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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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50 Ohm Board to Board Connector

I'm trying to build a tunable bandpass filter for 140 to 1500 Mhz, and the design requires that I move the signal from a PCB with an SMA connector to another mounted about 3mm above it. I'm using ...
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44 views

LED output with Photodiode and Function Generator

Some of my student and I are designing a Physics experiment involving a high power LED, a square wave from function generator (50 ohm output impedance) and a digital oscilloscope (1 MOhm imput ...
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2answers
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Converting 2.1V RMS DAC output to instrument level 6.35mm jack

I'm not quite sure how level and impedance matching works so I am hoping for an illuminating answer! I'm generating audio with a PCM5102A DAC. The datasheet of the chip specifies a 2.1V RMS output ...
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1answer
24 views

SMA Tee and impedance matching

I've asked a similar question before but this one is a bit different. I would like to split a microwave signal from a source and route one to the RF and the other to LO. I will intentionally ...
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2answers
106 views

Controlled Traces Length in SD card

I my new design I need to use SD card communication. I would like to match all the impedance traces and control the length of the traces. Regarding the controlled length, is there a rule of thumb to ...
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1answer
96 views

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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1answer
18 views

ADS Simulation: Schematic to find input impedace

I'm following a paper, using ADS, to find the input impedance of a shunt Schottky diode. The paper's schematic is Fig. 1, and my schematic is Fig. 2. The point is that, I could not get the same result ...
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1answer
71 views

Impedance matching in multi-layer circuits

In a new circuit design, I need some impedance matching for some high speed traces (i.e. Ethernet, USB, SD card...). Usually I define tracks width with this web tool https://www.eeweb.com/tools/...
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31 views

Input and Output Impedance of a SAW Filter

I am reading the datasheet of a SAW Filter B39162B4348P810. The datasheet doesn't say much about impedance of Input and Output ...
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2answers
128 views

(When) Can I use Cat5e wiring to carry a POTS signal to a DSL modem?

According to this answer by @asndre, It is very bad idea to use Cat5e-based wiring/cabling to establish a xDSL connection. However, my telephone/internet provider technician recommended -- and ...
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1answer
79 views

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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1answer
79 views

Differential Pair Reference Plane Coupling

I am routing LVDS pair on a flex board. The signal is 264MHz. I used Saturn PCB design to calculate width and spacing between conductors. The targeted impedance for diff pair is 100 ohms, which is ...
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Impedance matching of a RF power amplifier based on the s2p file

I'm designing the input/output impedance matching circuit for a RF power amplifier, based on the vendor supplied s2p file. I designed separately the input/output matching circuit at the given working ...
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1answer
30 views

Impedance matching between CSR8675 and a MM20 microphone

I'm building my own (rugged) headphone. I am planning to use a MM20-33639-000 microphone with CSR8675 DSP. My question here relates to impedance matching. Based on what I have read, most modern ...
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2answers
142 views

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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3answers
58 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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1answer
39 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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2answers
60 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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1answer
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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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1answer
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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0answers
35 views

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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1answer
65 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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1answer
31 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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1answer
52 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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1answer
78 views

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
54 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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1answer
80 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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5answers
175 views

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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1answer
94 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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1answer
50 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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8answers
6k 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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1answer
68 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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63 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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3answers
136 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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1answer
56 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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0answers
80 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
65 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
60 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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1answer
150 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
74 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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2answers
262 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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1answer
123 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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2answers
72 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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0answers
46 views

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
124 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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0answers
57 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
94 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
246 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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1answer
68 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 = -...