Questions tagged [impedance-matching]

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

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641 views

RF coil impedance matching inconsistant result

I'm trying to do impedance matching from a signal generator (60MHz with 50ohms impedance) to a copper wire coil (6 rounds). The coil is connected by a wire (~6 meters long) with resistance 0.9 ohms. ...
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1answer
957 views

Question about transformer reflected source

The following show the idea how a Thevenin equivalent source is used to replace the primary circuit of transformer. In textbook it is commonly stated that the load impedance sees an equivalent source ...
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1k views

Transmission line: Why do longer traces cause signal reflections?

As the question says, I want to know why do longer traces/longer lengths of non-terminated signals of the PCB cause reflections and not the short length ones? I am ignoring the negligible amount of ...
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1answer
236 views

Match impedance and net dimensions of RF power amplifier

this could sound a repeated answer but to me it seems to be not so trivial. Or at least, it is so due to my ignorance. I need to use an RF6886 power amplifier to interface it with a 50 ohm antenna. ...
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121 views

Increase impedance of a handset speaker

I currently have a 300 ohm speaker for a handset. I am trying to increase its impedance to 1k ohm (audio frequency 1k). At the moment the audio level is to low. A resistor in series doesn't help as ...
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1answer
63 views

How do you account for receiver sensitivity in tranceiver half wave dipoles?

if you are to design 2 halfwave dipoles, both can transmit to each other using 3 watts and have receiver sensitivity of -80dbm (a picowatt). Suppose they are 800m and have same height from ground. How ...
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789 views

Relation between reflection (coefficient) and bandwidth

I am reading into single stage microwave amplifiers and how to design for a specific gain (source 1, source 2 warning PDFs!). In both sources the claim is made that the highest bandwidth is achieved ...
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1answer
10k views

Impedance matching components with Ethernet

I’m designing a small switching circuit for 1000Base-T Ethernet and have a concern regarding impedance. The board design consists of 3 shielded Ethernet jacks and 4 DPDT relays (here) made for high ...
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Will an impedance matching network also act as a filter?

Will a matching impedance network also act as a filter? I'm using a pi network and am wondering if I should also add a filter. I designed the pi network by using the program SimSmith and it consists ...
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Does adding a 22 Ohm resistor help in impedance matching?

I read somewhere (sorry can't find the source) that adding 22 Ohms resistor on a digital line helps in matching impedance. Is it true? Is this a common value? Where should this be added? Near node A ...
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1answer
706 views

Ground plane and an impedance-controlled signal trace

I'm laying out a PCB for a project that has an HD-SDI input, which uses a 1.5GHz signal. I'm new to high-frequency considerations, so I'm struggling with a few concepts. Here is the schematic and ...
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138 views

Why deliberately mismatch impedances in RF?

My professor wants me to design a cascaded RF amplifier, with mismatched stages. The reasoning is to increase bandwidth. Is this correct? If so, can anyone elaborate on the theory why mismatching ...
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473 views

Why don't we use cascoding in RF amplifiers?

I need to design an RF amplifier with high gain. It seems every RF book teaches cascading, but not cascoding. Is there a disadvantage to cascoding? It seems like we don't need to match impedances with ...
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637 views

Wind high impedance transformer at home

Suppose I need to make transformer at home, but I am unable to wind 100k turns obviously, then can I just connect a resistor in series with a winding to achieve desired impedance? Will it have serious ...
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1answer
374 views

impedance matching single vs series capacitor

Im looking at a impedance matching circuit on a schematic that shows a .75pF capacitor pulled to ground. With my current board design I have a 1pF and a 3.3pF on the board already so I am thinking ...
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174 views

Matching impedance of the load after inverting

I have a very basic inverter circuit with a 2n3053. I basically need around 5V at the collector terminal when the base is at 0V. I am able to achieve this provided the load is not connected. When the ...
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Causes of ringing in a PCB

Im trying to understand the source of ringing at the termination point of a PCB traces before i delve into actually designing a PCB. For example, by 'termination point', I mean a clock signal ...
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1answer
108 views

How can the source impedance of an energy source be made zero?

