Efficient FPGA-based multistage two-path decimation filter for noise thermometer

This paper introduces an efficient Field Programmable Gate Array (FPGA) realization of a multistage decimation filter with narrow passband and very narrow transition band for noise thermometer application. The filter is composed of six stages, the first five stages are two-coefficient half-band filters and the last stage is a sharper transition half-band filter. For the last stage, we proposed a binary-scaled four-coefficient filter and two cascaded two-coefficient filters. The frequency responses and implementation area of different half-band filters are compared. In contrast to multirate techniques, we realized a frequency masking single rate filter, which consumes a larger area. The measured frequency response of the implemented filter is compared with the calculated one.