Abstract: In this paper, we discuss a practical way to filter an ECG signal in the background of interference signals. This will be achieved by designing the low pass filter (LPF) with Kaiser window of variable pass-band (four pass-bands) of type finite impulse response (FIR) using a digital programmable device (Cyclone II EP2C70F896C6 FPGA from ALTERA) placed on education and development board DE2-70, this filter is designed by VHDL with Quartus II 9.1 design environment and consists of two filters (LPF) connected on serial. The proposed method depends on keeping FIR filters coefficients constant for all required pass-bands and changing the cut off and sampling frequencies together so that the frequency response remains constant for all pass-bands, just these pass-bands sweep on the frequency domain and thereby the pass-band of the filter will be changed without changing its coefficients. Using FPGA to design digital FIR LPF enable as of realization parallel processing to achieve digital convolution algorithm in the real time, where 1500 operation of adding , shifting, multiplying and dividing can be done in 0.5 ms (sampling period) for digital samples of 10 bits length ,this equivalent 3 million operation per second where the general processor cannot do that.

Keywords: Variable PASS-BAND, ECG, FPGA, LPF, FIR