Title: CMOS Front Ends for Millimeter Wave Wireless Communication Systems (RF-CMOS geïntegreerde schakelingen voor millimetergolf draadloze communicatie)
Other Titles: CMOS Front Ends for Millimeter Wave Wireless Communication Systems
Authors: Deferm, Noël
Issue Date: 20-Jan-2014
Abstract: Today’s electronic communication possibilities and applications are endless. However, only 150 years ago the concept of the telephone was unknown. The history of electronic communication begins with the telegraph and a couple of years later the telephone in the 19th century. At the end of the same century, the foundations of wireless electronic communication were established. In the beginning, these electronic systems were bulky an impractical due to the large components like vacuum tube amplifiers. Thanks to the invention of the transistor and the integrated microprocessor, these communication systems could be miniaturized and integrated into portable systems that we all use today like smartphones, laptops and tablets.History has also learned us that the demand for data rate over wireless channels rapidly increases, from several kilobits per second in the early nineties to hundreds of megabits for today’s high speed wireless links. But even these high speed links cannot support the applications of the (near) future like wireless uncompressed (Ultra) high-definition video streaming or gigabit wireless LAN, for which data rates in the order of 10 gigabit per second and even higher are required. Therefore, new solutions have to be developed to support these high data rate links, both today and in the future. One of the most promising solutions is to shift the wireless carrier frequency from the currently used microwave bands (e.g. 2.4GHz, 5GHz) towards themillimeter wave frequency spectrum (60GHz, 85GHz, 94GHz, 120GHz) where high modulation bandwidths are available which can support gigabit per second wireless data streaming.This work focuses on the development of circuit and system design techniques for millimeter wave wireless communication systems above 90GHz and fabricated in nanometer scale CMOS technologies. The scaling of CMOS technologies over the past decades has lead to transistors with gate lengths in the nanometer scale range. Thanks to this scaling, the speed of the MOS transistors has also increased towards a maximum frequency of oscillation above 300GHz for the latest technology nodes. So CMOS has become a millimeter wave technology, but with the great advantages of the high integration capabilities.Although the speed of the CMOS transistors has increased, the target operation frequency of the circuits in this work (above 90GHz) is still close to the technology’s maximum frequency of oscillation. So coping with a low power gain is one of the major design challenges in CMOS at millimeter wave frequencies. Also, the transistors tend to show inherent potential unstable behavior, which makes multistage amplifier and system design a real challenge. Furthermore, the metal stack of CMOS technologies is not optimized for the design of high frequency passives, which will result in a decreased performance of traditional matching circuit topologies. At system level, problems like the implementation of the millimeter-wave chip interface and bandwidth and linearity requirements of the ADC’s, DAC’s and up- and downconversion circuits emerge.To solve the above mentioned problems, six different chips are designed in which circuit and system level solutions are proposed and implemented. Three different multistage differential W-band amplifiers are designed in which capacitive neutralization is extensively applied to improve the gain and stability properties of the transistors. The adoption of transformers and differential slow-wave transmission lines in the impedance matching networks resulted in small chip footprints, while improving the performance of the amplifiers even more. High gains ranging from 11dB up to 18dB and high output powers up to 8dBm were measured which confirms the efficiency of the adopted circuit design techniques.A combination of two stability analysis techniques is also proposed to accurately predict the common mode and differential mode stability behavior of multistage amplifiers. On the one hand, pole-zero stability analysis, which is excellent to predict the frequencies of possible oscillations and their dependency of one single design parameter is used. On the other hand, K-factor and stability circle based analysis is adopted to get better insight in the load and source impedances causing possible unstable behavior. Combining both techniques has lead to a robust stability analysis technique which not only makes it possible to identify the cause of the oscillation and its frequency, but also gives better insight in possible stabilization solutions. Direct digital modulation schemes were applied in three different F-band and D-band transmitters which has lead to new digital modulation system topologies. These direct carrier modulator topologies have resulted in a relaxation of the requirements of the upconverter and made it possible to omit the wideband, high speed digital-to-analog converters. Also the design complexity of these systems could be considerably reduced. An F-band ASK transmitter supporting data rates up to 5Gb/s and a 120GHz 10Gb/s PSK transmitter were designed, implemented and successfully measured. A fully integrated 120GHz Star-QAM transmitter, which combines both modulation techniques of the previously mentioned transmitters, capable of supporting a 10Gb/s wireless data link was also successfully measured. The integration of a frequency generator, modulator, power amplifier, baseband circuits and bondwire antenna has lead to a fully integrated solution which solves the problem of millimeter wave interfacing an hereby closes the gap between a laboratory chip solution an a real-life application.
Publication status: published
KU Leuven publication type: TH
Appears in Collections:ESAT - MICAS, Microelectronics and Sensors

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