13
votes
Accepted
What is Negative Inductance?
In your case, the inductance is calculated from the reactance and then plotted. If the reactance is capacitive, and inductance is plotted, it appears negative.
You have an inductor with a capacitive ...
- 3,177
12
votes
What is Negative Inductance?
An unbalanced RLC filter will appear inductive and capacitive (negative inductance) about the resonant frequency. This filter appears to be very underdamped series-shunt filter.
There appears to be a ...
- 148k
11
votes
Why is there a solder mask opening over a microstrip line?
It appears that there is no soldermask on that board at all, and the opening you are referring is in the copper. When it comes to RF or other high-frequency signals, surrounding objects play a large ...
- 21.6k
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
9
votes
USB trace impedance calculations, with termination resistors
question 1:
This doesn't seem right
The default Er is 4, but usually the ER for standard FR4 is around 4.6. Although for this calculation you will need the effective Er because the top of the trace ...
- 369
9
votes
Why is there a solder mask opening over a microstrip line?
Because at RF, solder mask behaves differently than air; especially, it has higher losses.
Also, yes, even if it was lossless, the materials below and above the microstrip affect the wave impedance. ...
- 100k
7
votes
Accepted
Avoiding microstrip line to become CPWG
Where the proximity to a ground conductor only happens for a short length of track, a small fraction of a wavelength, you can regard it as an extra lumped capacitance to ground.
Depending on the ...
- 174k
7
votes
Accepted
Qucs simulation of quarter wave microstrip stub doesn't match ideal calculaton
And ideally, the speed of light is \$ \frac{c}{\sqrt{\epsilon_r}} \$
In coaxial cable, where all the EM field is confined within the same dielectric, this is true.
In microstrip, most of the EM field ...
- 134k
6
votes
Difference between Antenna and Filter
Your assumption seems to be that filtering only one time is enough.
That might be true but it might also not be true, it depends factors like:
How much filtering outside your band of interest is ...
- 81.4k
6
votes
Accepted
Feasibility of rat-race as RF mixer without active devices
some sort of active device (sometimes diodes)
This suggests that you deem diodes to be active devices, so presumably a passive device means no diodes. In that case, a structure that's passive will ...
- 174k
5
votes
RF PCB Design Basics - RF traces golden surroundings
This is either co-planar waveguide, or co-planar waveguide above ground. There appear to be filled vias in the top ground, so these almost certainly go a ground in the next layer down. CPWaG is a nice ...
- 174k
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
5
votes
High frequency PCB Design for Low Noise Amplifier
1)What is the purpose of the capacitors in the circuit?
The datasheet tells you that C1 and C2, suggested values of 1 uF, are needed for biassing at low frequencies. As the IC is specified down to 9 ...
- 174k
4
votes
Accepted
Difference between Antenna and Filter
The antenna resonates at a particular frequency
Not true.
A whip (monopole) antenna (for example) produces an optimum output level for frequencies that are close to one-quarter wavelength. It will ...
- 473k
3
votes
RF PCB Design Basics - RF traces golden surroundings
This answer just covers the part of the question about the reason for gold plating.
The gold finish provides a smoother surface than most other available finishes. Roughness increases the loss of ...
- 1,799
3
votes
RF Ground Stitching in Proteus Ares 8
Use Pads instead of Vias.
Create a component with one pad called Ex: stitchingVia.
Place as many as you want in the schematic. and connect them to GND.
in the PCB part
View the pad properties and ...
- 369
3
votes
Accepted
Vias Size for Microstrip
You can design your via to minimize the discontinuity it introduces in your transmission line.
Basically this means balancing the inductance introduced by the via with the capacitance between the via ...
- 134k
3
votes
Accepted
How to draw microstrip line in EAGLE?
Microstrip simply means a controlled-impedance trace on one of the surface layers. A stripline is the same, except on an internal layer.
A Microstrip is just a regular track but you determine its ...
- 21.6k
3
votes
Accepted
How does RF Coax cable impedance + Microstrip impedance mismatch affect power transfer
You will lose some power, but probably not an unacceptable amount - especially if the input of the receiver is in the 40 to 50 Ohm range. I get a gamma of -0.19 for coax to ms which is less than 0.2 ...
- 1,601
3
votes
Accepted
Design of microstrip tranmission line
'The' quadrature coupler does not relate to microstrip transmission line.
If you bring a second transmission line 'close' to a first, so that some field is shared, then you get two coupled ...
- 174k
3
votes
Accepted
What are the extra microstrip elements on this RF amplifier board for?
Those small islands are there for tuning the input and output impedances seen by the power amplifier. They're not to be removed! Another example (it's common practice, in fact):
You can solder ...
- 5,841
3
votes
Qucs simulation of quarter wave microstrip stub doesn't match ideal calculaton
As advised by The Photon, I redid my calculation to compensate for the effect of an inhomogeneous microstrip surrounded by air. To do this, rather than using the \$ \epsilon_{r} \$ of the substrate, ...
- 7,467
3
votes
Best way to connect coax along a microstrip
What is the best (=best coupling to the circuit) way I can make the connection in this situation?
The best = 'lowest loss coupling' you can make to the microstrip is to cut a small section out of the ...
- 174k
3
votes
Accepted
Properly grounding an SMA connector (bottom ground plane only)
A connector usually has to introduce some mismatch; in fact the edge launches (the 'official' name for your connector) was designed to minimize that.
In practice I agree with you, the line is short ...
- 8,744
2
votes
Accepted
Microstrip design
Given your specifications a Lange coupler could be a good option although it's far from being the easiest one to manufacture. However, its very wide bandwidth (if that's what you need) offsets all of ...
- 5,841
2
votes
Accepted
Connecting micro-strip line and stub
You will often be able to get better results in simulation if you model something simpler than the real world. However, the purpose of using simulation is not to get good simulation results, but as a ...
- 174k
2
votes
Grounded Coplanar - Impedence calculation of microstrip - Advance Design System software (ADS)
The model in ads called CPWG - Coplanner waveguide with lower ground plane.
You can find it both in the line calc and the copplanar transmission line library.
- 1,199
2
votes
RF Ground Stitching in Proteus Ares 8
For completeness, in Proteus 8.8 and above, Zone Stitching is supported directly by the ARES: See this LabCenter instructional video on YouTube.
- 703
2
votes
RF Ground Stitching in Proteus Ares 8
You can create a new pad to use as a via. Someone asked similar questions about Proteus and its uses HERE and LabCenter responded to answer a few questions. The bit you are interested in would be what ...
- 12.2k
2
votes
Impedance calculation results between grounded coplanar waveguide and microstrip
GCPW with large spacings is effectively microstrip, yes.... So why do
I get different impedance results in both simulators? I think I still
don't get the point. Is the GCPW simply not made to ...
- 21
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