# Questions tagged [s-parameters]

Scattering parameters or S-parameters (the elements of a scattering matrix or S-matrix) describe the electrical behavior of linear electrical networks when undergoing various steady state stimuli by electrical signals.

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### Unable to replicate Twisted IFA antenna S-parameter curve using ANSYS HFSS 15

I am attempting to replicate the S-parameter curve for an antenna design as described in the paper "Antenna Design and Analysis" with DOI: 10.1109/LAWP.2009.2015345 using ANSYS HFSS 15. Here ...
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### How to conduct temperature variant EM simulations in HFSS?

I want to conduct temperature variant EM simulations in HFSS i.e. simulate s parameters of a CPW at various temperatures. I am using a temperature variant material using thermal modifiers. I have also ...
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### Using Kirchhoff's voltage law for calculating S-parameters

Consider the following circuit: for which I'd like to calculate the S-parameters of the impedance $Z$ (and assuming $Z_G$ = $Z_L$ = $Z_0$). Will it be correct to use the Kirchhoff's voltage ...
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### S-parameters of a matching network

I have the following matching network designed for $\omega=2\pi\cdot 1GHz$ and I want to calculate $S_{11}$ and $S_{21}$. The normal definitions/calculation setup for S11 that I use are in the ...
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### S21 calculation

In this post It mentioned that there's a factor 2 in S21 value. But I'm still don't understand why there's a 2 in it. My schematic is shown below. Shouldn't S21 = Vout/Vgen? My question is: where is ...
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### Transimpedance Amplifier Gain ac and S-parameter Analysis

I'm currently working on finding the transimpedance gain of a transimpedance amplifier. However, I've encountered an issue where I get different gains when performing AC analysis compared to S-...
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### How to create schematic of common mode choke that reflect on Common mode, differential mode and mixed mode? [closed]

I aim to create a schematic that can replicate the results exactly as seen in the measured S4P file. I have conducted the measurement using a VNA and am attempting the schematic simulation in CST. ...
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### S-parameter of cascaded system, port impdance

I have a question about the s parameter of the cascades system. Assuming that there are two system A,B as shown in the figure and each has an s-parameter measured at 50ohm port, I understand that the ...
1 vote
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### How are SPICE files created compared to S4P files generated from a VNA?

When measuring impedance versus frequency using the same data in both SPICE and S4P formats, why do I obtain different results? COMMON MODE IMPEDANCE Common mode impedance 10514 Ohm at 79.1 MHz S4P ...
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### Challenges in Bandwidth in Common mode Choke Modeling

I'm currently working on characterizing a common mode choke (CMC). However, I'm encountering difficulties aligning the bandwidth of my model with the measured results. Specifically, when I attempt to ...
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### Why is a bandwidth discrepancy occurring despite consistent Q factors in the given Graph?

I was trying to do curve fitting the common-mode choke in CST Studio according to the selected S4P file from TDK (ACT1210G-800-2P-TL05). However, the common-mode impedance measured from the file does ...
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### Why my Common mode choke with 2 turns showing multiple Peaks in the graph?

I analyzed the CMC choke by Wurth Electronics (part no: 744830039080) using VNA and obtained the insertion loss for both common mode and differential mode. The graphs match with the datasheet: While ...
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### AC analysis of a Bias Tee

I am designing a bias tee here and wondered whether it actually works or not? Hence I conducted an AC analysis instead of S-parameters (after verifying that s parameters are okay). The bias tee has ...
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### How do you de-embed a shorted 2-port fixture?

I've been working through reproducing Steve Sandler's 2-port shunt-through measurements (2019 SIJ article, Picotest slide-deck). My target is to measure capacitors with ESR down to 1 mΩ with an ...
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### Matched junction S parameters

This question was asked in a competitive exam in India. Two-port S matrix is assumed here. For matched junction S parameters, which of the following is correct ? (a) S11 not equal to 0 (b) S11 equal ...
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### RF Reactive power splitter S21 and S12 is equal, when return loss is not

When measuring a 4-way reactive power splitter the S-parameters at the frequency of interest(400 MHz) looks like this: S11: -34 dB S22: -3dB S21 = S12 = -6dB With IN being port 1 and OUT 1 being port ...
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### Parameter Sweep in ADS by Keysight?

