T Junction, Cross Junction, Bends in Microstrip for MMWave IC Layout
I have an IC layout design at over 50 GHz using T Junction, Cross Junction and Bends in the Microstrip Interconnect.
I need to turn them into lumped models so I can run transient simulations that might not work with the EM simulated models of them.
What models should I use for the lumped models of each ?
Thank you.
Don't be pessimist, Transient Simulator will accept EM Model defined by s-parameters.
But EM simulation must be done carefully and precisely.
Thank you BigBoss.
What do you mean carefully and precisely ?
Do I have to use the same frequency sweep and steps in the transient simulation as in the EM simulations?
Is that even possible If I am correct here ?
Thank you.
Can you understand Transient Simulation ?
Important things are frequency sweep range and steps in the EM simulations.
Most circuit simulator treats S-parameter as convolution by FIR filter approximation in Transient Analysis.
fmax of S-parameters has to be far larger than 1/delta_time in transient analysis.
delta_f of S-parameters has to be far small than 1/max_delay.
Also you have care about fmin or DC value of S-parameters.
There are another treatment of S-parameter in transient analysis.
That is rational model fitting which is similar to lumped components modeling.
BB-Spice-Model generator is categorized as this.
In this case, fmin and fmax are not so important.
However delta_f is important.
See https://www.edaboard.com/showthread.php?377517
If you are using time domain EM (CST or FDTD), make sure your energy limit is low enough so that you don't have ripple on S-parameters from residual energy in the DUT.
If you are an ADS user, there is a nice tool to check if S-parameters are reciprocal and passive:
From a schematic, do Tools > Data File Utilities > Check/View S-Parameters
