Microwave Engineering Europe - June 2008 - (Page 20)

20 60 GHZ WIRELESS 60 GHz: Achieving the ultimate wireless dream Using sophisticated design and fabrication techniques, research labs are getting closer to realizing 60 GHz chips in silicon. When that happens, consumer price points can be met and wireless design becomes a whole new ballgame. But ﬁrst, engineers must overcome ﬁve major challenges. By Els Parton and André Bourdoux, IMEC W ireless communication in the 60 GHz frequency band promises to enable exciting applications ranging from downloads at video kiosks to connections between laptop and printers. While the standardization committee is preparing the launch of the new standard (probably in 2009), research groups worldwide are racking their brains on the challenges associated with the use of this millimeter-wave portion of the RF spectrum. Within reach of consumers With all the current hype on 60 GHz, one might forget that 60 GHz wireless communication has been around for awhile, more speciﬁcally in the James-Bond sphere of high-security communications and military satellite-to-satellite communications. Traditionally, 60 GHz radios rely on the extraordinary characteristics of expensive gallium arsenide (GaAs) material. Today, the advances in silicon processing technology (CMOS) enable smaller transistors with higher switching speed, making them more realistic candidates for the analog circuits in 60 GHz radios. The advantage of an analog radio frontend in CMOS technology instead of GaAs is that it can be seamlessly integrated with the digital radio baseband on one chip, resulting in a smaller one-chip, ‘cheap’ 60 GHz radio. A James Bond technology comes within reach of consumer electronics. In the short term, early 60 GHz multichip are being based on high speed silicongermanium (SiGe) circuits. However, it is expected that the second generation of these radios will rely solely on plain silicon CMOS processes with true one-chip solutions. The latter could appear on the market by 2010. Why 60 GHz? In 2001, the Federal Communications Commission (FCC) allocated a substantial block of 7 GHz in the 57-64 GHz band for unlicensed use. This ‘unlicensed’ aspect is a Figure 1: Worldwide spectrum allocation in the 60 GHz band. great advantage since this means that operators do not need to spend signiﬁcant time and money to obtain a license from its national authority. Furthermore, this unlicensed band is available throughout the world, meaning that a worldwide harmonization around 60 GHz is possible (see Figure 1). Of course, the main advantage of the wide bandwidth available at 60 GHz is that it enables high data rate wireless communication with capabilities far beyond current wireless standards (all below 10 GHz). An apparent disadvantage of 60 GHz communication — its high propagation attenuation — turns into an advantage for short-range applications: immunity to interference, high security characteristics and frequency reuse. A world of possibilities opens Thinking of high data rate (up to 5 Gbit/s) short-distance (3 to 5 m) wireless communication, one can easily name dozens of applications. So let’s just limit ourselves to the application domains that are described by the IEEE standardization committee as user cases: • Wireless high-deﬁnition multimedia interface (HDMI). Uncompressed video can be wirelessly transmitted from a DVD player to a ﬂat screen. • Fast up and download of high-deﬁnition movies. Users can download high- deﬁnition movies from a video kiosk onto their mobile device or at home can download a movie from their mobile device onto the computer. • Wireless docking station. A laptop computer can be wirelessly connected to the network, the display, an external drive, the printer, a digital camera etc. The challenges A world of possibilities, but also a world of technological challenges arises with the 60 GHz band. First of all, such a huge carrier frequency — an order of magnitude higher than current standards — imposes a lot of hazards to the analog and antenna designers. Moreover, when you aim at developing single-chip 60 GHz radios, using silicon CMOS technology, the technological challenge is even greater. The 45 nm technology node for CMOS is required to realize these radios, but only research centers that have ready access to these advanced technology nodes can get insight into the analog characteristics of the 45 nm transistors. A second challenge is the huge bandwidth of 7 GHz at which the 60 GHz radios have to work (from 57 to 64 GHz). This means the operating frequencies can vary about 15 percent as compared to only 3 percent for Wi-Fi (from 2.4 to 2.485). This is especially hard for the front-end, synthesizer and antenna design. Thirdly, the analog-to-digital converters and digital-to-analog converters have to Microwave Engineering Europe ● June 2008 ● www.mwee.com http://www.mwee.com

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Microwave Engineering Europe - June 2008 Contents Comment News Cover Feature Designing and Simulating a Wireless LAN Antenna 60GHz: Achieving the Ultimate Wireless Dream New Radar Developments Include HFETs to Challenge DMOS/LDMOS and a 77-GHz CMOS PA for Automotive Applications Testing Raises Concerns Over 802.11-Based High-Speed Bluetooth IP2 & IP3 Design Considerations with Direct Conversion I/Q Demodulator Receiver Products Calendar

Microwave Engineering Europe - June 2008

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