A 500 °C Active Down-Conversion Mixer in Silicon Carbide Bipolar Technology

Abstract

This paper presents an active down-conversion mixer for high-temperature communication receivers. The mixer is based on an in-house developed 4H-SiC BJT and down-converts a narrow-band RF input signal centered around 59 MHz to an intermediate frequency of 500 kHz. Measurements show that the mixer operates from room temperature up to 500 • C. The conversion gain is 15 dB at 25 • C, which decreases to 4.7 dB at 500 • C. The input 1-dB compression point is 1 dBm at 25 • C and-2.5 dBm at 500 • C. The mixer is biased with a collector current of 10 mA from a 20 V supply and has a maximum DC power consumption of 204 mW. High-temperature reliability evaluation of the mixer shows a conversion gain degradation of 1.4 dB after 3-hours of continuous operation at 500 • C.

A SiC BJT-Based Negative Resistance Oscillator for High-Temperature Applications

“…The post-failure analysis showed that the oscillations ceased due to the dielectric breakdown of the DC block capacitor in the feedback (CB 3 ). Although similar capacitors were utilized successfully for many hours at 500 • C in our previous work [11], such failures indicate the intrinsic reliability issues associated with utilizing the commercial passives beyond their rated temperatures. This demonstrates the need to develop in-house HT capacitors similar to the ones reported in [9].…”

“…High-temperature capacitors from Presidio Components Inc. (rated up to 250 • C) were used for C L , C T and CB 1 -CB 3 . Similar capacitors were used previously up to 250 • C in [10], [14] and 500 • C in [11]. The capacitors were connected to the LTCC using a HT silver epoxy by PELCO.…”

“…The oscillator employs an in-house SiC BJT and is prototyped on a low-temperature co-fired ceramic (LTCC) board. The circuit is designed to have an oscillation frequency of 59.5 MHz, which is dictated by the specifications that we envision for our HT communication system [10], [11].…”

Towards Silicon Carbide VLSI Circuits for Extreme Environment Applications

“…Digital and analog ICs realized in bipolar SiC technology using emitter-coupled logic (ECL) have previously been demonstrated up to 500 ○ C [11][12][13][14], with a noise margin of 1 V [12]. An active down-conversion mixer realized using 4H-SiC BJT, for communication receivers, was recently reported working up to 500 ○ C [15].…”

Silicon Carbide BJT Oscillator Design Using S-Parameters

“…Commercial SiC MESFETs have been used to design HT oscillators working up to 200 ⁰C [2] and 470 ⁰C [3], while a SiC JFET has been employed in the 300 ⁰C oscillator presented in [4]. As shown in our recent work on HT mixers [5], SiC bipolar technology is another alternative for developing HT RF circuits. However, the conventional HT oscillator design methodology requires large-signal, high-frequency simulation models for the transistors, which are more challenging to develop for BJTs as compared to FETs.…”