Issue link: https://iconnect007.uberflip.com/i/393082
October 2014 • The PCB Magazine 23 WEARABLE ELECTRONICS continues nectivity, devices usually don't connect beyond a few meters and the connectivity becomes in- termittent with increased distance and body movement. In some popular fitness trackers the range is actually only a few centimeters. The reasons behind this have to do with antenna theory, but basically electromagnetic energy is not radiating from the source and propagating to the far-field (receiver) with enough energy to induce current and voltage i n the receiver circuit, primarily because the effi- ciency and gain of an antenna are dependent on antenna physical dimensions and electrical characteristics for a given output power level. For wearable electronics, the physical dimen- sions are limited to within a form factor about the size of a quarter (24.3 mm diameter, Figure 2), and the red circles seen in Figure 5 show that, using conventional FR-4 materials and antenna design, both efficiency and gain drop way off at small sizes. This problem is much less evident at the larger dimensions possible inside mobile/portable devices such as smartphones, tablets, and laptops. But once the form factor becomes wearable and the antenna ground plane is limited to 13 x 13 mm or less, it is a different story. A California startup is taking a novel ap- proach. In this patent-pending process, mi- croscopic structures are used to create "engi- neered materials" in a 3D embedded SiP solu- tion incorporating coreless/anylayer technol- ogy providing electromagnetic band gaps in a wide range from a few hundred megahertz to figure 5: Comparative antenna performance vs. ground plane dimensions. (source: transsiP)