煤礦岔道報警系統(tǒng)的設(shè)計與仿真

中國礦業(yè)大學(xué)徐海學(xué)院2015屆本科生畢業(yè)論文中國礦業(yè)大學(xué)徐海學(xué)院本科生畢業(yè)設(shè)計姓名：學(xué)號：_____________學(xué)院：中國礦業(yè)大學(xué)徐海學(xué)院_______專業(yè)：_______電氣工程及其自動化_________設(shè)計題目：____煤礦電機車岔道報警系統(tǒng)研究_____專題：___________________________________指導(dǎo)教師：職稱：_____________2016年6月徐州中國礦業(yè)大學(xué)徐海學(xué)院畢業(yè)論文任務(wù)書專業(yè)年級學(xué)號學(xué)生姓名__________任務(wù)下達日期：2015年12月5日畢業(yè)論文日期：2016年3月7日至2016年6月9日畢業(yè)論文題目：畢業(yè)論文專題題目：畢業(yè)論文主要內(nèi)容和要求：第一章首先介紹了課題的應(yīng)用背景然后總結(jié)了運用在車輛上的測距方法研究現(xiàn)狀,并對各自應(yīng)用情況和常用背景建模方法做了綜述。第二章首先分析了系統(tǒng)總體功能需求,比較了多種設(shè)計方案然后根據(jù)要求,確定系統(tǒng)設(shè)計方案,并進行總體設(shè)計最后介紹了系統(tǒng)的主要功能芯片。第三章首先闡明了基于的系統(tǒng)硬件架構(gòu)然后具體說明液晶顯示模塊等。第四章首先說明了單片機系統(tǒng)的軟件開發(fā)環(huán)境和調(diào)試工具然后詳細(xì)闡述了單片機控制程序等。第五章首先介紹調(diào)試的一般流程，分別從軟硬件角度對煤礦岔道報警系統(tǒng)進行調(diào)試，得到結(jié)論。第六章首先說明了系統(tǒng)開發(fā)與調(diào)試中遇到的主要問題,并給出解決方法然后對本人所完成的工作和本文創(chuàng)新點做了總結(jié),并提出今后進一步研究的方向。指導(dǎo)教師簽字：中國礦業(yè)大學(xué)徐海學(xué)院2015屆本科生畢業(yè)論文鄭重聲明本人所呈交的畢業(yè)論文，是在導(dǎo)師的指導(dǎo)下，獨立進行研究所取得的成果。所有數(shù)據(jù)、圖片資料真實可靠。盡我所知，除文中已經(jīng)注明引用的內(nèi)容外，本畢業(yè)論文的研究成果不包含他人享有著作權(quán)的內(nèi)容。對本論文所涉及的研究工作做出貢獻的其他個人和集體，均已在文中以明確的方式標(biāo)明。本論文屬于原創(chuàng)。本畢業(yè)論文的知識產(chǎn)權(quán)歸屬于培養(yǎng)單位。本人簽名：日期：_____________中國礦業(yè)大學(xué)徐海學(xué)院畢業(yè)論文指導(dǎo)教師評閱書指導(dǎo)教師評語（①基礎(chǔ)理論及基本技能的掌握；②獨立解決實際問題的能力；③研究內(nèi)容的理論依據(jù)和技術(shù)方法；④取得的主要成果及創(chuàng)新點；⑤工作態(tài)度及工作量；⑥總體評價及建議成績；⑦存在問題；⑧是否同意答辯等）：成績：指導(dǎo)教師簽字：年月日中國礦業(yè)大學(xué)徐海學(xué)院畢業(yè)論文評閱教師評閱書評閱教師評語（①選題的意義；②基礎(chǔ)理論及基本技能的掌握；③綜合運用所學(xué)知識解決實際問題的能力；④工作量的大小；⑤取得的主要成果及創(chuàng)新點；⑥寫作的規(guī)范程度；⑦總體評價及建議成績；⑧存在問題；⑨是否同意答辯等）：成績：評閱教師簽字：年月日中國礦業(yè)大學(xué)徐海學(xué)院畢業(yè)論文答辯及綜合成績答辯情況提出問題回答問題答辯委員會評語及建議成績：答辯委員會主任簽字：年月日學(xué)院領(lǐng)導(dǎo)小組綜合評定成績：學(xué)院領(lǐng)導(dǎo)小組負(fù)責(zé)人：年月日中國礦業(yè)大學(xué)徐海學(xué)院2016屆本科生畢業(yè)論文目錄1緒論 附錄1附錄2#include<reg52.h>#include<intrins.h>#include<absacc.h>#include"ad.h"#defineLcd_BusP0#defineDisp_On0x3f//開顯示#defineDisp_Off0x3e//關(guān)顯示#defineCol_Add0x40//列地址#definePage_Add0xb8//頁地址#defineStart_Line0xc0//起始頁#defineucharunsignedchar#defineuintunsignedint#defineulongunsignedlongsbitTrig=P1^0;//產(chǎn)生脈沖引腳//sbitEcho=P3^2;//回波引腳sbitcs1=P2^3;sbitcs2=P2^4;sbitEnable=P2^2;sbitDi=P2^0;sbitRW=P2^1;sbitLcd_Rst=P2^5;sbitbeep=P2^7;ucharge,shi,bai,temp,outcomeH,outcomeL;//自定義變量bitsucceed_flag;//測量成功標(biāo)志/*****************************字模,此字體下對應(yīng)的點陣為：寬=16x16*****************************/unsignedcharcodeChinese_character[][32]={/*--文字:徐--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*/0x10,0x88,0xC4,0x33,0x00,0x20,0x10,0x28,0x24,0xE3,0x24,0x28,0x10,0x20,0x20,0x00,0x01,0x00,0xFF,0x00,0x20,0x11,0x0D,0x41,0x81,0x7F,0x01,0x05,0x09,0x31,0x00,0x00,/*--文字:海--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*/0x10,0x60,0x02,0x0C,0xC0,0x10,0x08,0xF7,0x14,0x54,0x94,0x14,0xF4,0x04,0x00,0x00,0x04,0x04,0x7C,0x03,0x00,0x01,0x1D,0x13,0x11,0x55,0x99,0x51,0x3F,0x11,0x01,0x00,/*--文字:學(xué)--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*/0x40,0x30,0x11,0x96,0x90,0x90,0x91,0x96,0x90,0x90,0x98,0x14,0x13,0x50,0x30,0x00,0x04,0x04,0x04,0x04,0x