Patterned Ground Shields For Silicon RFICs – Part 2: What Universe Are We In?
In Part I, we used Sonnet® to investigate the current in the surface of the silicon substrate that is induced by a spiral inductor. Since it is an inductor, we were expecting the substrate current to be induced magnetically. After all, inductors are just little magnets, and we would expect inductively induced current in any nearby conductor. The silicon substrate is a conductor, kind of, right? In addition, the magnetically induced current should flow parallel to (and in the opposite direction of) the current in the spiral inductor. This behavior obeys a special case of Clerk Maxwell’s equations known as Lenz’s Law. This is all, to use American slang, a “slam-dunk”1, hardly even worth checking.
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