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1. Reconfigurable Radios Employing Ferroelectrics: Recent Progress on Reconfigurable RF Acoustic Devices Based on Thin-Film Ferroelectric Barium Strontium Titanate

   Milad Koohi, Amir Mortazawi (May 2020, IEEE microwave magazine)

   null (Ed.)

   Wireless communication has become an integral part of our lives, continuously improving the quality of our everyday activities. A multitude of functionalities are offered by recent generations of mobile phones, resulting in a significant adoption of wireless devices and a growth in data traffic, as reported by Ericsson [1] in Figure 1. To accommodate consumers' continuous demands for high data rates, the number of frequency bands allocated for communication by governments across the world has also steadily increased. Furthermore, new technologies, such as carrier aggregation and multiple-input/multiple-output have been developed. Today's mobile devices are capable of supporting numerous wireless technologies (i.e., Wi-Fi, Bluetooth, GPS, 3G, 4G, and others), each having its own designated frequency bands of operation. Bandpass filters, multiplexers, and switchplexers in RF transceivers are essential for the coexistence of different wireless technologies and play a vital role in efficient spectrum usage. Current mobile devices contain many bandpass filters and switches to select the frequency band of interest, based on the desired mode of operation, as shown in Figure 2. This figure presents a schematic of a generic RF front end for a typical mobile device, where a separate module is allocated for the filters. Each generation of mobile devices demands a larger number of RF filters and switches, and, with the transition toward 5G and its corresponding frequency bands, the larger number of required filters will only add to the challenges associated with cell-phone RF front-end design. 

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2. Non-volatile RF and mm-wave Switches Based on Monolayer hBN

   https://doi.org/10.1109/IEDM19573.2019.8993470  

   Kim, Myungsoo; Pallecchi, Emiliano; Ge, Ruijing; Wu, Xiaohan; Avramovic, Vanessa; Okada, Etienne; Lee, Jack C.; Happy, Henri; Akinwande, Deji (December 2019, IEEE IEDM)

   Non-volatile radio-frequency (RF) switches based on hexagonal boron nitride (hBN) are realized for the first time with low insertion loss (≤ 0.2 dB) and high isolation (≥ 15 dB) up to 110 GHz. Crystalline hBN enables the thinnest RF switch device with a single monolayer (~0.33 nm) as the memory layer owing to its robust layered structure. It affords ~20 dBm power handling, 10 dB higher compared to MoS 2 switches due to its wider bandgap (~6 eV). Importantly, operating frequencies cover the RF, 5G, and mm-wave bands, making this a promising low-power switch for diverse communication and connectivity front-end systems. Compared to other switch technologies based on MEMS, memristor, and phase-change memory (PCM), hBN switches offer a promising combination of non-volatility, nanosecond switching, power handling, high figure-of-merit cutoff frequency (43 THz), and heater-less ambient integration. Our pioneering work suggests that atomically-thin nanomaterials can be good device candidates for 5G and beyond. 

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3. Mobile near-field terahertz communications for 6G and 7G networks: Research challenges

   https://doi.org/10.3389/frcmn.2023.1151324  

   Petrov, Vitaly; Bodet, Duschia; Singh, Arjun (March 2023, Frontiers in Communications and Networks)

   Following the current development of the wireless technology landscape, and with respect to the constant growth in user demands, it is inevitable that next-generation mobile wireless networks will use new frequency bands located in the sub-terahertz and terahertz (THz) spectrum to complement the existing microwave and millimeter wave (mmWave) channels. The feasibility of point-to-point stationary THz communication links has already been experimentally demonstrated. To build upon this breakthrough, one of the pressing research targets is making THz communication systems truly mobile. Achieving this target is especially complicated because mobile THz wireless systems (including WLANs and even cellular access) will often operate in the near-field due to the very large (even though physically small) electrical size of the high-gain antenna systems required for making high-rate communication links feasible at such frequencies. This perspective article presents several key prospective research challenges envisioned on the way to designing efficient mobile near-field THz wireless access as a part of 6G and 7G wireless landscapes. 

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4. Radio frequency transmitter based on a laser frequency comb

   https://doi.org/10.1073/pnas.1903534116  

   Piccardo, Marco; Tamagnone, Michele; Schwarz, Benedikt; Chevalier, Paul; Rubin, Noah A.; Wang, Yongrui; Wang, Christine A.; Connors, Michael K.; McNulty, Daniel; Belyanin, Alexey; et al (April 2019, Proceedings of the National Academy of Sciences)

   Since the days of Hertz, radio transmitters have evolved from rudimentary circuits emitting around 50 MHz to modern ubiquitous Wi-Fi devices operating at gigahertz radio bands. As wireless data traffic continues to increase, there is a need for new communication technologies capable of high-frequency operation for high-speed data transfer. Here, we give a proof of concept of a compact radio frequency transmitter based on a semiconductor laser frequency comb. In this laser, the beating among the coherent modes oscillating inside the cavity generates a radio frequency current, which couples to the electrodes of the device. We show that redesigning the top contact of the laser allows one to exploit the internal oscillatory current to drive a dipole antenna, which radiates into free space. In addition, direct modulation of the laser current permits encoding a signal in the radiated radio frequency carrier. Working in the opposite direction, the antenna can receive an external radio frequency signal, couple it to the active region, and injection lock the laser. These results pave the way for applications and functionality in optical frequency combs, such as wireless radio communication and wireless synchronization to a reference source. 

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5. Dataset for Spectrum Coexistence in Passive Sensing and Wireless Communication

   https://doi.org/10.21227/968t-td34  

   Alam, Ahmed_Manavi Alam; Farhad, Md_Mehedi Farhad; Al-Qwider, Walaa Al-Qwider; Owfi, Ali Owfi; Koosha, Mohammad Koosha; Mastronarde, Nicholas Mastronarde; Afghah, Fatemeh Afghah; Marojevic, Vuk Marojevic; Kurum, Mehmet_ Kurum; Gurbuz, Ali Gurbuz (January 2024, IEEE DataPort)

   In our ever-expanding world of advanced satellite and communications systems, there's a growing challenge for passive radiometer sensors used in the Earth observation like 5G. These passive sensors are challenged by risks from radio frequency interference (RFI) caused by anthropogenic signals. To address this, we urgently need effective methods to quantify the impacts of 5G on Earth observing radiometers. Unfortunately, the lack of substantial datasets in the radio frequency (RF) domain, especially for active/passive coexistence, hinders progress. Our study introduces a controlled testbed featuring a calibrated L-band radiometer and a 5G wireless communication system. In a controlled chamber, this unique setup allows us to observe and quantify transmission effects across different frequency bands. By creating a comprehensive dataset, we aim to standardize and benchmark both wireless communication and passive sensing. With the ability to analyze raw measurements, our testbed facilitates RFI detection and mitigation, fostering the coexistence of wireless communication and passive sensing technologies while establishing crucial standards. 

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