7 Analytical model for the radiated emissions from the slot of a rectangular enclosure:

This chapter describes the derivation of an analytical model for the radiated emissions from an enclosure with three closed and one open edge depicted in Figure 7.1. A trace above the ground plane of the PCB couples to the cavity and causes radiation from the slot of the enclosure. Intended applications of this model are fast predesign investigations on the influences of enclosure dimensions, placement of potentially critical components, and the PCB layer stack. Especially the first resonances of parallel-plane structures depend mainly on the maximum overall enclosure dimensions in x and y direction and not so much on details of the enclosure shape. Therefore, the model provides good first order information even about quantitative emission values for practical enclosures. The in depth description of the model derivation in this chapter shall provide guidance for the derivation of such enclosure models with different boundaries, for example, an enclosure with connector slots on the front and the back edges.

Figure 7.1: A trace on the PCB couples to the cavity and causes radiation from the cavity slots.

Subsections

• 7.1 Analytical cavity model for a rectangular enclosure with three closed edges and one open slot
  • 7.1.1 Derivation of the cavity model with the separation method
  • 7.1.2 Summary of the analytical cavity model of the rectangular enclosure with a slot on one edge
  • 7.1.3 Interpretation of the analytical model
  
  
• 7.2 Analytical consideration of the radiation loss and a model for the free space radiation from the enclosure slot
  • 7.2.1 Calculation of the far field from the slot field distribution
  • 7.2.2 Derivation of an admittance matrix for the consideration of the radiation loss at the cavity field simulation
  • 7.2.3 Introduction of the radiation loss admittance matrix into the cavity model matrix
  • 7.2.4 Summary of the equations for the introduction of the radiation loss into the cavity model and the far field calculation
  
  
• 7.3 Comparison of the analytical model results to HFSS^® simulations and measurement results
• 7.4 Radiation diagrams for the rectangular enclosure with a slot on one edge

C. Poschalko: The Simulation of Emission from Printed Circuit Boards under a Metallic Cover