Questions tagged [smith-chart]

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Smith chart tutorial question

I am looking at a Smith Chart tutorial on the antenna-theory.com website. Unfortunately, I'm confused by one of the examples given...I don't get the same answer, so it's safe to say I'm doing ...
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1answer
51 views

RLC equivalent model and Impedance Smith Chart

I have done some impedance measurements on an unknown 1 port device. I have measured its impedance at different frequencies (from 10 MHz to 600 MHz) and I have seen it on the normalized (on 50 Ohm) ...
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1answer
33 views

How is a transmission line with a different characterisitc impedance shown on the smith chart?

A transmission line can be shown on the smith chart as a clockwise rotation, each 180 degrees corresponding to a quarter wavelength. But this is when the characteristic impedance (Z0) of the ...
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2answers
32 views

Where would a pure inductive or capacitive load be placed on a Smith chart, assuming the TL impedance is real?

I'm a new HAM operator, and just started learning about the amazing tool that is Smith charts; and it got me wondering what the edge case of a pure inductive or capacitive load would be? Since the ...
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2answers
78 views

Smith Chart for Dummies

I am not just an electrical engineering noobie, I'm an electrical engineering dummy. (No, you can't use me for testing your newly designed electric chair.) What I need is a simple, direct answer, to ...
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0answers
25 views

What is the Intuition behind the Stability Factor (K) in Microwave Amplifiers?

In microwave amplifier design, there is a Rollett's stability factor (included below), which determines if the amplifier can be unstable. If K > 1, the amplifier is always stable, and if not, it could ...
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1answer
31 views

Can a Unilateral Amplifier be Unstable?

When designing microwave amplifiers, stability is an important factor to consider. Stability is usually measured with the K factor. In a unilateral network, S_12 = 0, and this makes the K factor ...
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1answer
168 views

How to interpret s parameters including S21 on Smith chart on VNA display

I'm trying to become re-acquainted with S parameters, VNA, and transmission lines for some projects at work. I'm using Agilent, Advanced Design Simulator, to practice on the computer and to get the ...
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2answers
100 views

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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0answers
62 views

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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1answer
199 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
64 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
46 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
140 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
349 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
53 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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2answers
508 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
5k 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
642 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
549 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
238 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
252 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
2k 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
281 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
137 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
979 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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2answers
250 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
732 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
534 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
2k views

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
2k views

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
456 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 ...