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Questions tagged [impedance-matching]

Impedance matching is a process of making one impedance equal to another another.

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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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52 views

Output impedance and loudness

I've a DAC for headphones (GeekOut 720) which has two output jacks with different impedances: 47 Ohm (with a large headphone icon next to it) and 0.47 Ohm (with a small headphone icon next to it). I'...
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Is this a two capacitor reactance matching network? And is there anyway we can determine the source impedance of the nfc chip device?

My teammate found this configuration from a paper: http://infocenter.nordicsemi.com/pdf/nwp_026.pdf , and there is no explanation for the two Cp capacitors connected to ground. We needed to do ...
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33 views

How do I design a MOSFET based amplifier with constraints

I am designing an amplifier using two MOSFET stages. The input is taken from a sensor and is to be amplified by a factor of 25. The output (of these two transistors) will be fed to a detector with a ...
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36 views

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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43 views

Impedance-matched antenna with an extra capacitor

I'm looking at the a schematic for an ESP8285 module, and I am curious about what they are doing with the antenna. The module is the PSF-B85 (by ITEAD: the version with a chip antenna). The antenna is ...
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37 views

What is the Q-factor when doing Pi-matching?

What is the Q-factor when doing Pi-matching? There appears to be multiple Q factor formulas and I am not sure which to use.
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81 views

Connection between RF output to the source for minimum loss and maximum power transfer

The bottom device in the left image is an RF generator with ratings 230V, 15A (max), 13.56 MHz and variable controllable output power up to 1250 W. The top device is an auto match. The metal strip ...
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Help required to design a suitable energy harvester for TENG

So I am in the process of desgining a scalable Triboelectric Nanogenerator(TENG) through which I can easily harvest and store electricity in a battery or a capacitor. A TENG can be modelled as voltage ...
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48 views

Modern piezo microphone impedance-matching circuit

I want to record sound with a piezo transducer. I am connecting it to my sound card's input which has a good mic pre-amp. The levels are quite good and the sound seems quite clear but there's a lack ...
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27 views

The meaning and role of the phase in antenna measurements with VNA

VNA measurements of an antenna return Z, RL, Xs, Rs... and also phase. I usually check Z=50 and Xs=0 to reach the max Return Loss and the lowest SWR 1.0:1, without having care of phase values. ...
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47 views

How to design a 180 degree phase inverter for the feedback?

I am currently working on a multi-stage wideband amplifier (80-110 GHz) design with the goal of having 5-6 dB for each stage. The transistor that I am using has the transit frequency around 300 GHz (...
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What is the precise meaning of “matching impedance” for an ultra-wide band antenna, and how to do that?

Well, actually, I'm not sure I really understand what is the meaning of matching impedance, even for an ordinary antenna, but I can figure out the following: if you send a signal to the antenna, then ...
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3answers
47 views

Equivalent Characteristic Impedance for Different Trace Widths

Suppose I have a PCB trace that needs to be impedance matched, but the trace width changes as it travels from its source to its destination. Something like this: The 5mil trace would have a certain ...
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58 views

Matching impedance network for an LC ladder network

Let's say I have a 5 stage L-C ladder network with L= 4.7 micro Henry and C= 60 pF. The characteristic impedance of the network becomes 280 ohms (square root(L/C)). However, from circuit analysis, the ...
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Output impedance of STM32H743 MCU?

How do I find the output impedance of the STM32H743 (and potentially other similar devices)? I've looked through the datasheet (DS12110 Rev 5) and the reference manual (RM0433 Rev 5) however haven't ...
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55 views

Effects of impedance mismatch on RF signals from antenna

I'm building an antenna array that operates at high frequencies (around 2 GHz). I want to use a SDR dongle that has a 75 ohm input impedance as receiver, I've also bought the coax cable, a 4 way ...
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49 views

Impedance matching a dual frequencies

Does anyone know of any impedance matching techniques to match at two different frequencies? Where the impedance at both desired frequencies are different (both the real and imaginary components)? ...
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Impedance matching network

Can anyone suggest tools or reading material that discusses how to impedance match for multiple frequency bands (where they are not multiples of one another)? For example, the input impedance of my ...
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Why is 50 Ω often chosen as the input impedance of antennas, whereas the free space impedance is 377 Ω?

In order to efficiently deliver power to a different part of a circuit without reflection, the impedances of all circuit elements need to be matched. Free space can be regarded as a further element, ...
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61 views

Why does the capacitor part of the electret mic have very high impedance and why is a FET used to solve the problem?

As far as I understand a FET is used for impedance conversion of the capacitor part of the electret microphone. I dont understand the meaning of that. The reason is given that the capacitor itself ...
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42 views

Removing the imaginary part of input impedance of a Monopole in HFSS

I am building a Monopole in HFSS for my project. Its structure is shown here : The input impedance at the desired frequency is : Now i need to eliminate the imaginary part , so that the voltage and ...
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Differential impedance calculations for non symmetric dielectrics

So I'm able to calculate differential impedance on the top and bottom layers of a 12 layer rigid-flex design I'm working on, but I'm not confident about my calculation for a few internal differential ...
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3answers
117 views

Measure impedance of PCB antenna with very small ground plane

I have recently been designing different PCB antennas with very small ground planes due to design restrictions. I use a VNA to measure the impedances, but am having trouble measuring them correctly. ...
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30 views

Calculating the maximum antenna voltage

Given a transmitter driving 13dBm into a 50Ω load, what is the peak voltage at the antenna connector? By my calculations, 13dBm is 19.95mW. Given P=V^2/R, V=sqrt(P*R). So the peak voltage would be ...
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Some questions regarding impedance matching and tuning

For maximum power transfer in a circuit impedance matching is performed: Similarly from the transmitter antenna to the receiver/load one can think the total impedance from antenna to the receiver as ...
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Reflection on a matched transmission line

A matched load with source using a transmission line (assume real load and matched using quarter wave transformer) should not have any reflection ideally. But we can see that the load impedance is ...
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3answers
64 views

Why is impedance matching and maximum power transfer aimed in radio transmission?

