Planning for Devices Beyond mmWaves

Planning for Devices Beyond mmWaves

March 22, 2019
When mmWave frequency bands become occupied, the need will arise for even higher-frequency THz devices.

Much has been written recently about the growing need for components, devices, and circuits at millimeter-wave (mmWave) frequencies from 30 to 300 GHz. The need is fueled by applications such as advanced driver-assistance systems (ADAS) and 5G cellular communications systems that are taking advantage of the wide bandwidths available at those frequencies, especially when compared to the very occupied bandwidths at lower RF and microwave frequencies.

But what happens when the mmWave range also becomes congested? Researchers from the Department of Electrical Engineering and Computer Science at the Massachusetts Institute of Technology (Cambridge, Mass.) are looking ahead to when even higher-frequency devices will be in demand, in the terahertz (THz) frequency range, and whether available semiconductor technologies can provide such devices to serve THz applications.

Because of the need to generate and detect THz-range frequencies (300 to 3000 GHz), transistors fabricated on silicon (Si) or silicon-germanium (SiGe) materials cannot simply be scaled or miniaturized to achieve sufficiently high maximum frequency of oscillation (fmax) to generate those frequencies. Silicon-based devices have been used for amplifier designs at frequencies of about 0.2 to 0.3 THz, but signal generation at frequencies above that range—when using silicon-based devices—requires harmonic generation.

Despite the limitations of silicon-based substrate materials, the researchers point to several innovative device designs on SiGe to hint at the possibilities of silicon for THz applications. This includes a 1-THz radiation source based on 130-nm SiGe heterojunction-bipolar-transistor (HBT) technology. The device integrates 91 coherent radiators within a 0.1-mm2 chip area, with a multifunctional slot resonator that has a fundamental oscillation frequency (f0) of 250 GHz. Radiation is used at multiples of the fundamental frequency to produce the 1-THz output frequency.

The high density of such coherent radiation arrays, when fabricated on relatively small chip sizes of about 10 mm2, yield devices with relatively narrow bandwidths at 1 THz. Material parameters such as consistency of thickness and dielectric constant are critical to achieving performance consistency at 1 THz. But a THz laser chip of this type could provide the signal generation and sensing functions needed for practical short-range communications (within tens of meters) at extremely high data rates for wireless communications systems beyond the mmWave frequency range.

See “Filling the Gap,” IEEE Microwave Magazine, April 2019, pp. 80-93.

About the Author

Jack Browne | Technical Contributor

Jack Browne, Technical Contributor, has worked in technical publishing for over 30 years. He managed the content and production of three technical journals while at the American Institute of Physics, including Medical Physics and the Journal of Vacuum Science & Technology. He has been a Publisher and Editor for Penton Media, started the firm’s Wireless Symposium & Exhibition trade show in 1993, and currently serves as Technical Contributor for that company's Microwaves & RF magazine. Browne, who holds a BS in Mathematics from City College of New York and BA degrees in English and Philosophy from Fordham University, is a member of the IEEE.

Sponsored Recommendations

Wideband MMIC LNA with Bypass

June 6, 2024
Mini-Circuits’ TSY-83LN+ wideband, MMIC LNA incorporates a bypass mode feature to extend system dynamic range. This model operates from 0.4 to 8 GHz and achieves an industry leading...

Expanded Thin-Film Filter Selection

June 6, 2024
Mini-Circuits has expanded our line of thin-film filter topologies to address a wider variety of applications and requirements. Low pass and band pass architectures are available...

Mini-Circuits CEO Jin Bains Presents: The RF Engine of the 21st Century

June 6, 2024
In case you missed Jin Bains' inspiring keynote talk at the inaugural IEEE MTT-S World Microwave Congress last week, be sure to check out the session recording, now available ...

Selecting VCOs for Clock Timing Circuits A System Perspective

May 9, 2024
Clock Timing, Phase Noise and Bit Error Rate (BER) Timing is critical in digital systems, especially in electronic systems that feature high-speed data converters and high-resolution...