12
votes
Standard 2.54/1.27mm pinheader impedance
You are overthinking this issue. For 4 MHz you shouldn't have any concerns. For example, all PC mainboards use 2x5 headers for on-board USB 2.0 connections to front panel USB, and they operate at 240 ...
- 42.4k
11
votes
Accepted
Unexpected low characteristic impedance using the JLCPCB impedance calculator
JLCPCB
Let's first consider the case of JLCPCB.
The last time I investigated the issue, JLCPCB's calculator was based on a lookup table using the model and results from Polar Instruments Si9000. ...
- 7,467
8
votes
Accepted
What is a guided mode?
A mode is a configuration of the electromagnetic field that is stable as the system evolves in time according to Maxwell's equations. Mathematically, it's an eigenstate of the differential equations ...
- 134k
7
votes
Accepted
What is the simple meaning of TE10 waveguide
A \$TE_{10}\$ mode has one lobe in the E-field strength pattern in the x direction (the longer transverse direction) and 0 lobes in the y direction.
A \$TE_{11}\$ mode has one lobe in the E-field ...
- 134k
5
votes
Accepted
What makes the band of an antenna broader than others?
Very broadly speaking, it's the Q of the antenna (if seen as a resonant element) that makes it more or less broadband. The higher the Q, the "more efficient" it transfers energy, but the lower it's ...
- 1,246
5
votes
What is a guided mode?
I would typically use "guided mode" to refer to a mode moving down a waveguide. For example, the LP01 mode of an optical fiber would be a guided mode. The opposite of a guided mode would ...
- 18.2k
5
votes
Unexpected low characteristic impedance using the JLCPCB impedance calculator
Check the higher-up (calculators) page; Chemandy has two other microstrip formulas as well.
The Wadell variant gives 75.25 ohms for the given dimensions, and IPC-2141, 83.93 ohms. It seems likely JLC ...
- 45.6k
4
votes
Accepted
Impedance mismatch vs Signal attenuation
The impedance mismatch doesn't cause actual loss, it just makes some of the power reflect away from the load. You are interested in a parameter called "reflection loss" that can be calculated. \$\...
- 753
4
votes
Accepted
Designing a 50Ω coplanar waveguide on 1.6mm FR4
Your trace width and spacing calculate out as a 50 ohm trace on a couple of calculators I checked, so that should be okay.
But I see a couple of other issues you should look out for:
In the original ...
- 134k
4
votes
Accepted
Standard 2.54/1.27mm pinheader impedance
To solve this, you need at more serious software than your standard PCB trace analyzer. I found a free tool to do this, MMTL electromagnetics simulator, it uses method of moments. MMTL stands for "...
- 3,696
4
votes
Accepted
Reflection coefficient formula
This is from a previous answer of mine. To understand reflections (and reflection coefficient) we can set up a thought experiment: -
Assume a cable (transmission-line or t-line) of characteristic ...
- 473k
3
votes
Phase and group velocity of wave
The frequency cannot change.
What happens to the speed and wavelength depends on what sort of waveguide it is.
If it's a TEM waveguide, like coax or microstrip, then the phase and group velocity ...
- 174k
3
votes
What are the waveguide modes of twisted pairs as discussed here?
At a certain frequency, you start getting issues because you can fit more than one wavelength in between the wire pairs. This is also the reason coaxial cable and it's connectors get smaller as we go ...
- 12.6k
3
votes
Accepted
Can closed metal box work as a wave-guide for wireless transmitter?
It at least means it's working as a cavity.
There are three easy to describe regimes that a closed metal box may work in, when there's an RF field inside (and a few more that aren't so simple).
a) ...
- 174k
3
votes
How to generate microwave band frequencies like 85GHz? Is there a DIY device or parts kit to do this?
Searching for 76 GHz transmitter comes up with many hits, such as the following for a 76-81 GHz device, although it appears to be a sensor:
https://www.ti.com/product/IWR1642
Here is a transmitter for ...
- 7,645
3
votes
Which stackup to choose for JLPCB FR4 up to ~10GHz
It really depends on the material of the PCB. If you just went with Isola FR408 YMMV because the dielectric constant might vary from your calculations of the design
Here is an example that a user ...
- 88.8k
3
votes
Accepted
Conformal Mapping in Electrostatics: t-plane
The next story is based on guesses. A less random answer is inserted to the end after the questioner gave more details.
Assume the wavequide is in parallel with the z-axis. All planes which are ...
2
votes
Coplanar waveguide - Calculator question
Scaling all dimensions by the same factor leaves you with the same impedance. However, it does not leave you with the same frequency range. These two are completely independent.
Beware that you have ...
- 174k
2
votes
Accepted
Microwave Waveguide system tuning
Water cooling depends greatly fluid dynamics of flow such as any good water radiator design. The objective is to transfer heat across a thin channel while it is flowing thru the channel, with minimal ...
- 148k
2
votes
Coplanar Waveguide Calculations PCBS, AppCAD v.s. Online calculators
Compare the two: -
One gives an electrical length of 0.0871 wavelengths and the other gives 0.086
One gives a \$Z_0\$ of 53.3 ohms and the other gives 53.1 ohms
One of the calculators asks for metal ...
- 473k
2
votes
RF Design - Antenna Feed-line Parameters
None of the calculations I've come across seem to care about the
length
As with any high-frequency transmission line, the matching impedance is determined by the inductance per unit length divided ...
- 473k
2
votes
Accepted
What is the mode of a square waveguide \$TE_{11}\$ that is deformed into a circle?
Dominant mode in rectangular waveguide is TE10 and in circular
waveguide is TE11.
Rectangular to circular waveguide transition convert dominant TE10
mode of rectangular waveguide to TE11 ...
- 88.8k
2
votes
Accepted
Metallic Waveguide Boundary
Maxwell's Equation: \$\mathbf{\nabla} \times \mathbf{H} = \epsilon \frac{\partial \mathbf{E}}{\partial t}\$
Expanding and using \$E_z=0\$ for TE, we get: \$\frac{\partial H_z}{\partial y}\$ gives \$...
- 66
2
votes
Waveguides Equivalent Circuits
It is written that it allows propagation at any frequency.
The concern is whether the waveguide supports low frequencies, not whether it supports extremely high frequencies.
Hollow waveguides have ...
- 134k
2
votes
Cut-off frequency in ideal waveguides
Below cutoff frequency, there is no energy flowing in to the waveguide. Everything you try to feed in is reflected back. And as there is no energy flowing, no losses are needed. You only see so called ...
- 753
2
votes
Accepted
Elliptical polarization and waveguides
Let's directly answer your questions, first, then address your misconception:
So, I'll say that waves in waveguides are simply linearly polarized
That can't be the case. How would you, in a round ...
- 100k
2
votes
Accepted
Dielectric slab waveguide
1) this is as an ideal structure to teach the basics of propagation inside a dielectric slab. The real guiding structure of course has walls if one wants to embed it in a photonic chip
2) This ideal ...
2
votes
What is the impedance looking into a length of coaxial cable that is short-circuited at the far end and a half wave-length long?
Since the joint of 2 waveguides must be created with two 1/4λ lengths, the shorted end will create an open circuit at the joint so that even metal conduction is unnecessary as the current is choked. ...
- 148k
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
Accepted
Waveguides and optical fibres
Microwave waveguides are generally made as small as possible while maintaining performance at the frequencies of interest. This is done by selecting a propagation mode and designing the vertical and ...
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