Questions tagged [impedance-matching]
Impedance matching is a process of making one impedance equal to another another.
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CAN-Bus: Wire Impedance vs Terminal Resistor
I'm seeing several pre-fabricated "CAN-Bus" cables with (2) DB9, 120 ohm terminal resistor connections, while the cable's impedance is 100 ohms.
A. What is the purpose for this mismatch?
B. ...
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Does a power amplifier dissipate power in its source impedance?
If I have a power amplifier (or other signal generating device) that has a source impedance of 50 Ohms and drives 1W into a 50 Ohm load, does it also dissipate 1W in its source impedance?
My current ...
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PCB design for high-frequency differential lanes (PCIe and USB)
I have designed an M2 adapter which converts from KeyE to KeyM.
Practically this means my board can be inserted into a KeyE slot, and it can host a KeyM SSD.
Gray rectangle is the KeyM socket on my ...
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Impedance matching before or after connector
Suppose I have a device which needs to have its impedance matched to some incoming generator at one specific frequency. This device is placed on a PCB and a trace is connecting it to a 50 Ohm SMA ...
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Power analysis of transmitting antenna equivalent circuit
I'm currently taking a course about antennas, based on the book "Antenna Theory: Analysis and Design" by Constantine A. Balanis.
The Thevenin equivalent circuit for a transmitting antenna is ...
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Impedance considerations
I'm desiging a PCB which uses USB (2.0) and PCIe (2.1).
USB is not that fast, however it's said its impedance might have to be correctly set to around 90Ohm +/- 15%.
Now on the other hand, PCIe's ...
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LVDS to Singled-Ended - Transmission Line Balun Matching
I need to convert a LVDS clock into a single-ended signal. In the past I've used a voltage balun with a center tap on the secondary but I haven't found any good past 1GHz. I need to get to 2GHz in ...
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Can reactive components affect resistive impedance of circuit (Smith chart question)
I'm failing to understand something. Impedance matching by complex conjugate can be defined as this: "For two impedances to be complex conjugates, their resistances must be equal, and their ...
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Why does "impedance matching" in the context of reflections demand that resistive impedance and reactive impedance are treated separately?
I have assumed that for reflections, Ohm had to be matched between source and load, but resistive and reactive impedance did not have to be matched separately. I was told this is wrong, and that ...
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Impedance matching in RF and complex conjugate (Maximum power transfer theorem)
The "maximum power transfer theorem" states that "maximum power transfer occurs when the load impedance is equal to the complex conjugate of the source impedance", that "for ...
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Matching a 50 Ω amplifier output to a 50 Ω SMA connector on a PCB
Silly question:
Say I have an amplifier with a 50\$\Omega\$ output and I want to connect it to an SMA connector. As far as I understand I need to match the 50 ohms to maximize the power transmitted. ...
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Impedance matching a function generator and a laser source
I am using a function generator to generate a sine input to a modulated laser. The function generator has output settings of 50 Ω and High-Z, while the laser for some reason has a 1 kΩ input impedance....
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Resources for impedance matching networks
I am working on my first hobby PCB design project that includes RF components. On one hand, I have a 2.5GHz WiFi signal and an 868Mhz LoRa signal.
I copied the matching networks from the reference ...
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Why is the balun transformer shorted and not simply removed?
I use a normal balun to match my 300 ohm antenna to my 75 ohm tuner
(for "over-the-air" digital TV):
I opened this balun up and found the typical circuit:
Since the second coil from the ...
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Weired result of Ltspice Zin measurement, Phase shift of -104°
I am trying to measure the input impedance of this amplifier to design a matching network for it. But the input impedance I get has a phase of -104° at the frequency of interest. I thought that Phase ...
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Impedance matching 133 MHz - Topology and terminating resistor concerns
I am using the QSPI bus of the RP2040 to talk to a flash chip. I am also putting 8 more chips (PSRAMs) on that bus in my design, and a second RP2040 to load them. The datasheet for the RP2040 isn't ...
