A high temperature variable gain amplifier based on GaN HEMT devices for downhole communications

• Published in: 2017 IEEE International Symposium on Circuits and Systems (ISCAS) pp. 1 - 4
• Main Authors: Ehteshamuddin, Mohammed, Salem, Jebreel M., Dong Sam Ha
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.05.2017
• Subjects: downhole communications; extreme environment electronics; Gain; Gallium nitride; GaN VGA; HEMTs; High temperature VGA; Impedance; Logic gates; Temperature distribution; Temperature measurement
• ISSN: 2379-447X
• DOI: 10.1109/ISCAS.2017.8050376

The decay 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 real-time data logging, results in a growing demand for robust, high temperature RF circuits. This paper presents a high temperature IF variable gain amplifier (VGA) for downhole communications, which is capable of operating at 230 °C. The proposed VGA is prototyped using GaN on SiC HEMT technology. Measured results at 230 °C show that the VGA has a peak gain of 27 dB at the center frequency of 97.5 MHz, and a dynamic range of 29.4 dB. The input P1dB compression at the peak gain is -11.57 dBm at 230 °C, and -3.63 dBm at 25 °C. The input and output return losses are above 12 dB across the entire temperature range from 25 °C to 230 °C. The maximum power gain and dynamic range drop by 1 dB and 4.7 dB, respectively, at 230 °C. The maximum power dissipation of the VGA is 176 mW under the peak gain at 230 °C.