http://www.antennasys.com/antennasys-blog/2010/6/24/apple-iphone-4-antennas.html
Here's a short excerpt. Visit the site to read the entire article.
http://www.antennasys.com/antennasys-blog/2010/6/24/apple-iphone-4-antennas.html
Here's a short excerpt. Visit the site to read the entire article.
I saw the photo of the frame of the iPhone in the slideshow at the end of Steve Job's keynote address at the Developer's Conference. There are three gaps in the stainless steel band which are allegedly part of the antenna system. I have not had alot of time to analyze their structure, nor do I have one in my hands yet. So, either it is public relations hokum, or those slots are really part of the antenna structure. They do appear to be active, based on observations.
In the first generation iPhone (which I am currently using), the antennas were on the back of the phone, near the bottom. There was a piece of plastic on the bottom covering the antennas, so you knew where they were. I developed a way to hold the phone which avoided covering this area with my hand, similar to the Gizmodo article linked above. It is worth stepping back a moment and asking the question, "Why are the antennas placed where my hand is MOST likely to cover it?" It's a fair question.
The FCC puts strict limits on the amount of energy from a handheld device that may be absorbed by the body. We call this Specific Absorbtion Rate, or SAR. In the olden days, when I walked ten miles to school in three feet of snow, uphill in both directions, cell phones had pull-up antennas. This allowed the designer to use a half-wave antenna variant, and put the point of maximum radiation somewhat away from the users cranium. Of course, most people did not think it was necessary and kept the antenna stowed. Motorola's flip phone acutally had a second helical antenna that was switched into place when this was the case. But, more importantly, SAR rules were not yet in effect.