Design Of The Intermediate Frequency Filter For WSN Nodes Application

In recent years,with the rapid development of wireless communication technology and CMOS analog circuit technology,the performance requirements of radio frequency(RF)front-end receivers for wireless sensor networks have become higher and higher,and intermediate frequency(IF)filter circuits have the functions of image rejection and channel selection,and they are used as RF.The important module in the front-end receiver is one of the difficulties in the design of the entire receiver.Based on the 0.18?m CMOS process,this paper designs an IF filtering circuit module suitable for low-IF front-end RF front-end receivers in wireless sensor networks,including two parts: image rejection filter and active band-pass filter.Firstly,the development history and research status of the filter are introduced,and the filters in different approximation modes are compared and analyzed.The circuit implementation scheme is determined according to the requirements of the RF front-end receiver.A high-linearity transconductance operational amplifier is designed based on the sourcelevel negative feedback cross-coupled differential pair structure.Based on this,a second-order Butterworth image rejection filter is designed,and then a passive LC circuit synthesis method is used to design 3rd order active bandpass filter.Simulation results show that the image rejection filter has a center frequency of 1.2 MHz,-3 dB bandwidth of 736 kHz,gain of 21.83 dB at 1.2 MHz,an attenuation of-8 dB at-1.2 MHz,and an image rejection ratio of 29.8 dB;The designed active bandpass filter has a center frequency of 1.2 MHz,-3 dB bandwidth of 337.2 kHz,and gain of 4.354 dB at 1.2 MHz.Its performance index meets the design requirements..