【正文】 m) short, it was also According to the homophonic Modem, affectionately known as cat. 它是一個(gè)將以得到數(shù)字信息的電子設(shè)備。 Its goal is to produce to facilitate the transmission of analog signals and can be restored by decoding the original digital data. 工作原理、操縱面板及電源等部分組成。接口 Line the two sides can municate thousands of miles away from each call is given in regular intervals are equipped with relay amplification equipment to ensure clear voice. 在這些設(shè)備上若再配置Modem，則能通電話的地方就可傳輸數(shù)據(jù)。 Usually there are three ways of working Modem: hang up mode, call mode, online. 電話線未接通是掛機(jī)方式；雙方通過電話進(jìn)行通話是通話方式；Modem已聯(lián)通，進(jìn)行數(shù)據(jù)傳輸是聯(lián)機(jī)方式。音頻 receiver, the signal logic 0, Frequency 20 25Hz, the signal logic 1, frequency of 2225Hz. (2)相移鍵控(PSK) ：高速的Modem常用四相制，八相制，而四相制是用四個(gè)不同的相位表示00、011四個(gè) The technology allows 3 00bps to 600bps Modem transmission of information, and therefore not only improve the line to improve the signal modulation rate when the transmission rate makes sense, but the control plexity, high cost, eightphase system more plex. (3)相位幅度調(diào)制(PAM) ：為了盡量提高傳輸速率，不提高調(diào)制速率，采用相位調(diào)制和幅度調(diào)制結(jié)合的方法。過程進(jìn)入聯(lián)機(jī)方式。 Modem and puter to connect the data circuit munications equipment DCE and data terminal equipment DTE the interface between. DCE與DTE之間的接口是計(jì)算機(jī)網(wǎng)絡(luò)使用上的一個(gè)重要問題。 DTE data terminal equipment connected with the analog channels called data circuit equipment munications equipment DCE, as the Modem is DCE. DTE與DCE之間的連接標(biāo)準(zhǔn)有CC IT ，與EIARS423A兼容，是一種半平衡電氣特性接口 The connection between the DTE and DCE standards CC IT , and EIARS423A patible, is a semibalanced electrical characteristics of interfaces 普通的Modem通常都是通過RS232C串行口信號(hào)線與計(jì)算機(jī) (RS RemendStandard this is the abbreviation), which in 1969 recognized by the international organization. RS232的定義包括電氣特性(如電壓值)、機(jī)械特性(如接頭形狀)及功能特性(如腳位信號(hào))等。 RS23 2 can be a very simple munication standard, if not using hardware flow control, then at least only use three signal lines, can be fullduplex transmission operation. RS232的電氣特性是屬于非平衡傳輸方式，抗干擾能力較弱，故傳輸距離較短，約為15米左右而已。 (1) send a signal: that TXD (transmit data signal line) and RXD (receive data signal lines). 經(jīng)由TXD傳送和RXD接收的信息格式為：一個(gè)傳送單位(字節(jié))由起始位、數(shù)據(jù)位、奇偶校驗(yàn)位和停止位組成。 RS232C serial port signal is divided into three categories: transmission signal, the signal and ground contact. (1)傳送信號(hào)： It allows a sending device to a receiving device to send information。標(biāo)準(zhǔn)。連接。 Any munication stations always have to include DCE and DTE, therefore to establish a unified standard interface, especially for public data networks are important. 數(shù)據(jù)終端設(shè)備DTE是產(chǎn)生數(shù)字信號(hào)的數(shù)據(jù)源或接收數(shù)字信號(hào)的數(shù)據(jù)宿，或者是兩者的結(jié)合，像計(jì)算機(jī)終端、打印機(jī)、傳真機(jī)等就是DTE。s handshake process into the online. 正常使用時(shí)，由使用者通過控制電話機(jī)或Modem前面板的按鍵、內(nèi)部開關(guān)實(shí)現(xiàn)三種方式間的轉(zhuǎn)換。 It can be 16 different phase and amplitude level, so that the Modem 1200bps 19200bps data transmission signal. 該種Modem一般用于高速同步通信中。數(shù)，如調(diào)相ModemBell212A型。 (1) frequency shift keying (FSK): with a special scope to distinguish between audio send data and receive data. 如調(diào)頻ModemBell103型發(fā)送和接收數(shù)據(jù)的二進(jìn)制邏輯被指定的專用頻率是:發(fā)送，信號(hào)邏輯0、頻率1070Hz，信號(hào)邏輯頻率1270Hz；接收，信號(hào)邏輯0、頻率20 25Hz，信號(hào)邏輯頻率2225Hz。 both the phone call is a call mode。 Ordinary telephone lines in the 300 ~ 3400Hz voice bandwidth, range, use it to transmit digital signals, the signal must also be in the range of frequencies. 常用的調(diào)制方法有三種:頻移鍵控(FSK)、相移鍵控(PSK) 、相位幅度調(diào)制(PAM)。 Data terminal equipment to the binary form of the serial signal data sent by the interface to convert the internal logic levels into the send part, by the modulation circuit modulates the signal line required to send to the line. 接收部分接收來自線路的信號(hào)，經(jīng)濾波、反調(diào)制、電平轉(zhuǎn)換后還原成數(shù)字信號(hào)送入數(shù)字終端設(shè)備。二進(jìn)制 　　調(diào)制解調(diào)器由發(fā)送、接收、控制、模擬信號(hào)調(diào)制到模擬載波信號(hào)上進(jìn)行傳輸，并解調(diào)收到的附錄1：模擬輸入/輸出通道電路附錄2：英文原文調(diào)制解調(diào)Modem詞條簡(jiǎn)介它涉及到硬件電路的設(shè)計(jì)、軟件的編寫及調(diào)試，還有相關(guān)軟件的使用。在設(shè)計(jì)數(shù)控直流恒流源的過程中，我深切體會(huì)到，實(shí)踐是理論運(yùn)用的最好檢驗(yàn)。圖410（6）加入噪聲數(shù)據(jù)，再運(yùn)行程序，觀察調(diào)制后的頻譜圖，如圖411所示。（3）加載數(shù)據(jù)到數(shù)據(jù)區(qū)，觀察輸入數(shù)據(jù)特性，如圖46和47所示。(3)。word 030FBH,036B AH,03C56H,041 ,04C3FH,05133H,055F5H word 08001H,08028H,0809FH,08164H,08277H,083D7H,08584H,0877CH word 030FBH,02B 1FH,O2528H,01 Fl AH,018F9H,012C8H,00C8CH,00648H 待濾波數(shù)據(jù)開始進(jìn)入循環(huán)緩沖區(qū)的首位STM Data_I3,AR5STM Data_I2b+63,AR1STM fqpsk,AR4STM noise,AR6STM fqpsk,AR7FIR: RPTZ A,63 MACD *AR1,coeff,A STH A,2,*AR5+% STM Data_12b,AR3 MVDD *AR2,*AR3 MAR *AR2+% STM Data_12b+63,AR1QPSK STH A,2,TEMP CALL Carrier LD 7FFFH,15,A LD TEMP,16,A RPT 10 NOP MPYA TONERL RPT 10 NOP ADD *AR6+%,13,B,A STH A,*AR4+% B FIRCarrier:LD SIN18K,AADD K_SINSTP,AAND 7FH,ASTL ADD SIN_TABLE,AREADA TONERLLD TONERL,ASTL A 1, TONERLRET.dataCoeff:.word 100, 19, 82, 156. , 94, 27, 143.word 189 , 128, 31, 221 340, 296, 51, 343.word 738, 937, 764, 152, 800, 1808, 2464, 2341.word 1133, 1223, 4484, 8130, 11469, 13813, 14656, 13813.word 11469, 8130, 4484, 1223, 1133, 2341, 2464, 1808.word 800, 152, 764, 937, 738， 343, 51, 296.word 340, 221, 31, 128, 189, 143, 27, 94.word 163, 156, 82, 19, 100， 0, 0, 0SIN_TABILE 通過這樣處理，可以在保證運(yùn)算精度的條件下有效解決溢出問題[28]。判斷是否出現(xiàn)DTSTH A, max_m 。結(jié)果只保留前高16位STM N_ERROR, n_error_ptr$block_end:Geigel算法的C54x匯編語(yǔ)言定點(diǎn)實(shí)現(xiàn)如下：LD *ref_ptr+%, 16, AABS A 。實(shí)現(xiàn)式中的Σ求和，ref_ptr指向x(n)MACR *ref_ptr+0%, *n_error_ptr+, A 。在實(shí)現(xiàn)數(shù)字濾波BNLMS、Geigel算法時(shí)就使用了這些技巧，具體見下面的程序。利用C54x的圓周尋址方式(用%表示)管理緩沖區(qū)的數(shù)據(jù)，可避免每次對(duì)緩沖區(qū)的數(shù)據(jù)進(jìn)行搬移，大大減少指令開銷，提高運(yùn)行效率。圖44 輸入數(shù)據(jù)頻譜圖圖45輸出數(shù)據(jù)頻譜圖最后，將程序移植為聞亭公司的TMS320VC5409評(píng)估板的MCBSP0的中斷服務(wù)程序，并將形成的可執(zhí)行文件加載到評(píng)估板上運(yùn)行。⑨輸入一個(gè)新數(shù)據(jù)替代New緩沖區(qū)中最老的數(shù)據(jù)。⑥保存和輸出結(jié)果（結(jié)果在BH中）。②設(shè)置循環(huán)緩沖區(qū)指針，AR2指向New緩沖區(qū)中最新的數(shù)據(jù)，AR3指向O1d緩沖區(qū)中最老的數(shù)據(jù)[24]。輸入數(shù)據(jù)的歸一化處理可通過設(shè)置A/D轉(zhuǎn)換的參考電平來實(shí)現(xiàn)。必須注意：其低N位為零，其中N為最小N值。在數(shù)字信號(hào)處理中的FIR、卷積等運(yùn)算中，循環(huán)尋址具有極其重要的意義。在選擇不同的結(jié)構(gòu)時(shí)，應(yīng)考慮它們所引入的誤差，并用高級(jí)語(yǔ)言進(jìn)行定點(diǎn)仿真，以比較不同結(jié)構(gòu)下誤差的大小