18 May 2010
A LPF passes low frequency signals while attenuating the amplitude of signals with higher frequencies at a frequency called the cutoff frequency. The cutoff frequency determines when frequencies of the input signal passes through the filter unattenuated and what signal frequencies gets attenuated. Below the cutoff frequency, signals with frequencies below the cutoff passes through unattenuated otherwise the signal gets attenuated when its frequency is above the cutoff frequency. Note that a high pass filter is opposite to a LPF and a bandpass filter is a cascade combination of a high-pass filter and low-pass filter. From a stereo perspective the low pass filter passes the bass frequencies and the high pass filter passes the treble audio signal. An equalizer basically consists of a whole bunch of bandpass filters connected in parallel. The low-pass filter exists in many different forms, but our focus here is in signal processing but it can be found in applications such as finance and image processing. You can think of a low pass filter as a smoother or averaging function removing the short-term variations or oscillations of a signal quantity. In finance for example, you take 120-day averages to determine long-term trends. The video will provide review what an ideal low pass filter is and provide a simple RC circuit as first-order filter. A Matlab demo is given to illustrate how ...