SIMPLIS Parts

1st Order Discrete Time Filter

The 1st Order Discrete Time Filter models a first order z-domain transfer function. The transfer function in the z-domain from the input I(z) to the output O(z) for the 1st order discrete filter is shown below:

The difference equation representing this transfer function is

For example, if N1, N0, and D0 have been set to 0, 0.1, and -0.99, respectively, the resulting 1st order discrete filter will have a DC gain of 10.0, a pole located at z=0.99, and no zero.

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Model Name:

1st Order Discrete Time Filter

Simulator:

This device is compatible with the SIMPLIS simulator.

Parts Selector
Menu Location:

Digital Functions | Discrete Time Filters

Symbol Library:

None - the symbol is automatically generated when placed or edited.

Model File:

None - the device model is generated before simulation.

Subcircuit Name:

SIMPLIS_DIGI1_D_DF_1POLE_Y

Symbols:

Multiple Selections:

Only one device at a time can be edited.

Editing the 1st Order Discrete Time Filter

To configure the 1st order discrete time filter, follow these steps:

  1. Double click the symbol on the schematic to open the editing dialog to the Parameters tab.
  2. Make the appropriate changes to the fields described in the table below the image.
Label Parameter Description

N1

Numerator constant term

N0

Numerator coefficient for z-1 term

Acquisition Time

Filter acquisition time in seconds

D0

Denominator coefficient for z-1 term

Initial Condition

Initial condition of the filter output

Examples

The test circuit used to generate the waveform examples in the next section can be downloaded here: simplis_034_1stordfilter_example.sxsch.

Waveforms

The POP waveforms below show that the DC input voltage to the filter is 0.5V and the DC output voltage is 5V, confirming that the DC gain of the 1st order discrete time filter is 10.

The following AC waveforms confirm that the DC gain is 20dB and the pole is approximately 1.6kHz.

Subcircuit Parameters

Because this 1st order discrete filter model is generated by a template script when the simulation is executed, a fixed model cannot be inserted into a netlist. The template script for this device is simplis_make_digital_filter_model.sxscr, which you, as a licensed user, can download in a zip archive of all built-in scripts.

To download this zip file, follow these steps:

Note: You will be prompted to log in with the user name and password given to you when you registered.

  1. Click here to go to the product-installation page on the SIMetrix website.
  2. Click Download Links in the first paragraph of the product-installation web page.
  3. Scroll down to the Built-in Scripts section.
  4. Right click on Download and select Save target as..., and then navigate to a location on your computer to save the zip file.