UHF頻段無線收發(fā)信機前端設(shè)計

為了提高現(xiàn)代工廠設(shè)備的調(diào)度效率，降低儀器儀表等測控數(shù)據(jù)的傳輸成本，壓縮設(shè)備體積等。利用收發(fā)芯片TH7122和分離器件相結(jié)合的方式設(shè)計了一款通信頻段為438～470 MHz的無線音／數(shù)兩用小型收發(fā)信機。數(shù)字調(diào)制方式采用MSK調(diào)制，同時可切換到音頻模式。其中接收機采用超外差一次變頻結(jié)構(gòu)，結(jié)合PIN管帶通調(diào)頻濾波器和外接LNA，用于鏡像抑制和降低噪聲。發(fā)射部分采用晶振拉動的方式間接調(diào)制VCO輸出，經(jīng)過芯片內(nèi)部放大、外接功率驅(qū)動電路和功率放大電路將發(fā)射功率增至5 W，再經(jīng)諧波濾波發(fā)射。經(jīng)過仿真實驗，輸出功率5 W，中頻10.7 MHz，接收靈敏度為-110 dB，鏡像抑制40 dB，均達到設(shè)計要求。

Abstract:

?In order to improve the dispatch efficiency of modern factory devices ， reduce the transmission cost of observe and control datas of instrumentation， and compress equipment volume， this paper designed a small wireless voice/digital dual purpose transmitter receiver which used transmitter receiver IC TH7122 and discrete device，and it worked in the frequency of 438~470MHz. The digital modulation system adopted MSK modulation， it also can be switched to the audio mode. The receiver adopted superheterodyne once frequency conversion， which combined with the PIN controlled bandpass filter to inhibit mirror frequency and the extral LNA to reduce noise figure. In the transmitter section，the crystal pulling way was used to indirectly modulate the VCO’s output. Through the internal amplifier enlarged and the external power driver and power amplifier circuit， the output power was increased up to 5W and transmitted by the harmonic filter.The simulation and testing results show that the output power is 5W， the medium frequency is 10.7MHz ， the rx-sensitivity is -110dB， and the mirror frequence restrain is 40dB. All the design requirements was reached.