Modern communication systems require high performance radio frequency (RF) and microwave circuits and devices. This is becoming increasingly challenging to realize in the content of cost/size constraints. Integrated circuits (ICs) satisfy the cost/size requirement, but performance is often sacri¯ced. For instance, high quality factor (Q factor) passive components are difficult to achieve in standard silicon-based
IC processes.<p>In recent years, microelectromechanical systems (MEMS) devices have been receiving increasing attention as a possible replacement for various on-chip passive elements, offering potential improvement in performance while maintaining high levels of integration. Variable capacitors (varactor) are common elements used in various applications. One of the MEMS variable capacitors that has been recently developed is built using deep X-ray lithography (as part of the LIGA process). This type of capacitor exhibits high quality factor at microwave frequencies.<p>The complementary metal oxide semiconductor (CMOS) technology dominates the silicon IC process. CMOS becomes increasingly popular for RF applications due to its advantages in level of integration, cost and power consumption. This research demonstrates a CMOS voltage-controlled oscillator (VCO) design which is used to investigate methods, advantages and problems in integrating LIGA-MEMS devices to CMOS RF circuits, and to evaluate the performance of the LIGA-MEMS variable capacitor in comparison with the conventional on-chip CMOS varactor. The VCO was designed and fabricated using TSMC 0.18 micron CMOS technology. The core of the VCO, including transistors, resistors, and on-chip inductors was designed to connect to either an on-chip CMOS varactor or an off-chip LIGA-MEMS capacitor to oscillate between 2.6 GHz and 2.7 GHz. Oscillator phase noise analysis is used to
compare the performance between the two capacitors. The fabricated VCO occupied an area of 1 mm^2.<p>This initial attempt at VCO fabrication did not produce a functional VCO, so the performance of the capacitors with the fabricated VCO could not be tested. However, the simulation results show that with this LIGA-MEMS capacitor, a 6.4 dB of phase noise improvement at 300 kHz offset from the carrier is possible in a CMOS-based VCO design.
| Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-07032007-153258 |
| Date | 04 July 2007 |
| Creators | Fang, Linuo |
| Contributors | Klymyshyn, David M., Dinh, Anh van |
| Publisher | University of Saskatchewan |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-07032007-153258/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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