductor in a circuit of low resistance, an A.C. flows. The circuit is said to oscillate at its natural frequency which, as we will show shortly, equals, i.e. its resonant frequency f0. Electrical resonance thus occurs when the applied frequency equals the natural frequency as it does in a mechanical system.. In Fig,2(a) , a charged capacitor C is shown connected across a coil L.C immediately starts to discharge, current flows and a magnetic field is created which induces an e. m. f. in L. This e. m. f. opposes the current . When C is completely discharged the electrical energy originally stored in the electric field between its plates has been transferred to the magnetic field around L. Fig.2(b) oscillator Fig.2(a) The LC circuit By the time the magnetic field has collapsed, the energy is again stored in C. Once more C starts to discharge but current now flows in the opposite direction, creating a magnetic field of opposite polarity. When this field has decayed, C is again charged with its upper plate positive and the same cycle is repeated. In the absence of resistance in any part of the circuit , an undamped sinusoidal A.C. would be obtained. In practice , energy is gradually dissipated by resistance as heat and a damped oscillation is produced. Oscillator As the resistance of an LC circuit increases, the oscillation decay more quickly. To obtain undamped oscillations, energy has to be fed into the LC circuit in phase with its natural oscillations to compensate for the energy dissipated in the resistance of the circuit. This can be done with the help of a transistor in actual oscillators. A simple tuned oscillator is shown in Fig.2(b). The LC circuit is connected in the collector circuit (as the load) and oscillations start in it when the supply is switched on . The frequency of the oscillations is given by, i.e. then natural frequency of the LC circuit. The transistor merely ensures that energy is fed back at the correct instant from the battery. The current bias for the base of the transistor is obtained through R . AMPLIFIER Introduction The term amplifier is very generic. In general, the purpose of an amplifier is to take an input signal and make it stronger (or in more technically correct terms, increase its amplitude). Amplifiers find application in all kinds of electronic devices designed to perform any number of functions. There are many different types of amplifiers, each with a specific purpose in mind. For example, a radio transmitter uses an RF Amplifier (RF stands for Radio Frequency); such an amplifier is designed to amplify a signal so that it may drive an antenna. This article will focus on audio power amplifiers. Audio power amplifiers are those amplifiers which are designed to drive loudspeakers. Specifically, this discussion will focus on audio power amplifiers intended for DJ and sound reinforcement use. Much of the material presented also applies to amplifiers intended for home stereo system use. The purpose of a power amplifier, in very simple terms, is to take a signal from a source device (in a DJ system the signal typically comes from a preamplifier or signal processor) and make it suitable for driving a loudspeaker. Ideally, the ONLY thing different between the input signal and the output signal is the strength of the signal. In mathematical terms, if the input signal is denoted as S, the output of a perfect amplifier is X*S, where X is a constant (a fixed number). The "*" symbol means? Multiplied by". This being the real world, no amplifier does exactly the ideal, but many do a very good job if they are