Fixed-Point Blockset    

Lead Filter or Lag Filter Realization

This section presents the realization for a lead filter or lag filter. The transfer function and difference equation, block parameters, and model design are discussed.

The FixPt Lead or Lag Filter is approximated by the z-domain transfer function

where K is the DC gain, a is a zero on the unit circle, and p is a pole on the unit circle. The realization is shown below.

As shown in the figure, the transfer function yields the difference equation

where k is the current time step, k - 1 is the previous time step, g = K(1 - p) is the modified gain, y(k) is the current output, y(k - 1) is the output from the previous time step, u(k) is the current input, and u(k - 1) is the input from the previous time step.

Parameters and Dialog Box

The dialog box and parameter descriptions for the lead or lag filter realization are given below.

Sample time
The time interval, Ts, between samples
Pole of filter
The pole, p, defined in the z-plane. A pole at +1 represents integral action
Zero of filter
The zero, a, defined in the z-plane. A zero at +1 represents derivative action
DC gain
The constant gain, K
Base data type
The processor's base data type
Accumulator data type
The processor's accumulator data type

Model Design Review

A brief review of the model design is given below. The design criteria reflect the rules presented in Design Rules.


 Derivative State-Space Realization