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34 Threads found on edaboard.com: Spectre Impedance
Cadence spectre does not like floating nodes,high impedance nodes,internal current loops etc.Therefore I used to use very high resistances to floating nodes, very small resistances to high valued capacitors to make it faking out.It's very messy simulator.
If you have access to spectre or any simulator which can measure S11, you can drive the line deferentially while varying the source impedance. The value of source impedance which minimizes S11 is your differential characteristic impedance. Same can be done for common mode.
Use "xmfr". "analogLib/xfmr" is a "transformer" as spectre Primitive. hoge (t1 b1 t2 b2) transformer n1=1 n2=sqrt(100/5) see "spectre -h transformer".
I tried to measure the input impedance of differential input stage of mixer using s2p analysis in Cadence spectre RF, I got same Z11 in following cases 1) When the Port connected deferentially 2) Using AnalogLib ideal_balun 3) Using RFlib balun (with Balanced output impedance set to 25 Ohms), with balanced output (...)
Hi, I'm trying to use spectre to get output impedance of following circuit 96600 I can do AC sweep and use Vout/Iout to see the output impedance VS frequency. But in this way i can not see the influence of input square wave switching. If i want to see the influence of this square wave, should i use PSS or PSP simulat
I am trying to design a rectifier block for an inductive link. However, I am facing issues with transient simulation in spectre, Cadence. As an example following is a simple resonant tank driven by an ac source with 50 ohm input impedance. The ac source is modeled by a sine voltage source with 50 ohm resistance in series. Series resonant tank consi
Hi, I have to simulate the gain of my designed LNA with certain antenna impedance as a source. I am using cadence spectre for the simulation. The problem is that cadence spectre provides n1port for importing S11 parameters of antenna, which is a passive port. Therefore, if i connect the n1port at LNA input to represent antenna, i (...)
hey iam designing an osc. and i need to see the impedance of the ct. across el LC tank and to check if it is -ve or not any advices on the method using spectre also i need to draw the impedance locus diagram across LC tank , any advices for the technique used (imag. Z on y axis vs real Z on xaxis) thanks
Hi guys, I've gotten something unsure about noise factor. Hope for help here. The Noise Factor is defined as below. N = (Na+G*Ns)/(G*Ns). Different Ns produces different N. And in Cadence spectre, the noise source is usually a port. The impedance of the port provides the thermal noise 4kTRB V^2, which is related to the value of R. Q1: What
Does any body know how to measure the lc tank quality factor with software(rf spectre .i.e cadence) and by calculations too? is it possible to get 900 ohm impedance of an lc tank ?(this lc tank was used for an lna load.)( l=5.49nH , c=651fF).the lna has a dc blocking cap of 2pF value after the tank. what is the relation between the (...)
is output port must be added for IIP3 measurement? if port needed what should be its impedance.iam getting different IIP3 results with and without the port and also different results for different port impedances.help me please.................
Hi Guys: I had integrated a buffer stage at the output of the designed VCO, for isolation. How do I measure the S21 and S12 plot of this buffer stage in spectre-RF to observe the isolation characteristic. Thanks in advance Rgds
is Z-parameter from s-parameter analysis in cadence spectre RF will give correct input impedance.I want to calculate input impedance of my Low noise amplifier circuit. Whether input impedance is equal to Z11 parameter.?thanks in advance
Hi, all. In spectre, we can get the node capacitance of the circuit. But these node caps only include the gate caps, excluding the junction caps. Does anybody know how to get the junction caps in spectre? i am not meaning just one transitor, I mean the node connected to every relevant transitor (especially to transistor source or drain).
we can use .print cap(node) to plot capacitor curves in hspice. But how do we do that in spectre? I found there was a captab option in transient analysis. But it seems that it only calculate a capacitors at one point... Is there any idea?
