Questions tagged [impedance-matching]

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

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32 views

TNT field solver - howto handle 'air' between ground plane and wire?

I'd like to match the impedance on one of my PCB traces. For this I chose to use TNT Field Solver. Suppose that the trace itself looks like this (trace width currently set to 0.8128mm = 812.8 micron)...
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11 views

even-mode to odd-mode impedance ratio for balun

How do we see from the following expressions that LARGE even-mode to odd-mode impedance ratio is very important for balun ? How to derive the two expressions involving Ya, Yb, Zoe,Zoo ?
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48 views

Tuning capacitance-matching circuit

I have designed an antenna for a WPT application. We already have a primary coil with a centered frequency of 13.56 MHz. We want to match the second coil at the same frequency and that's why we need ...
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2answers
67 views

maximum power transfer explanation

Please provide an intuitive explanation of maximum power transfer. This is a conceptual question therefore I want to ask with an example. I'm wondering in which cases impedance matching is used. For ...
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1answer
43 views

Calculate the voltage across a load resistor for complex transmission lines

The following parameters are given: 500m homogeneous transmission line. ...
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2answers
114 views

Confusion between the necessity of maximum voltage and maximum power transfer

This is a conceptual question therefore I want to ask with an example. I'm wondering in which cases impedance matching is used. For example, if one has a sensor which can be modeled as voltage ...
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1answer
33 views

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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98 views

Proof of Bode-Fano criterion

I was reading this thesis and it mentions Bode-Fano criterion almost in every chapter of this thesis. Could anyone advise about the derivation of bode-fano criterion? Note: The original proof is so ...
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1answer
56 views

Why this evaluation board use different track impedance than the right one? Ethernet PHY, routing

Im doing a design with a implementation of 1Gb ethernet switch, for that I bought a evaluation board to do it well. The problem is that in the layout of the ev board I can check that the track ...
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1answer
37 views

Power Contours for a Power Amplifier

I am having a bit of difficulty generating the power contours at a Pin where Pout is 17dBm. I am doing a PSS analysis in Cadence Virtuoso. I am sweeping the phase along with a parametric sweep of the ...
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2answers
68 views

Impedance matching and reflection

I have a simple question about reflection and impedance matching. Consider a voltage generator Vg with its output impedance Zg, and suppose it drives a load Zl. In order not to have reflection, we ...
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37 views

2.4 GHz Yagi Antenna Matching

I am building a 2.4 GHz Yagi antenna for a project, its bandwidth must be cover 2.4 to 2.5 GHz. I have already constructed the antenna and assembled it, what I need help is to properly match it to ...
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1answer
177 views

How to calculate the impedance of a rectifier?

I am working on RF energy harvesting. Now I am trying to calculate the impedance of the rectifier, in order to do the impedance matching. An antenna (50 ohm) receives RF signal (915 MHz) and finally ...
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49 views

3 port matching of a directional coupler

My goal is to apply resistive matching (L-pads/attenuators) to the ports of a Mini-Circuits ADC-10-4 directional coupler. I have a 3x3 impedance matrix derived from the available 3 port S-parameters. ...
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2answers
63 views

What does line impedance stabilization mean?

What exactly does line impedance stabilization mean? What parameters of line impedance are stabilized and how? How does line impedance / source impedance vary with frequency?
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1answer
56 views

Where to connect the VNA during matching network tuning

I'm trying to design the matching network between an antenna and its transmitter, running at 868MHz, as shown below. There's probably about 20mm between the transmitter output and the Pi network. ...
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2answers
117 views

STM32F407 50 Ohm PCB

For STM32F407, it is recommended by the company that a 4-layer PCB be used to realize impedance matching. However in the Discovery STM32F407, a 2-Layer PCB is used. Now I am designing a PCB for ...
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1answer
69 views

(Antenna impedance matching) How to find the load impedance

I'm working on a project that requires impedance matching and I'm going to match a 50 Ω antenna to a RF amplifier SST12LP22. However, I'm not sure how can I get the impedance of the amplifier from the ...
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1answer
88 views

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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1answer
59 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
59 views

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
69 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
223 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
202 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
39 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
122 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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44 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
230 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
172 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
215 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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0answers
112 views

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
46 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
195 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
70 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
42 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
106 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
44 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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1answer
87 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
43 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
130 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
34 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
67 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
84 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
60 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
140 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
322 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
197 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
60 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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8k 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
81 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 ...