operated within their advertised power ratings. The output of all amplifiers contain additional signal components that are not present in the input signal; these additional (and unwanted)characteristics may be lumped together and are generally known as distortion. There are many types of distortion; however the two most common types are known as harmonic distortion and inter modulation distortion. In addition to the "garbage" traditionally known as distortion, all amplifiers generate a certain amount of noise (this can be heard as a background "hiss" when no music is playing). More on these later. All power amplifiers have a power rating, the units of power are called watts. The power rating of an amplifier may be stated for various load impedances; the units for load impedance are ohms. The most common load impedances are 8 ohms, 4 ohms, and 2 ohms (if you have an old vacuum tube amplifier the load impedances are more likely to be32 ohms, 16 ohms, 8 ohms, and maybe 4 ohms). The power output of a modern amplifier is usually higher when lower impedance loads (speakers) are used (but as we shall see later this is not necessarily better). In the early days, power amplifiers used devices called vacuum tubes (referred to simply as "tubes" from here on). Tubes are seldom used in amplifiers intended for DJ use (however tube amplifiers have a loyal following with musicians and hi-fi enthusiasts). Modern amplifiers almost always use transistors (instead of tubes); in the late 60's and early 70's, the term "solid state" was used (and often engraved on the front panel as a "buzz word"). The signal path in a tube amplifier undergoes similar processing as the signal in a transistor amp, however the devices and voltages are quite different. Tubes are generally "high voltage low current" devices, where transistors are the opposite ("low voltage high current"). Tube amplifiers are generally not very efficient and tend to generate a lot of heat. One of the biggest differences between a tube amplifier and a transistor amplifier is that an audio output transformer is almost always required in a tube amplifier (this is because the output impedance of a tube circuit is far too high to properly interface directly to a loudspeaker). High quality audio output transformers are difficult to design, and tend to be large, heavy, and expensive. Transistor amplifiers have numerous practical advantages as compared with tube amplifiers: they tend to be more efficient, smaller, more rugged (physically), no audio output transformer is required, and transistors do not require periodic replacement (unless you continually abuse them). Contrary to what many people believe, a well designed tube amplifier can have excellent sound (many high end hi-fi enthusiasts swear by them). Some people claim that tube amplifiers have their own particular "sound". This "sound" is a result of the way tubes behave when approaching their output limits (clipping). A few big advantages that tube amplifiers have were necessarily given up when amplifiers went to transistors. What are Amplifier Classes? The Class of an amplifier refers to the design of the circuitry within the amp. There are many classes used for audio amps. The following is brief description of some of the more common amplifier classes you may have heard of. Class A: Class A amplifiers have very low distortion (lowest distortion occurs when the volume is low) however they are very inefficient and are rarely used for high power designs. The distortion is low because the transistors in the amp are biased such that they are half "on" when