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solder pads vs. patch antennas


Full Member level 3
Nov 26, 2014
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is it true, solder pads on PCB can act as microstrip patch antennas for matched frequencies?
Most wires, conductors (e.g. solder pads) do actually emit electromagnetic radiation when operated on general signals. They are not perfectly designed radiators like patch antennae are, for example, but they do function like an antenna of sorts.

Based on a system's requirement of power, signal integrity, accuracy or perfection of operation and putting into perspective the kind of signals and their frequencies that would be traversing into or out of the solder pads, people may want to simulate the electromagnetic radiation characteristics of the pads using software and factor that into the calculations of the performance metrics of the system to try and understand its effects on the system and balance or mitigate that through other circuit elements, design techniques or by trying to change the pattern of soldering.
Yes and no.

The shape of a pad without components is similar to a patch antenna, but ...
(1) The pad is much smaller. Your SMD components and the corresponding pads are only a small fraction of wavelength, the patch antenna length is 1/2 wavelength for resonance.
(2) The patch has open ends, the pad with placed components does not have that open end.

So don't worry, the pad will not radiate much at the design frequency. In most cases, it is small enough that it can be considered a shunt C to ground below.

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