Power Optimized Digital Decimation Filter for Medical Applications

A digital decimation filter for medical applications (NMRI) is designed and proposed in this paper. The digital decimation filter is one of the main blocks of Σ-Δ ADC .For a clinical NMRI systems, the resonating frequency being 64MHz for a magnetic field strength of 1.5 T. The decimation filter down samples the over sampled output of the Σ-Δ modulator to Nyquist sampling rate of 128MHz.. The power, speed and the area of operation are largely governed by decimation filters in Σ-Δ ADC. The digital decimation filter is based on Cascaded Integrated Comb (CIC) filter architecture. In this scheme the optimization of the two stage CIC structure is done and the power consumption is considerably reduced compared to the conventional CIC filter architectures. The proposed resolution filter is realised in 0.18μm CMOS technology which occupies an area of 0.088mm2and consumes a power of 2.67mW from a 1.5V supply.