I am trying to create a Parameter Sweep in Momentum (ADS circuit layout simulator). Does anyone know how to do that? ADS offers options to create a parameter sweep during design but not during layout (...
1 vote
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### How do I correctly calculate the S-parameters of cascaded lines?

Suppose I have two coupled transmission lines cascaded. I know the S parameters of both lines. From these S parameters, I can extra SA and SB S = [SA SB; SB SA] Now, I can find S_odd = SA-SB and ...
1 vote
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### Matching network for two-port with internally matched inputs/outputs

Background I had a lab in school where we were given an LNA with inputs/outputs matched to 50Ω, that will be connected to a 50Ω system: The task was to design the input and output matching networks: ...
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### How do you chain 2-port S-parameters onto a 1-port S-parameter?

With 2-port S-parameters, you can build up a circuit by chaining them together using ABCD or T-parameters, simply multiply the matrices: We have measured a complex single port S-parameter of an ...
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1 vote
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### How to plot standard deviation in Advance Design System (ADS) software?

I have measured several sets of data using a Vector Network Analyzer, and my data is in S-parameters format. How can I draw a standard deviation plot in ADS software based on my data?
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### How does the characteristic impedence of a lumped network work?

I'll take a textbook example to explain my problem. Find the scattering parameters of the 3 dB attenuator circuit shown in the figure: The solution reads: From (4.41), S11 can be found as the ...
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### Scattering matrix of quarter-wave transformer

I am trying to solve for the scattering parameters of a quarter wave transformer. The example that I am given is a transformer with characteristic impedance 100 Ohms, and the reference impedance (...
1 vote
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### Problem understanding lossless T-Junction divider

I am studying how the lossless T-Junction divider works. I am going to assume that the susceptance in the junction is 0 for simplicity, and it is not relevant to my question. The structure of a T-...
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### How do I calculate insertion loss for a dual input receiver?

Typically my test setup consists of: Antenna->Antenna Feed Cable->switches->Filter->LNA->Spec An feed Cable->Spec An I calibrate the cable loss by simply getting the S21 (S1 ...
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### S parameters calculation from VNA file

I am trying to validate that our broadband LNA(Low noise amplifier) is working correctly. I wanted to measure the S21 of the LNA, I calibrated the VNA for the specified frequency range and measured ...
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### Does insertion loss include return loss?

Does insertion loss include return loss? If we take a 3-ports circulator, does insertion loss from port 1 to port 2 consist of return loss of port 1, a power that leaks throug port 3 and power ...
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### S-Parameters Re-normalization

When we talk about S parameters for a certain number of ports we typically reference each port to a specific impedance, most of the time to one common $Z_0$ impedance, but in general terms to a ...
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### S-Parameters Power Loss

I am trying to calculate the power loss in a 2-port system, via the s-parameters. The actual system is a cavity with 2 waveguide ports and a dielectric mass. I know the power that is being pumped into ...
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### Applying an electrical field to a particle in Ansys HFSS

Does Ansys HFSS have the ability to show the applied electrical field to a particle? I designed a coplanar wave guide in this software, something like in this video. Is it possible to put a particle ...
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### Intuition for S-parameter formulas?

Wikipedia defines S-parameters as[1]: $$\boldsymbol{b} = \boldsymbol{Sa}$$ Where: $$a_i = \frac{1}{2}k_i (V_i + Z_i I_i)$$ $$b_i = \frac{1}{2}k_i (V_i - Z_i^* I_i)$$ Saying it is defined in [2], ...
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### Rollett stability factor - derivation and numerical meaning

For two-port networks, a value called the Rollett stability factor, K, can be derived, whose value can then be used to assess one of the criteria for the network to be unconditionally stable (K > 1)...
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### What is the difference between Smith charts plotting Z11 and S11?

