【正文】 ., also use the infrared. These high speed switching fluorescent lamps and backlights emit those optical and radio noises with spectrum extending over 1 MHz, which are so intense as to damage the ASK infrared wireless system even with a 500 kHz subcarrier. Thus the conventional ASK system can not perform an error free link near these lamps. Considering that high speed switching fluorescent lamps and TFT displays are being popular, it is of primary importance to avoid this interference for practical use of the infrared munication.The present paper describes a new ASK digital demodulation scheme with the use of a 1bit digital demodulator, which can improve the noise immunity of the conventional ASK infrared receiver with a 500 kHz subcarrier. Section 2 overviews ASK infrared data munication systems, and section 3 analyzes the optical noises in conjunction with their interference with ASK signals. Base on the analysis, section 4 discusses the main defect of the conventional ASK receiver, and proposes a new ASK digital demodulation scheme to overe it. Section 5 models an infrared munication mechanism under optical noises, and then sim ulates the output waveforms of an infrared receiver. Section 6 first describes an algorithm for removing such noises from the output waveforms, and then constructs a digital demodulator on the basis of this algorithm by means of a high level synthesis tool COMPASS Design Navigator [3]. Based on the experimented results, section 7 first pares the performance of the proposed ASK receiver with the conventional one, and then shows that this series of modeling, simulation, and noise removal mechanisms approximates very well the actual phenomena of optical noises, and therefore our ASK receiver is of great use in practice.2. ASK infrared data munication systemThe asynchronous data transmission among puters is widely used in serial munication systems, as illustrated in figure 1. There are two signal lines in this configuration。 etc. Especially for the short range munication, the Infrared Data Association has established a standard specification, and a variety of notebook Personal Computers (PCs) and Personal Digital Assistants (PDAs) with infrared munication capability have been available on the market.The infrared munication has disadvantages as well. An artificiallight source, like a fluorescent lamp emits intense infrared noises, and hence a photodetector of an infrared receiver is exposed directly to such environmental noises. The optical noises in typical office environments are mainly due to the daylight and tungsten and fluorescent lamps [4]. The daylight and tungsten light are stationary or slowly fluctuating, and generate the shot noises in a photodetector. Thus in the design of the infrared link we should take a special account of not only thermal noises but also shot noises [2]. On the other hand, the optical noises emitted from a fluorescent lamp flicker on and off with the line frequency (50 Hz or 60 Hz), and their spectrum ranges from the DC to over 100 kHz [1]. These optical noises have broad wavelengths, including the infrared one. To remove the visible light portion of the optical noises, it is effective to insert an optical filter in front of a photodetector, since it can suppress the visible light noises. Modulating the infrared signal onto a carrier at a several hundred kHz by ASK or FSK (Frequency Shift Keying) is also effective for avoiding the interference by fluorescent lamps, since low frequency noises can be removed by an electrical filter. Actually, an ASK infrared wireless system using a 500 kHz subcarrier has been built in more than two million notebookPCs and PDAs [5].However, the optical noise environments have been changed for this decade. A fluorescent lamp switching around 100 kHz has been on the market。 