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Simulators >> RF Simulators >> Envelope Time Step
https://designers-guide.org/forum/YaBB.pl?num=1037470949

Message started by RFICDUDE on Nov 16^th, 2002, 10:22am

Title: Envelope Time Step
Post by RFICDUDE on Nov 16^th, 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

Title: Re: Envelope Time Step
Post by Ken Kundert on Nov 16^th, 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

Title: Re: Envelope Time Step
Post by RFICDUDE on Nov 17^th, 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 ;D
Thanks
RFICDUDE