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PCB Newbie Stackup understand questions
I want to design a board with 6 layers up to 1.8mm thickness,120ohm diff and 90ohm diff ,SE 50 ohm
and the manufacturer sent me this stackup:
12 mil for SE-50ohm not too thick?
what is the material ...
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HDMI: What is the maximum acceptable differential impedance variation and for which length
Imagine I have a HDMI bus with differential impedance 100 Ohm and length 10cm
Imagine that for a segment of length "L" there is an impedance variation of "DELTA"
Question: in order ...
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Via for 50 Ohm impedence track to U.FL connector
There's a 4G LTE modem along with GNSS capability mounted on the bottom layer of a 4 layer PCB. Its a 4 layer PCB with JLC04161H-7628 Stackup. 50 Ohm impedance trace needs to go to U.FL connectors on ...
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Using a series of attenuators for a sampling HF transmission math or design errors/misunderstand/ignorance
TLDR: Why does my math not work.
SITUATION: I have a 1.5KW 50 ohm RF dummy load for ham radio and I'm trying to design a sample port for monitoring with a spectrum analyzer. I have now realized that ...
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Why does the normalized input admittance have to be 1 +j0 to achieve matched condition at MM'?
In section 2.11.1 in the book Fundamentals of Applied Electromagnets by Fawwaz T. Ulaby, it says that in order for the circuit below to be matched at MM', y-in must be y-in = 1+ j0. Why is this so? ...
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nRF52832 impedance matching values alternate solution
My question is all about to confirm or correct my understanding of impedance matching ckt. During fabrication we take care of transmission line of 50 Ω. Currently we have reference values as shown in ...
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USB audio (TRRS) to transformer for impedance matching
I'm kind of stuck, and not really sure where to look, or what to look up.
I need to take the output of a USB audio fongle that has a single 3.5mm jack (TRRS), into a break out cable, and then need to ...
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How to match a network over multiple frequencies?
I'm trying to match the following network using the Matching Network Designer so that the resistance curves (solid lines) get pulled towards the horizontal line and the reactance curves (dotted lines)...
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Why do LDMOS RF power transistors have a low real resistance?
I've been looking through datasheets for RF LDMOS amplifiers for use in an RF power amplifier. They typically have an input impedance that has some small real part of the resistance (<10 Ω) with a ...
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Matching network for a resistive matched source, line and load?
Suppose we have a well designed 50ohm antenna and source (as there are in many RFIC, and antennas), and we design/use a noticeable long 50 ohm trace/cable in between. If I recall right, this design ...
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Vector Network Analyser (VNA)
I am trying to achieve impedance matching using load-pull mechanism and I recently found out that on a Smith chart in the VNA, the S21 doesn't make any sense as I have to plot transmission parameters ...
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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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Audio line-out to amplifier line-in matching impedance and voltage
I am an electronics hobbyist. After reading online my understanding is that an op-amp buffer or JFET pre-amp can be used to match a medium (lower) input impedance with a high output impedance. In my ...
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1Gbps serial bus length matching
How tightly should trace lengths be matched for a 1Gbps serial databus? It seems to me that 100ps (15mm) should be more than sufficient. However:
The Raspberry Pi Computer Module 4 (CM4) datasheet ...
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Impedance matching for an antenna
I've been working on a project for school which involves designing matching networks for antennas (meant to be driven at 2.4 GHz) being connected to a 50 Ω line, and it led me to consider the ...
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Impedance matching
I am a newbie at microwave. I'm confused about impedance matching. So far just 50 Ω impedance stub in outside.
But in this example below I saw 75 Ω. I could use the Smith Chart but I didn't know how ...
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Sending square wave over PCB track
How is it possible to send a high frequency square wave over PCB track when it is not possible to match the impedance of the track to all the frequency components?!
Usually we match only the main ...
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Why should we choose a non-inverting op-amp in this context?
