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

摘要

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.