PCB Power Bus without Cable

printed circuit board power bus

This canonical geometry is basically a pair of perfectly conducting planes with a slightly lossy dielectric material between them. It emulates a printed circuit board power bus (or microstrip patch antenna), which can be a significant source of radiated emissions at frequencies corresponding to resonances of the cavity formed between the planes.

Modeling Notes:

  • θ=0° is the angle directly above the center of the top plate.

  • The frequency range 5 MHz - 2 GHz includes the following cavity resonances: TM10@566MHz, TM01@707MHz, TM11@906MHz, TM20@1.13GHz, TM21@1.33GHz, TM02@1.41GHz, TM12@1.52GHz, TM30@1.7GHz, TM22@1.81GHz, TM31@1.84GHz. Due to the source's location in the center of the shorter edge, we do not excite TMx1 resonances.


PCB size: 125 mm × 100 mm × 1 mm


Top layer: PEC
Middle layer: FR4, εr = 4.5, dielectric loss tangent = 0.015
Bottom layer: PEC


Voltage Source (1 V, 50 ohms ) or Current Source (0.02 A, 50 ohms )
Location: middle of the short edge


  1. Plot of the input impedance (5 MHz - 2 GHz )
  2. Plot of electric field ( 5 MHz - 2 GHz, 3 m, θ=0°, φ=0° )
  3. Plot of electric field ( 5 MHz - 2 GHz, 3 m, θ=90°, φ=90° )