A radial probe transition between a monolithic microwave integrated circuit (MMIC) and a waveguide has been designed for operation at frequency of 340 GHz and to be fabricated as part of a monolithic unit that includes the MMIC. Integrated radial probe transitions like this one are expected to be essential components of future MMIC amplifiers operating at frequencies above 200 GHz. While MMIC amplifiers for this frequency range have not yet been widely used because they have only recently been developed, there are numerous potential applications for them — especially in scientific instruments, test equipment, radar, and millimeter- wave imaging systems for detecting hidden weapons.
One difficult problem in designing and fabricating MMIC amplifiers for frequencies greater than 200 GHz is that of packaging the MMICs for use as parts of instruments or for connection with test equipment. To package an MMIC for use or testing, it is necessary to mount the MMIC in a waveguide package, wherein the cross-sectional waveguide dimensions are typically of the order of a few hundred microns. Typically, in an MMIC/waveguide module for a microwave frequency well below 200 GHz, electromagnetic coupling between the MMIC and the waveguides is effected by use of a microstrip-to-waveguide transition that is (1) fabricated on a dielectric [alumina or poly(tetrafluoroethylene)] substrate separate from the MMIC and (2) wirebonded to the MMIC chip. In the frequency range above 200 GHz, wire bonding becomes lossy and problematic, because the dimensions of the wire bonds are large fractions of a wavelength. In addition, fabrication of the transition is difficult at the small required thickness [typically of the order of 1 mil (25.4 μm)] of the dielectric substrate. The present design promises to overcome the disadvantages of the separate substrate/wire-bonding approach.
The radial probe design could readily be adapted to integration with an MMIC amplifier because it provides for the fabrication of the transition on a substrate of the same material (InP), width (310 μm), and thickness (50 μm) typical of substrates of MMICs that can operate above 300 GHz. The figure depicts the basic geometric features of the design. The conductive part of the transition would be deposited on the InP substrate. The transition (and the rest of the MMIC chip if the transition were integrated with the MMIC) would reside in a metal cavity 360 μm wide having a stepped vertical dimension of total height 200 μm. The metal cavity would be essentially a reduced-cross-section lateral extension of the waveguide. The waveguide would be of a standard rectangular cross section, known in the art as WR2.2, having dimensions of 559 μm by 279 μm. There would be a 50-μm backshort between one vertical side of the metal cavity and the near end of the waveguide. The transition is designed to effect coupling between the microstrip mode of the MMIC chip and the transverse electric 10 (TE10) electromagnetic mode of the waveguide. The choice of dimensions of the metal cavity and the waveguide is governed partly by the requirement that the cutoff frequency of the waveguide be less than the frequency of operation while the cutoff frequency of the transition's cavity must exceed the frequency of operation.
This work was done by Lorene Samoska and Goutam Chattopadhyay 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 Semiconductors & ICs category. NPO-43957
This Brief includes a Technical Support Package (TSP).
Integrated Radial Probe Transition From MMIC to Waveguide
(reference NPO-43957) is currently available for download from the TSP library.
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Overview
The document presents an overview of the Integrated Radial Probe Transition from MMIC (Monolithic Microwave Integrated Circuit) to Waveguide, identified by NTR Number: 43957, developed by NASA's Jet Propulsion Laboratory (JPL). This innovation is part of NASA's Commercial Technology Program, aimed at disseminating aerospace-related developments with broader technological, scientific, or commercial applications.
The primary focus of the document is on a newly designed probe transition that facilitates efficient coupling between MMICs and waveguides. The specifications of the probe transition include a width of 310 micrometers and a thickness of 50 micrometers, designed to fit within a metal cavity measuring 360 micrometers wide and 150 micrometers high. The waveguide it connects to is of the WR2.2 type, characterized by a large dimension ("a" dimension) of 0.0022 inches. Additionally, the backshort dimension of the probe is specified as 50 micrometers.
The document emphasizes the significance of this technology in enhancing communication systems, particularly in the context of aerospace applications. The integration of MMICs with waveguides is crucial for improving the performance and efficiency of microwave systems, which are essential for various applications, including satellite communications, radar systems, and other high-frequency technologies.
Furthermore, the document includes contact information for further inquiries, directing interested parties to the Innovative Technology Assets Management at JPL. It also contains a notice regarding the proprietary nature of the information and the importance of complying with U.S. export regulations.
Overall, the Integrated Radial Probe Transition represents a significant advancement in microwave technology, showcasing NASA's commitment to innovation and the potential for broader applications in both commercial and scientific fields. The document serves as a technical support package, providing essential details for stakeholders interested in the development and application of this technology.
