Microwave Engineering Europe - May 2008 - (Page 28)

28 UWB Reducing power consumption in ultrawideband chips By Gadi Shor, Chief Technology OfÆ cer, Wisair, www.wisair.com U ltrawideband (UWB) technology is a wireless radio technology for short-range, high-bandwidth communication at very low energy levels that uses a large portion of the radio spectrum. It is considered the most efﬁcient technology employed today in terms of joules per bit. Wireless USB, also known as Certiﬁed Wireless USB, is based on the UWB common radio platform from the WiMedia Alliance. Because it combines the speed and ease of use of USB 2.0 with the convenience of wireless technology, it holds great promise for a range of applications, including high-speed digital media transfer between devices in personal and home area networks. One especially sweet spot for UWB and Wireless USB is in mobile, battery-operated devices requiring high bandwidth and low power consumption. In fact, according to a recent ABI research study, shipments of UWB-enabled devices will grow from virtually nil today to more than 400 million in 2013. This growth stems from UWB’s application as a wireless enabler for mobile devices such as cellular phones, digital still cameras (DSCs), notebook computers and personal media players (PMPs). Such devices store large amounts of data in the form of photos, music and video, and therefore require the ability to move content from one device to another, including to home PCs or televisions. Although UWB makes wireless data transfer viable, a number of obstacles make its use challenging, including its small size and throughput. One key obstacle involves minimizing battery power consumption while still providing high throughput. Effectively addressing this challenge requires today’s UWB chip designers to adopt special design techniques and to take full advantage of Wireless USB’s outstanding power efﬁciency. Minimized power consumption and maximized throughput are critical requirements for today’s battery-operated mobile devices because of these devices’ usage scenarios. Imagine, for example, a consumer who uses a camcorder throughout When comparing a 4-Gbyte wireless data transfer performed by Bluetooth-, 802.11and UWB-enabled devices, the clear winner in terms of speed is UWB. Thanks to its superframe structure, UWB achieves signiﬁcantly lower power consumption than either that of Bluetooth or 802.11. the day. At the end of the day, upon returning home, the consumer ﬁnds that the device has only 10 percent of its battery power left, making it impossible to transfer its contents to another device. During typical usage, this is exactly the type of capability that today’s consumer demands. If the industry is to continue progressing toward the next phase of UWB/Wireless USB in mobile devices, this concern must be addressed. The problem, of course, is that UWB chip design poses a number of interesting technical challenges, not the least of which is that of slashing chip prices by migration to a single-chip CMOS solution affordable to average consumers. This single-chip implementation must include the radio, physical layer (PHY), WiMedia MAC layer, Wireless USB layer and all relevant interfaces. Because of the low power consumption requirement of mobile devices, realizing this low-cost design has become an even greater priority. Designing UWB solutions To successfully design a single-chip, CMOSbased UWB solution in support of emerging mobile devices and their low power consumption requirement, designers must adopt special design techniques to deal with the challenges that exist in several key chip development areas: • Radio. The implementation of a lowpower, high-frequency CMOS radio at 3 to 10 GHz requires that special techniques be used to reduce power consumption while still retaining the high-frequency, wide-bandwidth design’s sensitivity and linearity. • Hopping local oscillator. The hopping local oscillator is a unique on-chip element that must cover the entire 3- to 10-GHz range. It must also be able to change its frequency by 1 GHz within a few nanoseconds. Implementing this element while supporting the low-power requirement is extremely challenging and must therefore be carefully considered during the design process. • Viterbi decoder and FFT. In the UWB chip, the FFT/IFFT block and the Viterbi decoder work at a few hundred MHz, making them difﬁcult to implement. Because of this, the Microwave Engineering Europe ● May 2008 ● www.mwee.com http://www.wisair.com http://www.mwee.com

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Microwave Engineering Europe - May 2008 News Contents Comment Cover Feature: How to Succeed as a GaAs Foundry Wireless Networking: Wireless Coverage Where Everybody WINS Wireless Networking: Achieving Good Coexistence in the 2.4 GHz ISM Band GPS and Satellite: GPS developments: Galileo Moves Forward with Successful Giove-B Satellite Launch — Broadcom Targets AGPS in Mobile Phones and Devices Raising the Bar for the Radio: Making 802.11n Work Reducing Power Consumption in Ultrawideband Chips WiMax Catches Second Test Wave Products Calendar

Microwave Engineering Europe - May 2008

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