A monolithic microwave integrated circuit (MMIC) that includes a high-electron-mobility transistor (HEMT) has been developed as a prototype of improved frequency doublers for generating signals at frequencies >100 GHz. Signal sources that operate in this frequency range are needed for a variety of applications, notably including general radiometry and, more specifically, radiometric remote sensing of the atmosphere.

Figure 1. This MMIC HEMT Frequency Doubler occupies a chip with dimensions of 1.1 mm by 1.2 mm by 50 µm.
Heretofore, it has been common practice to use passive (diode-based) frequency multipliers to obtain frequencies >100 GHz. Unfortunately, diode-based frequency multipliers are plagued by high DC power consumption and low conversion efficiency. Moreover, multiplier diodes are not easily integrated with such other multiplier-circuit components as amplifiers and oscillators. The goals of developing the present MMIC HEMT frequency doubler were (1) to utilize the HEMT as an amplifier to increase conversion efficiency (more precisely, to reduce conversion loss), thereby increasing the output power for a given DC power consumption or, equivalently, reducing the DC power consumption for a given output power; and (2) to provide for the integration of amplifier and oscillator components on the same chip.

Figure 2. The Output Power and Conversion Loss of the frequency doubler were measured as functions of frequency.
The MMIC frequency doubler (see Figure 1) contains an AlInAs/GaInAs/InP HEMT biased at pinch-off to make it function as a class-B amplifier (meaning that it conducts in half-cycle pulses). Grounded coplanar waveguides (GCPWs) are used as impedance-matching transmission lines. Air bridges are placed at discontinuities to suppress undesired slot electromagnetic modes. Another combination of GCPWs also serves both as a low-pass filter to suppress undesired oscillations at frequencies below 60 GHz and as a DC blocker. Large decoupling capacitors and epitaxial resistors are added in the drain and gate lines to suppress bias oscillations. At the output terminal, the fundamental frequency is suppressed by a quarter-wave open stub, which presents a short circuit at the fundamental frequency and an open circuit at the second harmonic.

At an input power of 7 mW, the output power and conversion loss at an output frequency of 164 GHz were found to be 5 dBm (≈3.2 mW) and 2 dB, respectively, with a 3-dB output-power bandwidth of 14 GHz. This is the best performance reported to date for an MMIC HEMT frequency doubler above 100 GHz.

This work was done by Lorene Samoska of NASA's Jet Propulsion Laboratory, Vesna Radisic, Miro Micovic, Ming Hu, Paul Janke, Catherine Ngo, and Loi Nguyen of HRL Laboratories, LLC, and Matthew Morgan of Caltech. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Computers/Electronics category.

NPO-21197

Topics:
Amplifiers Capacitors Connectors and terminals Data acquisition and handling Electric power grid Electrical systems Electronic equipment Electronics & Computers Energy consumption Energy storage systems Remote sensing Transistors Waveguides
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164-GHz MMIC HEMT Frequency Doubler

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NASA Tech Briefs Magazine

This article first appeared in the September, 2003 issue of NASA Tech Briefs Magazine (Vol. 27 No. 9).

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Overview

The document discusses the development of a 164 GHz monolithic microwave integrated circuit (MMIC) frequency doubler utilizing a high-electron-mobility transistor (HEMT). This innovative technology was created by a team from NASA’s Jet Propulsion Laboratory and HRL Laboratories, LLC, and aims to improve signal generation for applications requiring frequencies above 100 GHz, such as radiometric remote sensing of the atmosphere.

Traditionally, passive diode-based frequency multipliers have been used to achieve frequencies over 100 GHz. However, these devices suffer from high DC power consumption and low conversion efficiency, making them less suitable for modern applications. The MMIC HEMT frequency doubler addresses these issues by employing the HEMT as an amplifier, which enhances conversion efficiency and reduces conversion loss. This results in higher output power for a given DC power input or lower DC power consumption for a specified output power.

The design features include an AlInAs/GaInAs/InP HEMT biased at pinch-off to operate as a class-B amplifier, which conducts in half-cycle pulses. Grounded coplanar waveguides (GCPWs) are utilized for impedance matching, while air bridges are incorporated to suppress unwanted electromagnetic modes. Additionally, a combination of GCPWs functions as a low-pass filter to eliminate oscillations below 60 GHz and as a DC blocker. The output terminal employs a quarter-wave open stub to suppress the fundamental frequency while allowing the second harmonic to pass.

Performance measurements indicate that at an input power of 7 mW, the frequency doubler achieves an output power of 5 dBm (approximately 3.2 mW) with a conversion loss of 2 dB at an output frequency of 164 GHz. The device also exhibits a 3-dB output power bandwidth of 14 GHz, marking it as the best-performing MMIC HEMT frequency doubler reported to date for frequencies above 100 GHz.

The document highlights the collaborative efforts of various researchers, including Lorene Samoska, Vesna Radisic, Miro Micovic, Ming Hu, Paul Janke, Catherine Ngo, and Loi Nguyen, showcasing the advancements in microwave technology that could significantly impact applications in atmospheric sensing and other fields. Overall, this MMIC HEMT frequency doubler represents a significant step forward in the quest for efficient high-frequency signal generation.