04,0x44,0x84,0x7E,0x06,0x05,0x04,0x04,0x04,0x04,0x04,0x00,/*--文字:院--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*/0x00,0xFE,0x22,0x5A,0x86,0x10,0x0C,0x24,0x24,0x25,0x26,0x24,0x24,0x14,0x0C,0x00,0x00,0xFF,0x04,0x08,0x07,0x80,0x41,0x31,0x0F,0x01,0x01,0x3F,0x41,0x41,0x71,0x00,/*--文字:王--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*/0x00,0x02,0x82,0x82,0x82,0x82,0x82,0xFE,0x82,0x82,0x82,0x82,0x82,0x02,0x00,0x00,0x40,0x40,0x40,0x40,0x40,0x40,0x40,0x7F,0x40,0x40,0x40,0x40,0x40,0x40,0x40,0x00,/*--文字:凱--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*/0x5E,0x50,0x50,0x5F,0x50,0x50,0xDE,0x00,0xFE,0x02,0x02,0xFE,0x00,0x00,0x00,0x00,0x00,0x7E,0x42,0x22,0x22,0x12,0x93,0x60,0x1F,0x00,0x00,0x3F,0x40,0x40,0x78,0x00,/*--文字:歌--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*/0x82,0xBA,0xAA,0xAA,0xBA,0x82,0xBE,0x82,0x20,0x18,0x0F,0xC8,0x08,0x28,0x18,0x00,0x00,0x1E,0x12,0x12,0x5E,0x80,0x7F,0x00,0x80,0x60,0x1C,0x03,0x1C,0x60,0x80,0x00,///*--文字:畢--*////*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*///0x00,0x00,0xFF,0x88,0x88,0x48,0x48,0x00,0x7F,0x88,0x84,0x84,0x82,0xE0,0x00,0x00,//0x04,0x04,0x05,0x04,0x04,0x04,0x04,0xFF,0x04,0x04,0x04,0x04,0x04,0x04,0x04,0x00,/*--文字:電--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*/0x00,0x00,0xF8,0x88,0x88,0x88,0x88,0xFF,0x88,0x88,0x88,0x88,0xF8,0x00,0x00,0x00,0x00,0x00,0x1F,0x08,0x08,0x08,0x08,0x7F,0x88,0x88,0x88,0x88,0x9F,0x80,0xF0,0x00,/*--文字:機--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*/0x10,0x10,0xD0,0xFF,0x90,0x10,0x00,0xFE,0x02,0x02,0x02,0xFE,0x00,0x00,0x00,0x00,0x04,0x03,0x00,0xFF,0x00,0x83,0x60,0x1F,0x00,0x00,0x00,0x3F,0x40,0x40,0x78,0x00,///*--文字:車--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*/0x00,0x08,0x88,0x48,0x28,0x18,0x0F,0xE8,0x08,0x08,0x08,0x08,0x08,0x08,0x00,0x00,0x08,0x08,0x09,0x09,0x09,0x09,0x09,0xFF,0x09,0x09,0x09,0x09,0x09,0x08,0x08,0x00,/*--文字:岔--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*/0x10,0x10,0x08,0x84,0x4A,0x39,0x08,0x08,0x88,0x09,0xFA,0x04,0x08,0x10,0x10,0x00,0x00,0x01,0x79,0x40,0x40,0x40,0x40,0x7E,0x40,0x41,0x40,0x40,0xF8,0x00,0x00,0x00,///*--文字:道--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*/0x40,0x40,0x42,0xCC,0x00,0x08,0xE9,0xAA,0xB8,0xA8,0xA8,0xAA,0xE9,0x08,0x00,0x00,0x00,0x40,0x20,0x1F,0x20,0x40,0x5F,0x4A,0x4A,0x4A,0x4A,0x4A,0x5F,0x40,0x40,0x00,/*--文字:報--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*/0x10,0x10,0x10,0xFF,0x10,0x90,0x00,0xFE,0x82,0x82,0x82,0x92,0xA2,0x9E,0x00,0x00,0x04,0x44,0x82,0x7F,0x01,0x00,0x00,0xFF,0x80,0x43,0x2C,0x10,0x2C,0x43,0x80,0x00,///*--文字:警--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*/0x12,0xEA,0xAF,0xAA,0xEA,0x0F,0xFA,0x02,0x88,0x8C,0x57,0x24,0x54,0x8C,0x84,0x00,0x02,0x02,0xEA,0xAA,0xAA,0xAB,0xAA,0xAB,0xAA,0xAA,0xAA,0xAA,0xEA,0x02,0x02,0x00,/*--文字:距--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*/0x00,0x3E,0x22,0xE2,0x22,0x3E,0x00,0xFE,0x22,0x22,0x22,0x22,0x22,0xE2,0x02,0x00,0x40,0x7F,0x20,0x3F,0x11,0x11,0x00,0x7F,0x42,0x42,0x42,0x42,0x42,0x43,0x40,0x00,/*--文字:離--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*/0x00,0x04,0