Wizards of Electromagnetism

When Dorothy arrives in Oz, she says to her dog, “Toto, I’ve a feeling we’re not in Kansas any more.”
 
Likewise, digital electronic engineers like yourselves are being thrown from your world of ones and zeros into a microwave “Oz” – with its splendid but puzzling reflections, impedances, and electromagnetics — and you’re saying “Toto, I’ve a feeling we’re not in binary any more.”
 
You’re right.

Hopefully this blog will prove a more reliable guide than the Lion, the Tin Man and the Scarecrow. We’ll try to help you become the Wizard of Electromagnetism.

In this first post, I’ll reference the posting that inspired this blog. It honored James Clerk Maxwell, born June 13th, 1831 in Edinburgh, Scotland, UK (also the birthplace, by the way, of Alexander Graham Bell). Maxwell synthesized previously unrelated observations, experiments, and equations of electricity, magnetism, and optics into a consistent theory and set of equations—Maxwell’s equations—demonstrating that electricity, magnetism and even light are all manifestations of the electromagnetic field.

James Clerk Maxwell with one of his colour wheels

Maxwell’s work has stood the test of time. Maxwell’s equations are consistent with the Lorentz transformation, and inspired Einstein’s special relativity. In this view, magnetism is not a separate force, but the simply the dynamics of the electric force with space-time distortion from charged bodies in relative motion (electrodynamics). If the electric field is interpreted as the probability of observing a photon, the equations are consistent with quantum mechanics (quantum electrodynamics). QED has even been extended to cover the weak nuclear force (responsible for beta decay) in the electroweak theory. Thus extended, the theory encompasses in principle all physical, chemical, and biological phenomena except gravity and the strong nuclear force (quarks and gluons and such). The bottom line is that you can take the solutions to the bank: unlike SPICE, there are no approximations.

EM solvers are now a standard signal integrity analysis tool. Although the equations are computationally expensive to solve, the results accurately reflect the distributed nature of multigigabit per second serial links, where the wavelength of the highest frequency component is shorter than the physical size of the backplane. This is in contrast to nodal solvers like SPICE, which use a lumped element approximation, and which ignore crosstalk due to magnetic induction in conductor loops (curl(E) = -dB/dt).

So this blog will pick up the thread from the post on my signal integrity blog to drill down on practicle applications of electromagnetism at microwave frequencies to digital electronics.