Questions tagged [smith-chart]
A graphical chart, named after the electrical engineer Phillip H. Smith, designed to help solve problems with transmission lines and impedance matching. Consider using this tag along with the "transmission-line", "impedance", "impedance-matching", "characteristic-impedance", and/or "rf" tags, as appropriate.
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Is my VNA broken or miscalibrated, or are these weird results normal?
My company got a new vector network analyzer recently and I'm using it to try to learn more about microwave circuits, especially the resonant cavities that we use in our measurement systems. I've seen ...
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Reflection coefficient on Smith chart moves in clockwise direction with frequency
If I plot the reflection coefficienct of an active network on the smith chart it moves in a clockwise direction with increase in frequency. How can we intuitively explain this?
I've noticed people ...
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Why are stability circles circles on a Smith chart?
I am new to basic concepts in amplifier stability, so the question might seem obvious, sorry if it is the case.
The amplifier stability translates into the equations for the reflection coefficients ...
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Calibrating a VNA
I am using the Siglent SSA3032A-R spectrum analyser which has a Vector Network Analyser (VNA).
Before measuring the impedance of an antenna under test so that I can match this antenna, I have to ...
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How to interpret S parameters on a Smith chart
I am trying to understand S parameters on RF transistors.
I chose the BFP840ESDH6327XTSA1 as my RF transistor, to operate it at 10 mA, 12GHz. The design should be optimal for simultaneously matching ...
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Tuning an antenna using a NanoVNA, Smith chart and impedance readings
I am new to antenna design and teaching myself how to optimize antennas using a VNA.
I have created a monopole antenna on a PCB (i.e. a single length of track.) The antenna can be fed via a PI network ...
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Transmission line and input impedance - Smith chart
According to "Smith Chart Supplement - Corrected Jan 2012"
https://www.arrl.org/files/file/Antenna%20Book%20Supplemental%20Files/22nd%20Edition/Smith%20Chart%20Supplement%20-%20Corrected%...
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WiFi (2,4G) Antenna Isolation. Why 3 capcitors version does not work
I need to isolate the antenna from the WiFi transmitter. There are some solutions on the market but none suitable for my application.
So I have started some experiments.
2x PCBs creating DIY ...
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Relationship between Smith chart and frequency response graph?
What is the relationship, if any, between a Smith Chart and a frequency response (magnitude and phase) graph?
If there is any relationship, what additional constraints or information (topology, port ...
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Double Stub Matching Impedance
I'm trying to understand the double stub matching impedance using Smith Chart.
Here is the diagram for the double stub impedance:
The impedance on the right has to appear purely resistive.
So ...
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which antennas is better for 433 Mhz 30dbi LoRa module [closed]
I am searching a antenna for LoRa module. my first priority is distance. which is more long range, it is better for me. There are 3, 433Mhz 3dBi antennas. Can you help me which is best and why? if you ...
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RF Matching Problem
I am having some fundamental issues trying to create an impedance matching network for an 868MHz antenna, I have a PI network between the antenna's connector and the antenna feed point
I have measured ...
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Meaning of S11 performing a clockwise arc circle about the smith chart origin?
I've tested a device with my VNA. It displays S11 in a Smith chart as a plot x(w) + iy(w) (w the frequency). Curiously, as w increases from 50KHz to 600MHz, the plot is an almost perfect 1/3 circle ...
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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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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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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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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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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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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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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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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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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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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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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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Self-resonance frequency of chip inductors
I am studying chip inductors and here's one of the frequency responses:
There is more than one resonance frequency for a single inductor. When we say inductor resonance frequency, it usually means ...
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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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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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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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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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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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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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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 6 pF PIN photodiode which driven by a 2.5 GHz optical ...
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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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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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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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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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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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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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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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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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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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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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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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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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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 ...
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