RF expert SkyCross calls for “Time Out” and teaching moment on mobile device antenna issues
Date: Fri, 08/06/2010 - 13:22
SkyCross, a global designer and manufacturer of antenna solutions, today urged mobile device manufacturers and consumers to take a time out from the “Antennagate” controversy to review radio-frequency (RF) issues and their effect on smartphone performance. As the wireless industry transitions to 4G technology, antenna issues will become more significant since multifunction smartphones require multiple antennas for full broadband connectivity.
SkyCross specializes in optimizing wireless connectivity in consumer electronics devices. Over the past 10 years, SkyCross has built a commercial knowledge base and an extensive portfolio of patented antenna designs and techniques for the mobile device, notebook, access point, and consumer device markets. SkyCross iMAT® is a technology for super fast broadband networks that enables a single device antenna to deliver the performance benefits of multiple antennas without creating interference issues. Last year the company shipped more than 100 million antennas to device manufacturers worldwide.
“It’s true that antennas in smartphones and other handheld wireless devices are affected by the way in which the user holds the device,” said Charles A. Riggle, SkyCross Vice President of Marketing and Business Development. Antennas on the Apple iPhone4 are exposed to the user’s touch, and the so-called “hand effect” is magnified due to the conductive nature of human skin on these metal antenna elements. “Apple is a premier design innovator, but more extensive device tests are often necessary to observe these behaviors and identify a remedy before launching a product,” he said. “Frequently, it works better if the OEM can focus on the coolness of the design and the rich feature content and leave wireless performance to those whose sole focus is RF. This puts functional expertise where it is best carried out on both sides of the product solution.”
A non-conductive coating could have been applied on the metal ring around the iPhone4 to protect the exposed antennas from unintended signal attenuation when the user’s hand crosses the so-called “antenna gap.” Alternatively, after the phone was manufactured, a low-cost, one-inch “bandage” could have covered up the gap, making bumpers unnecessary. Since every single phone model is different, hand effect must be minimized through an iterative design process of moving and adjusting the antenna structure until the device meets mobile operator and regulatory performance goals established for that particular device in multiple usage cases.
“In antenna design, there is an age-old conflict in the compromise between form and function,” Riggle explained. “Antenna engineers are constantly challenged to do more with less and develop new ways of incorporating radiating structures into phones in the smallest space possible while still meeting mobile operator radiated-performance tests and adhering to mandatory RF regulatory requirements.”
Designing antennas for today’s complex multi-band smartphones is both an art and a science. Antenna designers must balance the technical challenge of designing antenna elements that are effective radiators of the signals transmitted and received in as many as 10 operating frequency bands with the mechanical challenge of placing these antenna elements into a device that fits in a consumer’s pocket, is mostly a metal and glass screen, and also has cameras, speakers, a keyboard, and a big battery.
On the technical side, the antenna must be large enough to efficiently transmit radio signals without reflecting RF energy back into the transceiver as heat, which wastes battery power. The antenna must radiate those signals on channels as low as 700MHz where the wavelength of the transmitted signal may actually be larger than the phone itself, and as high as 5GHz where the signal propagates a significantly lesser distance per unit of power output.
On the mechanical side, the antenna must be small enough to allow sleek, thin, and compact phone designs. It must also be located within the device to maximize its ability to get signals into and out of the phone without exceeding government power and RF exposure limits. Also, antennas must be designed not to create interference or be affected by nearby objects such as transceiver modules, speakers and digital cameras.
“Apple’s genius was in utilizing a major mechanical design element as the device antenna,” Riggle continued. “With the metal ring around the perimeter of the iPhone4 for the main radiating elements of the antenna, Apple eliminated the need to reserve dedicated volume within the phone for these antennas. That made the device more compact, allowed the screen to occupy as much of the front surface as possible, and enabled use of a larger battery to increase usage time between charges. Since the phone must operate on numerous frequency bands, multiple antenna elements were incorporated into the metal ring with small gaps between major radiating structures. These gaps caused problems.”
“Apple’s problem spotlights how important the design of antennas can be,” Riggle said. “After all, antennas are the only parts of a device that touch the mobile network and are crucial for the reliable high-speed connectivity demanded by subscribers of today’s 3G and 4G wireless networks.”