n the last decade, most research efforts in the communi-cations industry have focused on systems with bit rates

of 0.3 Mb/s–100 Mb/s over a radio frequency range of 100Mhz–5 GHz. These systems include second-/third-/fourth-generation (2G/3G/4G) cellular, Bluetooth, and wirelessLAN (WLAN) technologies for mobile phones andportable computers. With an explosive increase of datacontent delivered to mobile devices, there is an urgentneed to further increase the throughput of such mobilenetworks at least tenfold. Although recent wireless stan-dards, such as IEEE 802.11n, have been developed in anattempt to address such a need, they do not offer gigabits-per-second throughput. One reason for the limit inthroughput is due to the scarcity of available bandwidth inthe low gigahertz frequency spectrum. Consequently, manyemerging gigabits-per-second wireless systems are exploit-ing the use of millimeter wave (mm-wave) or even sub-mm-wave range.

Concurrent with renewed interest in mm-wave communi-cation, imaging applications in the mm-wave regime areexperiencing resurgent interest due to the increasing threatsof terrorism, global warming, and biological warfare. Inter-estingly, imaging can also be viewed as a communicationsystem, but of a different class where the sender can also bethe receiver, and the data received can be autonomouslyprocessed to provide critical information to the sender (e.g.,the detection of tumors). In contrast to applications duringthe Cold War period with detection range on the order ofthousands of kilometers, recent research focuses on shortdetection ranges on the order of a few meters to detect con-traband or toxic gases. Emerging applications, such as drugdetection and screening, require further reduction in thedetection range, down to a few centimeters.

Millimeter-wave communications is projected to be afast-growing market with a projected growth of 121 percentin 2010 worldwide for the equipment market segmentalone. Moreover, it is expected that 70 percent of mm-waveequipment will be deployed in backhaul networks by 2015.Such a steep rise in the demand for mm-wave devices isfueled by the integration of mm-wave circuitry in low-costsilicon technology. Ten years ago, few people thought such

high-frequency operation was feasible in silicon. However,mm-wave in low-cost silicon has steadily transitioned frommostly academic research to major segments of the com-munications industry, including, the wireless transmission ofhigh-definition TV from set-top boxes to LCD panels, andseamless connections between smartphones and multimediadevices. Likewise, in imaging, many applications are takingadvantage of the portability offered through highly integrat-ed low-cost silicon imagers to detect lethal weapons anddisease agents or to perform medical diagnostics.

Complementary metal oxide semiconductor (CMOS)technology has been the technology of choice for low-costintegration. In the last decade, CMOS technology has scaledfrom 130 nm to 40 nm and is now suitable for sub-terahertzoperation. However, many challenges remain, such as lossysilicon substrates that result in poor isolation and low Qcomponents. Low supply voltage also leads to insufficientpower handling. Additionally, intricate cross-coupling due tointegration of both digital and mm-wave blocks further exac-erbates circuit implementation. Finally, modern silicon tech-nology has complex design for manufacturing (DFM)requirements on metal density to achieve acceptable chipyields. Such DFM requirements may degrade passive com-ponent performance and induce extra design burden.

In this issue of Topics in Circuits for Communications,we have selected two articles that mark recent progress inmulti-gigabits-per-second sub-teraherz wireless transceiversfor portable broadband communications, and low-powersmall-form-factor mm-wave silicon imagers for portableimaging applications.

In the first article, “Silicon VLSI Catches the Millime-ter Wave,” the authors address the challenges to realize alow-latency multi-gigabits-per-second wireless link in thepresence of significant path loss and antenna directionalityat mm-wave frequency. The article discusses the formula-tion of link budgets in mm-wave frequencies, and providesan overview of architecture and circuit techniques thatmeet the challenges of power-efficient mm-wave circuitdesigns. The authors then discuss the design of a 2 × 2phase-arrayed CMOS transmitter chip that achieves multi-gigabits per second with 80 mW from a 1 V supply. Such

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TOPICS IN INTEGRATED CIRCUITS FOR COMMUNICATIONS

Charles Chien Zhiwei Xu Stephen Molloy

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mm-wave technology enables the replacement of HDMIcables for high-definition video and audio equipment, andsharing of multimedia contents among portable and datastorage devices, as prescribed by the use scenarios in theIEEE 802.15.3c standard.

