The Research Of The Key Techniques Of Intermediate Frequency Module Of WIA(Wireless Sensor Network For Industrial Application)

WIA is the Wireless Networks for Industrial Automation of China, which can beadapted to complicated industrial environment and meet the harsh industrialrequirement. The receiver needs being high sensitivity and with large dynamic range,which raises a very strict requirement for analog intermediate frequency part design.In this paper, the analog intermediate circuit mainly includes three parts: Gm-Clow-pass filter, Gm-C complex band-pass filter and programmable gain amplifier(PGA). And the prototype of Gm-C low-pass filter is a5thorder Butterworth filter,obtaining active filter through element analog; Gm-C obtains the function of complexband-pass filter through a3rdorder Butterworth filter and the frequency shifttechnology, obtaining active filter through element analog. All of the filters use thetechnology of CMFB sharing to reduce power dissipation. Four serial stages areemployed in the PGA and the first and second stages are fixed gain stages while thegains of the third and fourth stages are variable. Each stage uses open loop structureso as to reduce the power dissipation.In this paper, to increase the degree of linearity, all of the Gm-C filters weredesigned by using the technology of cross coupling source degeneration and improvedfilter system structure. To increase the bandwidth of each gain higher than4MHz,PGA uses the structure of source degeneration resistor paralleled with capacitor. Thecommon mode sampling method uses resistor balance sampling, making the gainapproximate to the ratio of common mode sampling resistor and resourcedegeneration resistor, which increase the gain accuracy. This design uses thetechnology of TSMC18RF CMOS1P6M, the layout area is1410μm×2060μm. Thestimulation results show that the adjustable bandwidth range of low-pass filter isbetween1.75MHz and5.64MHz, covering signal bandwidth of2.0MHz, its NF is24.72dB and IIP3is13.8dBm; the adjustable bandwidth range of Gm-C complexband-pass filter is between0.44MHz and2.96MHz, covering signal bandwidth from0.5MHz to2.0MHz, its NF@2.0MHz bandwidth is24.84dB and IIP3is13.0dBm.The gain range of PGA is between0dB and62.9dBm, whose error is less than0.5dB.The NF of PGA is23.32dB@the maximum gain and the IIP3is18.3dBm@theminimum gain. Overall stimulation of the analog IC of intermediate frequency wasdone on the condition that the input voltage of sinusoidal wave is Vpp=50mV andoutput voltage is Vpp=600mV. The measured results of IM3are58dB/62dB respectively, which meets the basic system requirements.