x04,0xF4,0x84,0xCC,0xAD,0x96,0x94,0xAC,0xCC,0x84,0xF4,0x06,0x04,0x00,0x00,0x00,0xFE,0x02,0x1A,0x16,0x12,0x13,0x12,0x16,0x1A,0x72,0x82,0x7E,0x00,0x00,/*--文字:危--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*/0x00,0x20,0x10,0xE8,0x24,0x27,0xA4,0xA4,0xA4,0xA4,0xB4,0xAC,0x20,0x20,0x00,0x00,0x80,0x40,0x30,0x0F,0x00,0x00,0x3F,0x40,0x40,0x44,0x48,0x47,0x40,0x70,0x00,0x00,/*--文字:險--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=16x16--*/0x00,0xFE,0x22,0x5A,0x86,0x40,0x20,0x50,0x4C,0x43,0x4C,0x50,0x20,0x40,0x40,0x00,0x00,0xFF,0x04,0x08,0x07,0x40,0x44,0x58,0x41,0x4E,0x60,0x58,0x47,0x40,0x40,0x00,};unsignedcharcodeE[][16]={/*--文字:0--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=8x16--*/0x00,0xE0,0x10,0x08,0x08,0x10,0xE0,0x00,0x00,0x0F,0x10,0x20,0x20,0x10,0x0F,0x00,/*--文字:1--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=8x16--*/0x00,0x10,0x10,0xF8,0x00,0x00,0x00,0x00,0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00,/*--文字:2--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=8x16--*/0x00,0x70,0x08,0x08,0x08,0x88,0x70,0x00,0x00,0x30,0x28,0x24,0x22,0x21,0x30,0x00,/*--文字:3--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=8x16--*/0x00,0x30,0x08,0x88,0x88,0x48,0x30,0x00,0x00,0x18,0x20,0x20,0x20,0x11,0x0E,0x00,/*--文字:4--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=8x16--*/0x00,0x00,0xC0,0x20,0x10,0xF8,0x00,0x00,0x00,0x07,0x04,0x24,0x24,0x3F,0x24,0x00,/*--文字:5--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=8x16--*/0x00,0xF8,0x08,0x88,0x88,0x08,0x08,0x00,0x00,0x19,0x21,0x20,0x20,0x11,0x0E,0x00,/*--文字:6--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=8x16--*/0x00,0xE0,0x10,0x88,0x88,0x18,0x00,0x00,0x00,0x0F,0x11,0x20,0x20,0x11,0x0E,0x00,/*--文字:7--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=8x16--*/0x00,0x38,0x08,0x08,0xC8,0x38,0x08,0x00,0x00,0x00,0x00,0x3F,0x00,0x00,0x00,0x00,/*--文字:8--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=8x16--*/0x00,0x70,0x88,0x08,0x08,0x88,0x70,0x00,0x00,0x1C,0x22,0x21,0x21,0x22,0x1C,0x00,/*--文字:9--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=8x16--*/0x00,0xE0,0x10,0x08,0x08,0x10,0xE0,0x00,0x00,0x00,0x31,0x22,0x22,0x11,0x0F,0x00,/*--文字:c--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=8x16--*/0x00,0x00,0x00,0x80,0x80,0x80,0x00,0x00,0x00,0x0E,0x11,0x20,0x20,0x20,0x11,0x00,/*--文字:m--*//*--宋體12;此字體下對應(yīng)的點陣為：寬x高=8x16--*/0x80,0x80,0x80,0x80,0x80,0x80,0x80,0x00,0x20,0x3F,0x20,0x00,0x3F,0x20,0x00,0x3F,};voiddelay_20us(){ucharbt;for(bt=0;bt<200;bt++);}/***************************************************************///外部中斷0，用做判斷回波電平INTO_()interrupt0//外部中斷是0號{outcomeH=TH1;//取出定時器的值outcomeL=TL1;//取出定時器的值succeed_flag=1;//至成功測量的標(biāo)志EX0=0;//關(guān)閉外部中斷}/***********************延時子程序***********************/voiddelay(unsignedintk){unsignedinti;unsignedintj;for(i=0;i<k;i++)for(j=0;j<20;j++);}/***********************寫命令左***********************/voidwrite_cmd_1(unsignedcharcommand){cs1=1;cs2=0;Di=0;RW=0;Lcd_Bus=command;delay(0);Enable=1;delay(0);Enable=0;}/***********************寫命令右***********************/voidwrite_cmd_2(