Several different experimental monolithic microwave integrated circuit (MMIC) amplifiers have been designed to operate in frequency bands ranging from 350 to 500 GHz and were undergoing fabrication at the time of reporting the information for this article. Probes for on-wafer measurement of electrical parameters [principally, the standard scattering parameters (“S” parameters)] of these amplifiers have been built and tested as essential components of systems to be used in quantifying the performances of the amplifiers. These accomplishments are intermediate products of a continuing effort to develop solid-state electronic amplifiers capable of producing gain at ever-higher frequencies, now envisioned to range up to 800 GHz. Such amplifiers are needed for further development of compact, portable imaging systems and scientific instruments for a variety of potential applications that include detection of hidden weapons, measuring winds, and measuring atmospheric concentrations of certain molecular species.

Figure 1. Gains of Seven Single-Stage MMIC Amplifiers built around advanced InP HEMTs were predicted in computational simulations.
Seven of the experimental MMIC amplifiers are single-stage amplifiers; two are three-stage amplifiers. Conceptually, each amplifier is built around an InP-based high-electron-mobility transistor (HEMT) having a gate length of 35 nm, which has been developed at Northrop Grumman Corporation. It was previously demonstrated that the particular HEMT can be fabricated with a high degree of reproducibility, that its electrical characteristics are accurately represented by a device model needed to design an MMIC that incorporates it, and that an experimental single-stage MMIC built around it exhibits 5 dB of gain at 345 GHz.

The seven present single-stage amplifier designs were derived from that of the 345-GHz MMIC amplifier. They were designed by use of the aforementioned device model, with modified layouts chosen to satisfy requirements for both (1) compatibility with the HEMT manufacturer’s fabrication rules and (2) matching impedances at the affected frequency bands in the 350-to-500 GHz range. The designs utilize several different matching-circuit topologies, some of which resemble topologies heretofore required for multi-stage amplifiers. Figure 1 shows the gains of the single-stage amplifiers as predicted by computational simulations. The two three-stage amplifiers were designed to operate at frequencies from 400 to 500 GHz, with peak gains in the approximate range of 11 to 13 dB.

Figure 2. Wafer Probes are mounted on the terminals of a network analyzer, with the probe tips in contact with a calibration substrate.
The wafer probes were designed and built for use with a two-port swept-vector network analyzer that operates in the frequency range of 325 to 500 GHz. This network analyzer has been fully characterized for reproducibility and dynamic range. The probes include WR2.2 waveguides and waveguide-to-coaxial transitions developed at Cascade Microtech and Portland State University (see Figure 2). The insertion loss of the waveguide-to-coaxial transitions has been measured to be about 7 dB at 325 to 500 GHz.

This work was done by Lorene A. Samoska and King Man Fung of Caltech; Michael Andrews of Cascade Microtech, Inc.; Richard Campbell of Portland State University; and Linda Ferreira and Richard Lai of Northrop Grumman Corp. 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-45588

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This Brief includes a Technical Support Package (TSP).
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MMIC Amplifiers and Wafer Probes for 350 to 500 GHz

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NASA Tech Briefs Magazine

This article first appeared in the June, 2010 issue of NASA Tech Briefs Magazine (Vol. 34 No. 6).

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Overview

The document is a Technical Support Package from NASA's Jet Propulsion Laboratory (JPL) detailing advancements in MMIC (Monolithic Microwave Integrated Circuit) amplifiers and wafer probes designed for operation in the frequency range of 350 to 500 GHz. This work is part of a broader initiative to enhance the performance of heterodyne receivers used in planetary, Earth science, and astrophysics applications.

The primary focus of the research is to achieve gain at critical frequencies, particularly the water spectral line at 557 GHz and other significant spectral lines around 640 GHz, such as ClO, HCl, and ozone. These advancements are expected to improve the capabilities of submillimeter-wave circuits, which are essential for high-performance scientific instruments.

The document outlines the unique capabilities developed at JPL for measuring S-parameters, noise figures, and power of solid-state circuits up to 500 GHz, with plans to extend this capability to 800 GHz. The collaboration with Northrop Grumman Corporation has been pivotal, particularly in the development of a 35 nm gate-length transistor that has demonstrated remarkable yield and reproducibility. This collaboration has enabled the design and measurement of circuits, including low noise amplifiers and voltage-controlled oscillators, achieving unprecedented performance levels.

Notably, the document reports the successful design and measurement of a single-stage MMIC amplifier with a gain of 5 dB at 345 GHz, showcasing the effectiveness of the new device models. The research indicates that the Maximum Available Gain/Maximum Stable Gain for a single-stage amplifier is projected to reach 5 dB per stage at 600 GHz, a significant milestone in the field.

The document also includes acknowledgments of contributions from various collaborators, including device modeling and fabrication efforts. It references publications and previous work that support the findings presented.

Overall, this Technical Support Package highlights JPL's commitment to advancing submillimeter-wave technology, which is crucial for future scientific missions and applications. The developments in MMIC amplifiers and wafer probes not only enhance JPL's testing capabilities but also position the laboratory at the forefront of high-frequency research, paving the way for innovative solutions in aerospace and beyond.