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1. Over-the-air transmission of Zak-OTFS with spread pilots on the sub-THz communication testbed

   Parisi, C; Khammammetti, V; Calderbank, R; Huie, L (December 2025, IEEE)

   Looking towards 6G wireless systems, frequency bands like the sub-terahertz (sub-THz) band (100 GHz - 300 GHz) are gaining traction for their promises of large available swaths of bandwidth to support the ever-growing data demands. However, challenges with harsh channel conditions and hardware non-linearities in the sub-THz band require robust communication techniques with favorable properties, such as good spectral efficiency and low peak-to-average power ratio (PAPR). Recently, OTFS and its variants have garnered significant attention for their performance in severe conditions (like high delay and Doppler), making it a promising candidate for future communications. In this work, we implement Zak-OTFS for the over-the-air experiments with traditional point pilots and the new spread pilots. Notably, we design our spread pilot waveforms with communications and sensing coexisting in the same radio resources. We define the system model and the signal design for integration onto our state-of-the-art sub-THz wireless testbed. We show successful data transmission over-the-air at 140 GHz and 240 GHz in a variety of signal-to-noise ratio (SNR) conditions. In addition, we demonstrate integrated sensing and communications (ISAC) capabilities and show PAPR improvement of over 5 dB with spread pilots compared to point pilots. 

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2. Viscoelastic bandgap in multilayers of inorganic–organic nanolayer interfaces

   https://doi.org/10.1038/s41598-022-14257-z  

   Khadka, Rajan; Ramanath, Ganpati; Keblinski, Pawel (June 2022, Scientific Reports)

   Abstract Incorporating molecular nanolayers (MNLs) at inorganic interfaces offers promise for reaping unusual enhancements in fracture energy, thermal and electrical transport. Here, we reveal that multilayering MNL-bonded inorganic interfaces can result in viscoelastic damping bandgaps. Molecular dynamics simulations of Au/octanedithiol MNL/Au multilayers reveal high-damping-loss frequency bands at 33 ≤ ν ≤ 77 GHz and 278 ≤ ν ≤ 833 GHz separated by a low-loss bandgap 77 ≤ ν ≤ 278 GHz region. The viscoelastic bandgap scales with the Au/MNL interface bonding strength and density, and MNL coverage. These results and the analyses of interfacial vibrations indicate that the viscoelastic bandgap is an interface effect that cannot be explained by weighted averages of bulk responses. These findings prognosticate a variety of possibilities for accessing and tuning novel dynamic mechanical responses in materials systems and devices with significant inorganic–organic interface fractions for many applications, e.g., smart composites and sensors with self-healing/-destructing mechanical responses. 

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3. Dynamic spectrum sharing between active and passive users above 100 GHz

   https://doi.org/10.1038/s44172-022-00002-x  

   Polese, Michele; Ariyarathna, Viduneth; Sen, Priyangshu; Siles, Jose V.; Restuccia, Francesco; Melodia, Tommaso; Jornet, Josep M. (May 2022, Communications Engineering)

   Abstract Sixth-generation wireless networks will aggregate higher-than-ever mobile traffic into ultra-high capacity backhaul links, which could be deployed on the largely untapped spectrum above 100 GHz. Current regulations however prevent the allocation of large contiguous bands for communications at these frequencies, since several narrow bands are reserved to protect passive sensing services. These include radio astronomy and Earth exploration satellites using sensors that suffer from harmful interference from active transmitters. Here we show that active and passive spectrum sharing above 100 GHz is feasible by introducing and experimentally evaluating a real-time, dual-band backhaul prototype that tracks the presence of passive users (in this case the NASA satellite Aura) and avoids interference by automatically switching bands (123.5–140 GHz and 210–225 GHz). Our system enables wide-band transmissions in the above-100-GHz spectrum, while avoiding harmful interference to satellite systems, paving the way for innovative spectrum policy and technologies in these crucial bands. 

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4. High-Gain, Broadband Radial Elliptical-Slot Array Antenna with Side-Lobe Mitigation for Low-Cost Satellite Communication Systems

   https://doi.org/10.1109/USNC-URSI52151.2023.10237445  

   Kakaraparty, Karthik; Roy, Sunanda; Mahbub, Ifana (July 2023, 2023 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (USNC-URSI))

   This paper presents a high-gain and broadband radial elliptical-slot array (RESA) antenna with side-lobe mitigation technique for low-cost satellite communication systems. The aperture of the proposed slot array antenna comprises a set of orthogonal elliptical slots with monotonic slot length variation alongside the radius of the aperture. The design comprises radiating slotted top plate and bottom ground plate parallel to one another separated by an optimal distance of 5.25 mm which is 1.05λ . The design is back-fed using a disk-head radiator probe. The overall dimensions of the proposed slot array antenna with the air-gap taken into account are 300×300×5.75mm3 . Simulation results show that the proposed slot array antenna has a broadband operating frequency range from 45 GHz to 110 GHz and beyond, covering both V and W frequency bands with a fractional bandwidth of 88.8%. The peak gain of the proposed design is 35.6 dBi at 60 GHz. The array exhibits a maximum half-power beam width of 9.5°, a low sidelobe magnitude of - 4.12 dBi and a overall simple design indicates its suitability for low-cost SATCOM (satellite communications) applications. 

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5. A 49-63 GHz Phase-locked FMCW Radar Transceiver for High Resolution Applications

   Liu, Xuyang; Maktoomi, Md Hedayatullah; Alesheikh, Mahdi; Heydari, Payam; Aghasi, Hamidreza (October 2023, IEEE European Solid State Circuits Conference)

   TPC of IEEE ESSCIRC Conference (Ed.)

   This paper presents an mmWave FMCW radar that can achieve sub-centimeter-scale range resolution at 14- GHz chirp-bandwidth while maintaining the radar range beyond 50 meters. To meet the requirements on power efficiency, chirp linearity, and signal-to-noise ratio (SNR), a phase-locked steppedchirp FMCW radar architecture is introduced. Specifically, a fully integrated radar transceiver comprising an interleaved frequency-segmented phase-locked transmitter and a segmented receiver architecture with high sensitivity is presented. The proposed design addresses the limitations of conventional typeII phase-locked loops (PLLs) in extending the radar bandwidth across multiple sub-bands with identical chirp profiles. Fabricated in a 22nm FD-SOI technology, the prototype chip comprises two sub-bands with 14 GHz of free-running bandwidth and 10 GHz of phase-locked bandwidth. The system achieves -101.7 dBc/Hz phase noise at 1 MHz offset, 8 dBm of effective isotropic radiated power (EIRP), 10 dB noise figure (NF), and 362.6 mW collective power consumption of transmitter and receiver arrays. 

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