unsignedcharcommand){cs1=0;cs2=1;Di=0;RW=0;Lcd_Bus=command;delay(0);Enable=1;delay(0);Enable=0;}/***********************寫數(shù)據(jù)左***********************/voidwrite_data_1(unsignedchardis_data){cs1=1;cs2=0;Di=1;RW=0;Lcd_Bus=dis_data;delay(0);Enable=1;delay(0);Enable=0;}/***********************寫數(shù)據(jù)右***********************/voidwrite_data_2(unsignedchardis_data){cs1=0;cs2=1;Di=1;RW=0;Lcd_Bus=dis_data;delay(0);Enable=1;delay(0);Enable=0;}/***********************清內(nèi)存左***********************/voidclear_1(void){unsignedcharj,k;cs1=1;cs2=0;write_cmd_1(Page_Add+0);write_cmd_1(Col_Add+0);for(k=0;k<8;k++){write_cmd_1(Page_Add+k);for(j=0;j<64;j++)write_data_1(0x00);}}/***********************清內(nèi)存右***********************/voidclear_2(void){unsignedcharj,k;cs1=0;cs2=1;write_cmd_2(Page_Add+0);write_cmd_2(Col_Add+0);for(k=0;k<8;k++){write_cmd_2(Page_Add+k);for(j=0;j<64;j++)write_data_2(0x00);}}/***********************顯示漢字16*16左************************/voidChinese_disp_1(unsignedcharpag,unsignedcharcol,unsignedcharn){unsignedchari=0;unsignedcharj=0;cs1=1;cs2=0;for(i=0;i<2;i++){write_cmd_1(Page_Add+pag+i);write_cmd_1(Col_Add+col);for(j=0;j<16;j++)write_data_1(Chinese_character[n][16*i+j]);}}/***********************顯示漢字16*16右***********************/voidChinese_disp_2(unsignedcharpag,unsignedcharcol,unsignedcharn){unsignedchari=0;unsignedcharj=0;cs1=0;cs2=1;for(i=0;i<2;i++){write_cmd_2(Page_Add+pag+i);write_cmd_2(Col_Add+col);for(j=0;j<16;j++)write_data_2(Chinese_character[n][16*i+j]);}}/***********************顯示英文16*8左************************/voidE_disp_1(unsignedcharpag,unsignedcharcol,unsignedcharn){unsignedchari=0;unsignedcharj=0;cs1=1;cs2=0;for(i=0;i<2;i++){write_cmd_1(Page_Add+pag+i);write_cmd_1(Col_Add+col);for(j=0;j<8;j++)write_data_1(E[n][8*i+j]);}}/***********************顯示英文16*8右***********************/voidE_disp_2(unsignedcharpag,unsignedcharcol,unsignedcharn){unsignedchari=0;unsignedcharj=0;cs1=0;cs2=1;for(i=0;i<2;i++){write_cmd_2(Page_Add+pag+i);write_cmd_2(Col_Add+col);for(j=0;j<8;j++)write_data_2(E[n][8*i+j]);}}/***********************液晶屏初始化***********************/voidinit_lcd(){Lcd_Rst=0;delay(100);Lcd_Rst=1;delay(100);write_cmd_1(Disp_Off);write_cmd_2(Disp_Off);write_cmd_1(Page_Add+0);write_cmd_2(Page_Add+0);write_cmd_1(Start_Line+0);write_cmd_2(Start_Line+0);write_cmd_1(Col_Add+0);write_cmd_2(Col_Add+0);write_cmd_1(Disp_On);write_cmd_2(Disp_On);}/***********************LCD顯示子程序***********************/voidad_display(ucharcj_data){ucharge_data,shi_data,bai_data;bai_data=cj_data/100;//取余運算shi_data=cj_data%100/10;//取余運算ge_data=cj_data%10;E_disp_2(4,0,bai_data);E_disp_2(4,8,shi_data);//2009042203E_disp_2(4,16,ge_data);E_disp_2(4,32,11);//cm}voiddisplay(ucharudata){unsignedchari;for(i=Start_Line;i<0xff;i++){//E_disp_1(0,0,0);//E_disp_1(0,8,0); //09Chinese_disp_1(0,0,0);Chinese_disp_1(0,16,1);Chinese_disp_1(0,32,2);Chinese_disp_1(0,48,3);Chinese_disp_2(0,16,4);Chinese_disp_2(0,32,5);Chinese_disp_2(0,48,6);Chinese_disp_1(2,0,7);Chinese_disp_1(2,16,8);Chinese_disp_1(2,32,9); //學(xué)號：Chinese_disp_1(2,48,10);Chinese_