A Resistive GaN-HEMT Mixer for a Cable Modem Operable up to 250°C for Downhole Communications

Abstract

It is necessary for the oil and gas industry to drill deeper due to decrease of easily accessible natural reserves. Temperatures of deep wells can exceed 210°C, and conventional cooling and heat extraction techniques are impractical in such a harsh environment. Reliable electronic designs that can sustain high temperature become necessary. This article presents a high-temperature passive radio frequency (RF) mixer for downhole communications. The proposed mixer is designed to upconvert or downconvert the incoming signal with low conversion loss (CL), high linearity, and reliable operation at the ambient temperature up to 250°C. GaN is a wide-bandgap technology that can provide a reliable operation at high ambient temperatures, and the proposed mixer adopts a commercial GaN high-electron-mobility transistor. Measurement results indicate that the proposed mixer achieves a CL of 7.1 dB at local oscillator (LO) power of 2.5 dBm for the downconversion from 230–253 to 97.5 MHz at 250°C and the input P1dB compression point lies at 5 dBm. The designed mixer also achieves 24.5 dB RF-to-intermediate frequency (IF) isolation and 28 dB LO-to-IF isolation at 250°C. The power dissipation of the mixer is virtually zero.