facilitates low cost and low power consumption。 offers high speed link without regulation。s puter and munication technologies.There are two alternatives for wireless munication。 總之，這次畢業(yè)設(shè)計(jì)為我今后繼續(xù)學(xué)習(xí)、深造奠定了基礎(chǔ)，我非常感謝各位老師、同學(xué)的支持與幫助。 這次畢業(yè)設(shè)計(jì)雖然功能還有待完善，但這次設(shè)計(jì)進(jìn)一步提高了我的自學(xué)能力、思維能力，知識(shí)面得到了進(jìn)一步的擴(kuò)展，運(yùn)用了所學(xué)的書本知識(shí)并鞏固了所學(xué)的專業(yè)理論知識(shí)，給予了我一次實(shí)踐鍛煉的好機(jī)會(huì)，為我以后的學(xué)習(xí)和工作積累了很多經(jīng)驗(yàn)，：首先要有一個(gè)明確的設(shè)計(jì)目標(biāo)，并收集有關(guān)的素材，其次可以通過多條途徑得到幫助去獲取知識(shí)，如上網(wǎng)查閱所需資料，虛心向有經(jīng)驗(yàn)者請(qǐng)教，同時(shí)也要強(qiáng)化自身知識(shí)的學(xué)習(xí)和積累，然后再把理論與實(shí)踐相結(jié)合，把所學(xué)知識(shí)運(yùn)用到實(shí)際的生活之中。從問題的提出到設(shè)計(jì)完成的環(huán)節(jié)，使我了解了開發(fā)一個(gè)項(xiàng)目所需要的步驟，同時(shí)也使我對(duì)通信系統(tǒng)的軟件設(shè)計(jì)思想有了新的認(rèn)識(shí)，掌握了一些新的方法，對(duì)于一些日常問題也能夠進(jìn)行獨(dú)立的尋找并加以解決，而且自己動(dòng)手能力和自學(xué)能力也有了一定的提高。由于時(shí)間，能力，國內(nèi)通信技術(shù)資料有限等原因，有些功能實(shí)現(xiàn)的并不完美，在已經(jīng)完成的程序中，也存在許多不盡人意的算法，也沒有統(tǒng)一優(yōu)化，系統(tǒng)有待進(jìn)一步改善，而這些問題也讓我充分認(rèn)識(shí)到了系統(tǒng)設(shè)計(jì)的困難。同時(shí)，通過編寫畢業(yè)設(shè)計(jì)說明書，我還基本掌握了文檔的編寫方法和格式。了解到數(shù)字調(diào)制的過程以及它的原理。在這次畢業(yè)設(shè)計(jì)過程中，我獨(dú)立設(shè)計(jì)和實(shí)現(xiàn)了2ASK、2FSK、2PSK以及2DPSK這四種數(shù)字調(diào)制演示系統(tǒng)的設(shè)計(jì)。這說明該數(shù)字調(diào)制仿真模型演示系統(tǒng)是成功的、符合理論的。從2ASK、2FSK、2PSK和2DPSK仿真演示的可視窗口中可以看到的各種波形里，可以明顯的看出隨機(jī)產(chǎn)生的基帶信號(hào)經(jīng)過調(diào)制解調(diào)后波形根本沒有產(chǎn)生任何變化，由于在此演示系統(tǒng)中我們沒有加入噪聲，也就是說此系統(tǒng)不受噪聲的影響。、。y2。解調(diào)波形39。axis( [ 0 , *( ls + 1), 3*(1 / 2), 3*(1 / 2) ] )。global ls。global sign_orign。 )。title ( 39。axis( [ 0 , *( ls + 1), 3*(1 / 2), 3*(1 / 2) ] )。global ls。global st。 )。title ( 39。plot(t, sign_orign)。global t?；鶐盘?hào)：function pushbutton3_Callback(hObject, eventdata, handles)axes()cla。載波信號(hào)39。% axis([0,1,1])。x= cos ( 2 * pi * 30* t )。 2DPSK數(shù)字通信調(diào)制演示系統(tǒng)圖形用戶界面實(shí)現(xiàn)這些按鈕的Matlab 語言程序如下：載波信號(hào)：function pushbutton1_Callback(hObject, eventdata, handles)axes()cla。帶通濾波器乘法器低通濾波器抽樣判決器逆碼變換解調(diào)信號(hào)本地載波2DPSK已調(diào)信號(hào) 2DPSK信號(hào)的極性比較法解調(diào)原理框圖在空白圖形用戶界面上規(guī)劃2DPSK的載波信號(hào)按鈕、基帶信號(hào)按鈕、DPSK調(diào)制按鈕、DPSK解調(diào)按鈕、返回按鈕以及兩個(gè)圖形可視窗口。2DPSK已調(diào)信號(hào)帶通濾波器相乘器低通濾波器抽樣判決器解調(diào)信號(hào)延遲T 2DPSK信號(hào)的差分相干解調(diào)法原理框圖2DPSK機(jī)型比較法解調(diào)原理：。基帶信號(hào)差分變換反相器載波輸入選相開關(guān)已調(diào)信號(hào) 2DPSK信號(hào)的鍵控調(diào)制法原理框圖2DPSK差分相干解調(diào)法原理：。選相開關(guān)的作用是當(dāng)輸入數(shù)字信息“0”時(shí)接相位0，當(dāng)輸入數(shù)字信息為“1”時(shí)接π。載波信號(hào)： 載波信號(hào)基帶信號(hào)： 基帶信號(hào)PSK調(diào)制： PSK調(diào)制PSK解調(diào)： PSK解調(diào) 2DPSK調(diào)制演示系統(tǒng)設(shè)計(jì)2PSK和2DPSK 調(diào)制的原理是相同的，2DPSK可以看作是相對(duì)碼的2PSK調(diào)制，二相相對(duì)移相鍵控2DPSK的查考相位不是未調(diào)波的相位，而是相鄰的前一碼元的載波相位。close(h)。)返回：function pushbutton5_Callback(hObject, eventdata, handles)h=gcf。 title(39。 end end end plot(t,psk)。 end else for j=m*500+1:(m+1)*500。 for