Ground plane

How exactly does a ground plane work? My understanding is that it's a large conductive surface which somehow eliminates ground noise. I might understand that if every point in the circuit at GND was directly connected to it. But, my breadboard advertises that it has a ground plane underneath, and it electrically connects it to only one point. How does that eliminate noise?

If I take a regular (no ground plane) breadboard, tape a sheet of aluminum foil underneath, and connect a wire from it to the ground tie point on the board, will this improve circuit performance?

Depends on the circuit, at moderate RF frequencies it will allow a circuit to function in the first place, whips can't work without a ground plain.

Have you ever seen a dipole antenna? A dipole is uniquely similar to a groundplane in a way. One side of the dipole can represent the top part on a ground plane and the elements coming out at an angle on the groundplane can represent the other side of the dipole. The opposite elements are angled in such a way for RF radiation and gain. You may ask as to why we have all these different antennas, the true purpose is usually to manipulate the radiation pattern and also the gain. The best antenna is an "isotropic antenna" which is practically impossible to achieve, but it provides a good reference when you compare it with real antennas.

Austin

Actually EN an isotropic antenna is not the 'best' antenna no matter how you look at it. It's simply a theoretical point radiator that puts out radiation in every direction 100% evenly, no antenna does this, just about no antenna would ever need/want to. The radiation pattern of a vertical dipole is a large toroid around the antenna, this is nearly ideal, this is also the same pattern as you get from a whip antenna with a good ground references, theoretically at the tip there is no radiation, this is good because ground based RF doesn't need to radiate up. In the case of aircraft it's a little more complicated because obviously you don't want to lose contact with aircraft directly overhead, so antenna arrays are used instead.

For RF circuits the ground plane will act as a return for the RF currents. But normal use of a ground plane for analog and digital circuits is to connect all ground points and decoupling capacitors to the ground plane. It reduces ground noise by providing a low impedance path for high frequency ground currents.

srobertjames said:

I might understand that if every point in the circuit at GND was directly connected to it. But, my breadboard advertises that it has a ground plane underneath, and it electrically connects it to only one point. How does that eliminate noise?

Click to expand...

Have a look for 'star grounding'. The idea is that voltage drops caused by currents through traces or wiring in one part of the circuit don't affect the reference gnd voltage to other parts of the circuit as they are all connected to a [low impedance] reference point.

We really need to know what type of circuit you are dealing with as a ground plane performs a number of different functions according to the type of circuit. It can have an enormous effect on high-frequency circuits and an amazing improvement for circuits that transmit.
In some cases they prevent transmission and in other cases they improve transmission.