Micromachined varactor with wide tuning range

Dec, A.; Suyama, K.

doi:10.1049/el:19970628

Cited by 51 publications

(21 citation statements)

References 2 publications

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“…Micromachined electro-mechanically tunable capacitors have been shown to exhibit an adequate -factor when they are fabricated in either an aluminum [12] or a polysilicon [13] surface micromachining technology. A low phase noise 714-MHz CMOS VCO with a high -factor aluminum micromachined tunable capacitor and an off-chip inductor has also been recently demonstrated [14].…”

Section: Introductionmentioning

confidence: 99%

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Micromachined electro-mechanically tunable capacitors and their applications to RF IC's

Dec

Suyama

1998

IEEE Trans. Microwave Theory Techn.

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222

113

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Micromachined electro-mechanically tunable capacitors with two and three parallel plates are presented. Experimental devices have been fabricated using a standard polysilicon surface micromachining process. The two-plate tunable capacitor has a measured nominal capacitance of 2.05 pF, a Q-factor of 20 at 1 GHz, and achieves a tuning range of 1.5 : 1. The threeplate version has a nominal capacitance of 4.0 pF, a Q-factor of 15.4 at 1 GHz, and a tuning range of 1.87 : 1. The tuning ranges achieved here are near theoretical limits. Effects due to various physical phenomena such as temperature, gravity, and shock are examined in detail. An RF voltage-controlled oscillator with an integrated inductor and a micromachined tunable capacitor is also demonstrated. The active circuit and the inductor have been fabricated in a 0.5-m CMOS process. The voltage-controlled oscillator has been assembled by bonding together the CMOS and the micromachined parts. The 1.35-GHz voltage-controlled oscillator has a phase noise of 098.5 dBc/Hz at a 100 kHz offset from the carrier.

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Section: Introductionmentioning

confidence: 99%

“…Therefore, with RF frequencies 10 000 times the mechanical bandwidth, these devices are unlikely to produce a significant amount of harmonic content. The main limitation of these devices, however, has been the fact that their tuning ranges thus far have been less than the theoretical calculations suggest [12], [13].…”

Section: Introductionmentioning

confidence: 99%

Micromachined electro-mechanically tunable capacitors and their applications to RF IC's

Dec

Suyama

1998

IEEE Trans. Microwave Theory Techn.

Self Cite

222

113

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“…Finally, the capacitor proposed in this work inhibits electrostatic force between the electrodes of the MEMS capacitor structure. In the MEMS capacitor field, electrostatic force is the main element that fails the device by causing so called "pull-in" effect [7] (top electrode is pulled down and contacts bottom electrode by the electrostatic force between the two electrode). The electrostatic force is a function of the area (A), applied bias (V) and the gap between the electrodes (y) (Eq.…”

Section: Device Verificationmentioning

confidence: 99%

A high fill-factor uncooled infrared detector with thermo-mechanical bimaterial structure

et al. 2007

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By adopting new capacitance reading scheme, a capacitive type uncooled infrared detector structure with high fill-factor and effectively controllable thermal conductance is proposed. Instead of conventional MEMS capacitor structure (i.e. an insulating gap between top and bottom electrodes), a capacitor with a floating electrode and two bottom electrodes has been applied to the infrared detector. Infrared absorber which also acts as the floating electrode of the capacitor is connected to the substrate via two bimaterial legs. These legs consist of two materials having large difference in thermal expansion coefficient (Al: 25ppm/K and SiO 2 : 0.35ppm/K), so that the legs are deflected according to the certain temperature change due to the infrared absorption. This leg's movement results in the displacement of the top electrode of the capacitor, and infrared is sensed by measuring the capacitance change. However, the one end tip of the bimaterial leg does not contain Al and consist of SiO 2 , solely. This leg design enables the absorber to be separated from the substrate thermally as well as electrically, because insulators usually have low thermal conductivity than metals more than an order. The capacitance change by the result of infrared absorption is read only through two bottom electrodes which are placed right under the absorber, and also perform as infrared reflectors. The design has advantages of enlarging fill-factor of the infrared detector, effective thermal conductance controlling and high sensitivity to IR. With only small dimensions of SiO 2 (10µm × 2µm × 0.2µm), the device can have low thermal conductance of 1.3×10 -7 W/K, so that the portion of the legs can be reduced in a pixel area. The device has fill-factor of 0.77 and 14%/K of sensitivity to infrared rays concerning 1~2K of temperature difference between the structure and the substrate.

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“…From mathematic deduction, the validation range of the above equation is obtained as d < x < 0 [4]. And if electrostatic force is bigger than 3 spring force, the suspended plate will be drew down on contact with the fixed plate.…”

Section: Mems-based Variable Capacitormentioning

confidence: 99%

Design and Simulation of a 2.4GHz MEMS-based Voltage Controlled Oscillator

Cao

Liu

Wang

2006

2006 CIE International Conference on Radar

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A 2.4GHZ voltage-controlled oscillator based on standard complementary and symmetrical LC circuit topology and micro electromechanical system (MEMS)-based variable capacitors for frequency tuning is demonstrated in this paper. This VCO operates at 2.4 GHz, achieves a phase noise of 109.8dBc/Hz, -129.5dBc/Hz, -144.0dBc/Hz of 100KHz, IMHz, 4MHz offset from the carrier respectively, exhibits a tuning range of 4.58%, and changes equably from 2.320 to 2.430GHz when tuning voltage is changed from 0 to 5V, which overmatches that of the standard one.

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Micromachined varactor with wide tuning range

Cited by 51 publications

References 2 publications

Micromachined electro-mechanically tunable capacitors and their applications to RF IC's

Micromachined electro-mechanically tunable capacitors and their applications to RF IC's

A high fill-factor uncooled infrared detector with thermo-mechanical bimaterial structure

Design and Simulation of a 2.4GHz MEMS-based Voltage Controlled Oscillator

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