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Envelope Time Step (Read 3947 times)
RFICDUDE
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Envelope Time Step
Nov 16th, 2002, 10:22am
 
I'm posting here because SourceLink is down for the weekend  >:(

I'm trying to get envelope simulation running efficiently, but I'm running into a problem. All I have in the simulation is one sinusoidal source at the clock frequency (100MHz) and another source at the envelope modulation frequency (100kHz). Each source is just terminated into a resistor. When I run the simulation the envelope time step is set to 10nsec for a majority of the simulation, so the simulation takes a while because it is essentially sampling the envelope at the clock rate. The simulator does recognize that the clock period is also 10nsec.

Is it possible that the envelope simulator is getting confused and thinks that the 100MHz signal is also part of the envelope modulation?

Any clues?

RFICDUDE
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Ken Kundert
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Re: Envelope Time Step
Reply #1 - Nov 16th, 2002, 10:22pm
 
RFIC dude,
   It hard to know what is going wrong without seeing your netlist. The most common error involves incorrectly specifying the clock. You should identify the source or sources that make up the clock by giving them a fundname and then giving the same name to the envelope following analysis using the clockname parameter. The low frequency sources should either not have a fundname or it should be a different one.

The following netlist works for me.
Code:
// Test circuit for Envelope Following
simulator lang=spectre

Vlo	lo 0   vsource type=sine freq=100MHz ampl=1 fundname="LO"
Rlo	lo 0   resistor r=50
Vrf	rf 0   vsource type=sine freq=100kHz ampl=1
Rrf	rf 0   resistor r=50

envelope envlp  start=1n stop=50us harmsvec=[1 3] clockname="LO" 


-Ken
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RFICDUDE
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Re: Envelope Time Step
Reply #2 - Nov 17th, 2002, 7:33am
 
Thanks for the reply Ken.
I just found my error for this simulation. I had tsab set to 5usec by mistake. This was obvious from the simulation output when I saw that the envelope time step was fixed to 10nsec up to 5usec of the simulation.

As usuall, it's pilot error Grin
Thanks
RFICDUDE
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