disp_2(2,0,11);Chinese_disp_2(2,16,12);Chinese_disp_2(2,32,13);Chinese_disp_1(4,0,14);Chinese_disp_1(4,16,15);Chinese_disp_1(6,32,16);Chinese_disp_2(6,16,17); ad_display(udata);//E_disp_2(4,0,2);//E_disp_2(4,8,3);//2009042203//E_disp_2(4,16,7);//E_disp_2(4,32,11);//cm//write_cmd_1(i);//write_cmd_2(i);//delay(3000);//調(diào)整滾動速度}}/***********主程序************/ucharad_zhi=0;voidmain(void){P1=0XFF;init_lcd();clear_1();clear_2();while(1){ad_zhi=ad_get();if((ad_zhi<60))//(ad_zhi>60)||{ beep=1;}elsebeep=0;display(ad_zhi);//cbs();}}翻譯部分英文原文RadioReceiverAblockdiagramforamodernradioreceiverisshowninFig..2-4.Theinputsignalstothisradioareamplitude-modulatedradiowaves.Thebasicelectroniccircuitsinclude:antenna,tuner,mixer,localoscillator,IFamplifier,audiodetector,AFamplifier,loudspeaker,andpowersupply.Fig.2-4ABlockDiagramForModernRadioReceiverAnyantennasystemcapableofradiatingelectricalenergyisalsoabletoabstractenergyfromapassingradiowave.Sinceeverywavepassingthereceivingantenna.Inducesitsownvoltageintheantennaconductor,itisnecessarythatthereceivingequipmentbecapableofseparatingthedesiredsignalfromtheunwantedsignalsthatarealsoinducingvoltagesintheantenna.Thisseparationismadeonthebasisofthedifferenceinfrequencybetweentransmittingstationsandiscarriedoutbytheuseofresonantcircuits,whichcanbemadetodiscriminateverystronglyinfavorofaparticularfrequency.Ithasalreadybeenpointedthat,bymakingantennacircuitresonanttoaparticularfrequency,theenergyabstractedfromradiowavesofthatfrequencywillbemuchgreaterthantheenergyfromwavesofotherfrequencies;thisalonegivesacertainamountofseparationbetweensignals.Stillgreaterselectiveactioncanbeobtainedbytheuseofadditionalsuitablyadjustedresonantcircuitslocatedsomewhereinthereceiverinsuchawayastorejectallbutthedesiredsignal.Theabilitytodiscriminatebetweenradiowavesofdifferentfrequenciesiscalledselectivityandtheprocessofadjustingcircuitstoresonancewiththefrequencyofadesiredsignalisspokenofastuning.Althoughintelligibleradiosignalshavebeenreceivedfromthestationsthousandsofmilesdistant,usingonlytheenergyabstractedfromtheradiowavebythereceivingantennamuchmoresatisfactoryreceptioncanbeobtainedifthereceivedenergyisamplified.Thisamplificationmaybeappliedtotheradio-frequencycurrentsbeforedetection,inwhichcaseitiscalledradio-frequencyamplificationoritmaybeappliedtotherectifiedcurrentsafterdetection,inwhichcaseitiscalledaudio-frequencyamplification.Theuseofamplificationmakespossiblethesatisfactoryreceptionofsignalsfromwavesthatwouldotherwisebetooweaktogiveanaudibleresponse.Theprocessbywhichthesignalbeingtransmittedisreproducedfromtheradio-frequencycurrentspresentatthereceiveriscalleddetection,orsometimesdemodulation.Wheretheintelligenceistransmittedbyvaryingtheamplitudeoftheradiatedwave,detectionisaccomplishedbyrectifyingtheradiofrequencycurrent.Therectifiedcurrentthusproducedvariesinaccordancewiththesignaloriginallymodulatedonthewaveirradiatedatthetransmitterandsoreproducesthedesiredsignal.Thus,whenthemodulatedwaveisrectified,theresultingcurrentisseentohaveanaveragevaluethatvariesinaccordancewiththeamplitudeoftheoriginalsignal