[iPhone 4 Teardown (3)] Unexpected Antenna Structure Blamed for Bad Reception

Jul 1, 2010 12:35 Nikkei Electronics Teardown Squad

Continued from [iPhone 4 Teardown (2)] Screws Indicate Change in Apple's Design Policy

Just before starting to tear down the iPhone 4, we heard the news that the reception of the iPhone 4 becomes unstable when it is held by the left hand.

The lateral sides of the iPhone 4 are made of metal. When closely looking at them, we found black slits in the lower left, lower right and upper areas. The reception allegedly becomes unstable when the lower left slit is covered by a hand.

When we covered the lower left slit with a hand, the number of reception bars gradually decreased from five to four and from four to three. When the slit was completely covered, it finally became zero, showing a sign of "no service."

Though it is possible that we tested the phone in a place with poor reception, we confirmed the decrease in the number of reception bars. And, when Apple Inc's cover called "Bumper" was attached to the iPhone 4, that phenomenon did not occur.

Before we started to break down the iPhone 4, the engineers assumed that the three slits separate an antenna from a ground plane and that, when the antenna and the ground plane are electrically connected by a hand, the reception becomes unstable. And the squad members agreed with it.

After tearing down all the components, we examined the three metal parts separated by the black slits by using a tester to confirm that the metal parts are electrically separated from one another. However, it turned out that the three metal parts are electrically connected to one another.

At first, we thought that the tester was not working correctly and repeated the test several times. But the results were the same.

Perplexed by the test results, the engineers started reexamining the disassembled parts of the iPhone 4. Then, they came up with a new theory that antenna elements exist inside the main body and the metal parts on the lateral sides together work as a ground plane.

We found parts that look like antenna elements in the speaker module located near the lower left slit. And the module is connected to the chassis by wiring. The new theory is that the 3G antenna of the iPhone 4 consists of those antenna elements and the ground plane (three metal parts) located on the lateral sides of the phone.

The wiring is connected to a portion located slightly below the lower left slit. And it seems that the reception becomes unstable when this portion is touched by a hand. This is the conclusion reached by the engineers.

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