Questions tagged [impedance-matching]
Impedance matching is a process of making one impedance equal to another another.
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Why does my calculation for transmission line reflection and transmission at a load have infinite solutions?
Take a transmission line with some characteristic impedance and insert a load somewhere along the line. What are the transmitted and reflected signals, given an sinusoidal input. Physically this ...
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Unusual chip antenna feed impedance matching
I'm designing a PCB with a RFANT3216120A1T ceramic SMD chip Bluetooth antenna.
The part is somewhat poorly documented and does not state the antenna impedance. The datasheet shows a test board with an ...
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Do audio impedance mismatches cause reflection (ie, 8-Ohm output to 20kOhm input) ? Does it matter?
I understand that audio source⇒input impedance mismatches are normal, and this answer provides a good reason as to why. However, having worked with RF more than audio, mismatches cause reflection that ...
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Maximizing magnitude of fields created by an antenna
I have a small loop antenna (\$C\$ = circumference<< \$\lambda\$ ). I am interested in the fields created by this loop at a distance \$D\$ along the z axis also small compared to \$\lambda\$.
I ...
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Impedance matching T/R switch
I do drive a piezo as transceiver. My transmitter provides square burst around 10Vpp which is too big for simply switching through a diode by dc biasing. I found out that bridge rectifier structure ...
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USB Data communication issue on a panelized pcba hardware test platform
I need some help..
I developed a test platform for the hardware tests of an electronic board panelized in sets of 10. The boards are placed on the test platform in their panelized form. As shown in ...
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Antenna complex input impedance into real impedance
I'm trying to design a loop antenna and make it resonate around 100 MHz.
Using a standard 50 ohms port, the resonating frequency is not at 100 MHz. Since I cannot change the geometry, I'm going to ...
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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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Single stub matching of loop antenna at 4.2 GHz
I am trying to match a loop antenna using the single stub matching technique.
Operation frequency: 4.2 GHz
Vacuum wavelength: 7.2 cm
Cable:
Impedance: 50 Ω
Velocity factor: 0.66
The antenna impedance ...
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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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Understanding impedance matching in RF PCB applications (STM32WB55)
I'm just getting into RF design since I inherited a board that uses an STM32WB55C for BLE. For now I want to start getting more familiar with the RF concepts since I don't have a lot of experience.
As ...
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Correct connection of a Wi-Fi board having both printed antennas and U.FL sockets
An RF part of a dual antenna Wi-Fi module from Aliexpress.
We can see coax sockets connected in parallel to printed antennas. Two external antennas and corresponding pigtails are part of the package.
...
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Which is preferred over differential pairs: trombones or sawtooths?
I have been told that trombones are much better to use than sawtooths, even if sawtooths may be prefered in some certians scenarios.
Here I have added trombones to the differential pairs. If I had ...
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Is it possible to simulate reflections by designing an RLC transfer function?
Assume that you're knowing the PCB stack and the geometry of the conductor.
You're computing the capacitance per mm and inductance per mm and also the total resistance of the conductor.
That means you ...
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Difference between characteristic impedance vs complex impedance
Are there any differences between complex impedance of antenna pcb trace vs characteristic impedance of antenna pcb trace.
This question rised up because of online pcb trace impedance calculator doesn'...
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How to match multiple impedance discontinuities?
I am trying to design a circuit to transmit various digital high frequency signals over cables, connectors and pcb to an oscilloscope. The simplified circuit looks like this:
simulate this circuit &...
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Impedance of different track widths - Should I compute the average width?
Assume that you having one track that goes from 0.11mm in width to 0.09mm in width.
I want to compute the impedance, but I need to select the width. What option should I select?
The largest width of ...
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RC filter cutoff and impedance
I wanted to create RC lowpass filter with cutoff frequency 15 kHz and output impedance 50 ohm. What should be R and C values? I'm a little confused how to interpret 50 ohm output impedance to ...
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Match 50 ohm impedance to LNA input impedance
I have following PCB version of circuit: on SMA input we have antenna strictly matched to 50 ohm, then we have regular RF switch IC, after RF switch impedance matching network and final stage is ...
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Operational amplifier layout- Controlled impedance
In the following picture, we can see a reference layout by Texas instrument for OPA838:
I noticed, in the polygon on the top layer, they have used a specific gap=0.5 mm, I wonder if they used a ...
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Layer stack up and impedance matching- 100 ohm
I have a 14 layer stack up as follows (the stack up is from EURO circuit):
I need to provide 100 Ohm differential impedance for my LVDS on layer 7, currently by the information from the manufacturer (...
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Calculating output impedance of amplifier to match to 50 Ω
Below is a schematic of an amplifier. The inductor used is a 1 μH inductor, emitter resistor is 2.2 kΩ. The bias resistors are both 200 kΩ. The capacitors are both 1 μF. I am planning to design a ...
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understanding the recommended impedance match for a SAW filter
I'm trying to understand the recommended impedance match for a TA0168A SAW filter input. The datasheet is https://www.rfmw.com/datasheets/taisaw/ta0168a%20_rev.2.0_.pdf
In my first circuit I'm trying ...
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Wideband Impedance Matching for Inductive Source/Load
I'm designing the frontend of a receiver and I want the output impedance to be 50Ω so that I can get as much power into the mixer. I tried placing a bandpass filter (image filter for 88-108MHz) in ...
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Optimal thin absorber of electromagnetic energy
I am a material engineer and have a question about a formula derivation regarding microwave absorption properties. I really cannot figure it out after days of trying. This should be simple for a ...