With regards to the Maximum Power Theorem (Princeton.edu); The theorem was originally misunderstood (notably by Joule) to imply that a system consisting of an electric motor driven by a battery ...
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4answers
7k views

Using a Dipole Antenna on a 50 ohm FM transmitter

First of all, while I'm not new to electronics, I'm new to the radio world. I am helping a friend overseas set up a community radio, and am getting everything set up over here before I ship it. I ...
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3answers
7k views

50 ohm terminator -- voltage divider?

OK, obviously I'm misunderstanding something. I have a RedPitaya, which is an oscope+generator. Its output impedance is 50\$\Omega\$. If I send a signal from its output to its input (which is 1M\$\...
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2answers
439 views

Buffering/matching large signal to drive 5 ohm capacitive load at 13MHz (RF)

I built a Pierce oscillator that generates 13.5MHz @ 7Vpp signal from a V_cc=12V. But I need to drive a capacitive load of 5 ohms @ 6Vpp. I'm not sure how to do this. First I need a buffer to prevent ...
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1answer
102 views

Analyzing reflection and transmission without a VNA

The wikipedia page for network analyzers mentions "reflection and transmission of electrical networks are easy to measure at high frequencies" but doesn't give any hint on how this is done or what it ...
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1answer
630 views

Impedance of waveguides shorter than 1/10 of wavelength

I read already several times that it is a common rule of thumb, that matching the impedance of a waveguide to the external network impedance is only necessary for waveguides longer than 1/10 of the ...
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1answer
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Impedance matching with only capacitors?

I need to do impedance matching for 33 + j32 ohm source and 16.5 + j0 ohm load. The copper traces adds 99 ohm impedance and 20 degree electrical length. According to smith Chart below, I need to use ...
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1answer
2k views

Balun/matching network question

I am having problem to verify what an app note (AN068) explains to calculate Balun values. I would appreciate if someone could tell me what/where am I doing wrong? The summary of the RF part: Blue ...
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907 views

Transmission Line Impedance Matching Basics

From what I understand, matching a load to a transmission line means that no signal is reflected from the load, which means that at the two sides of the connection point between the load and the ...
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1answer
728 views

Impedance Matching of Antenna and Amplifier

I've been doing a lot of research on impedance matching and I am just having a hard time understanding some of the specifics and I was wondering if someone here could help me out. I have a 50 Ohm ...
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45k views

What is the impedance of audio output of cell phones [closed]

What is the impedance of audio output in cell phone. I mean 3.5 jack for headphones. Is that somehow standardized? Do we know ranges among cellphones? Or mp3 players. I haven't found any information ...
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985 views

Wideband impedance matching of a power amplifier

I want to design the impedance matching circuit for an underwater acoustic power amplifier. Because the power amplifier should work in a range of frequencies, the output impedance changes due to the ...
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1answer
386 views

impedance matching to mechanical sensors?

I am working with 40 sensors and almost all the sensors are mechanical. I have some potentiometers converting mechanical displacement into voltage but the resistance of the voltage source is changing ...
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4k views

When is impedance matching necessary? Isn't it much less efficient on all other aspects?

I understand that discontinuities of the physical properties of conductors create reflections much like dioptres reflect a bit of light, but : in which cases does impedance matching become ...
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1k views

Transfer function and its magnitude

Can anyone make the transfer function and magnitude of the transfer function more intuitive for me? I understand using them but I feel like there is still a gap in my understanding. I would like to ...
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4answers
470 views

Impedance mismatch

When I connect an oscilloscope to a function generator use both oscilloscope cable (one connect to the scope and one connect to the FG), I got 700mVpp when outputing a sine wave of 1Vpp and 10kHz. ...
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27k views

Given a load, how do you calculate whether it is capacitive or inductive?

