A 4th-Order Programmable Channel Selection Filter for Acoustic and Ultrasonic Applications

This brief presents a programmable low-power 4thorder active biquad bandpass filter (BPF) designed using TSMC's 65-nm CMOS technology. The proposed filter consists of two second-order BPFs which are based on a gm-C topology. Each second-order filter utilizes a pair of input capacitors. The proposed BPF can provide non-overlapping frequency bands and it spans a total bandwidth between 3.5 kHz to 1.5 MHz by using a digital cell to control it. For the nominal center frequency of 100 kHz, the quality factor is equal to 8.4, and the quality factor remains approximately constant for all passbands. The dynamic range of this design is 61.6 dB for 1% total harmonic distortion (THD). By digitally controlling the biasing voltage, it is possible to change the center frequency of the proposed filter, and effectively the filter can be used to acquire a specific channel. The filter design, excluding the digital control cell, consumes a low power consumption equal to 24 μW. Hence, the proposed programmable channel selection filter shows an excellent performance as compared to existing work and offers a great potential for use in low frequency applications.