Filter: FIR & IIR Digital Filters

In

Data signal input.

Out

Filtered data output.

Schematic Symbol

FIR Filter (Using Frequency Response)

Window [Dropbox]

Select the window type. The rectangular window gives the fastest rolloff for a given order.

Frequency Type [Dropbox]

Choose from Digital or Analog. If Digital is selected, the passband frequency must be within 0 and 0.5. If Analog is selected, the passband frequency is in Hz and can be any positive value.

Passband From [Textbox]

Specify the passband start frequency. For low pass filters, this field is not available and is assumed to be 0.

Passband To [Textbox]

Specify the passband end frequency. For high pass filters, this field is not available and is assumed to be infinity.

Response Type [Dropbox]

Choose from Low Pass, High Pass or Band Pass. If Low Pass is selected, all frequencies below f2 are passed and above are rejected. If High Pass is selected, all frequencies below f1 are rejected and above are passed. If Band Pass is selected, all frequencies between f1 and f2 are passed and others are rejected.

Filter Order [Textbox]

Enter the desired filter order. A higher filter order provides a frequency response more closer to the ideal, but takes longer to compute.

FIR Filter (Using Coefficients)

Delimiter [Dropbox]

The Delimiter dropbox is a user-defined separator to define the coefficient list. Select from comma, tab, newline, space or enter your own.

Apply [Button]

To apply the entered coefficients, click on the Apply button.

Cancel [Button]

To cancel the changes made to the coefficients, click on the Cancel button.

FIR Coeffs [Textbox]

Enter or paste the FIR filter coefficients in the FIR Coeffs textbox, separated by the selected delimiter. This field is visible only if FIR filter type is selected.

The FIR filter equation is:       y[n] = a₀x[n] + a₁x[n-1] + a₂x[n-2] + a₃x[n-3] + ...

The coefficients should be entered in the following order:
a₀, a₁, a₂, ... , a_n-1, a_n

IIR Filter (Using Coefficients)

Delimiter [Dropbox]

The Delimiter dropbox is a user-defined separator to define the coefficient list. Select from comma, tab, newline, space or enter your own.

Apply [Button]

To apply the entered coefficients, click on the Apply button.

Cancel [Button]

To cancel the changes made to the coefficients, click on the Cancel button.

X-Coeffs [Textbox]

Enter or paste the IIR filter X-coefficients in the X-Coeffs textbox, separated by the selected delimiter. This field is visible only if IIR filter type is selected.

The coefficients should be entered in the following order:
a₀, a₁, a₂, ... , a_n-1, a_n

Y-Coeffs [Textbox]

Enter or paste the IIR filter Y-coefficients in the Y-Coeffs textbox, separated by the selected delimiter. This field is visible only if IIR filter type is selected.

The coefficients should be entered in the following order:
1, b₁, b₂, ... , b_n-1, b_n

Note that the first coeffecient is almost always 1.

Advanced Options

ByPass [Toggle Button]

Click on ByPass button to bypass the filter. This switches OFF the filtering behavior and lets the data pass through as it is. It is useful for debugging purposes.

Continuous Mode [Checkbox]

Check Continuous Mode checkbox if the data input to the filter in each new acquisition is time continuous data, that is, there is no discontinuity in the data. Uncheck this box if data from each new acquisition is not time continuous. For example, if the data source is a file or an oscilloscope, the continuous mode should be unchecked. If the data source is the SigGen Module, a sound card, or a real time DAS acquisition card, then the continuous mode should be checked.