Active 4th-Order N-path Filter with Wide Tuning Bandwidth Range

To meet the demand for multi-mode and multi-band RF receiver chips, and overcome the limitation of the fixed bandwidth of the traditional N-path filter, an active 4
^th
-order N-path filter with wide tunable bandwidth is proposed. The -3dB bandwidth can be tuned from 50 MHz to 200 MHz. The center frequency of two tunable 2
^nd
-order filters is controlled to move by tuning gm, and combining the tunable dual-frequency filter synthesis realizes the wide-range tuning of 4
^th
-order filter bandwidth. The center frequency of the 4
^th
-order filter can be tuned in the range of 0.5 GHz to 2 GHz with insertion loss <-3 dB, Pin-1dB linearity of the filter is better than - 5 dBm. The rectangle coefficient is better than 4:1. The filter is designed and fabricated in 55 nm CMOS process.