Questions tagged [impedance-matching]

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

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Impedance Matching between Two Antennas

In order to maximize power transfer, and minimize signal reflection, one would impedance match between a output load and an antenna and between an input load and an antenna. However, is there any ...
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124 views

Termination resistors using bipolar transistors for RS-485?

I am planning to use RS-485 on a network and I do not have too much experience on the standard but I understand that termination resistance must be provided for considerable lengths and transmission ...
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58 views

Why do (magnetic) absorber sheets work?

I understand how/why graded absorbers work - you achieve a match with free space by gradually varying the electromagnetic properties from "almost air" to strong absorption (either ...
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39 views

Differential Impedance vs length matching vs IC manufacturer requirements

I'm working on a PCB with a USB 3.0 controller (TUSB7320, Texas Instruments) with SuperSpeed signals and High Speed Signals. There are some specific requirements about impedance and length matching. ...
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41 views

Matched termination of a microstrip using absorber foam

I have open ended microstrips in an RF circuit (operation freq. 18 GHz) and they cause unwanted back reflection into the rest of the circuit. Now, I wonder if it is possible to eliminate / reduce ...
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28 views

How to match Transformer output Impedance for Ultrasonic Cleaning Transducer

I have a transformer outputting the 240VAC 40kHz. The Transducer is 50W, 4100pF, 10-20 Ohm at resonance, ~40kHz resonance) The Secondary of the transformer is 12mH. I am trying to match the impedance ...
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27 views

Matching circuit for GPS LNA needed?

Do you think I should add Pi matching circuit behind the dipole wire antenna input to achieve the highest LNA gain and low SWR and fine tune it by SimSmith program and NanoVNA ? The route is CPWG 50 ...
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80 views

Impedance Matching using Transmission line

Hi! I was looking at this research paper for Energy Harvesting through Rectanna and I stuck with this thing. The author, first, calculated the Rzin of the rectifier circuit. He had a source resistance ...
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1answer
58 views

LTC5599: why are these baseband inputs passed through 49.9 ohms and the capacitor + SPI

I'm designing a radar transceiver board using the LTC5599. In the datasheet for the part, there is a schematic that shows the circuit configuration for the evaluation board. Here is an image of the ...
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1answer
42 views

RF output matching using baluns: LTC6946

The datasheet that I refer to below can be found here: https://www.analog.com/media/en/technical-documentation/data-sheets/6946fb.pdf I have a question about baluns. In the datasheet for LTC6946 ...
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1answer
94 views

Parallel Termination in a Transmission Line

Suppose we have a parallel termination like this on a high-speed trace: If the line impedance \$ Z_o \$ and \$R \$ are matched, then there are no reflections from load to cause any ringing at the ...
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Is there a typical "Active Directivity" for LDMOS components?

Active Directivity is a measure of how much an amplifier's source match potentially affects its output impedance, or its load match affects its input impedance. High active directivity is a good thing....
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300 views

Where should I place my RF test point?

So I am starting to make my first RF circuit board. We will be using a PSoC4 BLE chip as the transceiver. I'm doing my best to follow their application notes, specifically this one. I should add an ...
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75 views

Will the antenna be detuned by the presence of the MHF3 plug in parallel?

This is a design question. Below is the layout of a project that involves some features, including an ESP32 circuit and its antenna: The part of the schematic related to both images is: THE PROBLEM: ...
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1answer
47 views

Thermoelectric Generator Impedance Matching

I have a TEG that has an output IxV curve like this: That should mean something like this: I need a simple circuit to regulate the voltage around 12 V while enabling at least ~10 W for some load I ...
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118 views

How to match two impedances which both have an imaginary component?

I am designing a matching network for an inverted F antenna, the source RF pin impedance is 30 Ω + j10 Ω (source IC is an ESP32-D0WDQ6, datasheet here, RF pin impedance in section 2.5 on page 7). I ...
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313 views

Why are common mode chokes with 90 ohm @ 100 MHz recommended for USB 2.0 Hi-Speed data lines?

