Results 1 - 10 of 146

Micromachined devices for wireless communications

by Clark T.-C. Nguyen, Linda P. B. Katehi, Gabriel M. Rebeiz - PROC. IEEE , 1998
"... An overview of recent progress in the research and development of micromachined devices for use in wireless communication sub-systems is presented. Among the specific devices described are tunable micromachined capacitors, integrated high-Q inductors, micromachined low-loss microwave and mm-wave fi ..."
Abstract - Cited by 58 (12 self) - Add to MetaCart
An overview of recent progress in the research and development of micromachined devices for use in wireless communication sub-systems is presented. Among the specific devices described are tunable micromachined capacitors, integrated high-Q inductors, micromachined low-loss microwave and mm-wave filters, low loss micromechanical switches, microscale vibrating mechanical resonators with Q’s in the tens of thousands, and miniature antennas for mm-wave applications. Specific applications are reviewed for each of these components with emphasis on methods for miniaturization and performance enhancement of existing and future wireless transceivers.

Technology for Timing and Frequency Control

by Clark T. -c. Nguyen - IEEE Int. Frequency Control/Precision Time & Time Interval Symposium, Aug 2005
"... Abstract—An overview on the use of microelectromechanical systems (MEMS) technologies for timing and frequency control is presented. In particular, micromechanical RF filters and reference oscillators based on recently demonstrated vibrating on-chip micromechanical resonators with Q’s>10,000 at 1 ..."
Abstract - Cited by 54 (2 self) - Add to MetaCart
Abstract—An overview on the use of microelectromechanical systems (MEMS) technologies for timing and frequency control is presented. In particular, micromechanical RF filters and reference oscillators based on recently demonstrated vibrating on-chip micromechanical resonators with Q’s>10,000 at 1.5 GHz, are described as an attractive solution to the increasing count of RF components (e.g., filters) expected to be needed by future multi-band wireless devices. With Q’s this high in onchip abundance, such devices might also enable a paradigmshift in the design of timing and frequency control functions, where the advantages of high-Q are emphasized, rather than suppressed (e.g., due to size and cost reasons), resulting in enhanced robustness and power savings. With even more aggressive three-dimensional MEMS technologies, even higher onchip Q’s have been achieved via chip-scale atomic physics packages, which so far have achieved Q’s>10 7 using atomic cells measuring only 10 mm 3 in volume, consuming just 5 mW of power, all while still allowing Allan deviations down to 10-11 at one hour. Keywords—MEMS, micromechanical, quality factor, resonator, oscillator, filter, wireless communications, mechanical circuit, chip-scale atomic clock, physics package. I.

Noise in RF-CMOS Mixers: A Simple Physical Model

by Hooman Darabi, Asad A. Abidi - IEEE Journal of Solid-State Circuits
"... Abstract—Flicker noise in the mixer of a zero- or low-intermediate frequency (IF) wireless receiver can compromise overall receiver sensitivity. A qualitative physical model has been developed to explain the mechanisms responsible for flicker noise in mixers. The model simply explains how frequency ..."
Abstract - Cited by 50 (1 self) - Add to MetaCart
Abstract—Flicker noise in the mixer of a zero- or low-intermediate frequency (IF) wireless receiver can compromise overall receiver sensitivity. A qualitative physical model has been developed to explain the mechanisms responsible for flicker noise in mixers. The model simply explains how frequency translations take place within a mixer. Although developed to explain flicker noise, the model predicts white noise as well. Simple equations are derived to estimate the flicker and white noise at the output of a switching active mixer. Measurements and simulations validate the accuracy of the predictions, and the dependence of mixer noise on local oscillator (LO) amplitude and other circuit parameters. Index Terms—Active mixers, CMOS integrated circuits, communication systems, integrated circuits, mixers, mixer noise, noise, nonlinear circuits, receivers. I.
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A 900-MHz/1.8-GHz CMOS Receiver for Dual-Band Applications

