Design Of A SOI CMOS 2MHz Complex Band-pass Filter

A wireless sensor network(WSN)is a wireless network which consists of spatially distributed autonomous sensors monitoring and recording the change of around environments.Nowadays,WSN has been used widely in plenty of industrial and civil applications.The performances of RF transceiver chips are the key of WSN communication quality,and the performances of filters determine the qualities of RF transceivers.Therefore,the design of a high performance filter is significant.In this paper,a complex bandpass filter for WSN low-IF receiver is designed in 0.28?m SOI CMOS process.The prototype of the complex band-pass filter is a Chebyshev I low pass filter.A Gm-C active low pass filter is synthesized by using gyrator based active resistors and inductors to substitute passive resistors and inductors in the passive low-pass filter.The complex band-pass filter is generated by shifting all the poles of the Gm-C active low-pass filter.The operational transconductance amplifiers(OTA)in Gm-C filter are Nauta OTAs having favorable frequency characteristics and capability to tune the Q factor and frequency characteristics of a Gm-C filter simultaneously.In addition,the Gm-C complex band-pass filter is tuned by a Phase-Locked Loop(PLL)based tuning system,so that the filter can archive the same performance in various conditions.The center frequency and bandwidth of the complex band-pass filter are both 2 MHz,according to the results of post simulations,in three different conditions(FF corner-40?,TT corner 27?,SS corner 85?),the errors of center frequency are less than 1.95%,the errors of bandwidth are less than 2.7%,the magnitudes of ripples in passbands are under 0.24 dB,the 1dB input compression points@2MHz are higher than 2.47 dBm,the image rejections@-2MHz are lower than-73 dB,the adjacent channel rejections@7MHz are lower than-80 dB,the total current dissipation of the complex band-pass filter is less than 1.45 mA with 2.5V supply.The current dissipation of core filter is less than 1.3mA.These results show that the performance of the complex band-pass filter satisfies the demand.The complex band-pass filter in this paper can efficiently reject image signal and adjacent signal,and has small in-band ripples.