"Chengju Yu" wrote in message >news:edaab599-0bfe-4619-ad84-3ed1f8a58ed9n@googlegroups.com...
Hello everyone,
To model a frequency-controlled resistor, I used the method including a >non-linear laplace form voltage control current source "GLaplace", that
some websites and >engineerings suggested.
I tried with a simple equation, R=1+f, when I do the AC sweep study in the >PSPICE, the model works fine as I attached figure as AC sweep, the
resistance changes from 1 >to 101 ohms when frequency changing from 1 to
100 Hz. And the voltage crossing that model is consistent with concept. In
AC sweep simulation, that model is working ok.
However when I simulate that in transient simulation with a simple 100Hz
sin wave, the resistance response of model is very inaccurate (the value is >far away from >R=1+100=101 ohms).
So I am not sure if those Glaplace model could be used in the transient >simulation.
Did anyone know any information related to that?
Any suggestions and comments would be appreciated.
What are you trying to achieve?
Typically, the point of a frequency dependant resistance is to simulate skin effect resistance for inductors.
This can be achieved by an LR ladder network.
If this is your goal, a better option is to use a model that gives the
correct 45 degs, 10db/dec characteristic. Pure frequency dependant resistors produce responses that are non real.
e.g.
.SUBCKT SkinEffectResistance_XN !0_A !1_B FMAX=110M K=0.49
* _SS_Symbol [<System>Functional.ssm] [SkinEffectResister]
*
*
V!1 !1_B B 0
V!0 !0_A A 0
* skin effect impedance variation with sqrt(F)
* set F0 to > max fequency of operation
.param FX={FMAX/100}
.param L={0.1*K/sqrt(FX)}
.param R={10*K*sqrt(FX)}
*
R8 Node8 A {R/128}
L8 Node8 B {L*128}
L1 Node1 B {L}
R1 Node1 A {R}
R6 Node6 A {R/32}
R5 Node5 A {R/16}
R4 Node4 A {R/8}
R3 Node3 A {R/4}
R2 Node2 A {R/2}
R0 B A {R}
R7 Node7 A {R/64}
L2 Node2 B {L*2}
L3 Node3 B {L*4}
L4 Node4 B {L*8}
L5 Node5 B {L*16}
L6 Node6 B {L*32}
L7 Node7 B {L*64}
*
.ENDS
There is an example in my freebee SuperSpice
http://www.anasoft.co.uk/
SkinEffectResistance.ssss
That demonstrates this.
Furthermore, there are sets of CoilCraft inductor models that fully
implement their inductors using that technique. The Model files should also
run directly in LTSpice.
-- Kevin Aylward
http://www.anasoft.co.uk/ SuperSpice
http://www.kevinaylward.co.uk/ee/index.html
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