by Stephen Wu , Behzad Razavi , 1998
"... A dual-band receiver employs the Weaver architecture with two tuned radio-frequency stages and a common intermediate-frequency stage to allow operation with 900-MHz and 1.8-GHz standards while using only two oscillators. Fabricated in a digital 0.6-"m CMOS technology, the receiver achieves ..."
Abstract - Cited by 39 (1 self) - Add to MetaCart
A dual-band receiver employs the Weaver architecture with two tuned radio-frequency stages and a common intermediate-frequency stage to allow operation with 900-MHz and 1.8-GHz standards while using only two oscillators. Fabricated in a digital 0.6-"m CMOS technology, the receiver achieves an overall noise figure of 4.7 dB and input third intercept point of 08 dBm at 900 MHz, and 4.9 dB and 06 dBm at 1.8 GHz. The voltage gain is 23 dB with a power dissipation of 75 mW from a 3-V supply.
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Frequency-Selective MEMS for Miniaturized Low-Power Communication Devices

by Clark T.-C. Nguyen , 1999
"... With Q’s in the tens to hundreds of thousands, micromachined vibrating resonators are proposed as integratedcircuit-compatible tanks for use in the low phase-noise oscillators and highly selective filters of communications subsystems. To date, LF oscillators have been fully integrated using merged C ..."
Abstract - Cited by 36 (12 self) - Add to MetaCart
With Q’s in the tens to hundreds of thousands, micromachined vibrating resonators are proposed as integratedcircuit-compatible tanks for use in the low phase-noise oscillators and highly selective filters of communications subsystems. To date, LF oscillators have been fully integrated using merged CMOS/microstructure technologies, and bandpass filters consisting of spring-coupled micromechanical resonators have been demonstrated in a frequency range from HF to VHF. In particular, two-resonator micromechanical bandpass filters have been demonstrated with frequencies up to 35 MHz, percent bandwidths on the order of 0.2%, and insertion losses less than 2 dB. Higher order three-resonator filters with frequencies near 455 kHz have also been achieved, with equally impressive insertion losses for 0.09 % bandwidths, and with more than 64 dB of passband rejection. Additionally, free-free-beam single-pole resonators have recently been realized with frequencies up to 92 MHz and ’s around 8000. Evidence suggests that the ultimate frequency range of this high- tank technology depends upon material limitations, as well as design constraints, in particular, to the degree of electromechanical coupling achievable in microscale resonators.

MOS transistor modeling for RF IC design

by Christian Enz - IEEE J. Solid-State Circuits , 2000
"... The design of radio-frequency (RF) integrated circuits (ICs) in deep-submicron CMOS processes requires accurate and scalable compact models of the MOS transistor that are valid in the GHz frequency range and beyond. Unfortunately, the currently available compact models give inaccurate results if the ..."
Abstract - Cited by 24 (0 self) - Add to MetaCart
The design of radio-frequency (RF) integrated circuits (ICs) in deep-submicron CMOS processes requires accurate and scalable compact models of the MOS transistor that are valid in the GHz frequency range and beyond. Unfortunately, the currently available compact models give inaccurate results if they are not modified adequately. This paper presents the basis of the modeling of the MOS transistor for circuit simulation at RF. A physical and scalable equivalent circuit that can easily be implemented as a Spice subcircuit is described. The small-signal and noise models are discussed and mea-surements made on a 0.25µm CMOS process are presented that validate the RF MOST model up to 10GHz. I.
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Integrated Circuit Technology Options for RFIC’sPresent Status and Future Directions

by Lawrence E. Larson, Senior Member - IEEE Journal of Solid-State Circuits , 1998
"... Abstract—This paper will summarize the technology tradeoffs that are involved in the implementation of radio frequency integrated circuits for wireless communications. Radio transceiver circuits have a very broad range of requirements—including noise figure, linearity, gain, phase noise, and power d ..."
Abstract - Cited by 19 (0 self) - Add to MetaCart
Abstract—This paper will summarize the technology tradeoffs that are involved in the implementation of radio frequency integrated circuits for wireless communications. Radio transceiver circuits have a very broad range of requirements—including noise figure, linearity, gain, phase noise, and power dissipation. The advantages and disadvantages of each of the competing technologies—Si CMOS and bipolar junction transistors (BJT’s), Si/SiGe HBT’s and GaAs MESFET’s, PHEMTS and HBT’s will be examined in light of these requirements. Index Terms—CMOS RF, low-noise amplifiers, monolithic radio architectures, radio receivers, wireless communications. I.
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Vibrating RF MEMS for Next Generation Wireless Applications