the amp is idling. As a result, a lot of power is dissipated even when the amp has no music playing! Class A amps are often used for "signal" level circuits (where power is small) because they maintain low distortion. Distortion for class A amps increases as the signal approaches clipping, as the signal is reaching the limits of voltage swing for the circuit. Also, some class A amps have speakers connected via capacitive coupling. Class B: Class B amplifiers are used in low cost, low quality designs. Class B amplifiers are a lot more efficient than class A amps, however they suffer from bad distortion when the signal level is low (the distortion is called "crossover distortion"). Class B is used most often where economy of design is needed. Before the advent of IC amplifiers, class B amplifiers were common in clock radio circuits, pocket transistor radios, or other applications where quality of sound is not that critical. Class AB: Class AB is probably the most common amplifier class for home stereo and similar amplifiers. Class AB amps combine the good points of class A and B amps. They have the good efficiency of class B amps and distortion that is a lot closer to a class A amp. With such amplifiers, distortion is worst when the signal is low, and lowest when the signal is just reaching the point of clipping. Class AB amps (like class B) use pairs of transistors, both of them being biased slightly ON so that the crossover distortion (associated with Class B amps) is largely eliminated. Class C: Class C amps are never used for audio circuits. They are commonly used in RF circuits. Class C amplifiers operate the output transistor in a state that results in tremendous distortion (it would be totally unsuitable for audio reproduction). However, the RF circuits where Class C amps are used employ filtering so that the final signal is completely acceptable. Class C amps are quite efficient. Class D: The concept of a Class D amp has been around for a long time, however only fairly recently have they become commonly used. Due to improvements in the speed, power capacity and efficiency of modern semiconductor devices, applications using Class D amps have become affordable for the common person. Class D amplifiers use a very high frequency signal to modulate the incoming audio signal. Such amps are commonly used in car audio subwoofer amplifiers. Class D amplifiers have very good efficiency. Due to the high frequencies that are present in the audio signal, Class D amps used for car stereo applications are often limited to subwoofer frequencies, however designs are improving all the time. It will not be too long before a full band class D amp becomes commonplace. Other classes: There are many other classes of amplifiers, such as G, H, S, etc. Most of these are variations of the class AB design, however they result in higher efficiency for designs that require very high output levels (500W and up for example). At this time I will not go into the details of all of these other classes as I have not studied them all in detail. Suffice to be aware that they exist for now. 中文譯文 無線電接收機 圖1為無線電接收機的方框圖,輸入信號為調(diào)幅無線電波。它的基本組成包括天線、調(diào)諧回路、混頻器、本振電路、中放放大器、檢波器、音頻放大器、喇叭、電源等。 圖1 無線電接收機框圖 任何天線系統(tǒng)既能輻射無線電波又能接收無線電波。任何經(jīng)過天線的無線電波均能在天線中感應(yīng)電壓，因此，接收機必須能夠從天線所收到的所有信號中分離出有用信號。這個分離過程是根據(jù)發(fā)射端發(fā)射的信號頻率不同，利用調(diào)諧回路完成的。調(diào)諧回路能夠有效地從眾多頻率中選擇出某一個特定頻率。通過天線調(diào)諧回路對某一特定頻率地諧振，可以使天線從這一特定頻率中吸收的能量比從其他平頻率中吸收的能量大得多，這樣，就從某種程度上實現(xiàn)了信號的分離。進(jìn)一步的選擇作用可以通過接收機中的某些經(jīng)過適當(dāng)調(diào)諧的諧振回路實現(xiàn)，以這種方式進(jìn)一步去除了有用信號以外的其他信號。