In this case, an analog filter should be used.ģ) For the single-chip microcomputer without multiplication and division running instructions, the workload of the program operation is relatively large. For example, if the sampling frequency is 100 Hz, it cannot filter out interference signals above 50Hz). RC Circuit Ⅱ First-order Low Pass Filter on Softwareġ) The use of digital filtering algorithms to achieve dynamic RC filtering can well overcome the shortcomings of analog filters.Ģ) This kind of algorithm is more practical when the simulation constant is required.ģ) It has a good inhibitory effect on periodic interference.ġ) Exit phase lag, resulting in low sensitivity.Ģ) It cannot filter out interference with a frequency higher than half of the sampling frequency (called the Nyquist frequency. Increasing the time constant requires increasing the value of R, and meanwhile, the leakage current increases accordingly, thereby reducing the filtering effect.įigure 6. When using this analog filter to suppress low-frequency interference, the filter is required to have a larger time constant and a high-precision RC network. This frequency is usually called the cutoff frequency. When ω=ωc, the gain is attenuated to 0.707, which is -3dB, and the phase lags by 45 degrees, corresponding to a low-pass filter. When ωωc, it is a straight line whose slope is proportional to -20dB/decade.
Logarithmic representation of amplitude-frequency characteristic: Taking the capacitor voltage as the output, the network function of the circuit is:Īmplitude and phase frequency characteristics: Step Response Curve of a First-order RC System 1.2 Frequency Domain Suppose the initial voltage of the capacitor is 0, where:įigure 2. Where, the unit of Ui is volts, the unit of RC is seconds, and τ=RC, get: Typical RC Circuit (DC, AC, and Pulse Signals can all use it) 1.1 Time Domain Not only can it be used to time circuits, it can also be used to filter out unwanted frequencies in a circuit and used in power supplies, like the one for your computer, to help turn ac voltage to dc voltage.įigure 1. The RC circuit has thousands of uses and is a very important circuit to study. Ⅲ Optimization Method- Filtering Coefficients Adjustment Ⅱ First-order Low Pass Filter on SoftwareĢ.2 Basic Algorithm of First-order RC Digital Filtering In this video, Passive RC Low Pass Filter has been discussed.
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