An Approach of Realizing a Linear-Phase Filter with a Multiple-Notched Property

There are many applications where signals with relatively low frequencies must be measured under the following conditions: 1) eliminating very low frequencies (such as slow fluctuations) from a reference level, 2) rejecting 50/60 Hz and their harmonics, 3) keeping linear-phase frequency characteristics. A filter based on a conventional microprocessor having the above conditions has been simply implemented by modifying the concept of the Cascaded Integrator Comb (CIC) filter. In this paper, we will describe the hardware, software, and noise analysis of the advocated filter.