in Eldo, there is also .pz analysis. maybe spectre will hace the similiar tool
I want to see output impedance of an amplifier. I know the method.. result->print->1/gds But I heard that there is xf analysis in spectre like in hspice. And I tried xf analysis, but I didn't get correct data. Please help me. Just I want to know the output impedance. 1. How to make the scheme for measurement? 2. How to setting th
If you think of the circuit as a blackbox, take the node you want to get the output impedeance of. instantiate a capacitor of a very high value in spectre (>1MegaF). Connect one terminal of the capacitor to the node you want ot measure the output impedance of, and connect the other terminal to an AC voltage source and have the AC magnitude as 1. Ru
Thanks
If you do ac analysis in spectre simulator, and then print the DC operating point of the interesting transistor, you will see gds and ro. Normally I treat 1/gds as the output impedance of the transistor, is that correct ? However, I still see that there is another paramater : ro, is it the same one ? which one should be used for analog de
the simulation just tell me the noise out/noise in=nf and added noise, but when I change the source impedance and temperature all of the three noise also changed,can anybody tell me based on what the noise data are given out especially noise in.
in spectre, maintian the DC input level and add a ac current at the output node, run ac simulation and get the ac voltage magnitude of the output node, the output resistance is equal to the ac voltage magnitude devided by the ac current, if the ac current is set to be 1A, then the output resistance will just be equal to the ac magnitude.
I am running noise simulation and it indicates that some of the major noise contribution comes from various s-parameter models in my circuit. How does spectre calculate the noise of those models? Technically s-parameter model does not contain any information about noise.
Hello all, I have a single ended 2 GHz amplifier , i am using spectre simulations to make S parameter simulations, and using simultanuous input output matching technique mentioned in Gonzalez book, my problem now is that the sourse impedance is 150 ohm and load impedance is 25 ohm, so what is the reference impedance of (...)
I am trying to characterize a 2-port network using spectre. Both the input and output impedances of this network is supposed to be 200ohm in the frequency band of interest. So I made two identical instances of this 2-port network. For the first instance, I connect PORT1 to the input and PORT2 to the output. For the second instance, I connect PO
In ADS , port component will accept complex impedances. Put Z=R+(-) jX value in "Port impedance" field. If you would change your imaginary part of your impedance simply write a equation like... Z=R+j*2*pi*freq*L or Z=R-j*(2*pi*freq*C)^-1 ADS accepts equations in component definition fields. spectre also (...)
the balun model in spectre (verilog-a) has an unbalanced input impedance of 50 Ohm and a balanced/differential output impedance of 50 Ohm. these impedance values can be varied. to my knowledge, if the diffrential output impedance is 50 Ohm, each output has an impedance of 25 Ohm. however, if (...)
I have a question when try to estimate a mixer's NF. How dose Cadence spectre calculate the NF of a mixer? I mean, if we are designing a mixer with onchip input from an LNA, then the input impedance of the mixer surely won't be 50Ω. So, when calculate the NF, which needs a value of Rs, dose it use the Zin of the mixer? If not, what is th
Hi Iam having problems with differential Lna simulation in spectre. I have designed a matching network that would step down the impedance to a low level . After that i have used an ideal balun from the rf lib and tried to simulate it. I also tried with a VCVS.Neither of these seem to work. My S21 is a straight line . BTW the (...)
Dear All : Does anyone know how to simulate the DC and AC impedance usihng Hspice or spectre , Any document for me reference ? Thanks
when design LNA, it is said to size the transistors to match the optimal source impedance to get lowest NF. But I don't know which simulation can get the noise impedance of the LNA? In most cases, it is not the same with input inpedance. i use cadence ic50, spectre and spectreRF. does anyone know which simulation can (...)
sp analysis in spectre
Maybe PAC in spectre can slove this question. Yibin.
I think you misunderstanding my question. I know you match Zin to 50ohm, but how do you measure Zin? you run sp analysis using spectre then look at Z11 (Re & IM) or ZM1 , right? And also, for LNA design, I think they are using some design method for simultaneous noise and power matching of the transistor. They sweep the thansistor size(emitte