Power Bus EMI Calculator

The maximum intensity of radiated emissions from a rectangular power bus structure can be derived based on an analytical cavity-resonator model. The effect of components mounted on the board is modeled by modifying the propagation constant of the waves within the power bus structure. The radiated field intensity is calculated using the equivalent magnetic current around the edges of the power bus structure together with the modified propagation constant [1-3]. The algorithm used to make the calculations below is described in [4].

Assumptions:
  • The power bus consists of two nearly rectangular solid planes.
  • The length and width of the planes are much greater than the dielectric thickness.
Power Planes

Length: mm
Width: mm
Thickness: mm

circuit board

Dielectric
Relative permittivity (εr):
Loss tangent (tanδ):

Source Parameters
Number of components (Nc):
Equivalent series resistance (Rc): Ohms
Connection inductance (Lc): nH
Maximum current (Ii): mA
Conducting plates
Conductivity (σ): ×107 S/m

Frequency Range
Minimum frequency (f1): MHz
Maximum frequency (f2): MHz

[1] Hwan Woo Shim, Development of Radiated EMI Estimation Algorithms for PCB EMI Expert System, Ph.D Dissertation, University of Missouri-Rolla, 2004.

[2] H. Shim, Y. Fu and T. Hubing, "Radiated Emissions from Populated Printed Circuit Boards due to Power Bus Noise," Proc. of the 2004 IEEE International Symposium on Electromagnetic Compatibility, Santa Clara, CA, USA, August 2004, pp. 396-400.

[3] H. Zeng, H. Ke, G. Burbui and T. Hubing, "Determining the Maximum Allowable Power Bus Voltage to Ensure Compliance with a Given Radiated Emissions Specification," IEEE Trans. on Electromagnetic Compatibility vol. 51, no. 3, Aug. 2009, pp. 868-872.

[4] C. Zhu and T. Hubing, "Maximum Radiated Emission Calculator: Power Bus Algorithm," CVEL-13-053, Oct. 13, 2013.

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