.Receivercircuitaremadeupaofanumberofstages.Astageisasingletransistorconnectedtocomponentswhichprovideoperatingvoltagesandcurrentsandalsosignalvoltagesandcurrents.Eachstagehasitsinputcircuitfromwhichthesignalcomesinanditsoutputcircuitfromwhichthesignal,usuallyamplified,goesout.Whenonestagefollowsanother,theoutputcircuitofthefirstfeedsthesignaltothesecond.Andsothesignalisamplified,stagebystage,untilitstrongenoughtooperatetheloudspeaker.RadioWavesRadioWavesareamemberoftheelectromagneticofwaves.Theyareenergy-carrierswhichtravelatthespeedoflight(ν),theirfrequency(?)andwavelength(λ)beingrelated,asforanywavemotion,bytheequationν=?*λwhereν=c=3.0*108m/sinavacuum(orair).Ifλ=300m,then?=ν/λ=3.0*108/(3.0*102)=106Hz=1MHz.Thesmallerλis,thelarger?.RadioWavescanbedescribedeitherbytheirfrequencyortheirwavelength.Buttheformerismorefundamentalsince,unlikeλ(andν),fdoesnotchangewhenthewavestravelformonemediumtoanother.RadioWavescantravelformatransmittingaerialinoneormoreofthreedifferentways.Surfaceorgroundwave..Thistravelsalongaground,thecurvatureoftheearth’ssurface.Itsrangeislimitedmainlybytheextenttowhichenergyisabsorbedformitbytheground.Poorconductorssuchassandabsorbmorestronglythatwater,andthehigherthefrequencythegreatertheabsorption.Therangemaybeabout1500kmatlowfrequencies(longwave,butmuchlessforv.h.f.).Skywave.Thistravelsskywardsand,ifitisbelowacertaincriticalfrequency(typically30MHz),isreturnedtoearthbytheionosphere.Thisconsistsoflayersofairmolecules(theD,EandFlayer),stretchingformabout80kmabovetheearthto50km,whichhavebecomepositivelychargedthroughtheremovalofelectronsbythesun’sultravioletradiation.Onstrikingtheearththeskywavebouncesbacktotheionospherewhereitisagaingraduallyrefractedandreturnedearthwardsasifby'reflection'.Thiscontinuesuntilitiscompletelyattenuated.Spacewave.Forv.h.f.,u.h.f.andmicrowavesignals,onlythespacewave,givingline-ofsighttransmission,iseffective.Arangeofupto150kmispossibleonearthifthetransmittingaerialisonhighgroundandtherearenointerveningobstaclessuchashills,buildingsortrees.OscillatorsElectricaloscillatorsarewidelyusedinradioandtelevisiontransmittersandreceivers,insignalgenerators,oscilloscopesandcomputers,toproduceA.C.withwaveformswhichmaybesinusoidal,square,sawtoothetc.andwithfrequenciesfromafewhertzuptomillionsofhertz.OscillatorycircuitWhenacapacitordischargesthroughaninductorinacircuitoflowresistance,anA.C.flows.Thecircuitissaidtooscillateatitsnaturalfrequencywhich,aswewillshowshortly,equals,i.e.itsresonantfrequencyf0.Electricalresonancethusoccurswhentheappliedfrequencyequalsthenaturalfrequencyasitdoesinamechanicalsystem..InFig,2-2(a),achargedcapacitorCisshownconnectedacrossacoilL.Cimmediatelystartstodischarge,currentflowsandamagneticfieldiscreatedwhichinducesane.m.f.inL.Thise.m.f.opposesthecurrent.WhenCiscompletelydischargedtheelectricalenergyoriginallystoredintheelectricfieldbetweenitsplateshasbeentransferredtothemagneticfieldaroundL.Bythetimethemagneticfieldhascollapsed,theenergyisagainstoredinC.OncemoreCstartstodischargebutcurrentnowflowsintheoppositedirection,creatingamagneticfieldofoppositepolarity.Whenthisfieldhasdecayed,Cisagainchargedwithitsupperplatepositiveandthesamecycleisrepeated.Intheabsenceofresistanceinanypartofthecircuit,anundampedsinusoidalA.C.wouldbeobtained.Inpractice,energyisgraduallydissipatedbyresistanceasheatandadampedoscillationisproduced.OscillatorAstheresistanceofanLCcircuitincreases,theoscillationdecaymorequickly.Toobtainundampedoscillations,energyhastobefedintotheLCcircuitinphasewithitsnaturaloscillationstocompensatefortheenergydissipatedintheresistanceofthecircuit.Thiscanbedonewiththehelpofatransistorinactualoscillators.AsimpletunedoscillatorisshowninFig.2-2(b).TheLCcircuitisconnectedinthecollectorcircuit(astheload)andoscillationsstartinitwhenthesupplyisswitchedon.Thefrequencyoftheoscillationsisgivenby,i.e.thennaturalfrequencyoftheLCcircuit.Thetransistormerelyensuresthatenergyisfedbackatthecorrectinstantfromthebattery.ThecurrentbiasforthebaseofthetransistorisobtainedthroughR.AMPLIFIERIntroductionThetermamplifierisverygeneric.Ingeneral,thepurposeofanamplifieristotakeaninputsignalandmakeitstronger(orinmoretechnicallycorrectterms,increaseitsamplitude).Amplifiersfindapplicationinallkindsofelectronicdevicesdesignedtoperformanynumberoffunctions.Therearemanydifferenttypesofamplifiers,eachwithaspecificpurposeinmind.Forexample,aradiotransmitterusesanRFAmplifier(RFstandsforRadioFrequency);suchanamplifierisdesignedtoamplifyasignalsothatitmaydriveanantenna.Thisarticlewillfocusonaudiopoweramplifiers.Audiopoweramplifiersarethoseamplifierswhicharedesignedtodriveloudspeakers.Specifically,thisdiscussionwillfocusonaudiopoweramplifiersintendedforDJandsoundreinforcementuse.Muchofthematerialpresentedalsoappliestoamplifiersintendedforhomestereosystemuse.Thepurposeofapoweramplifier,inverysimpleterms,istotakeasignalfromasourcedevice(inaDJsystemthesignaltypicallycomesfromapreamplifierorsignalprocessor)andmakeitsuitablefordrivingaloudspeaker.Ideally,theONLYthingdifferentbetweentheinputsignalandtheoutputsignalisthestrengthofthesignal.Inmathematicalterms,iftheinputsignalisdenotedasS,theoutputofaperfectamplifierisX*S,whereXisaconstant(afixednumber).The"*"symbolmeans?Multipliedby".Thisbeingtherealworld,noamplifierdoesexactlytheideal,butmanydoaverygoodjobiftheyareoperatedwithintheiradvertisedpowerratings.Theoutputofallamplifierscontainadditionalsignalcomponentsthatarenotpresentintheinputsignal;theseadditional(andunwanted)characteristicsmaybelumpedtogetherandaregenerallyknownasdistortion.Therearemanytypesofdistortion;howeverthetwomostcommontypesareknownasharmonicdistortionandintermodulationdistortion.Inadditiontothe"garbage"traditionallyknownasdistortion,allamplifiersgenerateacertainamountofnoise(thiscanbeheardasabackground"hiss"whennomusicisplaying).Moreontheselater.Allpoweramplifiershaveapowerrating,theunitsofpowerarecalledwatts.Thepowerratingofanamplifiermaybestatedforvariousloadimpedances;theunitsforloadimpedanceareohms.Themostcommonloadimpedancesare8ohms,4ohms,and2ohms(ifyouhaveanoldvacuumtubeamplifiertheloadimpedancesaremorelikelytobe32ohms,16ohms,8ohms,andmaybe4ohms).Thepoweroutputofamodernamplifierisusuallyhigherwhenlowerimpedanceloads(speakers)areused(butasweshallseelaterthisisnotnecessarilybetter).Intheearlydays,poweramplifiersuseddevicescalledvacuumtubes(referredtosimplyas"tubes"fromhereon).TubesareseldomusedinamplifiersintendedforDJuse(howevertubeamplifiershavealoyalfollowingwithmusiciansandhi-fienthusiasts).Modernamplifiersalmostalwaysusetransistors(insteadoftubes);inthelate60'sandearly70's,theterm"solidstate"wasused(andoftenengravedonthefrontpanelasa"buzzword").Thesignalpathinatubeamplifierundergoessimilarprocessingasthesignalinatransistoramp,howeverthedevicesandvoltagesarequitedifferent.Tubesaregenerally"highvoltagelowcurrent"devices,wheretransistorsaretheopposite("lowvoltagehighcurrent").Tubeamplifiersaregenerallynotveryefficientandtendtogeneratealotofheat.Oneofthebiggestdifferencesbetweenatubeamplifierandatransistoramplifieristhatanaudiooutputtransformerisalmostalwaysrequiredinatubeamplifier(thisisbecausetheoutputimpedanceofatubecircuitisfartoohightoproperlyinterfacedirectlytoaloudspeaker).Highqualityaudiooutputtransformersaredifficulttodesign,andtendtobelarge,heavy,andexpensive.Transistoramplifiershavenumerouspracticaladvantagesascomparedwithtubeamplifiers:theytendtobemoreefficient,smaller,morerugged(physically),noaudiooutputtransformerisrequired,andtransistorsdonotrequireperiodicreplacement(unlessyoucontinuallyabusethem).Contrarytowhatmanypeoplebelieve,awelldesignedtubeamplifiercanhaveexcellentsound(manyhighendhi-fienthusiastsswearbythem).Somepeopleclaimthattubeamplifiershavetheirownparticular"sound".This"sound"isaresultofthewaytubesbehavewhenapproachingtheiroutputlimits(clipping).Afewbigadvantagesthattubeamplifiershavewerenecessarilygivenupwhenamplifierswenttotransistors.WhatareAmplifierClasses?TheClassofanamplifierreferstothedesignofthecircuitrywithintheamp.Therearemanyclassesusedforaudioamps.Thefollowingisbriefdescriptionofsomeofthemorecommonamplifierclassesyoumayhaveheardof.ClassA:ClassAamplifiershaveverylowdistortion(lowestdistortionoccurswhenthevolumeislow)howevertheyareveryinefficientandarerarelyusedforhighpowerdesigns.Thedistortionislowbecausethetransistorsintheamparebiasedsuchthattheyarehalf"on"whentheampisidling.Asaresult,alotofpowerisdissipatedevenwhentheamphasnomusicplaying!ClassAampsareoftenusedfor"signal"levelcircuits(wherepowerissmall)becausetheymaintainlowdistortion.DistortionforclassAampsincreasesasthesignalapproachesclipping,asthesignalisreachingthelimitsofvoltageswingforthecircuit.Also,someclassAampshavespeakersconnectedviacapacitivecoupling.ClassB:ClassBamplifiersareusedinlowcost,lowqualitydesigns.ClassBamplifiersarealotmoreefficientthanclassAamps,howevertheysufferfrombaddistortionwhenthesignallevelislow(thedistortioniscalled"crossoverdistortion").ClassBisusedmostoftenwhereeconomyofdesignisneeded.BeforetheadventofICamplifiers,classBamplifierswerecommoninclockradiocircuits,pockettransistorradios,orotherapplicationswherequalityofsoundisnotthatcritical.ClassAB:ClassABisprobablythemostcommonamplifierclassforhomestereoandsimilaramplifiers.ClassABampscombinethegoodpointsofclassAandBamps.Theyhavethegoodefficien