Questions tagged [impedance-matching]
Impedance matching is a process of making one impedance equal to another another.
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Question about transformer reflected source
The following show the idea how a Thevenin equivalent source is used to replace the primary circuit of transformer.
In textbook it is commonly stated that the load impedance sees an equivalent source ...
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Ground plane and an impedance-controlled signal trace
I'm laying out a PCB for a project that has an HD-SDI input, which uses a 1.5GHz signal. I'm new to high-frequency considerations, so I'm struggling with a few concepts. Here is the schematic and ...
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How does this antenna match work?
I had a matching technique described to me by a professional broadcast engineer. Here's the problem: you have a vertical antenna with a low resonant impedance1, let's say \$38\Omega\$, but you need a ...
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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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Eliminate reflections on pulse signal transformer
I am trying to isolate an RLC ringdown signal via an RF signal transformer but I'm having trouble maintaining the signal integrity through the transformer. Below is the simple schematic describing my ...
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Power supply for toothbrush motor
I would like to connect an electric toothbrush motor (Braun Oral-B Type 4729) directly to external power supply. So far I have been trying at least 3 different DC power supply unit with appropriate ...
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Coax cable - capacitive load
I still have an understanding problem with impedance matched coaxial cable and its behaviour.
We do impedance matching to prevent reflections.
How does my signal source see the whole cable? At a ...
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Replacing RJ45 connector with another type connector
I am looking for a replacement for an RJ45 panel mount connector. Can I use any standard connector (picture below) for connecting Ethernet networks?
I know about cable impedance matching but I was ...
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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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Circuit that dumps RF energy on matched load. Can anyone help?
Background
Trying to protect my home against the RF irradiation by cellular tower nearby. Read an article that proposes 2 things:
Metal film, or fine metal mesh, which is grounded. This is used on ...
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How does SNR improve with impedance matching in a radio receiver?
I've seen basically every question and answer on here relating to impedance matching, and why you need it in RF but not in audio applications, and I'm still missing something.
I initially was ...
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How voltage and power transfer in cascaded amplifiers work?
When there are three amplifiers that are cascaded to produce higher gain:
The source resistance should be lower than input impedance of first amplifier
The output impedance of first amplifier should ...
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Is electrical impedance at its maximum or minimum, at the acoustic resonant frequency of the material?
For example, if piezo disc has lowest resonant frequency of 4kHz. At that frequency, would the electrical impedance be at its maximum or minimum?
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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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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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What does a 50 ohm coax "look like" when neither the source nor the load are matched to it, and the center conductor and shield are used for signals?
Say I have a π-network filter for which the inductor is on a separate board. For convenience, I use a 50 ohm coax (4" long, frequency is 13.56 MHz) to connect to the inductor, using the center ...
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why we must to follow 50ohm and 100ohm impedance in PCB boards? is it a standard value for all device input and output impedance? [duplicate]
In PCB / PWB boards we are following 50ohm impedance for single ended lines and 100ohm impedance for Differential lines? is it a standard value for all device input and output impedance? Each and ...
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Impedance matching audio transformer windings
I want to create an isolation, impedance matching, balancing transformer for a DI box.
I want it to work on Audio frequency and use a toroidal ferrite core.
The input is an electric guitar, so it ...
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terminated cable capacitance
As much as I know, the input impedance of a coaxial cable with a characteristic impedance of 50 \$\Omega\$ which is terminated with a 50 \$\Omega\$ load resistor, should be 50 \$\Omega\$ as well. This ...
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Impedance for a communications console
I'm working on some old school Zetron consoles for my summer job. They provide 2/4 wireline control to some base radios as well as I/O for aux operations like triggering relays to open/close doors ...
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Antenna pi-network matching High or low pass?
I am a beginner in RF system design and I have some questions.
I have a PCB trace antenna, I need to tune it to 2.45GHz, this is for Bluetooth low energy communication.
I want to use a pi-network for ...
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How can one value describe the impedance of a group of reactive components at all frequencies?
The author of the textbook containing this circuit states that the filter input and output impedance is given by:
Z = (L/C)^1/2
He then shows that by setting the source and load impedance to this ...
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Bad Reflection from SMA Board Connector at 4-8 GHz
recently I have tried to design a simple SMA-to-microstrip connector PCB intended for 4-8 GHz. The connectors used are vertical with surface-mounted centerpin (link).
The design idea was to simulate ...
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Chip antenna too good to be true?
I have the following setup:
Very small PCB - 25mm in diameter that hosts chip antenna;
I feed directly into antenna matching network with about 7.5cm coax via ufl connector;
There are no other ...
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CAN bus node impedance matching
Trying to understand the physical layer of CAN.
Most images that I see of a CAN network has the main network bus and then nodes that come off of this bus at a T for CAN_H and CAN_L it what I commonly ...
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Linear regulator after switching regulator
I need to power a board that works at 3.3V, and I have a regulated power of 12V.
I tried to use a single linear regulator like the TS2940 but the power required is so high that the heat produced was ...
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Induction heating
I was reading the working principles of induction heating and I think I understand the basics. Out of curiosity, I searched the Internet for a schematic and found one. However, the thing that confuses ...
