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1. Radio Frequency Directed Energy Weapon Mitigation via Passive Beamforming Reconfigurable Intelligent Surface

   https://doi.org/10.1109/USNC-URSI52151.2023.10237947  

   Anim, Kyei; Saleh Tajin, Md Abu; Dandekar, Kapil R. (July 2023, 2023 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (USNC-URSI))

   Reconfigurable intelligent surfaces (RISs) are an emerging transmission technology to aid wireless communication. However, the potential of using RIS to mitigate directed energy weapons (DEW) is not widely recognized. In this paper, we propose to leverage RIS (based on spiral antenna elements) to aid the mitigation of high-energy radio-frequency (RF) sources applied to a DEW. For example, integrating a broadband circularly-polarized antenna system with RIS technology can successfully mitigate DEW attacks across a wide range of frequencies regardless of how the radio waves are polarized. We simulated a spiral antenna that operates within a frequency band of 1.3 GHz to 7 GHz with a 3-dB axial ratio bandwidth (ARBW) covering from 2 GHz to 7 GHz. Full-wave simulation results show the potential promising application of RIS for the mitigation of DEW attacks. 

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2. A Full-Duplex Radio Using a CMOS Non-Magnetic Circulator Achieving +95 dB Overall SIC

   https://doi.org/10.1109/USNC-URSI.2019.8861766  

   Nagulu, Aravind; Chen, Tingjun; Zussman, Gil; Krishnaswamy, Harish (July 2019, in Proc. IEEE APS-URSI’19, July 2019.)

   Full-duplex (FD) wireless is an emerging wireless communication paradigm where the transmitter and the receiver operate simultaneously at the same frequency. One major challenge in realizing FD wireless is the interference of the TX signal saturating the receiver, commonly referred to self-interference (SI). Traditionally, self-interference cancellation (SIC) is achieved in the antenna, RF/analog, and digital domains. In the antenna domain, SIC can be achieved using a pair of separate TX and RX antennas, or using a single antenna shared by the TX and RX through a magnetic circulator, which is usually bulky, expensive, and not integrable with CMOS. Recent advances, however, have shown the feasibility of realizing high-performance non-reciprocal circulators in CMOS based on spatio-temporal modulation. In this work, we demonstrate a high power handling FD radio using a USRP SDR which employs SIC (i) at the antenna interface using a watt-level power-handling CMOS integrated, magnetic-free circulator, (ii) in the RF domain using a compact RF canceler, and (iii) in the digital domain. Our prototyped FD radio achieves +95 dB overall SIC at +15dBm TX power level. We analyze the effects of the circulator TX-RX non-linearity on the total achievable SIC 

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3. A Full-Duplex Radio Using a CMOS Non-Magnetic Circulator Achieving +95 dB Overall SIC

   Aravind Nagulu, Tingjun Chen (January 2019, URSI General Assembly and Scientific Symposium)

   Full-duplex (FD) wireless is an emerging wireless communication paradigm where the transmitter and the receiver operate simultaneously at the same frequency. One major challenge in realizing FD wireless is the interference of the TX signal saturating the receiver, commonly referred to self-interference (SI). Traditionally, self-interference cancellation (SIC) is achieved in the antenna, RF/analog, and digital domains. In the antenna domain, SIC can be achieved using a pair of separate TX and RX antennas, or using a single antenna shared by the TX and RX through a magnetic circulator, which is usually bulky, expensive, and not integrable with CMOS. Recent advances, however, have shown the feasibility of realizing high-performance non-reciprocal circulators in CMOS based on spatio-temporal modulation. In this work, we demonstrate a high power handling FD radio using a USRP SDR which employs SIC (i) at the antenna interface using a watt-level power-handling CMOS integrated, magnetic-free circulator, (ii) in the RF domain using a compact RF canceler, and (iii) in the digital domain. Our prototyped FD radio achieves +95 dB overall SIC at +15dBm TX power level. We analyze the effects of the circulator TX-RX non-linearity on the total achievable SIC. 

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4. Temperature Sensing Shape Morphing Antenna (ShMoA)

   https://doi.org/10.3390/mi13101673  

   Zeng, Wenxin; Wang, Wei; Sonkusale, Sameer (October 2022, Micromachines)

   Devices that can morph their functions on demand provide a rich yet unexplored paradigm for the next generation of electronic devices and sensors. For example, an antenna that can morph its shape can be used to adapt communication to different wireless standards or improve wireless signal reception. We utilize temperature-sensitive shape memory alloys (SMA) to realize a shape morphing antenna (ShMoA). In the designed architecture, multiple conjoined shape memory alloy sections form the antenna. The shape morphing of this antenna is achieved through temperature control. Different temperature threshold levels are used for programming the shape. Besides its conventional use for RF applications, ShMoA can serve as a multi-level temperature sensor, analogous to thermoreceptors in an insect antenna. ShMoA essentially combines the function of temperature sensing, embedded computing for detection of threshold crossings, and radio frequency readout, all in the single construct of a shape-morphing antenna (ShMoA) without the need for any battery or peripheral electronics. The ShMoA can be employed as bio-inspired wireless temperature sensing antennae on mobile robotic flies, insects, drones and other robots. It can also be deployed as programmable antennas for multi-standard wireless communication. 

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5. An Experiment-Based Comparison between Fully Digital and Hybrid Beamforming Radio Architectures for Many-Antenna Full-Duplex Wireless Communication

   https://doi.org/10.3390/electronics11010059  

   Megson, Gavin; Gupta, Sabyasachi; Hashir, Syed Muhammad; Aryafar, Ehsan; Camp, Joseph (January 2022, Electronics)

   Full-duplex (FD) communication in many-antenna base stations (BSs) is hampered by self-interference (SI). This is because a FD node’s transmitting signal generates significant interference to its own receiver. Recent works have shown that it is possible to reduce/eliminate this SI in fully digital many-antenna systems, e.g., through transmit beamforming by using some spatial degrees of freedom to reduce SI instead of increasing the beamforming gain. On a parallel front, hybrid beamforming has recently emerged as a radio architecture that uses multiple antennas per FR chain. This can significantly reduce the cost of the end device (e.g., BS) but may also reduce the capacity or SI reduction gains of a fully digital radio system. This is because a fully digital radio architecture can change both the amplitude and phase of the wireless signal and send different data streams from each antenna element. Our goal in this paper is to quantify the performance gap between these two radio architectures in terms of SI cancellation and system capacity, particularly in multi-user MIMO setups. To do so, we experimentally compare the performance of a state-of-the-art fully digital many antenna FD solution to a hybrid beamforming architecture and compare the corresponding performance metrics leveraging a fully programmable many-antenna testbed and collecting over-the-air wireless channel data. We show that SI cancellation through beam design on a hybrid beamforming radio architecture can achieve capacity within 16% of that of a fully digital architecture. The performance gap further shrinks with a higher number of quantization bits in the hybrid beamforming system. 

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