iPhone 4天线硬件设计无瑕疵？

Update:Apple says iPhone 4 problem is a math glitch

Experts say hardware antenna issues remain unresolved

by Rick Merritt

Perceived problems with cellular reception on the Apple iPhone 4are not due to a poor antenna design, but a faulty formula for reporting reception levels to users, according to a statement issued byAppleInc. Experts, however insist Apple is not telling the full story about the handset's novel antenna design.

"Some users have reported that iPhone 4 can drop four or five bars when tightly held in a way which covers the black strip in the lower left corner of the metal band,"Apple admitted in its statement released Friday (July 2).

However, the company has "gone back to our labs and retested everything, and the results are the same--the iPhone 4's wireless performance is the best we have ever shipped," the statement said.

The problem, according to Apple, is that "the formula we use to calculate how many bars of signal strength to display is totally wrong. Our formula, in many instances, mistakenly displays two more bars than it should for a given signal strength," the statement said.

Thus when users saw signals drop four or five bars, they were likely already in an area of weak coverage, the company claimed. "Their big drop in bars is because their high bars were never real in the first place," the statement said.

The rationale does not seem to address the problem reported in some cases that users had a usable signal but lost it when they covered the black strip in the lower left corner of the metal band.

Analysts at UBM TechInsights, who helped conduct a teardown of the iPhone 4, said the handset placed its cellular and GPS antennas in the case's frame. The black strip marked the space between the two antennas that, when bridged by a user holding his hand over it, changed the length and thus the performance of the antenna.

The Apple statement made no comment on the design of the antenna except to say "some have accused theiPhone 4of having a faulty antenna design."

"Absent sophisticated testing, it is hard to state with certainty whether Apple's claim that it's just a software problem is true or not," said David Carey, a senior UBM TechInsights analyst and founder of the Portelligent teardown service.

"The iPhone 4 antenna design is unique in that the basic internal antenna technology of today's cellphones is now exposed directly to the outside and to direct contact with the hand," Carey said. "Apple's design means it becomes possible for hand effects and degraded RF performance to be more pronounced [than with other handsets] it seems to me," he added.

Separately, the Anandtech Web site said the iPhone 4 in some ways has better cellular reception than competing phones it tested. However, it also said theiPhone 4is subject to greater signal loss than other phones depending on how the handset is held.

"Apple should add an insulative coating to the stainless steel [antenna] band, or subsidize bumper cases. It's that simple," the Anandtech reviewer said.

Apple said it will address the situation by "adopting AT&T's recently recommended formula for calculating how many bars to display for a given signal strength. We are also making bars 1, 2 and 3 a bit taller so they will be easier to see," the statement said.

"We will issue a free software update within a few weeks that incorporates the corrected formula. Since this mistake has been present since the original iPhone, this software update will also be available for the iPhone 3GS and iPhone 3G," the statement added.