RF/Microwave Devices

Magnetic Thick Films for Integrated Microwave Devices

This project is under DARPA's Magnetic Miniaturized and Monolithically Integrated Components (M3IC) program in the DARPA Microsystems Technology Office.

The objective of this effort is to develop thick-film magnetic materials that can be fabricated on semiconductor integrated circuits to enable highly miniaturized microwave components such as circulators and isolators operating in the 10 to 110 GHz frequency regime. These nonlinear, non-reciprocal components are critical for next generation radios, radar, and sensing systems for defense, consumer, automotive, and healthcare applications.

Miniaturization of Resonant Wireless Power Transfer System Components

Portable and wearable electronics require wireless charging to sustain mobile usage at convenient positions and locations. The goal is to develop a compact, highly power efficient wireless power transfer charging system operating at 6.78 MHz, which is compliant with the Rezence standard.The research scope includes development of a highly compact, high efficiency, ferrite-core receiver antenna; and a metamaterial lens to enhance WPT efficiency between the transmitter and the receiver.  In this work, we focus on WPT receiver modules for various portable and wearable consumable electronics with a power rating of ~10 W such as smart phones, radios, laptops, tablets, and military electronics. In future work, this technology could also be scalable to other power ranges, such as mW for biomedical implants to kW for automobiles.

Micromachining of Permanent Magnet Undulator Structures for Compact X-ray Sources

Research Objective

To investigate the use of advanced microfabrication technologies and MEMS-enabled magnetization methods in developing reduced-scale permanent magnet undulator structures (with fine pole pitch ~5 microns) while maintaining reasonable magnetic field strengths as well as efficient generation of brilliant, high energy (>10keV) mono-energetic x-rays from modest electron beam source energies (~200MeV).


An accelerated beam of electrons with relativistic velocities experiences an undulation when passing through a spatially periodic magnetic field. This undulation of the beam trajectory results in the generation of electromagnetic radiation from which intense, tunable x-rays can be produced.

Non-Bragg Resonance and Its Applications

This project studies on wave propagation in waveguide with periodical boundaries, in such a case, a new kind of resonance occurs. This new kind of resonance is very different from the traditional Bragg resonance.

In Non-Bragg resonance, the resonance frequency and bandwidth strongly depends on the geometric configuration of the waveguide, and, the resonance is tunable. Theoretical and experimental results show good agreements.

A Compact 5GHz WLAN Notched Bluetooth/UWB Antenna

The objective of the effort is to design a compact Bluetooth/UWB antenna design with 5GHz WLAN notchi function.


Among short-range wireless communication systems, Ultra-wideband (UWB) technology, with a frequency allocation of 3.1-10.6 GHz, has gained a lot of popularity from  researchers and the wireless industry alike due to the high data transfer rate (110-200 Mb/s) and low power consumption. However, since UWB covers the frequency spectrum of Wireless Local Area Network (WLAN) operating at 5.2 GHz (5150-5350 MHz) and 5.8 GHz (5725-5825MHz), a frequency notched function in the UWB antenna design is greatly desirable to avoid interferences from WLAN. Since 2002, various antenna structures and methods to notch a specific frequency band have been introduced. Moreover, a planar integrated antenna working on both Bluetooth and UWB has been recently introduced for systems operating in those two communication systems.


(1) UWB antenna design

(2) 5GHz frequency notch function

(3) Integrate Bluetooth antenna

A High Gain Circular Polarization Antenna using Metamaterial Slabs

The objective of the effort is to design a high gain circular polarization antenna using metamaterial slabs for satellite communication.


Mordern satellite communication systems often demand low-profile, wide bandwidth, high gain and circular polarization antennas. Traditionally, a reflector antenna, a horn antenna, and a microstrip array antenna are widely used to achieve high gain circular polarization. Recently, a metamaterial approach has been emerged as a promising method for a high gain antenna. However, a high gain circular polarization antenna using metamaterial remains as a big challenge.


(1) High gain antenna with metamaterial slabs

(2) Circular polarization for satellite communication systems

Wireless Shear Stress Sensor Array


Research Objectives

To develop a wireless shear-stress sensor array to provide three-dimensional, time-resolved, fluctuating skin friction data to aid turbulence model development.


Each sensor is effectively an LC tank made up of a variable-capacitance floating element and an integrated inductor. The sensing antenna is inductively coupled to the tank and can detect a change in the resonant frequency caused by a displacement of the floating element. An array is realized by designing each sensor to have it’s own unique resonant frequency. Then a single broad spectrum antenna can monitor the entire array.

Broader Impact

The realization of such an array will enable fundamental scientific studies of complex turbulent flows. It could also be implemented into a feedback control system for future air vehicles employing active flow control.

Ultra-Miniature Power Management for Microsystem Platforms

High density passive components (inductors, transformers, capacitors) are developed and integrated with high frequency (100-500 MHz) CMOS switching power conversion circuits. The  mm3-scale integrated converter will be capable of delivering >20 V from a battery source to enable mobile microsystems such as micro air vehicles and microrobots.

High-inductance-density air core inductors and transformers have been fabricated using a three-dimensional copper electroforming process. These devices have measured inductance densities > 100 nH/mm2  and quality factors > 20. Optimal performance is achieved in the range of 50 MHz - 500 MHz to enable next generation switching converters operating at very high frequencies.

SEM image of three-dimensional, stacked, air-core microinductor.