Background In the process of trying to fix an LNA input impedance match, we discovered we need to understand more about Smith charts! The question is the at the bottom of this post, here's some ...
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How do I subtract two S parameter curves and display the result? How do I do this for results from two different models in Advance Design System (ADS) software?
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### The meaning between raw and calibrated S parameters

VNA: E5071C Cal kit: 85033E DUT: cable end bandpass filter This figure shows measuring S21 of filter: Upper figure shows real part of S21 and lower one shows imaginary part of S21. Blue line is raw ...
1 vote
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### How vector network analyzer measures S-parameters of lumped element?

i've seen video lecture where S-parameters of 50 Ohm resistor placed in series between input and output port of VNA with reference resistance also of 50 Ohm are calculated by hand. S11 was calculated ...
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### Passive component S-Parameter measurement: Difference between series and shunt

Johanson provides S-parameter measurements for their RF capacitors in touchstone file format (see here). Specifically, looking at the S-Series files, they provide series and shunt type measurements. I ...
1 vote
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### S21 & S12 of a mismatched transmission line

I am trying to solve this problem: Since it is asking for a reference impedance of 50 Ω there will be a mismatch, and hence reflections at the Port 1 for calculation of S12. I already know S11 and ...
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### Given S-Parameters (or Y,Z,T,ABCD), how can you calculate $Q_C$ and $Q_L$ (or, how do you calculate ESR)?

Background I'm writing a .s2p/Touchstone library for Perl and I'm trying to get the Q value of a component given an S-parameter matrix. The Goal In this case I'm trying to get Q for a 10nF muRata ...
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### S parameter model of the capacitor

For same capacitor, there is no s-parameter model, so can we use the model from other manufacturer of the same spec. Eg: Caps with model - C0603C104K5RACTU - KEMET - Cap, Cer-X7R, 0.1uF, 50V, 10%, ...
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### Comparing scattering parameters in dB and magnitude+angle forms

We're trying to compare the scattering parameters from two parts (ADG902 and BF1101). Their datasheets use dB and mag/angle respectively. ADG902: BF1101: When trying to convert between the two, we ...
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### How to extract s2p file from a large-signal model? - ADS

I am working on a RF IC and I wish to extract s2p file from large-signal model (the large-signal model is available in producer company). How can I do that in ADS?
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### How to modify s2p file of an IC? - ADS

I have a s2p file of a RF IC which it contains frequency from 650 MHz to 1.1 GHz. I wish to modify s2p model so that two frequency 0 Hz and about 3.5 MHz is added to the s2p file. How can I do that ...
1 vote
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### What would be the S-parameters for an "ideal" shorted transmission line?

I seem to remember that the shorted- vs open-transmission line reflection is out of phase by 180-degrees. I'm new to the mathematics behind transmission line theory and I'm trying to figure out how ...
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### Which matrix index should be used when Y (admittance) is shown to compose a circuit segment mapped to an ABCD matrix? Y21? Other?

I would like to cascade a serial capacitor with a shunt inductor to form an L-match network by multipling two ABCD parameters and convert the result to S-parameters that represent the composite ...
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### What does $\beta$ represent with respect to the length of a transmission line?

The picture below shows the ABCD parameters for a transmission line of length $l$ from this video. Question: What does $\beta$ represent?
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### Are T-parameters the same thing as ABCD parameters?

S-parameters can be converted to either T-parameters or ABCD-parameters, and both are considered a "transfer matrix". The conversion from S-parameters to T- or ABCD-parameters are defined ...
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### How are S-Parameters and Reactance related, can one be calculated from the other?

I know that, for example, $X_L=2\pi f L$ will calculate reactance of an ideal inductor, but can this be calculated for a real component model? Given the S-Parameter values at some frequency from an ...
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