A 4.75–34.75 MHz digitally tunable active-RC LPF for >60dB mean RX IRR in 65nm CMOS

A third order active-RC Chebyshev low-pass filter for a mobile terminal receiver supporting carrier aggregation is presented. It has a 0.4 dB passband ripple, reconfigurable bandwidth (4.75-34.75 MHz), automatic RC tuning, and IQ-mismatch correction. The noise power spectral density referred to the filter input is 3.8pA/√Hz at 90 % of the bandwidth. The output referred third order intercept point (OIP3) is 39.4 dBm for a two tone input at 47 MHz and 70 MHz. By digitally controlling the passive circuit elements of the filter, the frequency dependent gain and phase IQ mismatch can be reduced, resulting in a remaining gain error below 0.35 % and a maximum phase error of 0.23 degrees. After calibration, the IQ matching is sufficient for a mean receiver image-rejection ratio of more than 60 dB. The current consumption is 39 mA from a 1.2 V supply.