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Matching circuit for piezo transducer
I am at the stage of designing a system that match impedance of the power output (half-bridge) to a piezo transducer operating at 1MHz (Max 60W of power). I calculated the piezo parameters from the ...
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Is the reason for guitar "tone suck", i.e. loss of high end frequencies with impedance mismatching, actually due to high reactance?
When connecting a guitar's output to an input with insufficiently high input impedance, the signal is undesirably filtered, which is referred to as "tone suck". To deal with this, it is ...
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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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How to reduce on-resistance and parasitic capacitance effects of my MUX setup?
I am designing a mux board to mux a flashing setup. Both UART and SPI lines are on 1.8V logic. The Mux chips have ~4-8ohms on-resistance and 1.7pF on-capacitance. Few questions:
Would I need buffers ...
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Coax cables, impedance matching and BNC extensions
I'm trying to understand how to do proper measurements with a Voltage Differential Probe ( TT-SI 9010. This probe has an output impedance of 50ohm and has a BNC (It doesn't specify it in the data ...
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What is the purpose of a shunt element in a balun?
I'm working on a balun for a differential front-end receiver and see that they quite often use a shunt element (inductor) across the differential pair.
From what I could gather is that when you insert ...
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Balun converting 100ohm single-ended trace to 50ohm single ended for spectrum analyzer
On my board, I have 100ohm differential pair traces connected to a 1:1 balun, so the signal impedance becomes 100ohm single ended. I would like to measure the signal spectrum with spectrum analyzer. ...
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Coax cables and input impedances
I'm doing a voltage measurement with the help of an Active Differential Probe (TESTEC TT-SI 9010) with an output voltage of +-7V. This voltages have rise times of the order 500ns.
The set up looks ...
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Incorrect Output of RF Mixer
I've designed a RF mixer (Gilbert Cell) which takes a RF frequency between 88-108MHz and a LO of 77.3-97.3MHz, I want to take the difference between the two so the IF is 10.7MHz. Currently, the output ...
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Is it possible to implement shunt stubs to replace shunt capacitors for differential matching?
I am reviewing the subject of stub matching. For example, consider Network D:
Example photo screen-shot from TI documentation: https://e2e.ti.com/cfs-file.ashx/__key/communityserver-discussions-...
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Can I add a resistors to add speakers?
I have a 2 channel stereo output from my laptop connected to a surround sound amp: all 5 speakers with an impedance of 4 ohms (front, rear and sub) play the stereo sound. The speaker connectors on the ...
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Chip antenna matching of a custom board equipped with a STM32WB55
I am planning on designing a custom board using a STM32WB55. I have followed the "How to develop RF hardware using STM32WB microcontrollers" (AN5165) Figure 9 design for the RF part, which ...
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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 don't people always use 50 ohm resistors when matching impedances?
Impedance matching when designing the RF receiver circuit and antenna design takes a lot of time and effort for VNA. People often use capacitors and inductors to match the impedance of the antenna ...
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Which antenna trace design is better?
I need to design an antenna trace (WiFi and Bluetooth) that connects an ESP32-S3 chip to an IPEX connector with an impedance matching circuit.
I have some constraints that I need to work around:
...
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Where do I place my matching network for an antenna?
Let's say I have a microcontroller with an antenna output. The characteristic impedance of the pin for the antenna output is x+jy. I want to then connect it to a 50-ohm antenna.
This is the part that ...
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Slight difference in equations for the design of resistive matching network
I'm currently reading trough an application note from Analog Devices 2, in particular the "A NARROW-BAND LC MATCHING EXAMPLE AT 100 MHz" section. I re-did the calculations by hand and got ...
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Impedance matching and termination resistor
I’m a little confused regarding impedance matching with resistors.
As far as I know, the impedance of a trace is a part of its characteristics and it can’t be measured with an ohmmeter. For example, ...
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Confusion About Impedance Matching For Single-Ended and Differential Lines
I understand that for single ended RF signals I must ensure that the characteristic impedance of the transmission line matches the load impedance (say 50 ohm). I am a bit confused for differential RF ...
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how can I calculate impedance matching for STM32WLE5 RF network?
I am attempting to compute an impedance matching network by following the guidelines outlined in the ST Application Note - AN5457. However, on page 24, the formula and calculations appear perplexing ...
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How to design an RF frontend for an FM receiver
I'm designing a RF receiver for FM Radio. I simulated the circuit in LTspice and got an output as shown below:
This is OK, but I would like the gain to be 24 dB across the range of 88-108 MHz.
The ...
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Connecting multiple loads in self-balancing parallel [closed]
I have three (or 'n', where n=3 at the moment) large LED panels that I want to run in parallel.
As we know (or should have known before the 'royal we' actually tried it!), just wiring them together in ...
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How can I calculate filter parameters between RF switch and antenna?
In the schematics en.MB1389-WL55JC-highband-E02_Schematic,
there's a Pi filter following the RF switch before it links to the SMA connector for the antenna.
Upon calculation, I found that the cutoff ...
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Intuitive explanation of shorted stub behaviour
Can someone please give me an intuitive explanation of shorted stub behaviour?
NOTE: This is not a duplicate of Intuitive explanation of open stub behaviour which has been narrowed to focus on open ...
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Intuitive explanation of open stub behaviour
Can someone please give me an intuitive explanation of open stubs?
I have the length-based mathematical derivation and explanation from my textbook, but I am looking for an intuitive one.
For example,...