If the impedance at the load has the form of \$Z = R + jX\$, where \$R\$ and \$X\$ are positive real numbers, then then network is called inductive. If \$Z = R - jX\$, then the network is called ...
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2answers
1k views

Balanced line impedance matching

Is there a way to convert a 100Ω balanced connection to a 200Ω balanced connection without using two baluns? I have a 2.4GHz baseband that I want to attach to a front end, but the baseband ...
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2answers
10k views

Effects of impedance matching between 50 and 75 Ohm coaxial cables for 10 Mbit/s, Manchester-coded signals (20 MHz)

TL,DR: This is quite a bunch of text because I have included plenty of background info. However, there will finally be a good, and precise question: Should I use an impedance matching network when ...
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1answer
685 views

Impedance line matching and component value matching

I have the following circuit for the SIM900's antenna connection, using the A10393 antenna from digikey: In closer look: First of all my knowledge on RF design is not great. My questions now are ...
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1answer
1k views

RF load (terminator) at the end of RF attenuator

Do I need to install RF terminator at the end of RF attenuator? Let's say that max power output for RM port is 50W and I'm using 100W 50dB attenuator. What if I was using 50W 40dB attenuator? Is there ...
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87 views

Impedance Matching for Amplifier Output [duplicate]

0 down vote favorite I needed some basic advice about impedance matching. I have an RF amplifier with 50 ohm output impedance, capable of generating 400W output power at 500kHz. I am trying to ...
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452 views

Antenna matching network topology

In tuning an antenna, there are multiple possible topologies that will take it to the middle of the smith chart. Some differences that I can see between them are: Component ESR (losses). Effect of ...
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2answers
742 views

Thevenin Impedance

If neither open-circuit voltage nor short-circuit current is zero, can we always find the Thevenin impedance by dividing open-circuit voltage by short-circuit current? Under what condition (in ...
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981 views

Impedance matching with unknown load

I somewhat know the answer to this question but just want to clarify. In order to design the impedance matching, I will need to know the load impedance and the source impedance to begin with. Correct? ...
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966 views

RF Energy Harvesting Project

I am presently working on an energy harvesting system using RF signals. I have read some of the other posts made on this topic and have learnt quite a few things. However, I have some questions that I ...
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Impedance of an Edge-Coupled Coplanar Waveguide With Ground

How can I compute the differential impedance of an Edge-Coupled Coplanar Waveguide With Ground? I couldn't find any free calculator online, so I wrote a small program which computes the the ...
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1answer
930 views

Line-out: why is there no impendance issue when plugging an amp rather than headphones?

Given that the input of an amplifier has very high impedance, while headphones have very low one, why can I plug either one or the other on the audio-out plug of my computer? Even with a degree on ...
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2k views

A poor man's alternative to a network analyzer for antenna matching

I'm doing a small board with a 915 MHz transceiver. A small helical antenna is used, which is located on board with a very short path (10 mm) from the IC, including balun and a matching network. There ...
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4k views

Antenna matching network. What? Why? How?

I'm designing a small board featuring a transmitter in the 900 MHz band. Since RF is definitely not my strongest subject, I'm basically trying to follow all the datasheet recomendations regarding ...
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2answers
2k views

How does this antenna match work?

I had a matching technique described to me by a professional broadcast engineer. Here's the problem: you have a vertical antenna with a low resonant impedance1, let's say \$38\Omega\$, but you need a ...
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3answers
1k views

Designing a test instrument to be connected to an oscilloscope

I'm working on a piece of test equipment that is intended to be hooked up to an oscilloscope to measure the waveforms it produces. Since that's its reason for being, I figured it made sense to provide ...
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3answers
1k views

Unbalanced pi- attenuator - Problem with simulation

I've been trying to simulate the asymmetric pi-attenuator example on this page with different source and load impedances: http://www.electronics-tutorials.ws/attenuators/pi-pad-attenuator.html I ...

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