As far as I know the RF amplifiers are voltage amplifiers. On the other hand, from transmitter to the receiver there is a lot of effort for impedance matching. But impedance matching aims max power ...
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1answer
50 views

Track impedance for CC1101 transceiver

I'm trying to make my own board for a CC1101 transceiver that will operate at 915 MHz. To do that, I'm just copying the reference design layout from the ...
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94 views

Impedence Matching of Antenna and Coaxial Cable

There is a scenario based question which is confusing for me Antenna had four rods each 15cm arranged as a plus sign. its brass shielding was cut and it had two 75 ohm coaxial cables in it. one 10 cm ...
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6answers
2k views

Does non-matching impedance of amplifier and speaker distort the sound?

I'm about to buy a pair of headphones and an audio interface with built in amplifier. The specs say that the amp's impedance is "<30 Ohms". The headphone I'd like to buy is a Beyerdynamic DT 990, ...
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2answers
69 views

About the impedance matching problem of this circuit

This is part of the pulse output circuit for cable fault location, but the pulse signal output to the cable is suppressed. I guess the reason for the impedance mismatch, but how can we achieve the ...
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157 views

Impedance Matching Resistors on MII Ethernet Lines

Microchip is taking forever to activate my account so I will ask this here... I am using the KSZ8081 PHY for MII Ethernet. https://www.mouser.com/ProductDetail/Microchip-Technology-Micrel/...
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90 views

Impedance mismatch in LISN for EMI/EMC test

I am currently designing LISN for CE-102 test.The schematic of the circuit is provided below. When I connect the circuit to the network analyzer the impedance is coming as shown below expected graph ...
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62 views

calibrating vector network analyzer with \$75\Omega \$ coax

I am new to electronics and I just began to use a vector notwork analyzer for some measurements. I calibrated my vector network analyzer with both ports connected to 50\$ \Omega \$ coax cables with ...
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RFID reader antenna matching

I am trying to connect a RFID reader chip to an W3113 antenna on PCB. As said in datasheets, the antenna pin of the reader chip has internal 50 ohm impedance and antenna W3113 also has 50 ohm ...
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80 views

Modeling impedance matching network

Background I'm looking at the RF (LNA_IN) pin of ESP32 as described in esp32_hardware_design_guidelines. According to this document, the output impedance of the RF pins of ESP32 are (30+j10) or (...
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49 views

Impedance matching in practice

I'm designing a PCB antenna with integrated circuits. Again the problem is impedance matching for maximum power transfer between the antenna and the circuits. To match the impedances I've got to ...
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2answers
90 views

physics behind the impedance matching performed in this case

On the website here: basic impedence matching, I found a way one would pick the right value for your coaxial cable given the generator's impedance and load impedance. I've always been told to just ...
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2answers
183 views

Impedance Matching: Minimum Reflection vs Maximum Power Transfer

The minimum reflection is achieved when the two "circuits" being connected have the same impedance. This makes sense because all the components of the wave can propagate without needing to be modified....
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59 views

What should the input mpedace of an antenna be, 50 ohm or other values?

I'm about to match an antenna and a half-wave rectifier using Schottky diode. Both of them are placed in one PCB (PCB antenna). The input impedance of the half-wave rectifier is 6 - j170 ohm at Pin = -...
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1answer
167 views

Circuit diagram of an oscilloscope with 50 ohm load impedance

I was told some oscilloscopes have 50 ohm impedance settings for radio frequency measurements for impedance matching (as opposed to one 1M ohm resistor and a 10pF capacitor in parallel for load ...
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2answers
150 views

Unbalanced to balanced variable impedance matching

I want to design an impedance matching transformer to convert an audio line from unbalanced ( stereo phono jack type) to a balanced type ( XLR jack with 600 ohms). What can be the easiest way around ? ...
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How Significant is VGA Impedance Matching?

I've seen a multitude of different resistor DAC solutions for a VGA signal, however they almost always have an impedance of >200 ohms per color, e.g. when I've been lead to believe that we want to ...
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1answer
104 views

How to increase sensitivity of audio-frequency pickup coil

I am building an instrument intended to pick up weak (~100 picotesla) 25 kHz oscillating magnetic fields with Faraday induction. As shown in the photo, I have a 4-layer solenoid coil for pickup ...
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1answer
81 views

differential routing without GND

I have task that I need to make adapter board which transforms gigabit ethernet connector RJ45 to another connector (not RJ45). I also have power connector to carry power one side to other. I need ...
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51 views

Difference in the characteristic impedance of a low frequency signal

In one of my PCB design, for a RS 485 signal termination resistor of 120 ohm is there. But the differential characteristics impedance of the signal is taken as 100 ohm instead of 120 and the signal ...
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2answers
131 views

Match impedance from 600 ohm/2kW tube amp to 8 ohm/25W speakers

Would you please help me to think how to choose an approximate transformer with the least losses for my application? No exact transformer available at market. Is it best, say, taking a 2600/8 ohms or ...
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2answers
195 views

Impedance Matching for Helical Antenna

I'm building a helical antenna at 1.7 GHz from scratch. Theory says that its characteristic impedance is 140 Ohm. The RF transmission line is 50 Ohm so there has to be an impedance transformer in ...
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3answers
133 views

Influence of I/O impedance in Butterworth passive filter design

I'm using a simple online simulator tool to build a passive Butterworth filter. An affirmation made in this page confused me: Enter the filter characteristic impedance. In all cases, unless you ...