by Clark T.-C. Nguyen , 2004
"... Micromechanical RF filters and reference oscillators based on recently demonstrated vibrating on-chip micromechanical resonators with Q’s>10,000 at 1.5 GHz, are described as an attractive solution to the increasing count of RF components (e.g., filters) expected to be needed by future multi-band ..."
Abstract - Cited by 19 (8 self) - Add to MetaCart
Micromechanical RF filters and reference oscillators based on recently demonstrated vibrating on-chip micromechanical resonators with Q’s>10,000 at 1.5 GHz, are described as an attractive solution to the increasing count of RF components (e.g., filters) expected to be needed by future multi-band wireless devices. With Q’s this high in on-chip abundance, such devices might also enable a paradigm-shift in transceiver design where the advantages of high-Q are emphasized, rather than suppressed, resulting in enhanced robustness and power savings. An overview of the latest in vibrating RF MEMS technology is presented with an addendum on remaining issues to be addressed for insertion into tomorrow’s handsets.

High-Q HF Microelectromechanical Filters

by Frank D. Bannon, III, John R. Clark, Clark T.-C. Nguyen , 2000
"... IC-compatible microelectromechanical intermediate frequency filters using integrated resonators with’s in the thousands to achieve filter ’s in the hundreds have been demonstrated using a polysilicon surface micromachining technology. These filters are composed of two clamped–clamped beam micromech ..."
Abstract - Cited by 19 (6 self) - Add to MetaCart
IC-compatible microelectromechanical intermediate frequency filters using integrated resonators with’s in the thousands to achieve filter ’s in the hundreds have been demonstrated using a polysilicon surface micromachining technology. These filters are composed of two clamped–clamped beam micromechanical resonators coupled by a soft flexural-mode mechanical spring. The center frequency of a given filter is determined by the resonance frequency of the constituent resonators, while the bandwidth is determined by the coupling spring dimensions and its location between the resonators. Quarter-wavelength coupling is required on this microscale to alleviate mass loading effects caused by similar resonator and coupler dimensions. Despite constraints arising from quarter-wavelength design, a range of percent bandwidths is still attainable by taking advantage of low-velocity spring attachment locations. A complete design procedure is presented in which electromechanical analogies are used to model the mechanical device via equivalent electrical circuits. Filter center frequencies around 8 MHz with ’s from 40 to 450 (i.e., percent bandwidths from 0.23 to 2.5%), associated insertion losses less than 2 dB, and spurious-free dynamic ranges around 78 dB are demonstrated using low-velocity designs with input and output termination resistances on the order of 12 k.

A 2.4-GHz CMOS Receiver for IEEE 802.11 Wireless LAN’s

by Behzad Razavi , 1999
"... This paper describes a radio-frequency receiver targeting spread-spectrum wireless local-area-network applications in the 2.4-GHz band. Based on a direct-conversion architecture, the receiver employs partial channel selection filtering, dc offset removal, and baseband amplification. Fabricated in a ..."
Abstract - Cited by 17 (0 self) - Add to MetaCart
This paper describes a radio-frequency receiver targeting spread-spectrum wireless local-area-network applications in the 2.4-GHz band. Based on a direct-conversion architecture, the receiver employs partial channel selection filtering, dc offset removal, and baseband amplification. Fabricated in a 0.6-"m CMOS technology, the receiver achieves a noise figure of 8.3 dB, s€Q s€Q s€Q of 09 dBm, s € s€P s € of +22 dBm, and voltage gain of 34 dB while dissipating 80 mW from a 3-V supply. Index Terms—Low noise amplifier (LNA’s), mixers, receivers, RF CMOS, wireless local area networks (LAN’s).