UHF频段无线收发信机前端设计

为了提高现代工厂设备的调度效率，降低仪器仪表等测控数据的传输成本，压缩设备体积等。利用收发芯片TH7122和分离器件相结合的方式设计了一款通信频段为438～470 MHz的无线音／数两用小型收发信机。数字调制方式采用MSK调制，同时可切换到音频模式。其中接收机采用超外差一次变频结构，结合PIN管带通调频滤波器和外接LNA，用于镜像抑制和降低噪声。发射部分采用晶振拉动的方式间接调制VCO输出，经过芯片内部放大、外接功率驱动电路和功率放大电路将发射功率增至5 W，再经谐波滤波发射。经过仿真实验，输出功率5 W，中频10.7 MHz，接收灵敏度为-110 dB，镜像抑制40 dB，均达到设计要求。

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.