When one looks at common mode chokes for USB 2.0 applications choke manufacturers always recommend CMC with a common mode impedance of 90 ohms @ 100 MHz. Example How does this relate to USB 2.0 ...
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36 views

Would joining pads of a pi-filter eliminate impedance changes from line to pad? Would it cause problems with alignment during reflow?

This is a 2 part question: Would joining the pads, such as on the lower pi-filter pictured, cause any problems with alignment of the components during reflow soldering? Would joining the pads result ...
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228 views

Differential Impedance Matching

Below is a small portion of a schematic which I have seen It mentions that the transmission line will have a differential impedance of 100ohms between them. In case of Single ended it would be 50 ...
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1answer
120 views

In practice, does the order of a series RLC-shunt circuit matter?

In simulation I'm finding that the image pictured below works well to optimize a complex impedance match. I know that Z = ZL + ZC + R, so in theory the order shouldn't matter---but in practice, with ...
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1answer
227 views

How to match RF output of 30 Ω + j10 Ω to microstrip IFA antenna with matching network?

I am designing a 4 layer PCB with an inverted F antenna (similar to image below, ground plane is larger than shown), and need to match the antenna to the source RF pin impedance of 30 + j10 ohms (...
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37 views

How should I model the DC power supply that powers the drain of an LDMOS RF power amplifier?

We would like to model a switching power supply for an LDMOS RF power amp so we can design the bias tee powering the drain to reflect as much RF as possible to keep RF out of the power supply. The ...
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1answer
33 views

large inductance compensation methodology in chip power delivery network

i am trying to learn on compensation networks design. Suppose our power delivery network from VDD to the chip has very high impedance at certain frequency. i know that we cn use smith chart to design ...
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1answer
64 views

Could impedance mismatch explain my distorted signal?

I have a custom PCB which scales and offsets an analogue signal, using an instrumentation op-amp (INA114). When I use a scope to look at the output, it looks distorted (see images below). When I use a ...
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27 views

Power gain values at the microwave amplifier

I have generated graphs in AWR software for signal gains, G_A, G_max, G_P and G_T, respectively. The amplifier I am using is "HMC141". Unfortunately, the values that came out look like this: ...
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211 views

Impedance matching vs LC filter

I have noticed in many papers, publications and in general application the use of LC filter for impedance matching. I wonder why this is the case? How is it that by using an LC filter, it can be used ...
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28 views

Stability of circuit with amplifier with filter and impedance matching on input and output

I recently asked a question about an amplifier with impedance matching at the input and output of the circuit. Now that I know the matching is greater, I wanted to generate a Smith chart regarding the ...
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1answer
41 views

Schematic of an amplifier with bandpass filter and impedance matching

I am having trouble creating a block diagram in PADS Professional Designer. My HMC414 amplifier (documentation: https://www.analog.com/media/en/technical-documentation/data-sheets/hmc414.pdf ) has IN ...
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1answer
74 views

Impedance matching of an amplifier circuit with a filter at the input and output

I created an amplifier circuit with a filter on the output. I did impedance matching on the input and then did matching on the output as well. From the graphs below, is the circuit more matched? ...
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40 views

Impedance matching - amplifier and surface acoustic wave (SAW) filter

How would I properly do impedance matching for the amplifier and saw filter at the output of the circuit?
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744 views

Using a miniature BNC connector on a PCB to measure high-frequency content with an oscilloscope

I am a power electronics engineer in R&D and often measure fast switching waveforms, specifically high bandwidth MOSFET gate signals. When connecting oscilloscope probes in the past I have found ...
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1answer
64 views

Impedance matching and power transfer

Big doubt of the day. For maximum power transfer we use a source impedance equal to the load impedance (conjugate for AC, to be exact). We match for reflection too, but that's another story. Assuming ...
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56 views

