The employment of the resin back cover improved flexibility of antenna layout in the iPhone 3G. The main antenna for W-CDMA and GSM is mounted on the bottom of the chassis, while the sub-antenna for wireless LAN, Bluetooth and GPS is mounted on the upper part of the chassis.

"Antennas should be located as far as possible from each other to prevent radio wave interference," said an engineer from a Japanese parts manufacturer. "They probably wanted to enhance the performances including sensitivity."

As for the iPhone 2G, the back cover of the chassis is composed of two parts, one made of metal and the other made of resin. And the antennas are concentrated on the bottom of the chassis, where the resin cover is located.

As a result of this structure, two long coaxial cables had to be used inside the chassis in order to connect the main board located at the upper part of the chassis to the antennas. The cables were grounded to prevent noise.

Moreover, the positional relation between the main board and the Li-polymer secondary battery was changed. In the iPhone 3G, the single-structure main board is placed on top of the Li-polymer secondary battery. This layout made it possible to create contact points on the main board for connecting the secondary battery and antennas (main and sub) to the main board.

In the iPhone 2G, the main board, the Li-polymer secondary battery and the antennas were positioned side by side. The main board was connected to the secondary battery by soldering three cables.

Cost reduced by using same manufacturers

Unlike its predecessor, the iPhone 3G has a single main board, and the main parts are concentrated on one side of the board. Comparing their parts on a functional basis, we found that Apple uses the same suppliers for most of the parts (Note 1). In particular, there were surprisingly fewer differences in the block related to application functions than in the wireless circuit block.

In the iPhone 2G, the main board was separated into a block for application functions and one for the wireless circuit. One engineer said, "I got the impression that the iPhone 2G was created by forcefully combining the main board of a music player such as the iPod with a mobile phone main board."

Note 1: iSuppli Corp estimates the production cost of the 8-Gbyte iPhone 2G at US$265.83 as of June 2007, while that of 8-Gbyte iPhone 3G is estimated at US$174.33 as of July 2008.

In the iPhone 3G, a number of main parts, including the RF circuit, the baseband circuit and the application processor, are mounted on a single printed circuit board (main board). In the iPhone 2G, the wireless circuit board was separate from the main board. The purposes of the parts are estimated by Nikkei Electronics. (Click to enlarge)

Main parts mounted on the main boards of the iPhone 3G and the iPhone 2G. Though there are some differences in functionality, it seems that the parts were purchased from the same manufacturers. The purposes of the parts are estimated by Nikkei Electronics. (Click to enlarge)

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