19
votes
Accepted
Unphysical voltage in SPICE simulation
Aha, you've discovered the (in)famous(?) RC network with gain!
You may find this of interest:
Synthesis of Passive RC Networks with Gains Greater than Unity, Epstein, Proc. IRE, vol. 39, no. 7, pp. ...
- 45.6k
4
votes
Accepted
Why does lumped discipline not hold as dimension approaches operating signal wavelength?
The signal timescales must be much larger than the propagation delay of electromagnetic waves through the circuit.
This part is pretty trivial, since the propagation of em waves is finite we have to ...
- 7,581
3
votes
How can I deal with the traveling waves associated with lumped impedance?
How can I handle problems where both characteristic impedance and
lumped impedance are present, as in the example below?
In your previous question you wrote this (that I believe applies in this ...
- 473k
3
votes
Design a passive amplifier
A "passive amplifier" is an oxymoron. No, you can't make an amplifier from R, L, C or other passive components.
- 31.7k
3
votes
Lumped-element delay lines using LC circuit
A lumped element delay line is mimicing real life and real life is a transmission line (t-line). Examples are (but not limited to): -
Coaxial cable
Twisted pair
A waveguide
A PCB track and ground ...
- 473k
3
votes
Why don't we talk about a signal reflection when we treat a lumped element model of a circuit?
Suppose we view the short transmission line as a two port network.
The input voltage and current are the same as the output voltage and current (magnitude and phase relationship).
The input voltage ...
- 19.1k
3
votes
Accepted
How is an inductor a lumped element?
It is important to realize that lumped circuit element conditions must hold only outside of the circuit elements. Otherwise you would not be able to have any dynamics (current or volatge changes) at ...
- 16.5k
2
votes
Accepted
Questions and confusions on transmission line theory and lumped element model
Coaxial-cable in the above illustration is a standard 50 Ohm intrinsic impedance BNC cable. I know its length and lets say it is 20 meters long. Since we use lumped element model we will not use 50 ...
- 134k
2
votes
Accepted
Explanation of lumped matter discipline
b) All insulators are dielectrics and all dielectrics can hold a charge.
Otherwise they are conductors. A floating conductor can hold a charge but not within a loop circuit. Also KCL defines node ...
- 148k
2
votes
Lumped parameter vs transmission line model for a piece of cable
The speed of propogation in a 'normal' coaxial cable, that is straight cylindrical conductors with an annular dielectric spacer, is entirely controlled by the dielectric constant of the spacer. For ...
- 174k
2
votes
Different 50Ohm-matched condition for different length of metamaterial waveguide
At the end, I found that it was due to a wrong meshing.
By ensuring the same mesh density in the two models, I can see the same reflection and extract the same equivalent lumped-element values of L ...
- 31
2
votes
Why does lumped discipline not hold as dimension approaches operating signal wavelength?
And not just the size of the circuit, but the size of each component must be small relative to the wavelength (for the signal at the speed of propagation). Otherwise, at any instant, a capacitor ...
- 4,851
2
votes
How can I replace lumped capacitor and inductor with microstrip line?
2.4 GHz is a fairly low frequency when it comes to trying to make useful L or C-equivalents with microstrip structures.
But instead of trying to make direct equivalents, you could consider some other ...
- 134k
2
votes
Unphysical voltage in SPICE simulation
If you are using super capacitors and superconducting wire (like you are in the simulation) then yes, it does seem kind of weird. But if you could build a system such as this then I would expect it to ...
- 88.8k
2
votes
Defining lumped and distributed elements according to signal travel time
when for all practical purposes, the electrical signal will travel instantaneously through the circuit element?
It won't. The speed of light is about 1 foot (30 cm) per nanosecond. When dielectric ...
- 134k
2
votes
Finding the reflection coefficient for a wave incident from the left into the first transmission line?
Is it correct to solve it as below?
You have to calculate the left-side input impedance and, to do that, you have to know the length of the line to the point where it "hits" the inserted ...
- 473k
2
votes
Accepted
How can I deal with the traveling waves associated with lumped impedance?
what is the reflection coefficient at the boundary between Z0 and Z1?
Here is an example of what I mean ...
Note that there is a "coefficient emission" of 1/2=50/(50+50) at the beginning.
...
- 15.7k
2
votes
Accepted
From the perspective of a progressive wave, what is lumped impedance?
Is lumped impedance lengthless?
Yes it is regarded as length-less. This means it doesn't behave like a transmission line. If its length is non zero then it wouldn't be a lumped impedance but, would ...
- 473k
1
vote
How can I deal with the traveling waves associated with lumped impedance?
A few transmission line fundamentals allow a straight forward algebraic approach for calculating the voltage reflection coefficient caused by the Z0 to Z1 junction.
Recall that an infinitely long ...
- 5,594
1
vote
How can I deal with the traveling waves associated with lumped impedance?
There's nothing mentioned of how long (=delay) the rightmost line has and of is there some load, too. I guess you want only a hint how to handle the case for the time period when there's no reflection ...
- 62
1
vote
Unphysical voltage in SPICE simulation
Here is a Maple sheet to calculate output ...
ff is log(f).
- 15.7k
1
vote
Accepted
Defining lumped and distributed elements according to signal travel time
My book goes on to describe that the travel time of the electrical
signal through the element cannot be ignored in distributed elements.
That is true.
But we are not talking about astronomical ...
- 473k
1
vote
Lumped Element Equivalent Circuit for Microstrip line
Your units for \$R\$ should be \$\rm\left[\Omega/m\right]\$, not just \$\rm\left[\Omega\right]\$. Similarly \$L\$ should be \$\rm\left[H/m\right]\$, \$C\$ should be \$\rm\left[F/m\right]\$, and \$G\$ ...
- 134k
1
vote
Accepted
Transmission line model VS lumped parameters models
A lumped parameter model uses R, L and C components connected together at nodes. Nodes have zero electrical length, zero capacitance to ground, and so enforce the same voltage at all times at all ...
- 174k
1
vote
Difference between a circuit developed using lumped elements and microstrip elements (transmission line)
Lo and Co are equivalent lumped elements to represent a ladder delay line of distributed inductance and capacitance.
The model comes from Heaviside's transmission line model but often quoted in ...
- 148k
1
vote
How does short length of transmission line approximate to a wire?
Background:
The equations derived in transmission line analysis are based off of standing waves. The idea is that the various impedance in the line and load will create reflections that will add and ...
- 153
1
vote
Accepted
Why don't we talk about a signal reflection when we treat a lumped element model of a circuit?
I think I found some clear answer. The key is the reflection. If the transmission line becomes so short that the signal transit time over the cable can be considered almost instantaneous in comparison ...
- 161
1
vote
Why don't we talk about a signal reflection when we treat a lumped element model of a circuit?
There are always reflections on any length of mismatched line but the general rule of thumb is that the energy of those reflections generally doesn't start to become problematic until the length if ...
- 473k
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