SIMPLIS Parts

Unit Delay

The Unit Delay models a single clock cycle delay in the z-domain. The transfer function in the z-domain from the input I(z) to the output O(z) for the Unit Delay is shown below:

The difference equation representing this transfer function is

As with the other devices in the Discrete Time Filter category, the unit delay is compatible with the SIMPLIS POP and AC Analyses.

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Model Name:

Unit Delay

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_UNIT_DELAY_Y

Symbols:

Multiple Selections:

Only one device at a time can be edited.

Editing the Unit Delay

To configure the unit delay, 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

Acquisition Time

Filter acquisition time in seconds

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_037_unitdelay_example.sxsch.

Waveforms

In the circuit example, a 100kHz sine wave with a 1V amplitude (+/- 1V peak) is applied to the input of the unit delay. The clock has a frequency of 1MHz, and the sampled input voltage is output on the same graph as the input voltage.

The following AC waveforms confirm that the DC gain is 0dB and that the phase change at 1/2 the sampling frequency is the expected 270 degrees.

Subcircuit Parameters

Because this unit delay 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.