A 5th-order Chebyshev active RC complex filter with automatic frequency tuning for wireless sensor networks application

A 5
^th
-order Chebyshev active RC complex filter for wireless sensor networks with automatic frequency tuning is presented in this paper. This filter is synthesized from 5
^th
-order low-pass LC prototype, and designed using leapfrog structure. An automatic frequency tuning is used to prevent the deviation of the RC constant of the filter. This filter is fabricated in TSMC 0.18μm CMOS process. The measurement results show that the passband gain of the filter is about 16dB and the ripple in the passband is about 1.5dB. It is centered at 2MHz with 2.45MHz of bandwidth after tuning. The image rejection ratio (IRR) is about 40dB and the adjacent channel rejuction (ACR) around 6MHz is about 55dB. The precision of the tuning system could be controlled to less than 3%. The filter consumes about 6.5mA totally with 1.8V power supply.