Research And Design Of An Analog Baseband Filter For Multi-mode Wireless Applications

Analog baseband filters used to filter the interference signal beyond the channel arevery important blocks in radio frequency transceivers. The valuable signal is selected byfilters can be processed by the successive blocks. In order to satisfy the demand ofconsumers, radio frequency transceivers should operate well under multimodecommunication. This puts forward stringent requirements on design of analog basebandfilters. Multimode communication and systems need analog baseband filters withbandwidths tunable over a wide range, while keeping the relative shape of the frequencyresponse fixed irrespective of the set bandwidth and maintaining an adequate dynamicrange. Meanwhile, analog baseband filters can’t be designed at cost of large size andhigh power dissipations.The design of a fifth-order, ChebyshevI type active-RC filter for multi-modewireless applications in TSMC0.18m CMOS technology is exhibited in this paper.This filter has two corner frequency of10MHz and50MHz. Leap-Frog structure isadopted to reduce the sensitivity of frequency on passive components. The test resultsshow that corner frequency fluctuate within±3%and passband ripple is less than0.6dB at10MHz and0.7dB at50MHz. The stopband attenuation is42.8dB and47.9dBwhile the corner frequency is10MHz and50MHz respectively. The IIP3is13.44dBmat10MHz and16.43dBm at50MHz. The simulation results show that the input noisedensity is28.54nV/sqrt(Hz)@2MHz and51.68nV/sqrt(Hz)@10MHz when thebandwidth is10MHz， and the input noise density is24.46nV/sqrt(Hz)@2MHz and73.05nV/sqrt(Hz)@50MHz when the bandwidth is50MHz. The test chip area of thefilter is1.28mm~2. The filter with buffer and bandgap draws62mA currents from1.8Vsupply。...