I need to build the cheapest amplifier possible knowing Rin, Rch, Vin <= 1 mV, Vout = 12 V and the simplified datasheet of four differents op-amps:
Here is my book's answer:
It is claimed that:
...
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Cannot trigger digital logic because half of source voltage is lost in impedance matching
I am using a 3.3V output of an NI controller over a coax transmission line. I have matched the termination resistor to the 50 Ohm source resistance. I need to use this output signal to control three ...
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Differential pair for Ethernet on Olimex boards
Just out of curiosity I was looking into ESP32 based boards such as EVA, GATEWAY, POE, POE-ISO by Olimex and found the differential pair used for Ethernet is all different sizes (i.e.: width and space ...
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When should an unmatched antenna be measured with a cable length in even multiples of a half-wavelength?
A few years ago someone told me that if you use a cable which has a length of an even half-wavelength multiple for the frequency being tested, then the impedance measured at the end of that cable will ...
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Impedance matching transformer simulation
Here is an example of a transformer that converts 10Ohm load into 1kOhm
And the AC simulation result
From my understanding the source sees the transformer as an inductor in parallel with a converted ...
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Is a source and a load matching network needed for impedance matching?
I am looking to use a SX1280 LoRa IC with a Abracon ACAG0801-2450-T antenna. However, I am a little confused about the impedance matching.
The SX1280 reference design uses this as the matching circuit:...
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Binomial matching (RF & microwave)
In a Binomial Matching Transformer, we're expecting the reflection coefficient to be the following function:
\$\Gamma(\theta)=A(1+e^{-2j\theta})^N\$
What is the philosophy behind assuming this ...
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How can I match the impedances in this circuit?
I have a pre-amplifier with 93.1 Ω output impedance connected to a main amplifier with input impedance of 1000 Ω via 75 Ω co-axial cable.
The signals are very small pulses from a measurement device ...
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Measuring a balanced matching network
I'm working with a Silicon Labs EFR32G12 Wireless MCU and I'm following their design guides for developing the matching network for the device. However, I saw that in one of their design notes (here), ...
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Is this SI4455 RF matching network well placed?
I'm designing a shielded module based on the SI4455 RF chip from Silabs. I read the datasheet and the design guidelines are pretty straightforward, I had no issues replicating most of the reference ...
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Can improper loading (receiver/preamp with too low impedance) of a dynamic microphone cause magnetic damping in the moving coil?
Reading about impedance-bridging in mic signal amplification got me thinking about this (please correct me if I'm deeply misunderstanding some fundamental concepts here)...
A dynamic microphone is ...
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What happens if you use L or C components in RF filters above their resonant frequency?
We have been optimizing filters (BP, HP, LP) by dropping a set of .s2p files into Microwave Office and letting the optimizer choose what works "best", but I started to wonder if that was a ...
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Impact of circuit length in high frequency circuit
I learned that after the RF antenna, we need to determine the matching circuit and calculate the line impedance depending on the FR4 characteristics.
I also learned that after we got the surface ...
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Does the L/C-shunt vs C-shunt/L order of an L-match matter?
Two different sites with L-match calculators show different LC schematics as shown below. Note that Schematic 1 shows C1 on the source-side and Schematic 2 shows C1 on the load side. Both sites ...
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How does one test an AM antenna matching network?
I'm lost. I need to test two AM matching networks. I was not given training and I'm a newborn compared to every other guy in AM Radio out there.
I do own a osciloscope with Bode plot generator but I ...
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Building an attenuator
I need to build a basic attenuator and wonder if someone could help.
I have updated my post to try and make it clearer what my problem is:
One end of circuit is a WiFi headset unit. Mic output is 2.5 ...
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Why doesn't the whole signal get absorbed by the termination resistor in high-speed designs?
We normally parallelly terminate with a matching (50 Ω) resistor in high-speed designs. Normally, the load/receiver is high impedance, but if we terminate it with a 50 Ω resistor, wouldn't the whole ...
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