There is no inherent "time step" in LTspice. If you are thinking of a discrete-time system, then you need to add a "clock" (a pulse at some convenient frequency would work), and a sample/hold circuit. A second S/H can implement the t-1 function if the sample period is 1.
If this is a continuous time system, then a delay line or B element (either with delay of 1 second) will provide provide D(t-1). Another B element will sum the two with offset of a.
Jim Wagner
Oregon Research Electronics
On Jul 14, 2013, at 10:35 PM, feabyl wrote:
--- In LTspice@..., Andy <Andrew.Ingraham@...> wrote:
feabyl wrote:
How to implement an expression D(t)=D(t-1)+ a ?
Is that D(t-1) as in D(t - 1sec)?
If so, you can implement a 1 second time delay in either of two ways:
1. A (properly terminated) lossless transmission line (T-element) with a
delay of 1 second.
2. A behavioral source (B-element) with a delay of 1 second.
If the '-1' is supposed to represent the previous internal timestep in
LTspice, I don't think there is a way to do that. (But I'm not saying it
is impossible.)
Regards,
Andy
Thank you for the options suggested.Could you give an idea how to implement 1 sec delay using B-element.
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