將不同頻率的無線電波加以區(qū)別的能力稱為選頻，將諧振回路的頻率調(diào)在有用信號頻率上的過程稱為調(diào)諧。 盡管接收的有用信號來自幾千里以外，但如果經(jīng)過放大，通過天線獲得的信號還是具有令人滿意的效果。放大過程可能應(yīng)用在對檢波前的射頻電流，這種情況稱為射頻放大；也可應(yīng)于檢波后，這種情況稱為音頻放大。放大器的應(yīng)用使令人滿意的接收成為可能，否則，有些太弱的信號不能獲得好的收聽效果。 從射頻信號中重視被傳輸?shù)脑夹盘柕倪^程稱為檢波或解調(diào)。如果有用信號在發(fā)射時是通過改變信號的振幅（即調(diào)幅），則檢波就是通過對射頻電流進(jìn)行整流完成的。整流電流隨著原始調(diào)制信號而變化，從而沖縣了原始的有用信號，這樣，已調(diào)波被整流而產(chǎn)生的電流可以被看成隨原始信號幅度變化的平均值電流。 接收機的電路由多級組成。每級由晶體管與提供工作電壓、電流和信號電壓、電流的元件相連構(gòu)成，每級都有輸入回路，它讓信號進(jìn)入；有輸出回路，它讓通常是放大后的信號輸出。當(dāng)一級接一級時，第一級的輸出回路將信號饋送給第二級，信號經(jīng)過逐級放大，直到足以推動揚聲器。 無線電波 無線電波是電磁波大家族中的一員，它們攜帶能量且以光速在空氣中傳播，它們的頻率與波長相關(guān)，即任何電磁波傳播時，有 ν=?* λ 這里，ν=c=3.0*108 m/s（在空氣中），如果λ=300m,則?=ν/λ=3.0*108 /(3.0*10 2)=106Hz.=1MHz。波長λ越小，頻率?越高。 無線電波既能用頻率又能用波長來描述。但前者更常用，因為頻率不像速度，不會因傳播媒介的改變而變化。 從天線電波輻射出去的無線電波通常以三種形式傳播。 （a）地表波或地波。這種波按地球表面的曲度，沿地表面?zhèn)鞑ァＫ膫鞑シ秶邢?，其能量易被地表面吸收。惡劣的地形條件如沙漠比水面更易吸收能量。頻率越高，能量被吸收得越多。低頻波（長波）的傳播范圍約為1500千米。高頻波的查范圍要小得多。 （b）天波。沿天空傳播，若低于某個關(guān)鍵頻率（如30MHZ），會被電離層反射回地面。電離層由空氣分子層組成（包括D、E、F層），位于地球上方80千米到500千米處，它由于太陽紫外線的輻射而失去電子，因而帶正電荷。反射回地面的天波又從地面反射回電離層，并再次被反射回地面，如此反復(fù)多次直到能量完成衰減。 (c) 空間波。甚高頻、超高頻和微波只能以空間波的形式才能有效 傳播，空間波也稱視距傳播。如果天線架設(shè)很高且沒有障礙阻隔，如高山、建筑物、大樹等，空間波的傳播距離可達(dá)150千米 振蕩器 電子振蕩器廣泛用于廣播、電視發(fā)射機、接收機、信號發(fā)生器、示波器及計算機中，它被用來產(chǎn)生幾赫茲到幾百萬赫茲的各種波形，如正弦波、方波、鋸齒波等。 振蕩電路 在一個低阻的RC 回路中，電容通過電感放電，回路中有交流電流流過，則稱回路發(fā)生了振蕩，其振蕩頻率等于，正好等于它的諧振頻率 f0 。當(dāng)外加信號頻率等于回路的固有振蕩頻率時，回路發(fā)生諧振，這也和機械振動系統(tǒng)相似。 再圖2（a）中，一個充電的電容和一個電感線圈相連，電容立刻開始放電，電流流過電感并在其中產(chǎn)生磁場和感應(yīng)電動勢，這個感應(yīng)電動勢與電流相反。當(dāng)電容放電完成以后，兩金屬片之間電場中儲存的電場能全部轉(zhuǎn)變成了電感中的電磁能。 然后，電感對電容反充電，電場能重新儲存在電容中。當(dāng)電容再次放電，回路電流反相，再電感中產(chǎn)生極性相反的電磁場。然后電感再次放電，電容再次充電，電流再次反相，這個過程不斷重復(fù)。 若電路中無電阻，則可獲得無衰減的正弦交流電流。實際上，由于回路損耗電阻的存在，能量會逐漸以熱能的形式消耗掉，產(chǎn)生的 是一個逐漸衰減的振蕩波形。 圖2(b)調(diào)諧振蕩器 圖2(a) 振蕩電路 振蕩器 當(dāng)振蕩電路的電阻增加，振蕩迅速衰減。為了獲得不衰減的振蕩信號，必須對LC回路饋入能量，以補充因回路電阻而損耗的能量，這在實用振蕩電路中是通過晶體管完成的。 一個簡單的調(diào)諧振蕩器如圖2（b）所示，LC回路接在晶體管的集電極回路（作為負(fù)載），當(dāng)開關(guān)合上時，振蕩開始，振蕩頻率由LC回路的諧振頻率決定。晶體管只是將電源的能量饋給振蕩回路以保證正常的狀態(tài)，晶體管的基極偏置電流由電阻R獲得。 放大器 這種放大器是非常常見的，通常來說，這個放大器的目的是用來接收一個信號并使之放大，放大器常常應(yīng)用在各種電子設(shè)備中，用來執(zhí)行各種功能。各種不同類型的放大器有不同的用途。例如，音頻傳送使用RF放大器，（RF表示音頻）；這樣的放大器用來放大從天線接收來的信號，這篇文章將著重介紹音頻放大器，這種音頻放大器來驅(qū)動揚聲器。特殊的，下面討論的是為DJ和音頻放大，大部分的放大器應(yīng)用于家庭立體聲系統(tǒng)。 簡單來說，放大器的目的是從一個信號源得到一個信號并放大能使它去驅(qū)動揚聲器，唯一不同的是：輸出信號是輸入信號的放大。從數(shù)學(xué)角度來說，如果輸入信號定義為S，則輸出信號為X*S，X為放大系數(shù)常量。*代表乘運算。 在現(xiàn)實當(dāng)中，沒有一種放大器是理想的，在先進(jìn)的設(shè)備中它們能更好的工作。放大器的輸出包含一些輸入信號沒有的訊雜信號，這種訊雜信號被集中到一塊現(xiàn)象統(tǒng)稱為失真。------ 失真的類型很多，最常見的兩種失真是調(diào)諧失真和交調(diào)失真，額外的無用信號通常被成為失真，所有的放大器都能產(chǎn)生一定量的噪音，更詳細(xì)的內(nèi)容將在以后介紹。 放大器 所有放大器都有一定放大系數(shù)，它的基本單位被稱為瓦特。放大器的系數(shù)決定了它的負(fù)載阻抗，它的基本單位被稱為歐姆。常用的阻抗有8歐姆、4歐姆、2歐姆，當(dāng)?shù)妥杩关?fù)載被使用時放大器的放大系數(shù)會更高。 在早期，放大器設(shè)備是電子管來實現(xiàn)的，電子管很少被使用在DJ中，現(xiàn)代放大器都使用的是晶體管，晶體管和真空放大器在信號傳輸過程中經(jīng)歷了相似的過程，但他們工作環(huán)境有一些區(qū)別，電子管一般是高壓低流，而晶體管則相反，電子管的效率不是很高，并且會發(fā)熱，電子管放大器與晶體管放大器的一個最大的區(qū)別是真空放大器在音頻輸出上要求更高，高品質(zhì)的音頻傳輸器是很難設(shè)計的，設(shè)計起來更困難，更昂貴。晶體管放大器比電子管放大器更有實用價值，因為它具有高效、小而耐用，沒有音頻的傳輸是必須的，晶體管不需要周期性替換，與人們所通常認(rèn)為不同的是，好的電子管放大器能產(chǎn)生高品質(zhì)的聲音，有些人認(rèn)為電子管有他們獨特的“聲音”。這個“聲音”是當(dāng)他們達(dá)到極限時產(chǎn)生的結(jié)果。晶體管放大器代替了電子管放大器是有很大益處的。 放大器的種類 放大器的種類通常是按照放大電路來設(shè)計的，在音頻放大有許多種類，下面簡要介紹常用放大器的種類 A類 A類具有非常低的失真，盡管他們效率非常低，很少用在高效率放大器中。它的失真很低是因為當(dāng)空載時放大器工作在放大區(qū)的中點，結(jié)果，許多能量在無信號輸入時已經(jīng)被消耗掉了，因為A類放大器具有低失真的特性，所以常常當(dāng)在放大器的前級，作為在電路中信號到達(dá)電壓擺動的極限時，A類放大器的失真產(chǎn)生了消波，A類放大器是通過電容偶合連接揚聲器的。 B類 B類放大器通常被使用在廉價、低品質(zhì)設(shè)計中，比起A類放大器，B類放大器有更高的效率，然而，當(dāng)信號弱時會產(chǎn)生交迭失真，B類常常用在經(jīng)濟(jì)型電路中。在IC放大器出現(xiàn)之前，B類放大器一般用在收音機電路，便攜式收音機以及對音質(zhì)要求不高的電路中。 AB類 AB類在家庭立體聲和相似放大器最常用的一種放大器，AB類放大器綜合了A類B類放大器的優(yōu)點。它具有B類放大器的高效率和A類放大器的低失真。克服了B類弱信號失真和A類的削波失真。AB類