How to Calculate the Fringing Capacitance Between a Cylindrical Rod and an Infinite Ground Plane?

In summary: No, simulation will work fine. It just the professor thinks it cool to use equations instead of simulations when presenting the work.I see. In that case, I'll try to find a semi-analytical formula. Thanks for your help.
  • #1
z3phyr
4
0
Hi there
I've encounted a problem in which I'm required to calculate the total capacitance between the end of a cylindrial rod and an infinite ground plane.

I've attached a schematic drawing here. The gap between the rod if far smaller than the diameter.

http://picasaweb.google.com/lh/photo/igUbKtbtX7AiyLX5tsQFQg?feat=directlink

The part I can't figure out is the fringing capacitance from the sidewalls to the ground plane. I wonder if anybody has seem this problem before or know of any analytical/semi-analytical formula for estimating the fringing capacitance? I've done some numerical simulation with Ansoft Maxwell and I can definitely see a fringing field contribution that can not be neglected.

Greatly appreciated!
 

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  • #2
z3phyr said:
Hi there
I've encounted a problem in which I'm required to calculate the total capacitance between the end of a cylindrial rod and an infinite ground plane.

I've attached a schematic drawing here. The gap between the rod if far smaller than the diameter.

http://picasaweb.google.com/lh/photo/igUbKtbtX7AiyLX5tsQFQg?feat=directlink

The part I can't figure out is the fringing capacitance from the sidewalls to the ground plane. I wonder if anybody has seem this problem before or know of any analytical/semi-analytical formula for estimating the fringing capacitance? I've done some numerical simulation with Ansoft Maxwell and I can definitely see a fringing field contribution that can not be neglected.

Greatly appreciated!

Welcome to the PF. It would seem that simulation would be your best bet. What is the application? What accuracy do you need?
 
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  • #3
Hi Berkeman
Thanks for the reply. This is for the design of a combline/evanescent mode waveguide filter. Basically I'm trying to calculate the gap between the cylindrical post and the ground plane. It would be nice to have some formula for easy calculation and I'm almost certain that somebody, at sometime, must have tackled this problem. I just can't seem to find it in the literature...

berkeman said:
Welcome to the PF. It would seem that simulation would be your best bet. What is the application? What accuracy do you need?
 
  • #4
Cool problem. Is there a reason that the simulation route won't work for you?
 
  • #5
No, simulation will work fine. It just the professor thinks it cool to use equations instead of simulations when presenting the work...

berkeman said:
Cool problem. Is there a reason that the simulation route won't work for you?
 

1. What is capacitance and why is it important?

Capacitance is the ability of a material to store an electrical charge. It is an important concept in electronic circuits as it allows for the storage and release of energy, which is essential for many devices to function.

2. How is capacitance calculated?

Capacitance is calculated by dividing the charge stored on one of the conductors by the potential difference between the two conductors. It can also be calculated by multiplying the permittivity of the material by the surface area of the conductors and dividing by the distance between them.

3. What factors affect capacitance?

The factors that affect capacitance include the distance between the conductors, the surface area of the conductors, and the permittivity of the material between the conductors. Other factors such as the type of material used and the dielectric constant may also impact capacitance.

4. How is capacitance used in practical applications?

Capacitance is used in a variety of practical applications, including in electronic circuits, power transmission and distribution systems, energy storage devices, and sensors. It is also used in devices such as touch screens and capacitive sensors.

5. How can capacitance be increased or decreased?

Capacitance can be increased by increasing the surface area of the conductors, decreasing the distance between the conductors, or using a material with a higher permittivity. It can be decreased by doing the opposite - decreasing the surface area, increasing the distance, or using a material with a lower permittivity.

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