The second article, “CMOS Receivers for Active and Pas-sive mm-Wave Imaging” presents mm-wave imaging technol-ogy that can penetrate through fabric, textile materials, andfog. Such capability is leveraged by a multitude of applica-tions in remote sensing and security screening. Lending itselfwell to miniaturization, mm-wave imaging can further extendits usage into bio-imaging, spectroscopy, and endoscopy formedical care, and drug/food screening in portable form fac-tors. The authors introduce several mm-wave imagingapproaches based on detection methods and outline the sys-tem implementation challenges. In particular, the authorsdiscuss the role of silicon technology in mm-wave imagingand the associated difficulties in their implementation. As anillustration, the article describes three implementation exam-ples in 65 nm CMOS, including both active and passiveimaging, consuming 10 mW and occupying 0.013 mm2. Theimager chips have been built into a testbed to demonstratelive image capturing of various objects in real time.

We would like to take this opportunity to thank all theauthors and reviewers for their contributions to this series.Future issues of this series will continue to cover circuittechnologies that are enabling new microsystems for com-munication or other emerging applications. If the reader isinterested in submitting a paper to this Series, please sendyour paper title and an abstract to any of the Series Edi-tors for consideration.

BIOGRAPHIESCHARLES CHIEN (charles.chien@creonexsystems.com) is the president and CTOof CreoNex Systems which focuses on technology development for next-generation communication systems. Previously he has held various key rolesat Conexant Systems, SST Communications, and Rockwell. In his career, hehas architected several key products including a CMOS/SiGe chipset formultimedia over coax (MoCA), an IEEE 802.11abg WLAN RF CMOStransceiver and GaAs PA/RF switches, a wireless audio CMOS chipset forhome theatre in a box, CDMA2000 cellular RF CMOS transceivers, and low-power wireless networked sensors. He was also an assistant adjunct profes-sor at the University of California at Los Angeles (UCLA) from 1998 to2009. His interests focus mainly on the design of system on-chip (S0C)solutions for wireless multimedia and networking applications. He has pub-lished in various journals and conferences, and has authored a book enti-tled Digital Radio Systems on a Chip. He received his B.S.E.E. from theUniversity of California at Berkeley, and his M.S. and Ph.D. from UCLA. Hewas a member of the technical program committee of ISSCC from 1998 to2006.

ZHIWEI XU (xuzhw@yahoo.com) received his B.S. and M.S. degrees fromFudan University, Shanghai, China, and his Ph.D. from UCLA, all in electricalengineering. He held industry positions with G-Plus Inc., SST Communica-tions, Conexant Systems, and NXP Inc., where he did development for wire-less LAN and SoC solutions for proprietary wireless multimedia systems,CMOS cellular transceivers, MoCA systems, and TV tuners. He is currentlywith HRL Laboratories, working on software defined radios, high-speedADC, and analog VLSI. He has published in various journals and confer-ences, made one contribution to the Encyclopedia of Wireless and MobileCommunications, and holds five granted patents.

STEPHEN MOLLOY (smolloy@qualcomm.com) received M.S. and Ph.D. degreesin electrical engineering from UCLA in 1993 and 1997, respectively, wherehis research focused on low-power circuits and architectures for video sig-nal processing. This work led to the award of the Showman Prize fromUCLA in 1997, and resulted in over a dozen conference and journal publi-cations. He received his B.S. degree in electrical engineering from Rensse-laer Polytechnic Institute in 1991. He served as Associate Editor of the IEEEJournal of Solid-State Circuits from 2001 to 2004 and was a member of thetechnical program committee of the IEEE International Solid-State CircuitsConference from 1998 until 2005. He is currently vice president of engi-neering at Qualcomm, leading architecture development.

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