A Tunable Bandwidth Low-pass Filter for TD-SCDMA/TD-LTE Transmitter

This paper proposes a seven order Chebyshev low-pass filter,which is fabricated in UMC 0.18μm CMOS process and used for TD-SCDMA/TD-LTE transmitter.The filter is de- signed as active-RC structure consisting of a first order filter cascaded with three second order Tow-ThomasⅡ filters,and uses a decoder to control the tunable bandwidth in 1.6 MHz,3 MHz,5MHz,10MHz and 15MHz.The chip area is 1 059μm×867μm.The test result indi- cates that the current is 13mA under 1.8Vpower supply,and the bandwidths satisfy the design requirements of the protocols.The second frequency attenuation can reachover 50dB,and the in- put 3rd order intercept point(IIP3)is-4.385dBm.