【正文】 回路產(chǎn)生的本地信號(hào)一并送入混頻器，再經(jīng)中頻回路進(jìn)行頻率選擇，得到一固定的中頻載波（如：調(diào)幅中頻國際上統(tǒng)一為 465KHz 或 455KHz）調(diào)制波。 由于高放式收音機(jī)中高頻放大器只能適應(yīng)較窄頻率范圍的放大，要想在整個(gè)中波 頻段535kHZ— 1605kHZ 獲得一致放大是很困難的。經(jīng)高頻放大電路放大后，通過由二極管 D 和濾波電容 C1 構(gòu)成的檢波電路，將調(diào)幅信號(hào)包絡(luò)解調(diào)下來，得到調(diào)制前的音頻信號(hào)，再將音頻信號(hào)進(jìn)行低頻放大，送到喇叭，就完全還原成可聞的聲波信號(hào)。 廣播電臺(tái)播出節(jié)目是首先把聲音通過話筒轉(zhuǎn)換成音頻電信號(hào)，經(jīng)放大后 被高頻信號(hào)（載波）調(diào)制，這時(shí)高頻載波信號(hào)的某一參量隨著音頻信號(hào)作相應(yīng)的變化，使我們要傳送的音頻信號(hào)包含在高頻載波信號(hào)之內(nèi)，高頻信號(hào)再經(jīng)放大，然后高頻電流流過天線時(shí)，形成無線電波向外發(fā)射，無線電波傳播速度為 3108m/s ，這種無線電波被收音機(jī)天線接收，然后經(jīng)過放大、解調(diào)，還原為音頻電信號(hào)，送入喇叭音圈中，引起紙盆相應(yīng)的振動(dòng)，就可以還原聲音，即是聲電轉(zhuǎn)換傳送 —— 電聲轉(zhuǎn)換的過程。自 1920 年開發(fā)了無線電廣播的半個(gè)多世紀(jì)中，收音機(jī)經(jīng)歷了電子管收音機(jī)、晶體管收音機(jī)、集成電路收音機(jī)的三代變化，功能日趨增多，質(zhì)量日益提高。目前的無線電接收機(jī)不單只能收音，且還有可以接收影像的電視機(jī)、數(shù)字信息的電報(bào)機(jī)等。 【關(guān)鍵詞】 調(diào)頻收音機(jī)發(fā)展、調(diào)頻收音機(jī)、調(diào)頻收音機(jī)設(shè)計(jì) III Abstract Along with the development of science and technology, FM radios are widely used, especially consumer accounts for a sizeable market. Separation of ponents from the radio ponent of the integrated circuit ponents from the radio, FM radio technology has reached a very mature stage. From the ordinary AM radios to senior FM radios, FM radio to a higher technological content and high sound quality has been widely weled. The main research topics FM radio entire process of design, the circuit of the position, function, performance and principle. Design methods used two IC TA7335P and FS2204, the circuit design of a simple change. The main design ideas : from antenna input circuit, highfrequency amplifier, mixer circuit, the machine oscillation circuit, IF amplifier, Kamfrequency circuit, lowfrequency power amplifier, loudspeakers ponent. Design results of this project, basically meet the requirements with performance indicators. The shortings of the circuit noise is the sound quality, there is little distortion circuit, and so on, need to improve. 【 Key Words】 FM radio, FM radio, FM radio design IV 目錄 前言 ......................................................................................................................................................................1 第一章 收音機(jī)的基本工作原理 ....................................................................................................................2 最簡 收音機(jī)原理 ....................................................................................................................................2 超外差式收音機(jī) 原理 ............................................................................................................................2 第二章 調(diào)諧回路 ..............................................................................................................................................5 . 輸入調(diào)諧回路的作用與要求 .............................................................................................................5 輸入調(diào)諧回路的組成與工作原理 ....................................................................................................5 第三章 變頻回路 ...........................................................................................................................................6 變頻電路的作用與要求 .......................................................................................................................6 變頻電路的組成與變頻原理 ...............................................................................................................6 第四章 中頻放大電路、檢波和自動(dòng)控制增益電路 ...............................................................................9 中頻放電路 .............................................................................................................................................9 檢波和自動(dòng)控制增益電路 .............................................................................................................. 10 第五章 低放級(jí)與功放級(jí) ........................................................................................................................... 13 低放級(jí)電路 ........................................................................................................................................ 13 功率放大電路 .................................................................................................................................... 14 第六章 收音機(jī)的安裝與焊接 ................................................................................................................... 15 安裝注意事項(xiàng) .................................................................................................................................... 15 易發(fā)生的錯(cuò)誤 .................................................................................................................................... 15 元件的焊接 ........................................................................................................................................ 16 ............................................................................................................................................... 16 第七章 收音機(jī)調(diào)試流程 ........................................................................................................................... 18 檢查電路 ............................................................................................................................................ 18 收音機(jī)的調(diào)試 .................................................................................................................................... 18 出現(xiàn)的問題 ........................................................................................................................................ 20 總結(jié) ................................................................................................................................................................... 21 致謝 ................................................................................................................................................................... 22 參考文獻(xiàn) .......................................................................................................................................................... 23 附錄 ...................................................................