iPhone 4手机接收信号差，苹果教您如何解决

Poor antenna design may cause iPhone 4 issue

by Rick Merritt

Some users are experiencing cellular reception problems with the Apple iPhone 4 that one analyst said could be due to Apple's novel use of the smartphone's frame as an antenna. Apple acknowledged the problem in a statement advising users on how to hold the phone.

The Gizmodo Web site published comments and videos from users showing loss of cellular reception when the iPhone 4 was held in certain ways. PC Magazine confirmed the problems based on internal and external lab tests.

One teardown expert speculated the problem may be due to what appears to be Apple's decision to embed the phone's cellular and GPS antennas in the metal frame of the case. When a user's hand covers a functional break between the two antennas, the hand bridges signals across the break. That can change the length of the antenna and thus its performance.

"We haven't had a chance to test this theory yet," said Jeff Brown, vice president of business intelligence at UBM TechInsights that published a teardown of the iPhone 4.

In its teardown, UBM TechInsights showed a functional break in the frame believed to be used to separate the cellular and GPS antennas. The frame also includes a break on the opposite side that has no function other than to provide a balanced symmetric look.

The frame-based antenna may be something of an experiment with the iPhone 4. "I am not aware of any frame-based antenna" in other smartphones, Brown said.

Typically smartphones implement an antenna with a wire inside the phone or a folded piece of metal embedded in the acoustic chamber where speaker resides. "One of the benefits [of using the frame as an antenna] is it can save space for a bigger battery," Brown said.

Apple acknowledged the problem in a statement advising users not to cover the functional break, identified by a black strip on the phone's case.

“Gripping any mobile phone will result in some attenuation of its antenna performance, with certain places being worse than others depending on the placement of the antennas,” Apple said. “If you ever experience this on your iPhone 4, avoid gripping it in the lower left corner in a way that covers both sides of the black strip in the metal band, or simply use one of many available cases,” it concluded.

The issue—and Apple's recommendations for handling it—fly in the face of the company's tradition of carefully crafting compelling user experiences.

Apple also experienced an antenna problem with Wi-Fi networking on its iPad. After several users posted complains Apple said that under certain conditions, the iPad may not automatically rejoin a known Wi-Fi network after restart or waking from sleep. The issue can occur with some third-party Wi-Fi routers supporting multiple bands when users use the same network name for each network or use different security settings for each network, Apple said.