Customized Decimation and Multi-Fold Notch Filters Realized by DSP56309

Magnetotelluric exploration method is a powerful tool in oil and gas exploration, crust and earthquake research. The corresponding instrument system need to record low noise data at sample rate 2400 Hz, 150 Hz and 15 Hz or other triple frequencies simultaneously. Multi-fold notch filter is also need to remove 50/60 Hz power line interference. Commercial decimation filter chip, such as CS5376A, can only output sample data at fixed rate at given time. To satisfy the requirement of data acquisition in magnetotelluric exploration, 24-bit DSP56309 chip is used in measurement system. It does two-channel multi-stage decimation filtering and multi-fold 50/60 Hz notch filtering for 1-bit bit-stream output from DeltaSigma modulator CS5372A, and output data from ESSI and SCI at sample rate 2400 Hz, 150 Hz and 15 Hz simultaneously to ARM based embedded system. The design, realization and testing of decimation and multi-fold 50/60 Hz notch filter are described in paper.