Ground plane

Ground planes are typically made of copper or aluminum, and they are often located on the bottom of printed circuit boards (PCBs).

[3] Ground plane shape and size play major roles in determining its radiation characteristics including gain.

To function as a ground plane, the conducting surface must be at least a quarter of the wavelength (⁠ 1 /4⁠ λ) of the radio waves in radius.

At upper VHF and UHF, the metal skin of a car or aircraft can serve as a ground plane for whip antennas projecting from it.

So a monopole mounted over an ideal ground plane has a radiation pattern identical to a dipole antenna.

The feedline from the transmitter or receiver is connected between the bottom end of the monopole element and the ground plane.

The large conducting area of the ground plane has much lower impedance than a circuit trace, so the current pulses cause less disturbance.

When two traces run parallel, an electrical signal in one can be coupled into the other through electromagnetic induction by magnetic field lines from one linking the other; this is called crosstalk.

The two facing areas of copper create a large parallel plate decoupling capacitor that prevents noise from being coupled from one circuit to another through the power supply.