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Questions tagged [smith-chart]

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Smith chart of λ/4 Transmission Line

I came across the following slide on power combiner circuit and I have questions about it. Why traverse across the upper half circle ? Why "ZT-line is the geometric mean of Zout and Zin." ?
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S11 parameter measurements of NFC PCB antenna by VNA

I'm trying to measure the S11 parameter of the NFC PCB antenna (actually PCB coil) by VNA. Desired Smith chart pattern is like the below picture (probably with different values, because of different ...
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Single-Stub Matching - Smith Chart

My solution: I'm not sure if this is correct or not. I know I haven't solved the entire thing, my main issue is with matching the complex components.
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1answer
72 views

Interpreting scattering parameters on a Smith chart.

I'm trying to become reacquainted with microwave circuits and how to analyze them, especially with a VNA. Just to get some practice I'm using Keysite ADS simulator. To get the feel of it I used the ...
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1answer
49 views

S-Parameters, Smith Chart, and Reflection Coefficients

Please help guide my ignorance on this topic. From what I understand, S-parameters are reflection coefficients generalized to N-port systems (via an S matrix), but for a 1-port system, these converge ...
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1answer
42 views

Why real part of load change as we look through transmission line?

As we move from an imaginary load towards generator through a transmission line, we can see that real and imaginary part of that impedance changes. In fact, an ideal transmission line is comprised of ...
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1answer
106 views

Self-resonance frequency of chip inductors

I am studying chip inductors and here's one of the frequency response: There are more than one resonance frequencies exist in a single inductor. When we say inductor resonance frequency, it usually ...
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2answers
258 views

Find impedance matching in a quarter wave transformer

I would like to know if there is a way you can find the impedance that has to be set between the load \$Z_L\$ when it is complex and the characteristic impedance \$Z_0\$ to have impedance matching ...
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1answer
42 views

Mark specific frequencies in smithchart

I have a smithchart created by MATLAB using the following code (the S22 is a 801x1 vector obtained from a file): n = 801; fStart = 45*10^6; fStop = 15*10^9; f = linspace(fStart,fStop,n); figure() ...
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416 views

How to get complex reflection coefficients?

If I terminate a line with an open circuit, I'll get reflections of any incoming signals with the same phase (a reflection coefficient of 1). If I terminate the line with a short circuit, I'll get ...
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0answers
3k views

How do I convert S-parameters for impedance matching?

How do I derive the Z-parameters to calculate a matching network for a device? I'm not sure what terms to even search for as I get all sorts of information I am not familiar with. My task is to ...
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2answers
531 views

Finding unknown load using a smith chart

I am asked to find the impedance of an unknown load. The precise formulation is provided below: The following two step procedure was used to measure the value of an unknown load \$Z_{L}\$. The ...
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1answer
483 views

Stub matching at smith chart

I'd like to clarify some concepts about microwaves that I still can't understand it at all. I'm reading Pozar's Microwave Engineering, more specifically stub adaptation in the Smith Chart. The circuit ...
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2answers
197 views

Impedance Matching a capacitive source

I am trying to work out how to match a current source coupled with a capacitor to a 50 Ω load for maximum power transfer. Specifically I have a 6pf PIN photodiode which driven by a 2.5 ghz optical ...
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1answer
205 views

Smith chart plot from simulation is opposite from experiment?

I did a simulation of an antenna and replicated the antenna in an experiment however the simulation is coming out to be roughly the opposite. From the experiment I was expecting this plot to spiral ...
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1answer
1k views

How to plot Smith chart

I need to plot Smith chart, having frequency, VSWR, reflection coefficient and phase. I'm aware there's smithchart command in matlab and as an argument I should use ...
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1answer
264 views

What options do I have to measure directly impedance change (ohm) or deduce it indirectly from S-Parameters?

Basically I want to measure how impedance (Ohm) relative to Z0 (50 Ohm) waveguide is changing by varying a parameter. I currently measure the reflection coefficient S11 in a 1-port setup. Our VNA can ...
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1answer
132 views

Drawing Smith Chart from Network Analyzer file

I have a file as a .dat format taking from network analyzer. I want to plot Smith chart graph. The file has 3 columns which are frequency, S11(linear value), S11 (ang value) respectively. How can draw ...
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2answers
851 views

Smith Chart Conjugate Matching

In an example in Pozar's Microwave Engineering, a conjugate matching circuit for maximum gain is designed using Smith chart. In the shown Smith chart, the matching circuit for input is designed. We ...
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1answer
219 views

S11 all on the outside of the Smith Chart

How should someone conclude what's going on on a TX line that has a Smith Chart that goes around and around the outside? I've reworked a board and expected to see a curve pass close to (0,0), but what ...
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1answer
2k views

Balun/matching network question

I am having problem to verify what an app note (AN068) explains to calculate Balun values. I would appreciate if someone could tell me what/where am I doing wrong? The summary of the RF part: Blue ...
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2answers
689 views

Use of Smith charts

There are Smith charts with impedance and admittance coordinates and Smith charts with only impedance coordinates. I believe I learned how to use the first one. Is there any sense in studying how to ...
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1answer
519 views

RF amplifier load matching

I want to match RF power amp to aerial. There is no 50 ohm or 75 ohm transmission line inbetween. So, I consider my aim to be matching certain load-reflection coefficient (Γload) to a short circuit (...
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2answers
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What application do you use for plots?

What application do you use for creating plots? Years ago, I was using gnuplot and then matplotlib (which is just Python library). But none of those were perfect. For example, I was unable to create ...
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3answers
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Smith Chart Explanation

I'm working on designing some hopefully simple RF (912 MHz) attenuators. I need a few different levels of attenuation but each different attenuator can be fixed. I have prototyped one using just off ...
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1answer
453 views

Help with Matching circuit

I'm using a SAW filter which has balanced input and output. In the datasheet there is shown a matching application for 50ohms balanced output. But plotting the S22 parameters into a Smith Chart and ...
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1answer
2k views

Wideband Impedance Matching

I have designed a common-emitter RF amplifier, with input and output impedance matched for my load and source impedance. I have used Smith Chart for the matching. The matching is good for the ...