語音/文字短信無線發射機是嵌入式智能家居系統的重要部件，采用鎖相環式頻率合成器技術，利用MC145152 和MC12022 芯片組成鎖相環。輸出載波頻率35MHz，穩定度達到4×10-5，準確度達到3×10-5。由變容二極管V149 和集成壓控振蕩器芯片MC1648 實現對載波的調頻調制。末級功放選用三極管2SC1970，工作在丙類放大狀態，輸出功率達到20mW。采用PT2262 編碼器芯片和AT89S52單片機實現文字短信數據傳輸業務，以及對機號的選擇與控制等功能。音頻輸入和文字短信數據輸入可自動轉換，顯示采用128×64 點陣型液晶顯示。
關鍵詞： 無線電發射機、鎖相環、編碼器、單片機
Design of Wireless transmitter for Sound and Letter note Huang Zhiwei Liu hong Jiang Chenjun Fu xianchen （The College of Electrical Engineering , Nanhua University ,Hengyang 421001, China） Abstract: The wireless transmitter of sound and letter note is a important part of embedded intelligent home system. It adopts the phase-locked loop pattern of frequency synthesizing technology and uses the MC145152 and MC12022 chips to compose the phase-locked loop. The frequency of the carrier-wave is at 35MHz. The stabilization of the carrier-wave can be 4×10-5, the accuracy can be 3×10-5. The frequency modulation of the carrier-wave are realized by the capacity-changing diode V149 and the integration voltage-control oscillator MC1648 chip. The end power amplifier uses the transistor 2SC1970 to make it work in the third magnifying state, the output power reaches 20mW. It uses PT2262 encoder to realize the data transmission operation as well as the platform-choosing function. The AT89S52 is used as the controlling part of the whole system.The input of the Sound and
Letter note can be automatically transformed. The display adopts 128×64 lattice LCD to show.
Key word: wireless transmitter, PLL, encoder, microcontroller