On the electromagnetic radiation of printed-circuit-board interconnections

Large ground and supply layers on interconnected boards represent a radiating antenna structure which may be efficiently excited at its resonances by small high-frequency potential differences. Such potential differences between the boards mainly originate from the inevitable inductive impedance of the signal-current return path in the connector, usually provided by ground pins. The presented modeling approach is based on an antenna transfer function for the global interconnecting structure and a partial-inductance equivalent circuit for the connector. As shown by the example of a motherboard-daughterboard structure, the model enables a systematic study of the radiation mechanism, depending on signal/ground-pin configuration, as well as geometrical and electrical parameters. In conjunction with SPICE simulations of the connector equivalent circuit, the signal driver and receiver dynamic characteristic can also be properly included. Validation is provided by full-wave simulation and measurement results.