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Impedance matching for push-pull RF amplifier
I am working on the output matching network of a commercial push-pull class AB amplifier based on LDMOS BLF188. The output matching network consists of a 1:4 transformer and a Toroid with 8 turns The ...
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RF: Do I need a resistor at line driver output for impedance matching?
I have a digital RF signal (~50Mbps max) passing through SN74BCT25240, a 25-ohm octal buffer/driver. This is on a 4-layer PCB with a ground/power planes and proper bypassing, etc. I was wondering do I ...
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Impedance matching from PCB to cable
I am designing a PCB board connecting to a 2 meter long cable with 75 Ω impedance. I have an output buffer amplifier at the output of the PCB.
For the buffer op amp with 0 output impedance, should I ...
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Effect of small length impedance discontinuity in a transmission line
Consider this arrangement of a radio, a long coax cable, a small length of "random" cable and an antenna. The radio, the coax and the antenna all have the same impedance, but the random ...
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Designing GPS matching network with TESEO and chip antenna
I am new to designing for RF and have a question regarding the design of the matching network for a GPS module I am working on.
The datasheet of the chip antenna ANT161575ST-1202A1 recommends a ...
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Impedance matching L Network
I‘m trying to understand exactly what an L-section Network does. I understand it tries to eliminate the imaginary part of the impedance and match the real part. However I do not understand what ...
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Resistor network in between SAW Filter and Power Amplifier
I am going through user guide of Microchip's LoRaWan Gateway. The manual is over here. At page 48, I am struck at one resistor network and unable to understand it's ...
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VNA Tuning in Enclosure -- LiPo Battery Detuning Antenna
I've got a finished design, that I tuned the matching network using bare boards.
Say for example, my tuned TX board has an over-the-air 3 meter reading on my spectrum analyzer at -50dbm. (This is at ...
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Chip antenna PCB layouts
I am designing a layout for this Chip antenna "https://www.johansontechnology.com/datasheets/antennas/2450AT18B100.pdf". In the datasheet they have Test Board as an example layout. I have a couple of ...
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Adding voids underneath analog signal for improved impedance matching
Using a snapshot of an eval board design below as an example, voids are added to the ground plane on layer 2 (green) right underneath the analog signal path on layer 1 (yellow). This causes the analog ...
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Picking source resistance for impedance matching
I am trying to drive a piezoelectric transducer with maximum power transfer possible with minimum possible noise. In order to do that I am trying to implement LC matching circuit such as circuit ...
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Second order RLC filter and load resistance choice
In this 2nd order, low-pass filter circuit
simulate this circuit – Schematic created using CircuitLab
I am interested in the transfer function
$$ H(s) = V_L (s) / V_g (s) $$
which is (...
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Using a Dipole Antenna on a 50 ohm FM transmitter
First of all, while I'm not new to electronics, I'm new to the radio world. I am helping a friend overseas set up a community radio, and am getting everything set up over here before I ship it.
I ...
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What are the recommended CK, DQ, DQS, ADDR impedances for LPDDR4?
I am using a micron part with LPDDR4, in many datasheets from micron there are no references to a specific impedance for CLK, DQ, DQS, ADDR. The datasheet mentions that the LVSTL is tuneable, but what ...
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What is the link between conjugate matching efficiency and amplifier efficiency?
In the design of a class AB amplifier, there is part of the understanding that I miss. It is well-known that the maximum power transfer is achieved when the load impedance is the complex conjugate of ...
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Can I use 50 ohm cable with 75 ohm tv antenna?
Can I use 50 ohm cable with 75 ohm antenna (without any adapter)?
I found on the internet that 75 ohm cable can be a problem with 50 ohm antenna, but does vice versa make the same problem? Or the ...
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Differential Pair routing insight for USB 2.0 circuit involving a USB C connector with multiple D_N and D_P pins
I'm bringing USB 2.0 into a PCB design from a USB C receptacle. I've already accounted for the 5.1k resistors needed but I'm stumped on how best to run a differential pair with DP1, DP2, DN1 and DN2 ...
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Coax Cable Wave Impedance, Capacitive Load
I am studying the behaviour of cables over frequency, especially what a source sees, and have 2 Questions, as I did some simulations in LtSpice. As a model for the cable I used the "Lossy ...
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LC Filter / Matching - Why does this cap help?
this is my first question on the site, so please let me know if there's something I can do to write it more helpfully.
The Problem: I'm building a small radio. At the output of my mixer, I need to ...
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RF transmission line matching
I'm designing a board which contains an LTE module on it. I am a little confused about designing the trace between module and antenna.
As far as I know I need to match these:
Impedance of module's ...
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Impedance matching of USB device WITHOUT cable
If I understood correctly, when designing PCB with USB, the 90-ohm differential pair of D+/D- trace if for matching the USB cable differential impedance. Otherwise, there will be a signal reflection ...
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USB Softcore for FPGA : Extra resistor on FPGA transmitter pin
Have anyone used this USB softcore before ?
Why do we need extra resistance on the tx pin ONLY ?
Whichever pins you transmit on need to have resistors after them. The
exact values will depend ...
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Have you ever fried a wi-fi router by leaving it to work without its external antennas?
I wonder if a wi-fi router can be damaged if its external antennas are unscrewed?
Have you ever damaged such a router leaving it to work without antennas, like this:
Source
I know that there are ...
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