Matching network for complex source and load

I'm trying to match a complex source to a complex load with an LC network at 10 kHz only. For instance a 1626 + j2280 Ω source at 10 kHz to a 122k - j3.5*10^6 Ω load. Can someone provide or document ...
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184 views

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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99 views

How to find load impedance when input impedance and reflection coefficient over range of frequencies is known

I know that there's a relationship between input and load impedances and reflection coefficient and it's given by following expression: Г=(Zload - Zsource)/(Zload+Zsource) However, the problem is that ...
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2answers
243 views

How to calculate impedance of a PCB trace Antenna in Altium w.r.t. a given frequency?

I am keeping things abstract as I intend to learn and not just copy another design. So, suppose I am trying to design an antenna of impedance Z and frequency f. Now, in Altium 18, there is a feature ...
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127 views

Resistor circuit to correct impedance matching and attenuate signal by 10 decibels

I've got a Line Out on my amplifier with 100-600 ohm impedance (avg. 350). I have it connected to an effects pedal that has a 1M ohm input. Right now the signal is clipping from the amplifier and I ...
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76 views

Ferrite rod antenna matching network for SA606 RF input

I'm trying to hook a ferrite rod antenna up to an NXP SA606 mixer (https://www.nxp.com/docs/en/data-sheet/SA606.pdf) and I'm not quite sure if I'm interfacing correctly with the matching network. I ...
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289 views

How to match RF output of (30+j10) Ohms to 50 Ohm antenna with matching network?

I'm designing a matching network for a 2.4 GHz inverted F antenna on a PCB that I am also designing. I am using an ESP32-D0WDQ6 MCU, and reading from the datasheet, the output impedance for the RF pin ...
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1answer
114 views

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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1answer
108 views

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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2answers
132 views

Should RF output of (30+j10) Ohms be matched to 50Ohms for antenna matching network?

I'm designing a matching network for a 2.4GHz inverted F antenna. I am using an ESP32-D0WDQ6 MCU, and reading from the datasheet, the output impedance for the RF pins is (30+j10) Ohms. (DATASHEET in ...
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1answer
261 views

How to design a balun circuit for an RF application?

I am designing balun circuit for the first time. Baluns are mainly used to convert an unbalanced signal to a balanced one or vice versa, 50 ohm to 100 ohm impedance matching. Can somebody tell me how ...
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2answers
279 views

Understanding L-Pad attenuator

I'm not understanding the concept of L-Pad attenuator other than seeing it as another ordinary voltage divider to attenuate a voltage. Electronics-Tutorials: L-pad Attenuator gives the following ...
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967 views

Why is length matching performed with the clock trace length as the target length?

Length matching is performed mainly to avoid the skew generated among the parallel data lines/data bus width. All the high speed PCB design guideline suggest performing length matching with the clock ...
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1answer
140 views

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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What is Input Impedance Mismatching of differential Operational Amplifier?

I am new to design differential op-amp. I am not sure if my circuit will experience input impedance mismatching. Can anyone explain how input impedance mismatching will happen in differential op-amp? ...
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59 views

How can I match the FET's input and output impedance?

I'm designing a FET mixer, so I have to match the FET's input and output to in and out port's impedance(50 ohm). I don't have the S-parameters, but I can set wide range of parameters(GS-resistance, DS-...
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41 views

Calculating lengths of single-stub transmission line when all 3 characteristic impedances differ

Consider a transmission line circuit like the following but where \$Z_{o2}\$ was also unique (say \$Z_{o2}=7\,\Omega\$): I know how I would find \$l_1\$ and \$l_2\$ using smith charts: $$Re\left\{Y_n(...
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48 views

RS485 unmatched line - what will be the impact?

I am doing an experiment where I have a computer with an rs485 transceiver on it and data rate of 1Mbs. an rs485 30m long with Z0 of 120ohm (also have one with Z0 100ohm). at the end of the cable I ...

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