As phones continue to shrink, fitting antennas in and making them work correctly often comes down to trial and error
By Amy Thomson
Whatever you think of Steve Jobs‘ defense of the iPhone 4 and its reception issues, the Apple (AAPL) boss was right about one thing: Antennas are a technological challenge, one that engineers have wrestled with since before Gordon Gekko barked orders into his Motorola (MOT) DynaTAC from a beach in the Hamptons. And as phones continue to shrink, fitting antennas in and making them work correctly often comes down to trial and error, says Stephen Temple, a retired engineer who helped plan Europe’s GSM technology. “It would be fair to say that antenna design is a little bit of a dark art,” Temple says.
The $4,000 DynaTAC weighed in at almost two pounds and was eight inches long. Today’s phones often weigh less than four ounces and can be shorter than the DynaTAC’s 5-inch antenna even as they pack in features such as video cameras and QWERTY keyboards. Since the late 1990s, consumer tastes have turned against external antennas, which means they must be crammed inside the handset’s casing. Phones now receive different signals such as 3G, Bluetooth, and Wi-Fi, so they often have a half-dozen or more antennas. Reception can be affected by the amount of space around the antenna, the materials used elsewhere in the phone (plastic is less problematic than most metals), and whether the caller is right- or left-handed.
For most of today’s basic voice and data cell signals, the right antenna length is about three inches or seven inches. FM radio and broadcast TV antennas are longer, though antennas can be bent to fit inside tiny phones. The optimal length is half the frequency the antenna is designed to receive divided by the speed of light. Any longer or shorter, and the reception can suffer. Furthermore, “the [human] body has a major effect on the antenna because at different frequencies it acts differently,” says Stuart Lipoff, an electronics consultant.
The arrival of faster, fourth-generation networks will complicate design further. And as new categories of devices such as the iPad grow in popularity, it’s getting harder to design antennas that are appropriate for all their potential uses. In years past, antenna engineers tested phones held against a person’s head, says Jeff Shamblin, chief technology officer of Ethertronics, a San Diego antenna maker. Now, he says, “you have to test a cell phone sitting on a desk, in a user’s lap, [or] being used on speakerphone while operated with two hands.”
The bottom line: Antenna design has long been a problem for phonemakers, and complexity is growing as devices shrink.
With Connie Guglielmo
Thomson is a reporter for Bloomberg News.