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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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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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Matching network

I've noticed that there's a matching impedance technique that Keysight uses in its SMM (Scanning Microwave Microscopy). In this method, a coaxial cable is connected to the probe (an arbitrary load) ...
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37 views

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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5k views

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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57 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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35 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
103 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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28 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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47 views

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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66 views

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
59 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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42 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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70 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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1k 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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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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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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69 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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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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2answers
50 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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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
79 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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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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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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122 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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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
87 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
78 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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49 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
105 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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143 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
99 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 ...
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2answers
58 views

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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Matching for parallel loads

If there is one RF source with a known characteristic impedance, and there are multiple loads connected in parallel with each other, each with their own matching circuit, and if the electrical ...
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51 views

Impedance for TTL Hsync and Vsync Pulses

I'm just finishing up a sync combiner and audio/video PCB. I'm trying to impedance match my traces and I've done so for the 75 ohm RGB lines. Now I'm looking at the TTL level Hsync and Vsync lines ...
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1answer
72 views

Does bidirectional impedance matching matter?

For my own learning, I derived the following relationships for basic two-element impedance-matching networks. Apologies that I cannot create diagrams; they are not supported by touch devices. If \$...
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99 views

Can antenna VSWR be corrected?

For this antenna, which cites a VSWR of 1.4, can that be improved (decreased) with the use of a matching network? Could the matching network be between the feed cable and the board or must it be ...
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107 views

VGA impedance matching

i have VGA in one side of my circuit and I want to connect that to a connector with 50 ohm impedance. after that I must convert 50 ohm impedance to 75 ohm, because I have a vga cable in other side. in ...
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116 views

Is a matching network needed if the antenna feed line is very short?

When designing PCBs with RF functionality it is considered good practice to place pads for a matching network immediately before the antenna (or antenna connector). This allows you to compensate for ...
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62 views

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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53 views

How does this MMIC work?

I'm considering evaluating the NXP BGA28xx series MMIC for my application, a fixed-frequency special purpose AM receiver, because they're cheap they're very simple to wire up they claim to be ...
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109 views

W5500 Ethernet Chip Layout Advice/Help

I am working on a project that includes the W5500 circuit, this is the first time i had the opportunity to layout Ethernet Interface circuits. Schematic: Whole board and W5500 Module Layout ...
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2answers
43 views

Loss due to impedance matching in a filter

I have a quite basic question, after starting to re-read some RF theory. If a voltage source has a resistance of 50 ohms, and the equivalent impedance of a connected bandpass filter and its load are ...
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1answer
74 views

Routing Ethernet Connections

I am routing Ethernet traces from a Colibri iMX6ULL computer-on-module to RJ45 Ethernet connector (In-build Transformer). The layout design guide says that Ethernet ...
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30 views

Line/load matching for electric power transmission

Impedance matching is a critical topic for microwave engineering where the signal wavelength becomes comparable to the physical sizes of components. Substitution of distributed component models for ...
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2answers
138 views

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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1answer
52 views

Impedance Matching With L-Network, Terminology Issues

Note: Using L Networks I am having some confusion with the terminology of impedance matching. Specifically majority of questions i have done state match a load to the source impedance which i ...
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31 views

Keep potential difference fixed for transformer's output

I have a source consisting of V1, R1, L1, and L2 to which my load R2 is attached: For the load, I have 10 or 100 Ohms. 1) R2 = 10 Ohms: Vrms = 315 V, irms = 32 A, P = 10 kW 2) R2 = 100 Ohms: Vrms =...