antennarfidsmart-cardwirelesswiring
Here's a scan of a stripped MIFARE Ultralight smart card. Most of the wiring is the antenna which effectively consists of a single spiral track. The outer spiral turn clearly is a bit wider than the other turns while all the other turns have equal widths.
Why is the outer turn wider than the others?
This antenna is a modified form of the Yagi-Uda antenna. A basic Yagi antenna consists of three sections. A reflector, a driven element and a director. This is illustrated here:
You can clearly see each of these basic elements in the antenna you have purchased. The reflector at the left of your image serves to increase the directivity of the antenna by focusing the beam pattern towards and along the axis of the smaller directors.
The driven element is the somewhat circular section in the middle that attaches to the Balun. This element actually conducts the signal down the attached fly lead.
The directors are the short parallel elements that extend away from the driven element. The width of the directors determines the frequency at which they enhance the directivity of the antenna. A wideband antenna has many different width, parallel elements. The spacing between the elements affects the phase and hence the beam pattern of the antenna.
Yagi's rely on the principles of phased arrays for the large directivity (apparent gain) that they offer. The antenna you have purchased has taken this principle even further with its triple boom design. The addition of more directors to the system with a phase difference in two axis allows greater manipulation of the beam pattern and directivity of the antenna. The net result is an increase in the level of the received signal.
For maximum sensitivity, an antenna would be sized to the wavelength of the incoming signal. The sizes of most wires (traces) in a phone's circuit board are too small by maybe 2-3 orders of magnitude to be a good antenna for the wireless power signal. The size of wires inside the chips would be orders of magnitude smaller than that. The wireless power receiver wire loop is sized to resonate with the transmitter, and has circuitry to actively guide resonance. The frequencies involved in wireless power are very low compared to most of what's going on in a phone - kHz compared to GHz.
Any digital processing would be immune to noise so long as it remains well below the threshold of creating bit errors. The more sensitive parts of the phone to wireless power would be the analog areas, such as RF receiver and audio. Audio would be especially susceptible as the signal frequencies are closer together, both in the kHz range, although possibly still one or two orders of magnitude apart (4kHz for voice vs 100?kHz for power).
Most people don't use their phone while it's on the charger, so whatever problems are caused wouldn't usually be noticed, so long as no permanent damage is caused. Worst case scenario might be some missed calls, or bad-sounding audio if charged while connected to the stereo.
Best Answer
Probably for mechanical reasons. It is the feature nearest the edge, so it is more likely to get bent or cut. Making it wider makes it stronger so it is less likely to get damaged.