一种基于声表面波滤波器的868MHz频率调制电路设计

分析了现有各种UHF频段频率调制电路的特点,设计了一种基于声表面波滤波器的868MHz频率调制电路,给出了完整电路原理图,结合EWB仿真较为详细地阐述了设计思路。该频率调制电路由主振和频率选择反馈两部分组成,主振部分采用共基极的电容三端式振荡器,避免了集电结电容的密勒效应,频率选择反馈部分串有由声面波滤波器构成的高Q值窄带滤波器,该滤波器兼有稳定中心频率的作用。这种电路具有结构简单、低本低廉、中心频率稳定、带外残留少、调试方便等特点,已成功应用于自行开发的无线话筒中。该电路既可用于FM也可用于FSK,特别适合于无线话筒、无线对讲、无线耳机、无线遥控、无线数据采集等各种中、低档无线通信设备。

A kind of 868MHz frequency modulator design based on SAW resonator

This paper analyzed the performance of existing UHF frequency band frequency modulator,designed a kind of 868MHz frequency modulation circuit based on the surface-acoustic-wave(SAW)resonator and gave the complete schematics,elaborated the design mentality in detail by the EWB.This frequency modulator is composed of a main oscillator and a frequency selection feedback part,the main oscillator is a common-base configuration Colpitts oscillator,it can avoid the collector miller capacitance,the frequency selection feedback partial in series with a high Q value narrow band pass filter which constituted by the surface-acoustic-wave(SAW) resonator,it can stabilize the center frequency at the same time.This kind of circuit has the characteristics of structure simply,inexpensive,center frequency stabilization,band-reject remains few,debugging easy and so on.It can used in FM and FSK,especially suits in the wireless microphone,wireless talk-back,the wireless earphone,the wireless remote control,the wireless data acquisition and so on wireless communication equipment.