The decline of easily accessible reserves pushes the oil and gas industry to explore deeper wells, where the ambient temperature often exceeds 210 °C. The need for high temperature operation, combined with the need for real-time data logging has created a growing demand for robust, high temperature RF electronics. This thesis presents the design of an intermediate frequency (IF) variable gain amplifier (VGA) for downhole communications, which can operate up to an ambient temperature of 230 °C. The proposed VGA is designed using 0.25 μm GaN on SiC high electron mobility transistor (HEMT) technology. Measured results at 230 °C show that the VGA has a peak gain of 27dB at center frequency of 97.5 MHz, and a gain control range of 29.4 dB. At maximum gain, the input P1dB is -11.57 dBm at 230 °C (-3.63 dBm at 25 °C). Input return loss is below 19 dB, and output return loss is below 12 dB across the entire gain control range from 25 °C to 230 °C. The variation with temperature (25 °C to 230 °C) is 1 dB for maximum gain, and 4.7 dB for gain control range. The total power dissipation is 176 mW for maximum gain at 230 °C. / Master of Science / The oil and gas industry uses downhole communication systems to collect important information concerning the reservoirs such as rock properties, temperature, and pressure, and relay it back to the surface. The electronics in these communication systems have to withstand temperatures exceeding 210 °C. Current high temperature electronics are not able to handle such temperatures for extended periods of time. Advancements in semiconductor technologies allow for fabrication of semiconductors that withstand high temperatures, such as GaN (Gallium Nitride). This thesis describes the design of a VGA (variable gain amplifier), which is an essential part of a downhole communication system. The VGA is designed using GaN semiconductor technology. Measured results show that the VGA shows good performance from 25 °C to 230 °C without the use of any cooling techniques, and can thus be used to design nextgeneration robust, high speed downhole communication systems.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/74958 |
| Date | 07 February 2017 |
| Creators | Ehteshamuddin, Mohammed |
| Contributors | Electrical and Computer Engineering, Ha, Dong Sam, Dhillon, Harpreet Singh, Koh, Kwang-Jin |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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