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1. A Highly Efficient Dual-band Harmonic-tuned GaN RF Synchronous Rectifier with Integrated Coupler and Phase Shifter

   https://doi.org/10.1109/MWSYM.2019.8700900  

   Hoque, Md Aminul; Ali, Sheikh Nijam; Mokri, Mohammad Ali; Gopal, Srinivasan; Chahardori, Mohammad; Heo, Deukhyoun (June 2019, 2019 IEEE MTT-S International Microwave Symposium (IMS))

   This paper presents a dual-band RF rectifying circuit for wireless power transmission at 1.17 GHz and 2.4 GHz. A dual-band harmonic-tuned inverse-class F/class-F mode power amplifier using a 10 W GaN device has been utilized to implement the proposed rectifier with an on-board coupler and phase shifter. The matching circuit is precisely designed so that the circuit operates in inverse class F and class F mode in the lower and upper frequency bands using dual-band harmonic tuning, respectively. Measurement results show that the rectifier circuit has 78% and 76% efficiencies at 1.17 GHz and 2.4 GHz frequency bands, respectively. To the best of the authors' knowledge, this rectifier is the first demonstration of a dual-band harmonic-tuned synchronous rectifier using a GaN HEMT device with an integrated coupler and phase-shifter for a watt-level RF input power. 

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2. Investigation of Graphene Film as Ground Plane Material for RF and Microwave Electronics

   https://doi.org/10.1109/TCPMT.2025.3537653  

   Misra, Utkarsh; Kosamiya, Vishvajitsinh; Brooke_Anderson, Alissa; Li, Liguan; Liu, Ruoke; Guneroglu, Ugur; Spanopoulos, Ioannis; Wang, Jing (May 2025, IEEE Transactions on Components, Packaging and Manufacturing Technology)

   This study investigates the integration of reduced graphene oxide (rGO) films as ground plane in miniaturized RF/mm-wave systems for advanced thermal management applications. Traditional methods such as copper-based heat spreaders struggle to handle the increased power and tighter integration requirements of modern day RF/mmWave packaging. Due to rGO’s exceptionally high in-plane thermal conductivity (∼1100 W/mK), when compared with copper (∼400 W/mK), rGO emerges as a compelling candidate for thermal management in RF electronic packaging. This study investigates the use of rGO to form a ground plane in RF and microwave electronics, evaluating its performance through meticulous transmission line simulations and measurements. Our findings reveal that rGO ground planes exhibit high signal integrity, with an average loss of about 1 dB at 10 GHz and around 2 dB up to 26 GHz, comparable to the performance of traditional copper ground planes. These results indicate that rGO is a promising material for RF and microwave circuits, especially in applications requiring enhanced thermal management and mechanical flexibility. 

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3. LTE Spectrum Sharing Research Testbed: Integrated Hardware, Software, Network and Data

   https://doi.org/https://doi.org/10.1145/3131473.3131484  

   Marojevic, Vuk; Nealy, Randall; Reed, Jeffrey H. (October 2017, ACM WiNTECH 2017)

   This paper presents Virginia Tech’s wireless testbed supporting research on long-term evolution (LTE) signaling and radio frequency (RF) spectrum coexistence. LTE is continuously refined and new features released. As the communications contexts for LTE expand, new research problems arise and include operation in harsh RF signaling environments and coexistence with other radios. Our testbed provides an integrated research tool for investigating these and other research problems; it allows analyzing the severity of the problem, designing and rapidly prototyping solutions, and assessing them with standard-compliant equipment and test procedures. The modular testbed integrates general-purpose software-defined radio hardware, LTE-specific test equipment, RF components, free open-source and commercial LTE software, a configurable RF network and recorded radar waveform samples. It supports RF channel emulated and over-the-air radiated modes. The testbed can be remotely accessed and configured. An RF switching network allows for designing many different experiments that can involve a variety of real and virtual radios with support for multiple-input multiple-output (MIMO) antenna operation. We present the testbed, the research it has enabled and some valuable lessons that we learned and that may help designing, developing, and operating future wireless testbeds. 

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4. A Wideband Sliding Correlation Channel Sounder in 65 nm CMOS: Evaluation Board Performance

   Dipankar Shakya, Ting Wu (September 2021, IEEE transactions on circuits and systems)

   Abstract—Emerging applications such as wireless sensing, position location, robotics, and many more are driven by the ultra-wide bandwidths available at millimeter-wave (mmWave) and Terahertz (THz) frequencies. The characterization and effi- cient utilization of wireless channels at these extremely high frequencies require detailed knowledge of the radio propaga- tion characteristics of the channels. Such knowledge is developed through empirical observations of operating conditions using wireless transceivers that measure the impulse response through channel sounding. Today, cutting-edge channel sounders rely on several bulky RF hardware components with complicated interconnections, large parasitics, and sub-GHz RF bandwidth. This brief presents a compact sliding correlation-based chan- nel sounder baseband built on a monolithic integrated circuit (IC) using 65 nm CMOS, implemented as an evaluation board achieving a 2 GHz RF bandwidth. The IC is the world’s first gigabit-per-second channel sounder baseband implemented in low-cost CMOS. The presented single-board system can be employed at both the transmit and receive baseband to study multipath characteristics and path loss. Thus, the single-board implementation provides an inexpensive and compact solution for sliding correlation-based channel sounding with 1 ns multipath delay resolution. Index Terms—142 GHz, channel sounder, mmWave, on-chip baseband, PN sequence, RF hardware, sliding correlation, THz, XPD 

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5. WIRELESS AND STAND-ALONE SUBMARINE PROPELLER BASED ON ACOUSTIC PROPULSION

   Lee, J; Kim, E.S. (June 2022, Hilton Head Workshop 2022: A Solid-State Sensors, Actuators and Microsystems Workshop)

   This paper presents a wireless and stand-alone subminiature propeller based on acoustic propulsion for the underwater robotic applications. The acoustic propulsion is generated by a MEMS-based self-focusing acoustic transducer (SFAT), fabricated on 1-mm-thick lead zirconate titanate (PZT) substrate, and operated at its thickness mode resonant frequency of 2.32 MHz. A 100F lithium-ion capacitor (LIC) is used as a power source due to its high energy and power densities. A drive electronic circuit is implemented on a flexible printed circuit board (PCB) and delivers 30Vpp sinusoidal signal to the acoustic propeller. The completed system is 18 x 18 x 38 mm3 in volume and weighs 12.56 grams, resulting in a mass density of 1.020 g/cm3. The acoustic propulsion generated by the acoustic propeller is measured to be 18.68μN with the electrical power of 358.7mW consumed by the propeller. Both vertical and horizontal propulsions are demonstrated successfully in sodium polytungstate (SPT) solution. 

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