An active frequency doubler in the form of an InP-based monolithic microwave integrated circuit (MMIC) containing a high electron mobility transistor (HEMT) has been demonstrated in operation at output frequencies in the vicinity of 300 GHz. This is the highest frequency HEMT doubler reported to date, the next highest frequency active HEMT doubler having been previously reported to operate at 180 GHz. While the output power of this frequency doubler is less than that of a typical Schottky diode, this frequency doubler is considered an intermediate product of a continuing effort to realize the potential of active HEMT frequency doublers to operate with conversion efficiencies greater than those of passive diode frequency doublers. An additional incentive for developing active HEMT frequency doublers lies in the fact that they can be integrated with amplifiers, oscillators, and other circuitry on MMIC chips.
The circuitry of the doubler MMIC (see Figure 1) features grounded coplanar waveguides. Air bridges and vias are used to make contact with the ground plane. The HEMT is biased for Class-A operation (in which current is conducted throughout each cycle of oscillation), which would ordinarily be better suited to linear amplification than to frequency doubling. Ordinarily, class-B operation (in which current is conducted during about half of each cycle of oscillation) would be more suitable for frequency doubling because of the essential nonlinearity of partial-cycle conduction. The reason for the unusual choice of class A was that computational simulations had shown that in this case, the efficiency in class B would be less than in class A.
The input matching circuit of this doubler includes transmission lines that afford a good impedance match at the fundamental frequency, plus an open stub to prevent leakage of the second harmonic through the input terminals. The output circuit was designed to suppress the fundamental while providing a good match for the second harmonic.
In a test, this doubler was driven by an input signal at frequencies from 140 to 158 GHz and its output at the corresponding second-harmonic frequencies of 280 to 316 GHz was measured by means of a power meter connected to the MMIC via waveguide wafer probes and a high-pass (fundamental-suppressing) waveguide. The results of this test are summarized in Figure 2.
This work was done by Lorene Samoska and Jean Bruston of Caltech for NASA’s Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Semiconductors & ICs category.
NPO-30581
This Brief includes a Technical Support Package (TSP).
HEMT Frequency Doubler With Output at 300 GHz
(reference NPO-30581) is currently available for download from the TSP library.
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Overview
The document is a Technical Support Package from NASA's Jet Propulsion Laboratory, detailing the HEMT Frequency Doubler with an output at 300 GHz, referenced as NPO-30581. It serves to disseminate information about advancements in aerospace-related technologies that have broader scientific and commercial applications.
The introduction outlines the development of Monolithic Microwave Integrated Circuit (MMIC) power amplifiers and active multiplier chips fabricated using 0.1 µm InP High Electron Mobility Transistor (HEMT) technology. The document emphasizes the significance of these components in high-frequency applications, particularly in W-band (75-110 GHz) systems, and their potential use as drivers for local oscillators in heterodyne systems.
The document presents a measurement system schematic for the 300 GHz doubler, which utilizes a backward wave oscillator (BWO) as the W-band source, followed by a Millitech multiplier operating in the 140-170 GHz range. Waveguide wafer probes from GGB Industries are employed to connect the Millitech doubler to the MMICs, facilitating power delivery.
The advanced HEMT MMICs discussed include wideband medium power amplifiers designed with grounded co-planar waveguide topology. The document highlights the performance of a specific amplifier, referred to as PA1, which features a three-stage design with HEMTs configured for optimal output. The measured data indicates a broad operational bandwidth, showcasing the capabilities of these amplifiers in high-frequency applications.
Additionally, the document includes references to various studies and papers that provide further insights into the development and performance of MMICs and HEMTs across different frequency ranges. These references underscore the ongoing research and advancements in the field, contributing to the understanding of high-frequency electronics.
The Technical Support Package also provides contact information for further inquiries and emphasizes that the information is part of NASA's Commercial Technology Program, aimed at making aerospace-related developments accessible for wider technological applications. It concludes with a disclaimer regarding the use of the information and the absence of liability from the U.S. Government.
Overall, the document serves as a comprehensive resource for understanding the advancements in HEMT technology and its applications in high-frequency systems, highlighting NASA's commitment to fostering innovation in aerospace technology.
