Digital Filters

You will be able to: • Implement a digital filter in MATLAB. • Investigate how commercial filters work • Describe the transfer function of a filter Suppose the "raw" signal which is to be digitally filtered is in the form of a voltage waveform described by the function V = x (t) where t is time. This signal is sampled at time intervals h (the sampling interval). The sampled value at time t = ih is x i = x (ih) Thus the digital values transferred from the ADC to the processor can be represented by the sequence corresponding to the values of the signal waveform at times t = 0, h, 2h, 3h, ... (where t = 0 is the instant at which sampling begins). At time t = nh (where n is some positive integer), the values available to the processor, stored in memory, are Note that the sampled values xn+1, xn+2 etc. are not available as they haven't happened yet! The digital output from the processor to the DAC consists of the sequence of values In general, the value of yn is calculated from the values x 0 , x 1 , x 2 , x 3 , ... , x n. The way in which the y's are calculated from the x's determines the filtering action of the digital filter.