A group at UCLA, in collaboration with the Jet Propulsion Laboratory, has designed a voltage-controlled oscillator (VCO) created specifically for a compact, integrated, electronically tunable frequency generator useable for submillimeter-wave science instruments operating in extreme cold environments. The VCO makes use of SiGe heterojunction bipolar transistors (HBTs). The SiGe HBTs have a 0.13-micrometer emitter width. A differential design was used with two VCOs connected to form a quadrature signal. A 2.5-V supply is required to power the circuit. A cross-coupled CMOS pair is used for emitter-degeneration of the SiGe HBTs, and the design uses coupled load and base inductors. The circuit oscillates at 105 GHz. A linear superposition of VCOs has been designed to achieve four times the oscillation frequency of the fundamental oscillator.
This work was done by Alden Wong, Tim Larocca, and M. Frank Chang of UCLA , and Lorene A. Samoska of Caltech for NASA’s Jet Propulsion Laboratory. For more information, download the Technical Support Package (free white paper) at www.techbriefs.com /tsp under the Electronics/Computers category. NPO-47116
This Brief includes a Technical Support Package (TSP).
Silicon-Germanium Voltage-Controlled Oscillator at 105 GHz
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Overview
The document outlines the development of a Silicon-Germanium (SiGe) Voltage-Controlled Oscillator (VCO) designed to operate at submillimeter-wave frequencies, specifically targeting applications in extreme planetary environments. Conducted by NASA's Jet Propulsion Laboratory (JPL), this research aims to create a compact, low-power, and integrated frequency generator suitable for future space missions, such as those on Mars, the Moon, and Titan, where temperatures can drop to -180°C (93K).
The primary objective of this work is to address the challenges associated with traditional local oscillators (LOs), which typically require complex circuitry and high power consumption. Current technologies, such as dielectric resonant oscillators and klystrons, are not suitable for spaceflight due to their size, weight, and power demands. The proposed SiGe VCO aims to simplify the design by integrating multiple functionalities into a single chip, significantly reducing the overall mass and power requirements.
The document details the unique advantages of the quadruple-superimposed circuit topology used in the VCO, which allows for a higher conversion efficiency compared to conventional harmonic generation methods. The VCO employs a Colpitts oscillator design, which is more compact than other designs like Hartley, and utilizes inductive feedback to enhance performance. The oscillator generates fundamental tone signals at millimeter-wave frequencies, which are then combined to produce an output signal with four times the frequency of the original tones.
Recent advancements have led to the successful demonstration of a CMOS oscillator operating at 324 GHz, showcasing the potential of this linear superposition technique. The SiGe technology used in this work is particularly advantageous due to its capability to function at low temperatures, making it ideal for extreme environments.
Future iterations of this VCO design are expected to achieve even higher frequencies (up to 10 times the current capability) while consuming significantly less power and occupying less volume. The anticipated specifications for the packaged VCO include power consumption of less than 1W, a volume of 1 cubic inch, and a mass of 200 grams.
Overall, this research represents a significant step forward in the development of efficient, compact, and reliable oscillators for space science applications, paving the way for advanced instrumentation in challenging environments.
